Abstract Lippia javanica and Lippia scaberrima are used as herbal remedies and are commercially traded as health teas in southern Africa under the brands “Mosukujane” and “Musukudu”, respectively. This study evaluates the relationship between the presence of phenolic compounds and the antioxidant activities of infusions prepared from four Lippia species (L. javanica, L. scaberrima, L. rehmannii and L. wilmsii) indigenous to South Africa. The antioxidant activities of the infusions, determined by the 2,2-diphenylpycrylhydrazyl (DPPH) method, were also compared to those of popular black, green and herbal tea brands. Of the four indigenous species, infusions of L. javanica and L. wilmsii exhibited the highest antioxidant activities (EC50: 358 and 525 μg/ml, respectively) and contained the most phenolic compounds (14.8 and 14.5 mg/ml of dry weight gallic acid equivalent, respectively). Antibacterial activities of methanolic extracts of the four Lippia species were determined against four human pathogens (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa). The extract of L. javanica was the most active against all the pathogens tested. Those Lippia species (L. javanica and L. wilmsii) previously reported to produce higher levels of the pharmacologically active phenylethanoid glycosides verbascoside and isoverbascoside, portrayed stronger antioxidant and antibacterial activities. This study gives credence to the use of infusions of these Lippia species for their general health benefits.

Extracts of 16 South African Salvia species commonly used in traditional medicine to treat various microbial infections were investigated for in vitro antibacterial and antimycobacterial activities using the micro-dilution and respiratory BACTEC method, respectively. The microorganisms tested include two Gram-positive (Staphylococcus aureus and Bacillus cereus); two Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacterial strains and the common pathogen responsible for tuberculosis, Mycobacterium tuberculosis. Extracts of the majority of species exhibited moderate to good antibacterial activity with minimum inhibitory concentration (MIC) values ranging from 0.03 to 8.00 mg/ml. Promising activity was observed against M. tuberculosis (MIC≤0.50 mg/ml) with S. radula, S. verbenaca and S. dolomitica displaying the most favourable activity (MIC: 0.10 mg/ml). The antibacterial bioassay-guided fractionation of S. chamelaeagnea resulted in the isolation of four compounds: carnosol, 7-O-methylepirosmanol, oleanolic acid and its isomer ursolic acid as the active principles against S. aureus. The in vitro antibacterial and antimycobacterial activities may support the use of Salvia species in traditional medicine to treat microbial infections.

Our previous studies showed that recombinant £]-bungarotoxin B chain exhibited membrane-damaging activity. Given that membrane-damaging activity is crucial for bactericidal effect of antibacterial peptide, the causal relationship between membrane-damaging activity and antibacterial action of B chain was performed in this study. £]-bungarotoxin B chain exhibited a growth inhibition on Escherichia coli (Gram-negative bacteria), but marginally displayed bactericidal effect on Staphylococcus aureus (Gram-positive bacteria). Destabilization of lipopolysaccharide (LPS) layer and inhibition of lipoteichoic acid (LTA) biosynthesis on cell wall increased bactericidal effect of B chain on E. coli and S. aureus. B chain induced leakage and fusion of bacterial membrane-mimicking liposomes. Compared with LPS, LTA notably suppressed membrane-damaging activity and fusogenicity of B chain. B chain showed similar binding affinity with LPS and LTA. Circular dichroism measurement revealed that LPS- and LTA-binding differently induced conformational change of B chain. Taken together, our data indicate that antibacterial action of B chain is related to its ability to induce membrane permeability and fusogenicity, and suggest that LTA- and LPS- induced conformational change of B chain affect membrane-damaging activity, fusogenicity and antibacterial activity of B chain.

Orientador: Taís Maria Bauab / Banca: Eliana Aparecida Varanda / Banca: Daisy Nakamura Sato / Resumo: O gênero Maytenus (Celastraceae), atualmente compreende cerca de 80 espécies distribuídas por todo território brasileiro. A espécie Maytenus ilicifolia é conhecida popularmente pelos nomes de espinheira-santa, espinheira-diva, salva-vidas, sombra de touro, cancerosa e coromilho do campo, e utilizada contra hiperacidez e ulcerações do estômago. Com o objetivo de caracterizar o potencial biológico desta planta, foi estudada a atividade antibacteriana e antioxidante do extrato diclorometânico (DCM), frações, subfrações e duas substâncias puras (maitenina e catequina) isoladas das cascas de raízes de M.ilicifolia, obtidas por maceração a frio. Foi utilizada a técnica de diluição em microplacas frente às bactérias Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Bacillus subtilis ATCC 19659, Escherichia coli ATCC 25922 e Pseudomonas aeruginosa ATCC 27853. A concentração inibitória mínima (CIM) para o extrato e as substâncias testadas, expresso como a menor concentração capaz de inibir crescimento bacteriano foi avaliada em microplacas contendo meio líquido aos quais foram adicionados extratos, frações, substâncias puras e antibióticos, sendo estes últimos usados como controles positivos. Para a atividade antioxidante foram realizados ensaios espectrofotométricos do 2,2'-Azinobis-3-etilbenzotiazolina-6-acido sulfônico (ABTS.+); do íon hipoclorito (OCl-) e da taurina-cloramina (via oxidação do 3,3',5,5', tetrametilbenzidina), utilizando como padrões quercetina e cisteína. Foi demonstrada forte atividade da maitenina com CIM de 0,48 μg/mL para as bactérias Gram positivas, e a catequina não apresentou atividades contra as bactérias testadas. Na avaliação da atividade antioxidante o extrato DCM e a maitenina não foram tão eficazes quanto a atividade da catequina que... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The genus Maytenus (Celastraceae) currently includes 80 species distributed throughout the Brazilian territory. The species Maytenus ilicifolia popularly known by the names of "espinheira-santa", "espinheira-diva", "salva-vidas", "sombra de touro", "cancerosa" and "coromilho do campo", with activity against hyperacidity and gastric ulcers. In order to characterize the biological potential of this plant, was studied the antibacterial activity of the dichloromethane extract (DCM), fractions, subfractions and two substances (maitenin and catechin) isolated from the roots of M. ilicifolia obtained by cold maceration. To evaluation of the antimicrobial potential was used the microplates dilution technique using the bacteria Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Bacillus subtilis ATCC 19659, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. Minimum inhibitory concentration (MIC) for the extract and the substances tested, expressed as the lowest concentration able to inhibit bacterial growth, was evaluated in microplates containing liquid medium to which were added extracts, fractions, subfractions, pures substances and antibiotics, the latter being used as positive controls. For the antioxidant activity tests were performed spectrophotometric: 2,2 '-Azinobis-3-ethylbenzothiazoline-6- sulfonic acid (ABTS.+); of OCl- and taurinecloramine (via oxidation of 3,3', 5,5 ' , tetramethylbenzidine), using quercetin and cysteine as standards. It was demonstrated a strong activity to maitenin, with MIC of 0,48 μg/mL for Gram positive bacteria and catechin did not show activity against the bacteria tested. In the evaluation of antioxidant activity the extract DCM and maitenin... (Complete abstract click electronic access below) / Mestre

Thiopeptides are posttranslationally-processed macrocyclic peptide metabolites, characterized by extensive backbone and side chain modifications that include a six-membered nitrogenous ring, thioazol(in)e/oxazol(in)e rings, and dehydrated amino acid residues. Thiostrepton A, produced by Streptomyces laurentii ATCC 31255, is one of the more structurally complex thiopeptides, containing a second macrocycle bearing a quinaldic acid. Thiostrepton A and other thiopeptides are of great interest due to their potent activities against emerging antibiotic-resistant Gram-positive pathogens, in addition to their antimalarial and anticancer properties. The ribosomal origins for thiopeptides have been established, however, few details are known concerning the posttranslational modification steps. Alteration to the primary amino acid sequence of the precursor peptide provides an avenue to probe the substrate specificity of the thiostrepton A posttranslational machinery. The information gathered from current studies can also be used to refine thiostrepton’s structure-activity relationship, providing insight into the key features of its scaffold that impart specificity toward each biological target. A fosmid-dependent biosynthetic engineering platform for thiostrepton A was developed and a series of thiostrepton analogs were successfully produced adapting this method. The seventh residue of thiostrepton A is predicted to be critical for the metabolite’s antibacterial activity. Our results were consistent this hypothesis and demonstrated that substitution of Thr7 in the thiostrepton A precursor peptide disrupts both biological activity and successful biosynthesis of the analogs. The thiostrepton biosynthetic machinery’s tolerances toward structural variation at the second and fourth positions of the TsrA core peptide were probed by the saturation mutagenesis of Ala2 and Ala4, respectively. Eight thiostrepton Ala2 variants were isolated with two analogs truncated at the N-terminus by one amino acid, bearing a shortened quinaldic acid-containing macrocycle. Our results suggested that the identity of the core peptide second residue influences the biosynthesis of a thiostrepton analog, however, not essential for the antibacterial and proteasome inhibitory activities of the full-length variants. Additionally, the quinaldic acid loop size affects thiostrepton’s antibacterial potency, but is not critical for the proteasome inhibitory activity. Sixteen thiostrepton analogs were isolated from Ala4 mutagenesis studies. We demonstrated that the identity of the amino acid residue at the fourth position in the thiostrepton scaffold is not critical to inhibit either the ribosome or the proteasome in vitro.

>Magister Scientiae - MSc / Nanotechnology has emerged as a promising field in the quest to address health conditions. Green nanotechnology is a fairly new branch of nanotechnology, which aims to produce and utilize nanomaterials in a way that is safe for living organisms and their environment. Plant extracts are increasingly used in the green synthesis of gold nanoparticles (AuNPs), which involves the reduction of sodium tetrachloroaurate (III) dehydrate by phytochemicals present in the plant extract. It is probable that the green synthesised AuNPs are more biocompatible than chemically synthesised AuNPs as biomolecules of plant origin are involved in the synthesis process. Therefore, this study aimed to explore various water extracts from indigenous South African plants, which included Perlagonium capitatum, Otholobium bracteolatum, Gerbera linnae, Morrella quercifolia, Searsia lucida, Phylica bubescens, Euclea racemosa, Tetragonia fruticosa, and Searsia glauca for their potential to synthesize AuNPs and to investigate their toxicity towards several microorganisms known to cause skin infections. These organisms play a significant role in delaying the healing of wounds. The antimicrobial properties of nanoparticles are increasing exploited in the production of wound treatments.

Carissa lanceolata (conkerberry) is a perennial woody shrub used in traditional medicine by indigenous communities in Western Australia, the Northern Territory and Queensland for various medical conditions such as toothache, respiratory infections and the cleaning of sores, which all strongly indicate an antibacterial activity. A literature review revealed that the wood of this plant possesses significant antibacterial activity, which was found to be related to the presence of eudesmane type sesquiterpenes. C. edulis and C. carandus are frequently used in other traditional systems of medicine in different parts of the world, and thus have also been investigated for bioactive compounds and pharmacological properties. Some of these were found to be in line with the main findings of this work. Carissa lanceolata root was shown to exhibit significant antibacterial activity against both Gram negative and Gram positive organisms. A micro-broth dilution assay was performed on 96-well plates using resazurin as an indicator for microbial growth of Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. Bioassays carried out in this work showed that crude extracts of root bark and wood, particularly their polar constituents were more active against the four strains of bacteria tested. / Chemical investigation of the root bark revealed that it contains a volatile oil, which was isolated by steam distillation as well as solid phase micro extraction. It was found to consist of a single compound, which was identified as 2'-hydroxy acetophenone. The identity of this compound was confirmed by GC/MS and 1H NMR spectroscopy. Furthermore, the eudesmane-type sesquiterpene, carissone, was isolated from the root bark DCM and root wood hexane extracts. Its chemical identity was confirmed by IR, 1 [superscript] H and 13 [superscript] C NMR spectroscopy. The lignan, carinol, on the other hand, was isolated from the moderately polar fractions of the root wood MeOH extract. The obtained IR and 1 [superscript] H NMR data as well as Rf values all correspond to the literature. Two other yet unidentified compounds were isolated, but further studies into their chemistry and antibacterial activity were not possible in this current study. The antibacterial activity of the isolated compounds was considerable, with 2'-hydroxy acetophenone exhibiting the strongest effect, followed by carinol and then carissone.

Made available in DSpace on 2014-06-11T19:28:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-09Bitstream added on 2014-06-13T19:36:32Z : No. of bitstreams: 1 nogueira_lg_me_arafcf.pdf: 1061464 bytes, checksum: 0b8ec3ba710c3ab15f6b3d51c11fbadd (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O gênero Maytenus (Celastraceae), atualmente compreende cerca de 80 espécies distribuídas por todo território brasileiro. A espécie Maytenus ilicifolia é conhecida popularmente pelos nomes de espinheira-santa, espinheira-diva, salva-vidas, sombra de touro, cancerosa e coromilho do campo, e utilizada contra hiperacidez e ulcerações do estômago. Com o objetivo de caracterizar o potencial biológico desta planta, foi estudada a atividade antibacteriana e antioxidante do extrato diclorometânico (DCM), frações, subfrações e duas substâncias puras (maitenina e catequina) isoladas das cascas de raízes de M.ilicifolia, obtidas por maceração a frio. Foi utilizada a técnica de diluição em microplacas frente às bactérias Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Bacillus subtilis ATCC 19659, Escherichia coli ATCC 25922 e Pseudomonas aeruginosa ATCC 27853. A concentração inibitória mínima (CIM) para o extrato e as substâncias testadas, expresso como a menor concentração capaz de inibir crescimento bacteriano foi avaliada em microplacas contendo meio líquido aos quais foram adicionados extratos, frações, substâncias puras e antibióticos, sendo estes últimos usados como controles positivos. Para a atividade antioxidante foram realizados ensaios espectrofotométricos do 2,2'-Azinobis-3-etilbenzotiazolina-6-acido sulfônico (ABTS.+); do íon hipoclorito (OCl-) e da taurina-cloramina (via oxidação do 3,3’,5,5’, tetrametilbenzidina), utilizando como padrões quercetina e cisteína. Foi demonstrada forte atividade da maitenina com CIM de 0,48 μg/mL para as bactérias Gram positivas, e a catequina não apresentou atividades contra as bactérias testadas. Na avaliação da atividade antioxidante o extrato DCM e a maitenina não foram tão eficazes quanto a atividade da catequina que... / The genus Maytenus (Celastraceae) currently includes 80 species distributed throughout the Brazilian territory. The species Maytenus ilicifolia popularly known by the names of “espinheira-santa”, “espinheira-diva”, “salva-vidas”, “sombra de touro”, “cancerosa” and “coromilho do campo”, with activity against hyperacidity and gastric ulcers. In order to characterize the biological potential of this plant, was studied the antibacterial activity of the dichloromethane extract (DCM), fractions, subfractions and two substances (maitenin and catechin) isolated from the roots of M. ilicifolia obtained by cold maceration. To evaluation of the antimicrobial potential was used the microplates dilution technique using the bacteria Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Bacillus subtilis ATCC 19659, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. Minimum inhibitory concentration (MIC) for the extract and the substances tested, expressed as the lowest concentration able to inhibit bacterial growth, was evaluated in microplates containing liquid medium to which were added extracts, fractions, subfractions, pures substances and antibiotics, the latter being used as positive controls. For the antioxidant activity tests were performed spectrophotometric: 2,2 '-Azinobis-3-ethylbenzothiazoline-6- sulfonic acid (ABTS.+); of OCl- and taurinecloramine (via oxidation of 3,3', 5,5 ' , tetramethylbenzidine), using quercetin and cysteine as standards. It was demonstrated a strong activity to maitenin, with MIC of 0,48 μg/mL for Gram positive bacteria and catechin did not show activity against the bacteria tested. In the evaluation of antioxidant activity the extract DCM and maitenin... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:23:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-24Bitstream added on 2014-06-13T19:49:40Z : No. of bitstreams: 1 machado_bfmt_me_botib.pdf: 809978 bytes, checksum: dfad13979717e24ed1396c50d10ae323 (MD5) / Esta dissertação encontra-se dividida em introdução geral e 3 capítulos, sendo estes no formato de manuscritos a serem enviados para publicação em 3 periódicos distintos. Considerando a crescente utilização dos produtos naturais, especialmente dos obtidos a partir de plantas, objetivou-se estudar a ação antibacteriana de 27 óleos essenciais de uso em aromaterapia, sobre linhagens de Staphylococcus aureus (n=10), Escherichia coli (n=9), e Pseudomonas aeruginosa (n=9), isoladas de casos clínicos humanos, utilizando a metodologia dos discos (difusão) e determinação da concentração inibitória mínima (CIM) (diluição) em Mueller Hinton Ágar (Capítulo I). Verificou-se que as linhagens de S. aureus foram mais susceptíveis que as de Gram negativas, sendo que os valores de CIM90% foi de 0,21mg/mL para os óleos de pimenta negra (Piper nigrum) e tea tree (Melaleuca alternifolia) e 26,52mg/mL para o óleo de copaíba (Copaíba officinalis). Para E. coli, o óleo de canela (Cinnamomum cassia) foi o mais efetivo, com 2,0 mg/mL para CIM90% enquanto para P. aeruginosa o valor foi de 8,29 mg/mL com cravo da índia (Syzigium aromaticum). Utilizando valores de CIM obtidos in vitro foram selecionados 5 óleos (cravo da índia-Syzygium aromaticum, gerânio-Pelargonium graveolens, lavanda -Lavandula angustifolia, palmarosa-Cymbopogon martini e tea tree-Melaleuca alternifolia) e novamente sobre linhagens de Escherichia coli, Staphylococcus aureus e Pseudomonas aeruginosa, foi verificada a ação antibacteriana através da diluição individual de cada óleo em água e salina visando redução na contagem bacteriana em função do tempo (Capítulo II). Tanto nos ensaios em água quanto salina, verificou-se que o perfil de sensibilidade das linhagens bacterianas aos óleos essenciais foram próximos entre si, porém significativamente distintos comparados aos ensaios controles... / This thesis is divided into general introduction and three chapters, which are in the format of manuscripts to be submitted for publication in three separate journals. Considering the increasing use of natural products, especially those obtained from plants, aimed to study the antibacterial activity of 27 essential oils used in aromatherapy, on Staphylococcus aureus (n=10), Escherichia coli (n=9), and Pseudomonas aeruginosa (n=9), isolated from human clinical cases, using the methodology of the disks (diffusion) and determination of minimum inhibitory concentration (MIC) (dilution) on Mueller Hinton Agar (Chapter I). It was found that the strains of S. aureus were more susceptible than the Gram negative, and the values of MIC90% was 0.21 mg/mL for the oils of black pepper (Piper nigrum) and tea tree (Melaleuca alternifolia) and 26.52 mg/mL for oil Copaiba (Copaiba officinalis). For E. coli strains, the oil of cinnamon (Cinnamomum cassia) was the most effective, with 2.0 mg/mL for MIC 90% while for P. aeruginosa, the value was 8.29 mg/mL with clove (Syzigium aromaticum). Using MIC values obtained in vitro were selected five oils (cloves-Syzygium aromaticum, geranium-Pelargonium graveolens, lavender- Lavandula angustifolia, palmarosa-Cymbopogon martini and tea tree-Melaleuca alternifolia) and the bacteria Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa, antibacterial activity was checked by dilution of individual oil and saline water in order to reduce the bacterial count in function of time (Chapter II). Both tests in saline and water, it was found that the sensitivity of bacterial strains to essential oils were close together, but were significantly different compared to control tests. Essential oils have demonstrated the potential inhibitor of the three bacterial strains, and the results were different from those obtained in vitro-ágar with Gram negative... (Complete abstract click electronic access below)

It is evident that herbal medicines continue to be the mainstay of healthcare systems and source of livelihoods of many local communities in South Africa and other developing countries. As a result, there is an overwhelming dependence on medicinal products harvested from natural populations. This dependence has led to local extinction of some important medicinal plants that include Warburgia salutaris and Cassine transvaalensis in South Africa. Cultivation has great potential to relieve the pressure on natural populations. However, some traditional practitioners and scientists believe that cultivation may weaken medicinal properties and that increased secondary metabolites may form only under stress conditions, respectively. This is certainly true in some cases especially where infections with pathogens, browsing by herbivores or competition takes place in nature. It is however not clear how true this is with environmental stresses. The overall aim of this study was to evaluate to what degree different environmental conditions influenced antimicrobial and antioxidant activities of plants cultivated outside their natural environment. In order to address the aim of the study, exploratory and in-depth studies were undertaken. The exploratory study comprised long-lived Combretum collinum Fresen. (Combretacea), Terminalia sericea Burch. ex DC. (Combretaceae) and Sclerocarya birrea (A. Rich.) Hochst. (Anacardiaceae). Short-lived herbaceous Tulbaghia violacea Harv. (Alliaceae) and Hypoxis hemerocallidea Fish, C.A.Mey,&Avé- Lall, (Hypoxidaceae), were included as part of the exploratory study. The in depth studies were further undertaken, also with short-lived herbaceous Leonotis dysophylla Benth. (Lamiaceae), Bulbine frutescens (L.) Willd. (Asphodelaceae) and T. violacea. Acetone leaf extracts of all plants were studied for antimicrobial activity against bacteria (Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis) and fungi (Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus). Extracts were also studied for antioxidant activity against Trolox and L-ascorbic acid standard oxidants using 2,2’-azinobis-(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) and 2,2- diphenyl-2-picryl-hydrazyl (DPPH) free radicals, respectively. The exploratory study tested the effect of different rates of annual rainfall (≥870 mm/year, 651 mm/year and 484 mm/year) on the antibacterial activity of C. collinum, T. sericea and S. birrea growing in nature. The minimum inhibitory concentration (MIC) of acetone extracts of air-dried leaves was determined by using microplate serial dilution technique. Thin layer chromatography (TLC) and bioautography determined chemical constituents and antibacterial activity of extracts, respectively. The majority of extracts had low MIC values, which indicated good antibacterial activity against test bacteria (MIC of 240 μg/ml - 60 μg/ml). Leaf extracts of C. collinum and S. birrea against S. aureus (range of 390 – 100 μg/ml), E. coli (310 -70 μg/ml) and P. aeruginosa (520 - 70 μg/ml) had antibacterial activity increased significantly with low rate of annual rainfall. However, extracts of T. sericea against P. aeruginosa (240 - 100 μg/ml) and E. faecalis (150 - 820 μg/ml) had antibacterial activity significantly increased and decreased, respectively. Extracts of C. collinum and S. birrea against E. faecalis as well as T. sericea against S. aureus and E. coli did not show any clear correlation between activity and different rates of annual rainfall. Inconsistent results suggest that other factors in nature such as genetic variability, age difference, pathogens, herbivores or allelopathy (competition) might have influenced the antibacterial activity of extracts. The results indicate that the antimicrobial activity of plants growing in nature may be highly variable. In order to eliminate possible effect of those factors common in nature, another exploratory study was undertaken using clone T. violacea and H. hemerocallidea of similar age (Chapter 3). Plants were grown under controlled conditions that included irrigation with 1000 ml of distilled water in intervals of 3, 14 and 21 days outside natural environment. Dry mass of all plants was reduced significantly (P≤0.05) with watering interval of 21 days, which indicated the effect of water stress. Air-dried leaves of all plants were finely ground and extracted with acetone. Extracts had good antibacterial activity as attested by low MIC values (< 1 mg/ml) across watering intervals. Differences in the antibacterial activity of the extracts against test bacterial between water treatments were not statistically significant (P≤0.05). Furthermore, there was no clear correlation between the activity of extracts and water treatments in terms of the MIC and total activity values or chemical constituents. The results in general suggest that cultivation under optimal watering intervals may not necessarily weaken the biological activity of extracts. To complement the above findings, in depth studies were also undertaken with clone L. dysophylla, T. violaceae and B. frutescens of similar age growing under controlled conditions outside natural environment. The studies determined the influence of a wide range of water (50 ml – 500 ml) and temperature (15°C and 30°C) treatments on antibacterial, antifungal and antioxidant of extracts. With the exception of a crassulacean acid metabolism (CAM) plant, B. frutescens, transpiration, dry mass and leaf areas of the other two plants were reduced significantly (P 0.05) under high temperature of 30°C and lowest water supply of 50 ml. Acetone leaf extracts had some biological activity. Differences in the majority of antibacterial and antifungal activities of extracts between water and temperature treatments were not statistically significant. With the exception of the influence of temperature, the majority of the antioxidant activity of extracts was almost similar between water treatments. However, the significant reduction of the antioxidant activity of all extracts under high temperature of 30°C was indicative of great sensitivity to high temperatures. The overall findings suggest that the biological activity of plants is more likely to vary widely in nature than under controlled conditions outside the natural environment. This is an indication that natural environment cannot always guarantee high and stable biological activity. As a result, beliefs by some traditional practitioners and scientists that cultivation weakens medicinal properties and good secondary metabolites form only under stress, respectively, cannot be widely substantiated. Therefore, the study encourages cultivation of medicinal plants. It has potential to optimise yield of biomass production, and ensure uniform and quality biological activity as well as reduce misidentification. / Thesis (PhD)--University of Pretoria, 2012. / Paraclinical Sciences / unrestricted