Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used in the treatment of inflammation and pain (Escribano et al., 2003:203). Diclofenac, a classical NSAID, is considerably more effective as an analgesic, antipyretic and anti-inflammatory drug than other traditional NSAIDs, like indomethacin and naproxen (Grosser et al., 2011:986). However, the use of diclofenac is known for its many side effects, such as gastric disorders, while fluid and sodium retention are also commonly observed (Rossiter, 2012:391). Since topical diclofenac offers a more favourable safety profile, it is a valuable substitute for oral NSAID therapy in the treatment of osteoarthritis (Roth & Fuller, 2011:166). The benefits of topically applied NSAIDs, compared to oral administration and systemic delivery, include the easy cessation of treatment, should effects become troublesome (Brown et al., 2006:177), the avoidance of extensive, first-pass metabolism (Cleary, 1993:19; Kornick, 2003:953; Prausnitz & Langer, 2008:1261; Lionberger & Brennan, 2010:225), reduced systemic side effects (Colin Long, 2002:41), convenience of application and improved patient compliance (Cleary, 1993:19; Prausnitz & Langer, 2008:1261). An approach that is often applied in optimising the solubility and dissolution rate of poorly water soluble, weak electrolytes is to prepare a salt of the active pharmaceutical ingredient (API) (Minghetti et al., 2007:815; O’Connor & Corrigan, 2001:281-282). Diclofenac is frequently administered as a salt, due to the high partition coefficient and very low water solubility of this molecule (Fini et al., 1999:164). Formulating for efficacy (FFETM) is a software programme designed by JW Solutions to facilitate the formulation of cosmetic ingredients or solvents into a product that would optimally deliver active ingredients into the skin. The notion is built upon solubility, i.e. solubility of the active ingredient in the formulation and solubility of the formulation in the skin. This programme could also be employed to optimise amounts of predetermined ingredients, to propose formulations that would ensure optimal drug delivery, to calculate the skin delivery gap (SDG) and to demonstrate transdermal permeation of active ingredients and excipients (JW Solutions Software, 2013a). When the SDG is known, it mathematically indicates the optimal active ingredient and topical delivery vehicle to use (JW Solutions, 2013b). In this study, diclofenac sodium (DNa), diclofenac diethylamine (DDEA) and diclofenac N-(2- hydroxyethyl) pyrrolidine (DHEP) were each formulated in the following emulgels: * An emulgel optimised towards the stratum corneum (SC) (enhancing drug delivery into this layer and deeper tissues) (oily phase ~30%), * A more hydrophilic emulgel (oily phase ~15%), and * A more lipophilic emulgel (oily phase ~45%). Components of the oily phase and its respective amounts, as well as the SDG of formulations were determined by utilising the FFETM software of JW Solutions (2013a). The aqueous solubilities of DNa, DDEA and DHEP were determined and their respective values were 11.4 mg/ml, 8.0 mg/ml and 11.9 mg/ml, all indicative of effortless percutaneous delivery (Naik et al., 2000:319). Log D (octanol-buffer distribution coefficient) (pH 7.4) determinations for DNa, DDEA and DHEP were performed and their values established at 1.270 (DNa), 1.291 (DDEA) and 1.285 (DHEP). According to these values, diclofenac, when topically applied as a salt in a suitable vehicle, should permeate transdermally without the aid of radical intervention (Naik et al., 2000:319; Walters, 2007:1312). Membrane release studies were also carried out in order to determine the rate of API release from these new formulations. Results confirmed that diclofenac was indeed released from all nine of the formulated emulgels. The more hydrophilic DNa formulation released the highest average percentage of diclofenac (8.38%) after 6 hours. Subsequent transdermal diffusion studies were performed to determine the diclofenac concentration that permeated the skin. The more hydrophilic DNa emulgel showed the highest average percentage skin diffusion (0.09%) after 12 hours, as well as the highest average flux (1.42 ± 0.20 μg/cm2.h). The concentrations of diclofenac in the SC-epidermis (SCE) and epidermis-dermis (ED) were determined through tape stripping experiments. The more lipophilic DNa emulgel demonstrated the highest average concentration (0.27 μg/ml) in the ED, while the DNa emulgel that had been optimised towards the SC, had the highest concentration in the SCE (0.77 μg/ml). / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

Acne vulgaris is the single, most common disease that presents a significant challenge to dermatologists, due to its complexity, prevalence and range of clinical expressions. This condition can be found in 85% of teenage boys and 80% of girls (Gollnick, 2003:1580). Acne can cause serious psychological consequences (low self–esteem, social inhibition, depression, etc.), if left untreated, and should therefore be recognised as a serious disorder (Webster, 2001:15). The pathogenesis of acne is varied, with factors that include plugging of the follicle, accumulation of sebum, growth of Propionibacterium acnes (P. acnes), and inflammatory tissue responses (Wyatt et al., 2001:1809). Acne treatment focuses on the reduction of inflammatory and non–inflammatory acne lesions, and thus halts the scarring process (Railan & Alster, 2008:285). Non–inflammatory acne lesions can be expressed as open and closed comedones, whereas inflammatory lesions comprise of papules, pustules, nodules and cysts (Gollnick, 2003:1581). Acne treatment may be topical, or oral. Topical treatment is the most suitable first–line therapy for non–inflammatory comedones, or mildly inflammatory disease states, with the advantage of avoiding the possible systemic effects of oral medications (Federman & Kirsner, 2000:80). Topical retinoids were very successfully used for the treatment of acne in the 1980s. Their effectiveness in long–term therapies was limited though, due to local skin irritations that occurred in some individuals (Julie & Harper, 2004:S36). Vitamin A acetate presented a new approach in the treatment of acne, showing less side effects (Cheng & Depetris, 1998:7). In this study, vitamin A acetate and zinc acetate were formulated into semisolid, combination formulations for the possible treatment of acne. Whilst vitamin A controls the development of microcomedones, reduces existing comedones, diminishes sebum production and moderately reduces inflammation (Verschoore et al., 1993:107), zinc normalises hormone imbalances (Nutritional–supplements–health–guide.com, 2005:2) and normalises the secretion of sebum (Hostýnek & Maibach, 2002:35). Although the skin presents many advantages to the delivery of drugs, it unfortunately has some limitations. The biggest challenge in the transdermal delivery of drugs is to overcome the natural skin barrier. Its physicochemical properties are a good indication(s) of the transdermal behaviour of a drug. The ideal drug to be used in transdermal delivery would have sufficient lipophilic properties to partition into the stratum corneum, but it would also have sufficient hydrophilic properties to partition into the underlying layers of the skin (Kalia & Guy, 2001:159). Pheroid technology was also implemented during this study, in order to establish whether it would enhance penetration of the active ingredients across the skin. The Pheroid consists of vesicular structures that contain no phospholipids, nor cholesterol, but consists of the same essential fatty acids that are present in humans (Grobler et al., 2008:283). The aim of this study hence was to investigate the transdermal delivery of vitamin A acetate and zinc acetate, jointly formulated into four topical formulations for acne treatment. Vitamin A acetate (0.5%) and zinc acetate (1.2%) were formulated into a cream, Pheroid cream, emulgel and Pheroid emulgel. An existing commercial product, containing vitamin A acetate, was used to compare the results of the formulated products with. The transdermal, epidermal and dermal diffusion of the formulations were determined during a 6 h diffusion study, using Franz diffusion cells and tape stripping techniques. Experimental determination of the diffusion studies proved that vitamin A acetate did not penetrate through the skin. These results applied to both the formulations being developed during this study, as well as to the commercial product. Tape stripping studies were done to determine the concentration of drug present in the epidermis and dermis. The highest epidermal concentration of vitamin A acetate was obtained with the Pheroid emulgel (0.0045 ug/ml), whilst the emulgel formulation provided the highest vitamin A acetate concentration in the dermis (0.0029 ug/ml). Contrary, for the commercial product, the total concentration of vitamin A acetate in the epidermis was noticeably lower than for all the new formulations studied. Vitamin A acetate concentrations of the commercial product in the dermis were within the same concentration range as the newly developed formulations, with the exception of the emulgel that delivered approximately 31% more vitamin A acetate to the dermis, than the commercial product. Zinc acetate was able to diffuse through full thickness skin, although no flux values were obtained. To eliminate the possibility of endogenous zinc diffusion, placebo formulations (without zinc) were prepared for use as control samples during the skin diffusion investigation. The emulgel and Pheroid emulgel formulations were unable to deliver significant zinc acetate concentrations transdermally, although transdermal diffusion was attained from both the cream and Pheroid cream. Tape stripping experiments with placebo formulations relative to the formulated products revealed that zinc acetate concentrations in the epidermis and dermis were significantly higher when the placebo formulations were applied. However, the average zinc acetate concentration in the dermis, after application of the cream formulation, was significantly higher, compared to when the placebo cream was applied. It could therefore be concluded that no zinc acetate had diffused into the epidermis and dermis from the new formulations, except from the cream formulation. The zinc acetate concentration being measured in the epidermis thus rather represented the endogenous zinc acetate. The cream formulation, however, was probably able to deliver detectable zinc acetate concentrations to the epidermis. Stability of the formulated products was tested under a variety of environmental conditions to determine whether the functional qualities would remain within acceptable limits over a certain period of time. The formulated products were tested for a period of three months under storage conditions of 25°C/60% RH (relative humidity), 30°C/60% RH and 40°C/75% RH. Stability studies included stability indicating assay testing, the determination of rheology, pH, droplet size, zeta–potential, mass loss, morphology of the particles and physical assessment. The formulations were unstable over the three months stability test period. A change in viscosity, colour and concentration of the active ingredients were observed. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2011.

Acne vulgaris is the single, most common disease that presents a significant challenge to dermatologists, due to its complexity, prevalence and range of clinical expressions. This condition can be found in 85% of teenage boys and 80% of girls (Gollnick, 2003:1580). Acne can cause serious psychological consequences (low self–esteem, social inhibition, depression, etc.), if left untreated, and should therefore be recognised as a serious disorder (Webster, 2001:15). The pathogenesis of acne is varied, with factors that include plugging of the follicle, accumulation of sebum, growth of Propionibacterium acnes (P. acnes), and inflammatory tissue responses (Wyatt et al., 2001:1809). Acne treatment focuses on the reduction of inflammatory and non–inflammatory acne lesions, and thus halts the scarring process (Railan & Alster, 2008:285). Non–inflammatory acne lesions can be expressed as open and closed comedones, whereas inflammatory lesions comprise of papules, pustules, nodules and cysts (Gollnick, 2003:1581). Acne treatment may be topical, or oral. Topical treatment is the most suitable first–line therapy for non–inflammatory comedones, or mildly inflammatory disease states, with the advantage of avoiding the possible systemic effects of oral medications (Federman & Kirsner, 2000:80). Topical retinoids were very successfully used for the treatment of acne in the 1980s. Their effectiveness in long–term therapies was limited though, due to local skin irritations that occurred in some individuals (Julie & Harper, 2004:S36). Vitamin A acetate presented a new approach in the treatment of acne, showing less side effects (Cheng & Depetris, 1998:7). In this study, vitamin A acetate and zinc acetate were formulated into semisolid, combination formulations for the possible treatment of acne. Whilst vitamin A controls the development of microcomedones, reduces existing comedones, diminishes sebum production and moderately reduces inflammation (Verschoore et al., 1993:107), zinc normalises hormone imbalances (Nutritional–supplements–health–guide.com, 2005:2) and normalises the secretion of sebum (Hostýnek & Maibach, 2002:35). Although the skin presents many advantages to the delivery of drugs, it unfortunately has some limitations. The biggest challenge in the transdermal delivery of drugs is to overcome the natural skin barrier. Its physicochemical properties are a good indication(s) of the transdermal behaviour of a drug. The ideal drug to be used in transdermal delivery would have sufficient lipophilic properties to partition into the stratum corneum, but it would also have sufficient hydrophilic properties to partition into the underlying layers of the skin (Kalia & Guy, 2001:159). Pheroid technology was also implemented during this study, in order to establish whether it would enhance penetration of the active ingredients across the skin. The Pheroid consists of vesicular structures that contain no phospholipids, nor cholesterol, but consists of the same essential fatty acids that are present in humans (Grobler et al., 2008:283). The aim of this study hence was to investigate the transdermal delivery of vitamin A acetate and zinc acetate, jointly formulated into four topical formulations for acne treatment. Vitamin A acetate (0.5%) and zinc acetate (1.2%) were formulated into a cream, Pheroid cream, emulgel and Pheroid emulgel. An existing commercial product, containing vitamin A acetate, was used to compare the results of the formulated products with. The transdermal, epidermal and dermal diffusion of the formulations were determined during a 6 h diffusion study, using Franz diffusion cells and tape stripping techniques. Experimental determination of the diffusion studies proved that vitamin A acetate did not penetrate through the skin. These results applied to both the formulations being developed during this study, as well as to the commercial product. Tape stripping studies were done to determine the concentration of drug present in the epidermis and dermis. The highest epidermal concentration of vitamin A acetate was obtained with the Pheroid emulgel (0.0045 ug/ml), whilst the emulgel formulation provided the highest vitamin A acetate concentration in the dermis (0.0029 ug/ml). Contrary, for the commercial product, the total concentration of vitamin A acetate in the epidermis was noticeably lower than for all the new formulations studied. Vitamin A acetate concentrations of the commercial product in the dermis were within the same concentration range as the newly developed formulations, with the exception of the emulgel that delivered approximately 31% more vitamin A acetate to the dermis, than the commercial product. Zinc acetate was able to diffuse through full thickness skin, although no flux values were obtained. To eliminate the possibility of endogenous zinc diffusion, placebo formulations (without zinc) were prepared for use as control samples during the skin diffusion investigation. The emulgel and Pheroid emulgel formulations were unable to deliver significant zinc acetate concentrations transdermally, although transdermal diffusion was attained from both the cream and Pheroid cream. Tape stripping experiments with placebo formulations relative to the formulated products revealed that zinc acetate concentrations in the epidermis and dermis were significantly higher when the placebo formulations were applied. However, the average zinc acetate concentration in the dermis, after application of the cream formulation, was significantly higher, compared to when the placebo cream was applied. It could therefore be concluded that no zinc acetate had diffused into the epidermis and dermis from the new formulations, except from the cream formulation. The zinc acetate concentration being measured in the epidermis thus rather represented the endogenous zinc acetate. The cream formulation, however, was probably able to deliver detectable zinc acetate concentrations to the epidermis. Stability of the formulated products was tested under a variety of environmental conditions to determine whether the functional qualities would remain within acceptable limits over a certain period of time. The formulated products were tested for a period of three months under storage conditions of 25°C/60% RH (relative humidity), 30°C/60% RH and 40°C/75% RH. Stability studies included stability indicating assay testing, the determination of rheology, pH, droplet size, zeta–potential, mass loss, morphology of the particles and physical assessment. The formulations were unstable over the three months stability test period. A change in viscosity, colour and concentration of the active ingredients were observed. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2011.

Caffeine is frequently used in cosmetics due to its well-characterised skin permeation properties and is widely incorporated in cosmetic-related products intended for skin (Samah & Heard, 2013:631). Despite its polar characteristics (Dias et al., 1999:41), caffeine is an important biologically and cosmetically active compound (Herman & Herman, 2012:13). This active pharmaceutical ingredient (API) has a broad range of advantages in the world of cosmetics, including the improvement of microcirculation in the capillaries (Lupi et al., 2007:107), showing anti-cellulite activity in the fatty tissue (Velasco et al., 2008:24), anti-oxidation activity in sunscreens & anti-ageing products (Koo et al., 2007:964) and the stimulation of hair growth (Fisher et al., 2007:27). Caffeine has also shown significant decreases in UV-induced skin tumour multiplicity (Lu et al., 2001:5003, 5008) and has been proven to prevent photo-damaged skin, which includes the formation of wrinkles and histological alterations (Mitani et al., 2007:86). It is therefore clear that the challenge for the dermal delivery of the hydrophilic caffeine is for it to be retained in the specific skin layers (dermal delivery) where it can exert its action, rather than to permeate through the skin and into the hydrophilic systemic circulation (transdermal delivery) (Wiechers et al., 2008:10). In this study the calculated skin delivery gap (SDG) values, and the transdermal and dermal delivery of caffeine from three different semi-solid topical formulations were compared. The SDG theory was developed to evaluate the effectiveness of dermal delivery of API from topical formulations and is known as the ratio between the concentration required to achieve minimum effect relative to the concentration obtained at the target site (JW Solutions, 2011). During this study the principle of the SDG was investigated by using the formulating strategy, Formulating for Efficacy (FFE™), which aims to optimise skin delivery of APIs from different formulations. The SDG was therefore implemented and in vitro transdermal studies were utilised to ultimately prove or disprove the hypothesis of SDG on the prediction of the topical delivery of caffeine. The human skin consists of two distinctive layers namely the epidermis (including the stratum corneum (SC) and viable dermis) and the dermis (Menon, 2002:S3). The main barrier to dermal and transdermal permeation is the outermost layer of the skin, the SC (Fang et al., 2007:343). The difference between the target site for dermal and transdermal delivery of APIs is crucial to be mentioned. Dermal delivery includes the delivery of an API to the skin surface, SC, viable epidermis or dermis, whereas transdermal delivery requires the API to permeate all the way through the various skin layers and into the systemic circulation (Wiechers, 2000:42). Since this study involves the optimisation of the topical delivery of caffeine, the physicochemical properties of this API as well as those of the skin should be considered. As mentioned before, caffeine is a rather polar molecule (Dias et al., 1999:41), whereas the SC (lipophilic) provides the rate-limiting barrier to the percutaneous absorption of polar (hydrophilic) molecules, such as caffeine (Barry, 1983:105). Caffeine was incorporated into three different formulations: a gel and two creams (differing only in the ratio of the primary and secondary emollient). The three topical formulations each had different polarities, where the Gel represented the hydrophilic formulation (more polar than the skin), whereas the first cream, Cream 1 (containing 5% DMI and 9% glycerine), served as the intermediate formulation (similar polarity as the SC), and the second cream, Cream 2 (10% DMI and 4% glycerine), was the formulation less polar (therefore more lipophilic) than the SC. Franz cell type transdermal diffusion studies were performed on the three semi-solid formulations (Gel, Cream 1 and Cream 2). The diffusion studies were conducted over a period of 12 h, followed by the tape stripping of the skin directly after each diffusion study. Caucasian female abdominal skin was obtained with consent from willing donors. Ethical approval for the acquisition and use of the donated skin was granted under reference number NWU-00114-11-A5. The formulations each contained 1% of caffeine as API. The skin used for the diffusion studies was prepared with the use of a Zimmer Dermatome®. The receptor phase of each Franz cell was withdrawn at predetermined time intervals and subsequently analysed with high performance liquid chromatography (HPLC) in order to determine the concentration of caffeine that permeated through the skin. Stratum corneum-epidermis (SCE) and epidermis-dermis (ED) samples were prepared and left overnight at a temperature of 4 °C, and they were analysed the following day with the use of HPLC in order to determine the concentration of caffeine that had accumulated in the particular skin layers. The SDG value for each caffeine formulation was calculated and it was compared to the flux and tape stripping results obtained from the diffusion studies. To ultimately prove or disprove the SDG theory, the skin diffusion studies and tape stripping results were used to determine whether any difference occurred in the absorption or penetration of the API from the different formulations into the skin. The formulation with the intermediate polarity (Cream 1) produced the highest transdermal flux of caffeine due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. Cream 1 is sufficiently lipophilic to transport caffeine into the SC and at the same time sufficiently hydrophilic (more polar than Cream 2) to cause a greater driving force of caffeine through to the more hydrophilic epidermis, dermis and systemic circulation. The results from the tape stripping yielded that Cream 2 (the more lipophilic formulation) produced the highest concentration of caffeine into the SCE due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. The difference in polarity between the formulation and the API in Cream 2 was the greatest compared to the other formulations, which significantly increased the driving force of caffeine to partition into the SC (Wiechers et al., 2004:177). The hydrophilic gel showed the highest concentration of caffeine in the ED layer of the skin due to the hydrophilic compounds formulated in the Gel, which showed greater ability to partition into the aqueous dermis and viable epidermis (Imai et al., 2013:372). Cream 2 had the lowest calculated SDG value compared to that of the Gel and Cream 1. The smaller the delivery gap, the greater the delivery of the API should be into the skin (Wiechers, 2010). Considering this, it was expected that Cream 2 would deliver greater amounts of caffeine into the skin than the more hydrophilic formulations. Cream 2, which showed the lowest calculated SDG value delivered the highest amount of caffeine into the SCE during the diffusion studies. The calculated SDG values therefore are consistent with the concentration of caffeine in the SCE (the lowest SDG value produced the highest concentration of API in the SCE). However, no correlations were found between the calculated SDG values and ED delivery or the flux of caffeine. The final conclusion for this study is that the SDG theory proved to be effective and trustworthy regarding the delivery of caffeine into the SC. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

Caffeine is frequently used in cosmetics due to its well-characterised skin permeation properties and is widely incorporated in cosmetic-related products intended for skin (Samah & Heard, 2013:631). Despite its polar characteristics (Dias et al., 1999:41), caffeine is an important biologically and cosmetically active compound (Herman & Herman, 2012:13). This active pharmaceutical ingredient (API) has a broad range of advantages in the world of cosmetics, including the improvement of microcirculation in the capillaries (Lupi et al., 2007:107), showing anti-cellulite activity in the fatty tissue (Velasco et al., 2008:24), anti-oxidation activity in sunscreens & anti-ageing products (Koo et al., 2007:964) and the stimulation of hair growth (Fisher et al., 2007:27). Caffeine has also shown significant decreases in UV-induced skin tumour multiplicity (Lu et al., 2001:5003, 5008) and has been proven to prevent photo-damaged skin, which includes the formation of wrinkles and histological alterations (Mitani et al., 2007:86). It is therefore clear that the challenge for the dermal delivery of the hydrophilic caffeine is for it to be retained in the specific skin layers (dermal delivery) where it can exert its action, rather than to permeate through the skin and into the hydrophilic systemic circulation (transdermal delivery) (Wiechers et al., 2008:10). In this study the calculated skin delivery gap (SDG) values, and the transdermal and dermal delivery of caffeine from three different semi-solid topical formulations were compared. The SDG theory was developed to evaluate the effectiveness of dermal delivery of API from topical formulations and is known as the ratio between the concentration required to achieve minimum effect relative to the concentration obtained at the target site (JW Solutions, 2011). During this study the principle of the SDG was investigated by using the formulating strategy, Formulating for Efficacy (FFE™), which aims to optimise skin delivery of APIs from different formulations. The SDG was therefore implemented and in vitro transdermal studies were utilised to ultimately prove or disprove the hypothesis of SDG on the prediction of the topical delivery of caffeine. The human skin consists of two distinctive layers namely the epidermis (including the stratum corneum (SC) and viable dermis) and the dermis (Menon, 2002:S3). The main barrier to dermal and transdermal permeation is the outermost layer of the skin, the SC (Fang et al., 2007:343). The difference between the target site for dermal and transdermal delivery of APIs is crucial to be mentioned. Dermal delivery includes the delivery of an API to the skin surface, SC, viable epidermis or dermis, whereas transdermal delivery requires the API to permeate all the way through the various skin layers and into the systemic circulation (Wiechers, 2000:42). Since this study involves the optimisation of the topical delivery of caffeine, the physicochemical properties of this API as well as those of the skin should be considered. As mentioned before, caffeine is a rather polar molecule (Dias et al., 1999:41), whereas the SC (lipophilic) provides the rate-limiting barrier to the percutaneous absorption of polar (hydrophilic) molecules, such as caffeine (Barry, 1983:105). Caffeine was incorporated into three different formulations: a gel and two creams (differing only in the ratio of the primary and secondary emollient). The three topical formulations each had different polarities, where the Gel represented the hydrophilic formulation (more polar than the skin), whereas the first cream, Cream 1 (containing 5% DMI and 9% glycerine), served as the intermediate formulation (similar polarity as the SC), and the second cream, Cream 2 (10% DMI and 4% glycerine), was the formulation less polar (therefore more lipophilic) than the SC. Franz cell type transdermal diffusion studies were performed on the three semi-solid formulations (Gel, Cream 1 and Cream 2). The diffusion studies were conducted over a period of 12 h, followed by the tape stripping of the skin directly after each diffusion study. Caucasian female abdominal skin was obtained with consent from willing donors. Ethical approval for the acquisition and use of the donated skin was granted under reference number NWU-00114-11-A5. The formulations each contained 1% of caffeine as API. The skin used for the diffusion studies was prepared with the use of a Zimmer Dermatome®. The receptor phase of each Franz cell was withdrawn at predetermined time intervals and subsequently analysed with high performance liquid chromatography (HPLC) in order to determine the concentration of caffeine that permeated through the skin. Stratum corneum-epidermis (SCE) and epidermis-dermis (ED) samples were prepared and left overnight at a temperature of 4 °C, and they were analysed the following day with the use of HPLC in order to determine the concentration of caffeine that had accumulated in the particular skin layers. The SDG value for each caffeine formulation was calculated and it was compared to the flux and tape stripping results obtained from the diffusion studies. To ultimately prove or disprove the SDG theory, the skin diffusion studies and tape stripping results were used to determine whether any difference occurred in the absorption or penetration of the API from the different formulations into the skin. The formulation with the intermediate polarity (Cream 1) produced the highest transdermal flux of caffeine due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. Cream 1 is sufficiently lipophilic to transport caffeine into the SC and at the same time sufficiently hydrophilic (more polar than Cream 2) to cause a greater driving force of caffeine through to the more hydrophilic epidermis, dermis and systemic circulation. The results from the tape stripping yielded that Cream 2 (the more lipophilic formulation) produced the highest concentration of caffeine into the SCE due to the hydrophilic and lipophilic nature of caffeine and the formulation, respectively. The difference in polarity between the formulation and the API in Cream 2 was the greatest compared to the other formulations, which significantly increased the driving force of caffeine to partition into the SC (Wiechers et al., 2004:177). The hydrophilic gel showed the highest concentration of caffeine in the ED layer of the skin due to the hydrophilic compounds formulated in the Gel, which showed greater ability to partition into the aqueous dermis and viable epidermis (Imai et al., 2013:372). Cream 2 had the lowest calculated SDG value compared to that of the Gel and Cream 1. The smaller the delivery gap, the greater the delivery of the API should be into the skin (Wiechers, 2010). Considering this, it was expected that Cream 2 would deliver greater amounts of caffeine into the skin than the more hydrophilic formulations. Cream 2, which showed the lowest calculated SDG value delivered the highest amount of caffeine into the SCE during the diffusion studies. The calculated SDG values therefore are consistent with the concentration of caffeine in the SCE (the lowest SDG value produced the highest concentration of API in the SCE). However, no correlations were found between the calculated SDG values and ED delivery or the flux of caffeine. The final conclusion for this study is that the SDG theory proved to be effective and trustworthy regarding the delivery of caffeine into the SC. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

In pharmaceutical sciences, topical delivery is a transport process of an active pharmaceutical ingredient (API) from a formulated dosage form to the target site of action. For most topical delivery systems, the skin surface, or the specific skin layers, such as the outermost layer of the stratum corneum, the lipids amid the corneocytes within the stratum corneum, the corneocytes themselves, the epidermis, dermis, Langerhans cells, Merckle cells or the appendageal structures can be the target delivery location. When an API is delivered to the skin, it has to firstly diffuse from the formulation in which it is applied, to the skin surface. From there the API may partition into the stratum corneum, permeate across the stratum corneum and partition into the viable epidermis, from where it may partition further into the dermis and permeate across the dermis into the bloodstream (Wiechers, 2008:1-3, 7). With respect to the barrier function of the skin, the intercellular spaces within the stratum corneum contain lipids and its main purpose is to operate as a barrier to water-loss and to provide an imperative diffusional barrier to the absorption of APIs. This resistance is comprised of a complex interaction of lipids that creates a hydrophilic and lipophilic penetration pathway. The fundamental aspect underlying the impermeability of the skin, therefore, is the lipophilic nature of the stratum corneum (Bouwstra et al., 2003:4; Franz & Lehman, 2000:25; Walker & Smith, 1996:296). A common approach for the promotion of poorly penetrating APIs in transdermal delivery is the incorporation of chemical penetration enhancers in delivery systems, in order to promote the partitioning of an API into the stratum corneum. These chemicals are also referred to as accelerants, promoters and absorption promoters. Penetration enhancers are added to topical formulations and usually also partition into the stratum corneum, where they temporarily and reversibly disrupt its fundamental diffusional barrier properties, hence facilitating the absorption of an API through the skin (Büyüktimkin et al., 1997:358-359; Sinha & Kaur, 2000:1131; Walker & Smith, 1996:296). The mechanisms for the enhancement of diffusion of the API should therefore increase the solubility and partitioning of the drug from the formulation into the skin. It should further increase the solubility of the API within the skin and promote its permeability and diffusion coefficient (Rajadhyaksha et al., 1997:489). Fatty acids are recognised to effectively enhance the penetration of transdermally delivered hydrophilic and lipophilic APIs. Many penetration enhancers contain saturated and unsaturated hydrocarbon chains, and a popular fatty acid that has been used in this regard is oleic acid (Williams & Barry, 2004:609-610). It is believed that fatty acids disrupt the lipid organisation of the intercellular lipids within the stratum corneum to cause fluidisation of these bilayers, making the stratum corneum more permeable to APIs. Excipients with polar (hydrophilic) head groups and long hydrophobic chains i.e. fatty acids, can penetrate into the intercellular lipids of the stratum corneum and disrupt these endogenous lipid components, thereby increasing diffusion of an API within the skin (Barry, 2006:9-10; Hadgraft & Finnin, 2006:367-368; Kanikkannan et al., 2006:18; Williams & Barry, 2004:610). Natural oils are widely used in topical formulations and were an obvious choice in this study. Oils are liquids at room temperature, whereas fats are in solid form. They are relatively easy to obtain from both plants and animals. The main constituents of fats and oils are triglycerides comprising of fatty acids and a glycerol. Oils control the evaporation of moisture from the skin, spread easily and evenly and are partly metabolised in the skin to release valuable fatty acids (Fang et al., 2004:170,173; Lautenschläger, 2004:46; Mitsui, 1997:121-122). The focus of this study was not formulation per se, but included the formulation of avocado-, grapeseed-, emu-, crocodile, olive and coconut oil into semisolid emulgel- and two foam formulations. This was done in order to investigate the penetration enhancing properties of their fatty acid content on flurbiprofen which was chosen as the marker API. The emulgels containing the natural oils were compared to the same emulgel formulation containing liquid paraffin, and a hydrogel without the inclusion of an oil. Six natural oils were analysed by gas chromatography (GC) in order to quantify their fatty acid compositions, whilst also providing qualitative information by indicating the retention times of the materials with an alkyl chain composition (Mitsui, 1997:260). Data obtained with the GC indicated that olive- (76%), avocado- (68%), emu- (46%) and crocodile oil (40%) presented with high levels of oleic acid, also known as a mono-unsaturated fatty acid (MUFA). Lower levels of oleic acid were observed within grapeseed- (27%) and coconut oil (8%). The only oil demonstrating high levels of the poly-unsaturated fatty acid (PUFA), linoleic acid, was grapeseed oil (61%), whereas the remainder of the oils showed levels below 24%. Contrary, coconut oil seemed to have been the only oil high in saturated fatty acids (SFAs) and consisted of a lauric acid content of 52% and medium levels of myristic acid (21%). Average levels of palmitic acid (SFA) were found in crocodile- (21%) and in emu oil (21%), both of animal origin, whereas avocado-, grapeseed-, olive- and coconut oils from plants presented with levels below 15%. Stearic acid was also present in levels below 10% in all of these oils, with the oils of animal origin portraying the highest values. A method was developed and validated to determine the concentration of the marker flurbiprofen after diffusion from the formulations into the skin, as well as concentrations of the marker that diffused through the skin, by means of high performance liquid chromatography (HPLC). Franz cell membrane diffusion studies were conducted prior to the skin diffusion studies in order to verify the actual release of the marker from the semisolid formulations. Skin diffusion experiments were performed using dermatomed excised, human skin to which the six emulgel formulations, containing the natural oils, were applied. A comparative study was performed utilising liquid paraffin and a hydrogel, in order to compare the diffusion of the marker, flurbiprofen, into and through the skin. The two oil emulgel formulations that had indicated the best flux values were subsequently formulated into foam preparations in order to compare the penetration enhancement properties on flurbiprofen of these two oils in a foam preparation, to those in the equivalent emulgels. The data generated for all ten the formulations were compared, and the formulations that yielded the best results with regards to median flux values and the flurbiprofen concentrations within the stratum corneum-epidermis and epidermis-dermis, were identified. Application of the liquid paraffin emulgel (21.29 μg/ml) depicted the highest average concentration of the diffused lipophilic flurbiprofen within the stratum corneum-epidermis, followed by the olive oil foam (21.47 μg/ml), olive oil emulgel (17.82 μg/ml) and grapeseed oil emulgel (17.78 μg/ml). Very similar concentrations for the marker were demonstrated by the hydrogel (16.73 μg/ml) and crocodile oil emulgel (14.89 μg/ml), whereas a lower concentration was shown for coconut oil emulgel (7.18 μg/ml). The remainder of the formulations yielded concentrations below 3%, i.e. the avocado oil emulgel (2.72 μg/ml), the coconut oil foam (1.57 μg/ml) and finally the emu oil emulgel (1.25 μg/ml). The penetration of the marker, flurbiprofen, being trapped within the skin seemed to have been enhanced more by the oleic acid (UFA) containing emulgels and foam, especially. This was followed by oils containing high linoleic acid values, which indicated that the more kinked shaped the fatty acids, the more difficult it became to insert themselves within the lipid structures of the stratum corneum, with a resulting accumulation of the marker (Fang et al., 2003:318-319). It therefore seemed that those oils that predominantly consisted of unsaturated fatty acids (UFAs) (grapeseed-, crocodile- and olive oils) seemed to have increased the concentration of the diffused marker more significantly than those oils containing an almost even combination of MUFAs and PUFAs (avocado oil), or those mainly consisting of SFAs (coconut oil). Average concentrations of the diffused flurbiprofen found in the epidermis-dermis region of the skin for all of the formulations demonstrated low concentrations, ranging between 0.97 - 5.39 μg/ml, with the exception of the emu oil emulgel that presented with a higher concentration of 16.15 μg/ml. The reason for the high accumulation of the marker might have been as a result of epidermal proliferation, with subsequent accumulation of the marker within the epidermis-dermis due to high oleic- and linoleic acid values, as well as small amounts of palmitoleic acid present within this oil (Katsuta et al., 2005:1011). The resistance of the epidermis-dermis region to the general permeation of flurbiprofen might have been caused by its lipophilic nature, resulting in a reduced solubility within the hydrophilic environment of this region (Hadgraft, 1999:5). Median results from the skin diffusion studies demonstrated that the hydrogel (23.79 μg/cm2.h) had the highest flux, followed by the olive oil- (17.99 μg/cm2.h), liquid paraffin- (15.70 μg/cm2.h), coconut oil- (13.16 μg/cm2.h), grapeseed oil- (11.85 μg/cm2.h), avocado oil- (8.31 μg/cm2.h), crocodile oil- (6.68 μg/cm2.h) and emu oil emulgels (4.41 μg/cm2.h). The fact that the hydrogel presented a higher flux value for the marker could have been as a result of its high water content that had caused hydration of the skin. Hydration opens up the dense lipid structures inside of the stratum corneum, due to swelling of the corneocytes, with a subsequent increase in the marker‘s flux (Benson, 2005:28; Ranade & Hollinger, 2004:213). The high flux value of flurbiprofen with the liquid paraffin emulgel might also have resulted from the fact that it occluded the skin, which increased the hydration of the stratum corneum, with a subsequent increase in the flux (Mitsui, 1997:124; Thomas & Finnin, 2004:699). Results from the skin diffusion studies could be explained by the fact that the fatty acids differ in their hydrocarbon chain by (1) the length of the chain, and (2) the position- and number of the double bonds (Babu et al., 2006:144). It is suggested that fatty acids with hydrocarbon (lipophilic) chains between C12 to C14 (also present within coconut oil) have an optimal balance of the partition coefficient and its affinity for the skin (Ogiso & Shintani, 1990:1067). It appears as though the branched UFAs, especially oleic acid, present in high quantities in olive oil, were more powerful enhancers of the diffusion of the marker, flurbiprofen (Chi et al., 1995:270). Foam formulations were manufactured with the olive- and coconut oil emulgels that had demonstrated the best median flux values of flurbiprofen from the natural oil emulgel formulations. These formulated foams, however, did not significantly increased flux values for flurbiprofen through the skin, but only achieved values of 5.56 μg/cm2.h for the olive oil foam and 4.36 μg/cm2.h for the coconut oil foam formulations. The low flux values could have been attributed to the nature of the formulation itself, which was filled with trapped air that could have resulted in the formulation not making optimal direct contact with the available skin surface. Throughout this study, it became evident that olive oil, predominantly consisting of oleic acid (UFA), was most effective in enhancing the flux of the lipophilic marker, flurbiprofen, through the skin, closely followed by coconut oil consisting of SFAs, with lauric- and myristic acid as its main constituents. Better enhancement effects were observed with those oils containing high amounts of oleic acid (MUFA), than oils consisting of almost equal amounts of both PUFAs and MUFAs (avocado-, emu- and crocodile oil), or oils mainly consisting of PUFAs (grapeseed oil) as its main components, but their effect was not more significant than the oil containing SFAs (coconut oil) as its key components. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013.

A pharmaceutical dosage form is an entity that is administered to patients so that they receive an effective dose of an active pharmaceutical ingredient (API). The proper design and formulation of a transdermal dosage form require a thorough understanding of the physiological factors affecting percutaneous penetration and physicochemical characteristics of the API, as well as that of the pharmaceutical exipients that are used during formulation. The API and pharmaceutical excipients must be compatible with one another to produce a formulation that is stable, efficacious, attractive, easy to administer, and safe (Mahato, 2007:11). Amongst others, the physicochemical properties indicate the suitability of the type of dosage form, as well as any potential problems associated with instability, poor permeation and the target site to be reached (Wells & Aulton, 2002:337). Therefore, when developing new or improved dosage forms, it is of utmost importance to evaluate the factors influencing design and formulation to provide the best possible dosage form and formulation for the API in question. Delivery of an API through the skin has long been a promising concept due to its large surface area, ease of access, vast exposure to the circulatory and lymphatic networks, and non-invasive nature of the therapy. This is true whether a local or systemic pharmacological effect is desired (Aukunuru et al., 2007:856). However, most APIs are administered orally as this route is considered to be the simplest, most convenient and safest route of API administration. Since ibuprofen is highly metabolised in the liver and gastrointestinal tract, oral administration thereof results in decreased bioavailability. Furthermore, it also causes gastric mucosal damage, bleeding and ulceration. Another obstacle associated with oral API delivery is that some APIs require continuous delivery which is difficult to achieve (Bouwstra et al., 2003:3). Therefore, there is significant interest to develop topical dosage forms for ibuprofen to avoid side effects associated with oral delivery and to provide relatively consistent API levels at the application site for prolonged periods (Rhee et al., 2003:14). The aim of this study was to determine the influence of selected formulation factors on the transdermal delivery of ibuprofen. In order to achieve this aim, the physicochemical properties of ibuprofen had to be evaluated. The aqueous solubility, pH-solubility profile, octanol-water partition coefficient (log P-value) and octanol-buffer distribution coefficient (log D-values, pH 5 and 7.4) of ibuprofen were determined. According to Naik et al., (2000:319) the ideal aqueous solubility of APIs for transdermal delivery should be more than 1 mg.ml-1. However, results showed that ibuprofen depicted an aqueous solubility of 0.096 mg.ml-1 ± 25.483, which indicated poor water solubility and would therefore be rendered less favourable for transdermal delivery if only considering the aqueous solubility. The pH-solubility profile depicted that ibuprofen was less soluble at low pH-values and more soluble at higher pH-values. Previous research indicated that the ideal log Pvalues for transdermal API permeation of non steroid anti-inflammatory drugs (NSAIDs) are between 2 and 3 (Swart et al., 2005:72). Results obtained during this study indicated a log P-value of 4.238 for ibuprofen. This value was not included in the ideal range, which is an indication that the lipophilic/hydrophilic properties are not ideal, and this might therefore; contribute to poor ibuprofen penetration through the skin. Furthermore, the obtained log D-values at pH 5 and 7.4 were 3.105 and 0.386, respectively. Therefore, it would be expected that ibuprofen incorporated into a formulation prepared at a pH of 5 would more readily permeate the skin compared to ibuprofen incorporated into a formulation prepared at a pH of 7.4. A gel, an emulgel and a Pheroid™ emulgel were formulated at pH 5 and 7.4, in order to examine which dosage form formulated at which pH would deliver enhanced transdermal delivery. Obtained diffusion results of the different semi-solid formulations were furthermore compared to a South African marketed commercial product (Nurofen® gel) in order to establish if a comparable formulation could be obtained. An artificial membrane was used to conduct the membrane permeation studies over a period of 6 h, in order to determine whether ibuprofen was in fact released from the formulations through the membrane. Skin permeation studies were conducted using Franz diffusion cells over a period of 12 h where samples were withdrawn at specified time intervals. All the formulations exhibited an increase in the average cumulative amount of ibuprofen released from the formulations and that permeated the membrane when compared to Nurofen® gel. This increase was statistically significant (p<0.05) for the gel, emulgel and Pheroid™ emulgel at pH 7.4. The gel at pH 7.4 exhibited the highest cumulative amount of ibuprofen that permeated the membrane. Preparations formulated at a pH of 5, did not differ significantly from Nurofen® when the average cumulative amount of ibuprofen that permeated the membrane were compared. The following rank order for the average cumulative amount released from the formulations could be established: Gel (pH 7.4) >>>> Pheroid™ emulgel (pH 7.4) > Emulgel (pH 7.4) >>> Gel (pH 5)> Pheroid™ emulgel (pH 5) ≈ Emulgel (pH 5) > Nurofen® gel. On the other hand, all the formulations exhibited an increase in the average cumulative amount of ibuprofen that permeated the skin when compared to Nurofen® gel. This increase was statistically significant (p < 0.05) for the gel, emulgel and Pheroid™ emulgel at pH 5, as well as the emulgel and Pheroid™ emulgel at pH 7.4. The emulgel at pH 5 exhibited the highest cumulative amount of ibuprofen that permeated the skin. The following rank order for the average cumulative amount released from the formulations and that permeated the skin could be established: Emulgel (pH 5) >> Pheroid™ emulgel (pH 5) > Gel (pH 5) > Emulgel (pH 7.4)> Pheroid™ emulgel (pH 7.4) ≈ Emulgel (pH 7.4) >> Nurofen® gel > Gel (pH 7.4). From this rank order it was clear that a trend was followed where the pH of formulation also played a role in ibuprofen permeation. All the formulations exhibited a higher release rate and flux when compared to Nurofen® gel. This was statistically significant for the emulgel, gel and Pheroid™ emulgel at pH 7.4. The gel at pH 7.4 exhibited the highest release rate and flux. This was observed for the membrane and skin permeation studies. All the formulations (including Nurofen® gel) presented a correlation coefficient (r2) of 0.972 – 0.995 for membrane permeation studies, and 0.950 – 0.978 for skin permeation studies; indicating that the release of ibuprofen from each of the formulations could be described by the Higuchi model. Furthermore, all the formulations exhibited a prolonged lag time compared to Nurofen® gel which indicated that the ibuprofen was retained for a longer time by the base. This was statistically significant (p < 0.05) for the emulgel at pH 7.4, the gel and Pheroid™ emulgel at pH 5. The gel at pH 7.4 exhibited a lag time closest to that of Nurofen® gel and this difference could not be classified as statistically significant (p > 0.286). This was observed for the membrane and skin permeation studies. Nurofen® gel exhibited the highest ibuprofen concentration in the stratum corneum as well as in the epidermis followed by the gel at pH 7.4. However, results obtained for all the formulations indicated that topical as well as transdermal delivery of ibuprofen was achieved. The pH of a formulation plays an important role with respect to API permeation. Ibuprofen is reported to have a pKa value 4.4 (Dollery, 1999:I1); and by application of the Henderson-Hasselbach equation, at pH 5, 20.08% of ibuprofen will be present in its unionised form and at pH 7.4, 0.1% ibuprofen will exist in its unionised form. Since the unionised form of APIs is more lipid soluble than the ionised form, unionised forms of APIs permeate more readily across the lipid membranes (Surber & Smith, 2000:27). Therefore, it would be expected that ibuprofen formulated at pH 5 would be more permeable than formulations at pH 7.4. However, this did not correspond to the results (membrane studies) obtained in this study. It may be attributed to the solubility of ibuprofen in the different formulations. According to the pH-solubility profile of ibuprofen obtained in this study, it was more soluble at pH 7.4 than at pH 5. This was due to the fact that ibuprofen is a weak acidic compound, and for every 3 units away from the pKa-value, the solubility changes 10-fold (Mahato, 2007:14). However, with regard to the skin permeation studies, enhanced permeation was obtained with the formulations prepared at pH 5. This was in accordance with Corrigan et al., (2003:148) who stated that NSAIDs are less soluble and more permeable at low pH values, and more soluble and less permeable at high pH values. This was most probably due to the fact that unionised species, although possessing a lower aqueous solubility than the ionised species, resulted in enhanced skin permeation due to being more lipid-soluble. Finally, stability tests on the different semi-solid formulations for a period of three months at different temperature and humidity conditions were conducted to determine product stability. The formulations were stored at 25 °C/60% RH (relative humidity), 30 °C/60% RH and 40 °C/75% RH. Stability tests included: mass variation, pH, zeta potential, droplet size, visual appearance, assay, and viscosity. No significant change was observed for mass variation, pH, zeta potential and droplet size over the three months for any of the different formulations stored at the different storage conditions. In addition, no significant change in colour was observed for the gel and emulgel formulations at pH 5 and 7.4 over the three months at all the storage conditions. However, it was observed that the formulations containing Pheroid™ showed a drastic change in colour at all the storage conditions. This might have been due to oxidation of certain components present in the Pheroid™ system. Consequently, further investigation is necessary to find the cause of the discolouration and a method to prevent it. The gel formulated at pH 5 depicted the formation of crystals. This might have been due to the fact that the solubility of ibuprofen was exceeded, leading to it precipitating from the formulation. A possible contributing factor to the varying assay values obtained during the study might have been due to non-homogenous sample withdrawal. On the other hand, no significant change was observed for the emulgel and Pheroid™ emulgel formulated at pH 5 and 7.4. The emulgel and Pheroid™ emulgel formulated at pH 5 depicted relative instability (according to the International Conference on Harmonisation of Technical Requirements For Registration of Pharmaceuticals for Human Use, ICH) only at 40 °C/75% RH with a change in ibuprofen content of more than 5% (6.78 and 6.46%, respectively). The gel, emulgel and Pheroid™ emulgel at pH 7.4 exhibited the least variation in ibuprofen concentration at all of the storage conditions. This might indicate that the pH at which a semi-solid formulation is produced will have a direct influence on the stability of the product. No significant changes in viscosity (%RSD < 5) was observed for the gel and emulgel formulated at pH 7.4 and stored at 25 °C/60% RH. The remaining formulations at all of the specified storage conditions exhibited a significant change in viscosity (%RSD > 5) with a decrease in viscosity being more pronounced at the higher temperature and humidity storage conditions. A possible contributing factor to the change in viscosity over three months at the specified storage conditions might have been due to the use of Pluronic® F-127 (viscosity enhancer). This viscosity enhancer possesses a melting point of approximately 56 °C (BAST Corporation. s.a). The problem with this might have been the temperature (70 °C) at which the formulations were prepared. The higher preparation temperature might have caused the Pluronic® F-127 to degrade, thereby losing its ability to function appropriately. A balance must be maintained between optimum solubility and maximum stability (Pefile & Smith, 1997:148). Despite the lower skin permeation of the gel formulated at pH 7.4, this formulation performed the best, as it was considered stable (least variation during the 3 month stability test) and the obtained tape stripping results showed that this formulation depicted the highest ibuprofen concentrations in the stratum corneum and epidermis. Thus, topical as well as transdermal delivery were obtained. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013.

In pharmaceutical sciences, topical delivery is a transport process of an active pharmaceutical ingredient (API) from a formulated dosage form to the target site of action. For most topical delivery systems, the skin surface, or the specific skin layers, such as the outermost layer of the stratum corneum, the lipids amid the corneocytes within the stratum corneum, the corneocytes themselves, the epidermis, dermis, Langerhans cells, Merckle cells or the appendageal structures can be the target delivery location. When an API is delivered to the skin, it has to firstly diffuse from the formulation in which it is applied, to the skin surface. From there the API may partition into the stratum corneum, permeate across the stratum corneum and partition into the viable epidermis, from where it may partition further into the dermis and permeate across the dermis into the bloodstream (Wiechers, 2008:1-3, 7). With respect to the barrier function of the skin, the intercellular spaces within the stratum corneum contain lipids and its main purpose is to operate as a barrier to water-loss and to provide an imperative diffusional barrier to the absorption of APIs. This resistance is comprised of a complex interaction of lipids that creates a hydrophilic and lipophilic penetration pathway. The fundamental aspect underlying the impermeability of the skin, therefore, is the lipophilic nature of the stratum corneum (Bouwstra et al., 2003:4; Franz & Lehman, 2000:25; Walker & Smith, 1996:296). A common approach for the promotion of poorly penetrating APIs in transdermal delivery is the incorporation of chemical penetration enhancers in delivery systems, in order to promote the partitioning of an API into the stratum corneum. These chemicals are also referred to as accelerants, promoters and absorption promoters. Penetration enhancers are added to topical formulations and usually also partition into the stratum corneum, where they temporarily and reversibly disrupt its fundamental diffusional barrier properties, hence facilitating the absorption of an API through the skin (Büyüktimkin et al., 1997:358-359; Sinha & Kaur, 2000:1131; Walker & Smith, 1996:296). The mechanisms for the enhancement of diffusion of the API should therefore increase the solubility and partitioning of the drug from the formulation into the skin. It should further increase the solubility of the API within the skin and promote its permeability and diffusion coefficient (Rajadhyaksha et al., 1997:489). Fatty acids are recognised to effectively enhance the penetration of transdermally delivered hydrophilic and lipophilic APIs. Many penetration enhancers contain saturated and unsaturated hydrocarbon chains, and a popular fatty acid that has been used in this regard is oleic acid (Williams & Barry, 2004:609-610). It is believed that fatty acids disrupt the lipid organisation of the intercellular lipids within the stratum corneum to cause fluidisation of these bilayers, making the stratum corneum more permeable to APIs. Excipients with polar (hydrophilic) head groups and long hydrophobic chains i.e. fatty acids, can penetrate into the intercellular lipids of the stratum corneum and disrupt these endogenous lipid components, thereby increasing diffusion of an API within the skin (Barry, 2006:9-10; Hadgraft & Finnin, 2006:367-368; Kanikkannan et al., 2006:18; Williams & Barry, 2004:610). Natural oils are widely used in topical formulations and were an obvious choice in this study. Oils are liquids at room temperature, whereas fats are in solid form. They are relatively easy to obtain from both plants and animals. The main constituents of fats and oils are triglycerides comprising of fatty acids and a glycerol. Oils control the evaporation of moisture from the skin, spread easily and evenly and are partly metabolised in the skin to release valuable fatty acids (Fang et al., 2004:170,173; Lautenschläger, 2004:46; Mitsui, 1997:121-122). The focus of this study was not formulation per se, but included the formulation of avocado-, grapeseed-, emu-, crocodile, olive and coconut oil into semisolid emulgel- and two foam formulations. This was done in order to investigate the penetration enhancing properties of their fatty acid content on flurbiprofen which was chosen as the marker API. The emulgels containing the natural oils were compared to the same emulgel formulation containing liquid paraffin, and a hydrogel without the inclusion of an oil. Six natural oils were analysed by gas chromatography (GC) in order to quantify their fatty acid compositions, whilst also providing qualitative information by indicating the retention times of the materials with an alkyl chain composition (Mitsui, 1997:260). Data obtained with the GC indicated that olive- (76%), avocado- (68%), emu- (46%) and crocodile oil (40%) presented with high levels of oleic acid, also known as a mono-unsaturated fatty acid (MUFA). Lower levels of oleic acid were observed within grapeseed- (27%) and coconut oil (8%). The only oil demonstrating high levels of the poly-unsaturated fatty acid (PUFA), linoleic acid, was grapeseed oil (61%), whereas the remainder of the oils showed levels below 24%. Contrary, coconut oil seemed to have been the only oil high in saturated fatty acids (SFAs) and consisted of a lauric acid content of 52% and medium levels of myristic acid (21%). Average levels of palmitic acid (SFA) were found in crocodile- (21%) and in emu oil (21%), both of animal origin, whereas avocado-, grapeseed-, olive- and coconut oils from plants presented with levels below 15%. Stearic acid was also present in levels below 10% in all of these oils, with the oils of animal origin portraying the highest values. A method was developed and validated to determine the concentration of the marker flurbiprofen after diffusion from the formulations into the skin, as well as concentrations of the marker that diffused through the skin, by means of high performance liquid chromatography (HPLC). Franz cell membrane diffusion studies were conducted prior to the skin diffusion studies in order to verify the actual release of the marker from the semisolid formulations. Skin diffusion experiments were performed using dermatomed excised, human skin to which the six emulgel formulations, containing the natural oils, were applied. A comparative study was performed utilising liquid paraffin and a hydrogel, in order to compare the diffusion of the marker, flurbiprofen, into and through the skin. The two oil emulgel formulations that had indicated the best flux values were subsequently formulated into foam preparations in order to compare the penetration enhancement properties on flurbiprofen of these two oils in a foam preparation, to those in the equivalent emulgels. The data generated for all ten the formulations were compared, and the formulations that yielded the best results with regards to median flux values and the flurbiprofen concentrations within the stratum corneum-epidermis and epidermis-dermis, were identified. Application of the liquid paraffin emulgel (21.29 μg/ml) depicted the highest average concentration of the diffused lipophilic flurbiprofen within the stratum corneum-epidermis, followed by the olive oil foam (21.47 μg/ml), olive oil emulgel (17.82 μg/ml) and grapeseed oil emulgel (17.78 μg/ml). Very similar concentrations for the marker were demonstrated by the hydrogel (16.73 μg/ml) and crocodile oil emulgel (14.89 μg/ml), whereas a lower concentration was shown for coconut oil emulgel (7.18 μg/ml). The remainder of the formulations yielded concentrations below 3%, i.e. the avocado oil emulgel (2.72 μg/ml), the coconut oil foam (1.57 μg/ml) and finally the emu oil emulgel (1.25 μg/ml). The penetration of the marker, flurbiprofen, being trapped within the skin seemed to have been enhanced more by the oleic acid (UFA) containing emulgels and foam, especially. This was followed by oils containing high linoleic acid values, which indicated that the more kinked shaped the fatty acids, the more difficult it became to insert themselves within the lipid structures of the stratum corneum, with a resulting accumulation of the marker (Fang et al., 2003:318-319). It therefore seemed that those oils that predominantly consisted of unsaturated fatty acids (UFAs) (grapeseed-, crocodile- and olive oils) seemed to have increased the concentration of the diffused marker more significantly than those oils containing an almost even combination of MUFAs and PUFAs (avocado oil), or those mainly consisting of SFAs (coconut oil). Average concentrations of the diffused flurbiprofen found in the epidermis-dermis region of the skin for all of the formulations demonstrated low concentrations, ranging between 0.97 - 5.39 μg/ml, with the exception of the emu oil emulgel that presented with a higher concentration of 16.15 μg/ml. The reason for the high accumulation of the marker might have been as a result of epidermal proliferation, with subsequent accumulation of the marker within the epidermis-dermis due to high oleic- and linoleic acid values, as well as small amounts of palmitoleic acid present within this oil (Katsuta et al., 2005:1011). The resistance of the epidermis-dermis region to the general permeation of flurbiprofen might have been caused by its lipophilic nature, resulting in a reduced solubility within the hydrophilic environment of this region (Hadgraft, 1999:5). Median results from the skin diffusion studies demonstrated that the hydrogel (23.79 μg/cm2.h) had the highest flux, followed by the olive oil- (17.99 μg/cm2.h), liquid paraffin- (15.70 μg/cm2.h), coconut oil- (13.16 μg/cm2.h), grapeseed oil- (11.85 μg/cm2.h), avocado oil- (8.31 μg/cm2.h), crocodile oil- (6.68 μg/cm2.h) and emu oil emulgels (4.41 μg/cm2.h). The fact that the hydrogel presented a higher flux value for the marker could have been as a result of its high water content that had caused hydration of the skin. Hydration opens up the dense lipid structures inside of the stratum corneum, due to swelling of the corneocytes, with a subsequent increase in the marker‘s flux (Benson, 2005:28; Ranade & Hollinger, 2004:213). The high flux value of flurbiprofen with the liquid paraffin emulgel might also have resulted from the fact that it occluded the skin, which increased the hydration of the stratum corneum, with a subsequent increase in the flux (Mitsui, 1997:124; Thomas & Finnin, 2004:699). Results from the skin diffusion studies could be explained by the fact that the fatty acids differ in their hydrocarbon chain by (1) the length of the chain, and (2) the position- and number of the double bonds (Babu et al., 2006:144). It is suggested that fatty acids with hydrocarbon (lipophilic) chains between C12 to C14 (also present within coconut oil) have an optimal balance of the partition coefficient and its affinity for the skin (Ogiso & Shintani, 1990:1067). It appears as though the branched UFAs, especially oleic acid, present in high quantities in olive oil, were more powerful enhancers of the diffusion of the marker, flurbiprofen (Chi et al., 1995:270). Foam formulations were manufactured with the olive- and coconut oil emulgels that had demonstrated the best median flux values of flurbiprofen from the natural oil emulgel formulations. These formulated foams, however, did not significantly increased flux values for flurbiprofen through the skin, but only achieved values of 5.56 μg/cm2.h for the olive oil foam and 4.36 μg/cm2.h for the coconut oil foam formulations. The low flux values could have been attributed to the nature of the formulation itself, which was filled with trapped air that could have resulted in the formulation not making optimal direct contact with the available skin surface. Throughout this study, it became evident that olive oil, predominantly consisting of oleic acid (UFA), was most effective in enhancing the flux of the lipophilic marker, flurbiprofen, through the skin, closely followed by coconut oil consisting of SFAs, with lauric- and myristic acid as its main constituents. Better enhancement effects were observed with those oils containing high amounts of oleic acid (MUFA), than oils consisting of almost equal amounts of both PUFAs and MUFAs (avocado-, emu- and crocodile oil), or oils mainly consisting of PUFAs (grapeseed oil) as its main components, but their effect was not more significant than the oil containing SFAs (coconut oil) as its key components. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013.

A pharmaceutical dosage form is an entity that is administered to patients so that they receive an effective dose of an active pharmaceutical ingredient (API). The proper design and formulation of a transdermal dosage form require a thorough understanding of the physiological factors affecting percutaneous penetration and physicochemical characteristics of the API, as well as that of the pharmaceutical exipients that are used during formulation. The API and pharmaceutical excipients must be compatible with one another to produce a formulation that is stable, efficacious, attractive, easy to administer, and safe (Mahato, 2007:11). Amongst others, the physicochemical properties indicate the suitability of the type of dosage form, as well as any potential problems associated with instability, poor permeation and the target site to be reached (Wells & Aulton, 2002:337). Therefore, when developing new or improved dosage forms, it is of utmost importance to evaluate the factors influencing design and formulation to provide the best possible dosage form and formulation for the API in question. Delivery of an API through the skin has long been a promising concept due to its large surface area, ease of access, vast exposure to the circulatory and lymphatic networks, and non-invasive nature of the therapy. This is true whether a local or systemic pharmacological effect is desired (Aukunuru et al., 2007:856). However, most APIs are administered orally as this route is considered to be the simplest, most convenient and safest route of API administration. Since ibuprofen is highly metabolised in the liver and gastrointestinal tract, oral administration thereof results in decreased bioavailability. Furthermore, it also causes gastric mucosal damage, bleeding and ulceration. Another obstacle associated with oral API delivery is that some APIs require continuous delivery which is difficult to achieve (Bouwstra et al., 2003:3). Therefore, there is significant interest to develop topical dosage forms for ibuprofen to avoid side effects associated with oral delivery and to provide relatively consistent API levels at the application site for prolonged periods (Rhee et al., 2003:14). The aim of this study was to determine the influence of selected formulation factors on the transdermal delivery of ibuprofen. In order to achieve this aim, the physicochemical properties of ibuprofen had to be evaluated. The aqueous solubility, pH-solubility profile, octanol-water partition coefficient (log P-value) and octanol-buffer distribution coefficient (log D-values, pH 5 and 7.4) of ibuprofen were determined. According to Naik et al., (2000:319) the ideal aqueous solubility of APIs for transdermal delivery should be more than 1 mg.ml-1. However, results showed that ibuprofen depicted an aqueous solubility of 0.096 mg.ml-1 ± 25.483, which indicated poor water solubility and would therefore be rendered less favourable for transdermal delivery if only considering the aqueous solubility. The pH-solubility profile depicted that ibuprofen was less soluble at low pH-values and more soluble at higher pH-values. Previous research indicated that the ideal log Pvalues for transdermal API permeation of non steroid anti-inflammatory drugs (NSAIDs) are between 2 and 3 (Swart et al., 2005:72). Results obtained during this study indicated a log P-value of 4.238 for ibuprofen. This value was not included in the ideal range, which is an indication that the lipophilic/hydrophilic properties are not ideal, and this might therefore; contribute to poor ibuprofen penetration through the skin. Furthermore, the obtained log D-values at pH 5 and 7.4 were 3.105 and 0.386, respectively. Therefore, it would be expected that ibuprofen incorporated into a formulation prepared at a pH of 5 would more readily permeate the skin compared to ibuprofen incorporated into a formulation prepared at a pH of 7.4. A gel, an emulgel and a Pheroid™ emulgel were formulated at pH 5 and 7.4, in order to examine which dosage form formulated at which pH would deliver enhanced transdermal delivery. Obtained diffusion results of the different semi-solid formulations were furthermore compared to a South African marketed commercial product (Nurofen® gel) in order to establish if a comparable formulation could be obtained. An artificial membrane was used to conduct the membrane permeation studies over a period of 6 h, in order to determine whether ibuprofen was in fact released from the formulations through the membrane. Skin permeation studies were conducted using Franz diffusion cells over a period of 12 h where samples were withdrawn at specified time intervals. All the formulations exhibited an increase in the average cumulative amount of ibuprofen released from the formulations and that permeated the membrane when compared to Nurofen® gel. This increase was statistically significant (p<0.05) for the gel, emulgel and Pheroid™ emulgel at pH 7.4. The gel at pH 7.4 exhibited the highest cumulative amount of ibuprofen that permeated the membrane. Preparations formulated at a pH of 5, did not differ significantly from Nurofen® when the average cumulative amount of ibuprofen that permeated the membrane were compared. The following rank order for the average cumulative amount released from the formulations could be established: Gel (pH 7.4) >>>> Pheroid™ emulgel (pH 7.4) > Emulgel (pH 7.4) >>> Gel (pH 5)> Pheroid™ emulgel (pH 5) ≈ Emulgel (pH 5) > Nurofen® gel. On the other hand, all the formulations exhibited an increase in the average cumulative amount of ibuprofen that permeated the skin when compared to Nurofen® gel. This increase was statistically significant (p < 0.05) for the gel, emulgel and Pheroid™ emulgel at pH 5, as well as the emulgel and Pheroid™ emulgel at pH 7.4. The emulgel at pH 5 exhibited the highest cumulative amount of ibuprofen that permeated the skin. The following rank order for the average cumulative amount released from the formulations and that permeated the skin could be established: Emulgel (pH 5) >> Pheroid™ emulgel (pH 5) > Gel (pH 5) > Emulgel (pH 7.4)> Pheroid™ emulgel (pH 7.4) ≈ Emulgel (pH 7.4) >> Nurofen® gel > Gel (pH 7.4). From this rank order it was clear that a trend was followed where the pH of formulation also played a role in ibuprofen permeation. All the formulations exhibited a higher release rate and flux when compared to Nurofen® gel. This was statistically significant for the emulgel, gel and Pheroid™ emulgel at pH 7.4. The gel at pH 7.4 exhibited the highest release rate and flux. This was observed for the membrane and skin permeation studies. All the formulations (including Nurofen® gel) presented a correlation coefficient (r2) of 0.972 – 0.995 for membrane permeation studies, and 0.950 – 0.978 for skin permeation studies; indicating that the release of ibuprofen from each of the formulations could be described by the Higuchi model. Furthermore, all the formulations exhibited a prolonged lag time compared to Nurofen® gel which indicated that the ibuprofen was retained for a longer time by the base. This was statistically significant (p < 0.05) for the emulgel at pH 7.4, the gel and Pheroid™ emulgel at pH 5. The gel at pH 7.4 exhibited a lag time closest to that of Nurofen® gel and this difference could not be classified as statistically significant (p > 0.286). This was observed for the membrane and skin permeation studies. Nurofen® gel exhibited the highest ibuprofen concentration in the stratum corneum as well as in the epidermis followed by the gel at pH 7.4. However, results obtained for all the formulations indicated that topical as well as transdermal delivery of ibuprofen was achieved. The pH of a formulation plays an important role with respect to API permeation. Ibuprofen is reported to have a pKa value 4.4 (Dollery, 1999:I1); and by application of the Henderson-Hasselbach equation, at pH 5, 20.08% of ibuprofen will be present in its unionised form and at pH 7.4, 0.1% ibuprofen will exist in its unionised form. Since the unionised form of APIs is more lipid soluble than the ionised form, unionised forms of APIs permeate more readily across the lipid membranes (Surber & Smith, 2000:27). Therefore, it would be expected that ibuprofen formulated at pH 5 would be more permeable than formulations at pH 7.4. However, this did not correspond to the results (membrane studies) obtained in this study. It may be attributed to the solubility of ibuprofen in the different formulations. According to the pH-solubility profile of ibuprofen obtained in this study, it was more soluble at pH 7.4 than at pH 5. This was due to the fact that ibuprofen is a weak acidic compound, and for every 3 units away from the pKa-value, the solubility changes 10-fold (Mahato, 2007:14). However, with regard to the skin permeation studies, enhanced permeation was obtained with the formulations prepared at pH 5. This was in accordance with Corrigan et al., (2003:148) who stated that NSAIDs are less soluble and more permeable at low pH values, and more soluble and less permeable at high pH values. This was most probably due to the fact that unionised species, although possessing a lower aqueous solubility than the ionised species, resulted in enhanced skin permeation due to being more lipid-soluble. Finally, stability tests on the different semi-solid formulations for a period of three months at different temperature and humidity conditions were conducted to determine product stability. The formulations were stored at 25 °C/60% RH (relative humidity), 30 °C/60% RH and 40 °C/75% RH. Stability tests included: mass variation, pH, zeta potential, droplet size, visual appearance, assay, and viscosity. No significant change was observed for mass variation, pH, zeta potential and droplet size over the three months for any of the different formulations stored at the different storage conditions. In addition, no significant change in colour was observed for the gel and emulgel formulations at pH 5 and 7.4 over the three months at all the storage conditions. However, it was observed that the formulations containing Pheroid™ showed a drastic change in colour at all the storage conditions. This might have been due to oxidation of certain components present in the Pheroid™ system. Consequently, further investigation is necessary to find the cause of the discolouration and a method to prevent it. The gel formulated at pH 5 depicted the formation of crystals. This might have been due to the fact that the solubility of ibuprofen was exceeded, leading to it precipitating from the formulation. A possible contributing factor to the varying assay values obtained during the study might have been due to non-homogenous sample withdrawal. On the other hand, no significant change was observed for the emulgel and Pheroid™ emulgel formulated at pH 5 and 7.4. The emulgel and Pheroid™ emulgel formulated at pH 5 depicted relative instability (according to the International Conference on Harmonisation of Technical Requirements For Registration of Pharmaceuticals for Human Use, ICH) only at 40 °C/75% RH with a change in ibuprofen content of more than 5% (6.78 and 6.46%, respectively). The gel, emulgel and Pheroid™ emulgel at pH 7.4 exhibited the least variation in ibuprofen concentration at all of the storage conditions. This might indicate that the pH at which a semi-solid formulation is produced will have a direct influence on the stability of the product. No significant changes in viscosity (%RSD < 5) was observed for the gel and emulgel formulated at pH 7.4 and stored at 25 °C/60% RH. The remaining formulations at all of the specified storage conditions exhibited a significant change in viscosity (%RSD > 5) with a decrease in viscosity being more pronounced at the higher temperature and humidity storage conditions. A possible contributing factor to the change in viscosity over three months at the specified storage conditions might have been due to the use of Pluronic® F-127 (viscosity enhancer). This viscosity enhancer possesses a melting point of approximately 56 °C (BAST Corporation. s.a). The problem with this might have been the temperature (70 °C) at which the formulations were prepared. The higher preparation temperature might have caused the Pluronic® F-127 to degrade, thereby losing its ability to function appropriately. A balance must be maintained between optimum solubility and maximum stability (Pefile & Smith, 1997:148). Despite the lower skin permeation of the gel formulated at pH 7.4, this formulation performed the best, as it was considered stable (least variation during the 3 month stability test) and the obtained tape stripping results showed that this formulation depicted the highest ibuprofen concentrations in the stratum corneum and epidermis. Thus, topical as well as transdermal delivery were obtained. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013.

The progression of skin ageing in individuals is multifaceted and provoked by various aspects, including hereditary and a variety of environmental causes, for instance UV (ultra violet) radiation, resulting in the morphological modifications in the dermal layer of the skin (Makrantonaki & Zouboulis, 2007:40) Transformations caused by ageing skin, in which degenerative alterations exceed regenerative alterations are recognised by the thinning and wrinkling of the epidermis in conjunction with the appearance of lines, creases, crevices and furrows, particularly emphasised in lines of facial expressions (Aburjai & Natsheh, 2003:990). For human beings to continue to exist in a terrestrial atmosphere, the loss of water from the skin must be cautiously synchronised by the epidermis, a task dependent on the multifaceted character of the stratum corneum (Rawlings & Harding, 2004:43). The stratum corneum (SC) is responsible for the main resistance to the penetration of most compounds; nevertheless the skin represents as an appropriate target for delivery. The target site for anti-ageing treatment includes the epidermal and dermal layers of the skin. Therefore, the need to apply fatty materials to the skin is practically intuitive and may perhaps be as old as man’s existence itself (Lodén, 2005:672). Natural therapies have been used for several decades for taking care of skin illnesses and a wide variety of dermatological disorders, such as inflammation, phototoxicity, atopic dermatitis and alopecia areata (Aburjai & Natsheh, 2003:988). Using the skin as an alternative route for the administration of honeybush extracts for the treatment of ageing skin may be beneficial. Tea contains more than 500 chemical compounds, including, tannins, flavonoids, amino acids, vitamins, caffeine and polysaccharides. Tea polyphenols (flavonoids) have proven anti-inflammatory, antioxidant, antiallergic, antibacterial and antiviral effects (Aburjai & Natsheh, 2003:990). Unfortunately using the skin as an alternative route for administering drugs (transdermal drug delivery) has numerous limitations. One of these limitations is the barrier function of the skin (Naik et al., 2000:319). Because of the skin’s outstanding ability to protect the body against unwanted substances from its surroundings, it is necessary to use methods to enhance drug penetration through the skin. The aim of this study was to formulate two 2% semisolid formulations containing two different honeybush extracts as the active ingredient, and to determine which of the formulations deliver mangiferin and hesperidin best to the target site (dermis). Cosmetic formulations of a natural origin, is designed to protect the skin against exogenous or endogenous harmful agents, as well as to balance the dermal homeostatis lipids altered by dermatosis and ageing (Aburjai & Natsheh, 2003:988). Stability tests over a three month period were also performed on the different formulations. To determine the stability of the different semi-solid formulations, the formulated products were stored at 25 °C/60% RH (relative humidity), 30 °C/60% RH and 40 °C/75% RH. HPLC analysis was used to determine the concentrations of the ingredients in all the formulated products. Other stability tests included appearance, pH, viscosity, mass loss, zeta potential and particle size determination. Unfortunately a change in colour, viscosity, zeta potential, mass loss, particle size and concentration of the ingredients in both the formulations, indicated that the products were unstable from the first month of stability testing. A 2% Cyclopia maculata cream as well as a 2% Cyclopia genistoides cream was formulated. Franz cell diffusion studies as well as membrane release studies were performed over a 12 h period, followed by tape stripping experiments to determine which semi-solid formulation delivered mangiferin and hesperidin the best to the dermal layer of the skin. The results of the different formulations were compared. Unfortunately there was no significant penetration by any of the honeybush extracts. Results were inconclusive and unquantifiable due to unconvincing penetration results. The antioxidant properties of both the extracts and the active ingredients were calculated. Antioxidant studies by the use of the TBA-assay method were done to determine whether the honeybush extracts, mangiferin and hesperidin as well as their semisolid formulations had any antioxidant activities. Both the honeybush extracts and the semisolid formulations showed promising results. Mangiferin and hesperidin did not show any antioxidant activity on their own, therefore the assumption can be confirmed that plants do function synergistically. A clinical study was also conducted to see whether honeybush extracts have the potential to hydrate the skin, counteracting the symptoms and signs of skin ageing. Clinical efficacy studies were done to determine whether the honeybush formulations had any skin hydrating effects in the treatment against skin ageing. The results were statistically inconclusive and variations between the subjects were very high due to skin variations at different skin sites. There was however a trend that Cyclopia genistoides performed the best. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013.