Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

No description available.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Additional advisors: Yogesh K. Vohra, Renato P. Camata, Herbert C. Cheung, Craig A. Elmets. Description based on contents viewed June 23, 2009; title from PDF t.p. Includes bibliographical references.

Para minimizar os efeitos danosos a pele causados pelas radiações ultravioleta (UV), novos produtos cosméticos contendo filtros solares tem sido desenvolvidos e estão disponíveis no comércio. Consequentemente é necessário o desenvolvimento e validação de métodos analíticos para determinação quantitativa desses filtros solares em produtos cosméticos. O objetivo desta pesquisa foi a determinação quantitativa e simultânea dos filtros solares químicos, tais como, benzofenona-3, metoxicinamato de octila e salicilato de octila contidos em preparações cosméticas, por cromatografia líquida de alta eficiência (CLAE) e espectrofotometria no UV/visível. Paralelamente foi determinado o FPS para as amostras utilizando a espectrofotometria no uv/visível. A separação e determinação quantitativa pelo método cromatográfico foi realizada usando uma coluna LiChrospher® 100 RP-18 (5µm), fase móvel constituída de metanol-água (85:15, v/v), com vazão de 1,0mL/min e detecção no UV a 310nm. Os coeficientes de correlação e percentuais de recuperação para benzofenona-3, metoxicinamato de octila e salicilato de octila foram de 0,9999 e98,9%; 0,9995 e 99,9%;0,9998 e 98,9%, respectivamente. A média do desvio padrão relativo foi de 0,6%. A determinação espectrofotométrica só foi possível quando os filtros em estudo estão de forma isolada nas preparações cosméticas. O método espectrofotométrico foi validado a 287nm, 310nm e 306nm para benzofenona-3, metoxicinamato de octila e salicilato de octila, respectivamente; os coeficientes de correlação foram de 0,9998; 0,9999; 0,9998, respectivamente. O percentual de recuperação para a amostra comercial contendo apenas metoxicinamato de octila foi de 99,6%. A média do desvio padrão relativo foi de 0,5%. O Fator de Proteção Solar (FPS) determinado pelo método espectrofotométrico, para as preparações comerciais, não correspondeu aos mesmos valores rotulados. / In order to minimize the damaging effects to the skin caused by the ultraviolet (UV) radiation, several cosmetic products containing sunscreens has been developed and are available commercially. Consequently, it is necessary to develop and validate an analytical method for quantitative determination of sunscreen agents in cosmetic products. The aim of this research was to develop a high performance liquid chromatographic and a UV / visible spectrophotometric quantitative method for simultaneous determination of chemical sunscreens benzophenone-3, octyl methoxycinnamate and octyl salicylate contained in cosmetic product. At the same time, the Sun Protection Factor (SPF) was determined for the samples using UV / visible spectrophotometry. The separation and quantitative determination was achieved using a LiChrospher® 100 RP-18 (5µm) column, a mobile phase constituted of methanol-water (85: 15, v/v), a flow-rate of 1.0 mL/min and UV detection at 310nm. The correlation coefficient and percentage of recovery for benzophenone-3, octyl methoxycinnamate and octyl salicylate were 0.9999 and 99.05%; 0.9995 and 100.55%; 0.9998 and 98.05%, respectively. The average relative standard deviation (RSD) was 0.6%. The spectrophotometric determination was possible only when the sunscreens studied were in an isolated form, in cosmetic preparations. The spectrophotometric method was validated at 287nm, 310nm and 306nm for benzophenone-3, octyl methoxycinnamate and octyl salicylate, respectively. The correlation coefficients were 0.9998, 0.9999 and 0.9998, respectively. The percentage of recovery for commercial sample containing only octyl methoxycinnamate was 99.6%. The average relative standard deviation (RSO) was 0.5%. The Sun Protection Factor (SPF) determined by the spectrophotometric method, in the commercial preparations, did not corresponded to the labeled values.

Para minimizar os efeitos danosos a pele causados pelas radiações ultravioleta (UV), novos produtos cosméticos contendo filtros solares tem sido desenvolvidos e estão disponíveis no comércio. Consequentemente é necessário o desenvolvimento e validação de métodos analíticos para determinação quantitativa desses filtros solares em produtos cosméticos. O objetivo desta pesquisa foi a determinação quantitativa e simultânea dos filtros solares químicos, tais como, benzofenona-3, metoxicinamato de octila e salicilato de octila contidos em preparações cosméticas, por cromatografia líquida de alta eficiência (CLAE) e espectrofotometria no UV/visível. Paralelamente foi determinado o FPS para as amostras utilizando a espectrofotometria no uv/visível. A separação e determinação quantitativa pelo método cromatográfico foi realizada usando uma coluna LiChrospher® 100 RP-18 (5µm), fase móvel constituída de metanol-água (85:15, v/v), com vazão de 1,0mL/min e detecção no UV a 310nm. Os coeficientes de correlação e percentuais de recuperação para benzofenona-3, metoxicinamato de octila e salicilato de octila foram de 0,9999 e98,9%; 0,9995 e 99,9%;0,9998 e 98,9%, respectivamente. A média do desvio padrão relativo foi de 0,6%. A determinação espectrofotométrica só foi possível quando os filtros em estudo estão de forma isolada nas preparações cosméticas. O método espectrofotométrico foi validado a 287nm, 310nm e 306nm para benzofenona-3, metoxicinamato de octila e salicilato de octila, respectivamente; os coeficientes de correlação foram de 0,9998; 0,9999; 0,9998, respectivamente. O percentual de recuperação para a amostra comercial contendo apenas metoxicinamato de octila foi de 99,6%. A média do desvio padrão relativo foi de 0,5%. O Fator de Proteção Solar (FPS) determinado pelo método espectrofotométrico, para as preparações comerciais, não correspondeu aos mesmos valores rotulados. / In order to minimize the damaging effects to the skin caused by the ultraviolet (UV) radiation, several cosmetic products containing sunscreens has been developed and are available commercially. Consequently, it is necessary to develop and validate an analytical method for quantitative determination of sunscreen agents in cosmetic products. The aim of this research was to develop a high performance liquid chromatographic and a UV / visible spectrophotometric quantitative method for simultaneous determination of chemical sunscreens benzophenone-3, octyl methoxycinnamate and octyl salicylate contained in cosmetic product. At the same time, the Sun Protection Factor (SPF) was determined for the samples using UV / visible spectrophotometry. The separation and quantitative determination was achieved using a LiChrospher® 100 RP-18 (5µm) column, a mobile phase constituted of methanol-water (85: 15, v/v), a flow-rate of 1.0 mL/min and UV detection at 310nm. The correlation coefficient and percentage of recovery for benzophenone-3, octyl methoxycinnamate and octyl salicylate were 0.9999 and 99.05%; 0.9995 and 100.55%; 0.9998 and 98.05%, respectively. The average relative standard deviation (RSD) was 0.6%. The spectrophotometric determination was possible only when the sunscreens studied were in an isolated form, in cosmetic preparations. The spectrophotometric method was validated at 287nm, 310nm and 306nm for benzophenone-3, octyl methoxycinnamate and octyl salicylate, respectively. The correlation coefficients were 0.9998, 0.9999 and 0.9998, respectively. The percentage of recovery for commercial sample containing only octyl methoxycinnamate was 99.6%. The average relative standard deviation (RSO) was 0.5%. The Sun Protection Factor (SPF) determined by the spectrophotometric method, in the commercial preparations, did not corresponded to the labeled values.

Graduation date: 1995

Protection from the negative effects of solar radiation can be achieved by wearing protective clothing, avoiding exposure to sunlight or by the application of topical sunscreens. In this thesis, a number of studies were designed to determine if quercetin is suitable for use as a topical sunscreen.<p> The first objective was to determine if quercetin could protect against UV-induced lipid oxidation. Quercetin is twice as effective at preventing UVB-induced oxidation as preventing UVA-induced oxidation.The difference between UVA- and UVB- induced oxidation is believed to be due to the presence of an excited state form of quercetin in the UVA system. <p> The second objective was to determine the UV photostability of quercetin in solution. Three photoproducts of quercetin form regardless of whether UVA or UVB radiation is used. These photoproducts are 2,4,6-trihydroxybenzaldehyde, quercetin depside and hydroxytyrosol. . The slow rate of formation, less than 20% loss of starting material over 11 hours, and non-toxic nature of the photoproducts indicate that photostability of quercetin is not an obstacle to its use as a sunscreen.<p> The third objective was to determine the ability of quercetin to inhibit photosensitization by ketoprofen. Quercetin was shown to be effective in preventing decomposition of ketoprofen until it was consumed in the formation of the three quercetin photoproducts. This abilty of quercetin to prevent ketoprofen photosensitization indicates a beneficial effect for the use of quercetin as a topical sunscreen.<p> The fourth objective was to determine if quercetin can prevent UV-induced damage in a biological system. Quercetin was found to significantly reduce secretion of matrix metalloprotease 1 (MMP-1) upon UVA or UVB exposure, but had no effect on secretion of tumor necrosis factor á (TNF-á) in HaCaT cells. , Topical application of quercetin to UVA or UVB exposed EpiDerm skin mimics significantly reduced both MMP-1 and TNF-á secretion.<p> These results indicate that quercetin is effective in decreasing or eliminating several harmful effects of UVA and UVB radiation in the skin without major loss of starting material and without formation of toxic photoproducts. As such, quercetin appears to be a good candidate for inclusion into topical sunscreen formulations.

Protection from the negative effects of solar radiation can be achieved by wearing protective clothing, avoiding exposure to sunlight or by the application of topical sunscreens. In this thesis, a number of studies were designed to determine if quercetin is suitable for use as a topical sunscreen.<p> The first objective was to determine if quercetin could protect against UV-induced lipid oxidation. Quercetin is twice as effective at preventing UVB-induced oxidation as preventing UVA-induced oxidation.The difference between UVA- and UVB- induced oxidation is believed to be due to the presence of an excited state form of quercetin in the UVA system. <p> The second objective was to determine the UV photostability of quercetin in solution. Three photoproducts of quercetin form regardless of whether UVA or UVB radiation is used. These photoproducts are 2,4,6-trihydroxybenzaldehyde, quercetin depside and hydroxytyrosol. . The slow rate of formation, less than 20% loss of starting material over 11 hours, and non-toxic nature of the photoproducts indicate that photostability of quercetin is not an obstacle to its use as a sunscreen.<p> The third objective was to determine the ability of quercetin to inhibit photosensitization by ketoprofen. Quercetin was shown to be effective in preventing decomposition of ketoprofen until it was consumed in the formation of the three quercetin photoproducts. This abilty of quercetin to prevent ketoprofen photosensitization indicates a beneficial effect for the use of quercetin as a topical sunscreen.<p> The fourth objective was to determine if quercetin can prevent UV-induced damage in a biological system. Quercetin was found to significantly reduce secretion of matrix metalloprotease 1 (MMP-1) upon UVA or UVB exposure, but had no effect on secretion of tumor necrosis factor á (TNF-á) in HaCaT cells. , Topical application of quercetin to UVA or UVB exposed EpiDerm skin mimics significantly reduced both MMP-1 and TNF-á secretion.<p> These results indicate that quercetin is effective in decreasing or eliminating several harmful effects of UVA and UVB radiation in the skin without major loss of starting material and without formation of toxic photoproducts. As such, quercetin appears to be a good candidate for inclusion into topical sunscreen formulations.

Solar ultraviolet radiation is known to have deleterious effects on human skin and is a major cause of skin cancer. Therefore, the topical application of sunscreen preparations has gained wide usage for skin protection. These preparations typically contain a variety of chemical absorbers that absorb ultraviolet (UV) radiation and physical blockers that scatter, absorb and reflect UV light. The efficacy of sunscreens can be estimated by the Sun Protection Factor (SPF) which depends on the UV filters present in the formulations. However, although some of these commercial sunscreens have beneficial effects, they can also have undesirable results. It is known that the sunscreens undergo electronic excitation when exposed to UV light which may make them susceptible to photochemical modification. The production of reactive intermediates (e.g. free radicals) and stable photoproducts, either due to photoisomerisation or photofragmentation is a major concern because these species may be toxic and may lead to a reduction in efficacy. Hence a study of the photochemistry of these chemical absorbers found in commercial sunscreens is of great importance. Photostability and broad-spectrum studies of some Australian commercial sunscreen products were undertaken by means of spectrophotometric and chromatographic methods. The sunscreen products dissolved in methanol solutions were irradiated using simulated solar radiation. High performance liquid chromatography (HPLC) was used to identify and quantify the active chemical ingredients. UV spectrophotometry was used to monitor the spectral absorbance before and after UV exposure of the formulations. Our results show that some of the evaluated photoactive chemical absorbers currently used in sunscreens are unstable upon UV radiation. This was mainly due to either photoisomerisation and/or photofragmentation of some active chemical ingredients. An examination of the photochemistry of 2-ethylhexyl-p-methoxycinnamate (2- EHMC), an ultraviolet B absorber that was found in all the suncare products investigated in this study was undertaken. Irradiation of dilute (~ 10-6 M) solutions of EHMC with wavelengths of light greater than 300 nm results in trans - cis photoisomerisation leading to a photostationary equilibrium mixture. However, pure or concentrated solutions of 2-EHMC upon prolonged irradiation showed additional photoproducts. These were isolated by preparative high performance liquid chromatography (HPLC) and characterised by nuclear magnetic resonance (1H NMR) spectroscopy, which was used to identify them as [2 +2] cycloadducts of 2-EHMC. There are 13 possible dimers formed via a [2+2] cycloaddition reaction mechanism across the ethylenic double bond, however only the stable and energetically favoured isomers were isolated. In addition, ab initio molecular orbital calculations have been used to investigate the structures and the transition states of the various dimers resulting from the cycloaddition reactions. Geometry optimizations and energy calculations were performed with the Gaussian 98 program, using the B3LYP density functional and 6-31+G (d) basis set. GaussView was used to visualize the transition state structures. The theoretical calculations predicted the most stable dimer forms. The trans-trans configuration at the cyclobutane ring of the 2-EHMC adduct gave relatively more stable photoproducts. The theoretical results have been confirmed by HPLC isolation experiments, which together with the UV spectra of the different products; verify the presence of the different conformers of 2-EHMC. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2009.

No description available.