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Commercial sunscreen products are used to protect the skin against hannful ultraviolet (UV) radiation that can induce skin cancer at high dosage. These products contain UV filters that can reflect, scatter or absorb UV light. The chemical UV filters responsible for the absorption of UV radiation can be photochemically modified and as a result reduce the efficacy of the sunscreen formulation. This study focused on the possible use ofplant polyphenols as potential stabilisers of photo-unstable sunscreen chemical absorbers. The photo-instability of some sunscreen absorbers results in radical formation; this prompted the use of the plant, Sutherlandia microphylla (Cancer Bush plant), as a potential photostabiliser. The Cancer Bush plant is used by the indigenous people of South Africa to treat AIDS and cancer. The radical scavenging properties of polyphenolic compounds present in the plant are possibly responsible for the plant's anti-tumour and anti-IDV properties. Therefore, these Cancer Bush polyphenols could possibly be used to photostabilise photo-unstable sunscreen absorbers. Potential polyphenolic photostabilisers from the Cancer Bush plant were extracted by means of various polyphenolic extraction methods. These extracts were analysed by gas chromatography (GC), high-performance liquid chromatography (HPLC), UV spectroscopy and gas chromatography-mass spectrometry (GC-MS). The phenolic content and the antioxidant activity ofthese extracts were investigated by means of the Folin-eiocalteu reagent (FCR) and the diphenylpicrylhydrazyl (DPPH) radical assays respectively. Polyphenols were also extracted from various Rooibos teas and compared with those extracted from the Cancer Bush plant. Both the Cancer Bush and various Rooibos tea extracts were found to contain simple phen~lics and potential polyphenolic compounds. The Cancer Bush extracts as well as the Rooibos tea extracts together with the specific polyphenols, epicatechin and rutin, were assessed for their ability to photostabilise sunscreen absorbers. The photostability of the chemical absorbers in the absence and in the presence of the polyphenol extracts was investigated by UV spectroscopy, by monitoring their absorption spectra during irradiation with solar-simulated radiation. These extracts inhibited the photodegradation of the absorber avobenzone. The photostability of avobenzone is solventIntroduction III dependent hence the investigations were carried out in three solvents, namely, cyclohexane, ethyl acetate and dimethylsulfoxide. Additionally, the cause ofthe instability ofavobenzone in these solvents was investigated by means of DV spectroscopy, HPLC and nuclear magnetic resonance spectroscopy. The oxygen dependency of the photo-instability of avobenzone was also determined. The photo-instability of avobenzone was found to occur as a result of photoisomerisation and!or photodegradation, depending on the solvent. Avobenzone photoisomerised extensively in dimethylsulfoxide and photodegraded appreciably in cyclohexane, whereas both processes occurred to a similar extent in ethyl acetate. Photoisomerisation only occurred in the presence of oxygen whereas photodegradation occurred irrespective of oxygen. The Cancer Bush and various Rooibos tea extracts as well as other polyphenols photostabilised avobenzone in ethyl acetate and dimethylsulfoxide but not in cyclohexane. This photostabilisation effect was potentially due to the radical scavenging ability of polyphenols which prevented the oxygendependent photoisomerisation, but not the oxygen independent photodegradation process from occurring. / Thesis (M.Sc.)-Chemistry-University of KwaZulu-Natal, 2005

The topical application of sunscreens is widely practised to protect healthy and photosensitive skins from the sun. The benzophenone-derived sunscreens, e.g. 2-hydroxy-4-methoxy benzophenone-5-sulphonic acid (or benzophenone-4) and 2-hydroxy-4-methoxy benzophenone (or benzophenone-3), were ranked as the second and third most frequently used sunscreens, respectively, by the United States Food and Drug Administration (FDA) in 1996. These sunscreens are categorised as being 'safe' and 'effective'. However, it is well known that the parent compound, benzophenone, undergoes rapid hydrogen abstraction reactions on irradiation and is an extremely powerful radical generator. In addition, benzophenone has been shown to be a potent photosensitizer of thymine dimers in deoxyribose nucleic acid (DNA). More astounding to the sunscreen industry is the recent discovery that a group of non-steroidal anti- inflammatory drugs (NSAIDs) having the benzophenone backbone, e.g. ketoprofen, not only form thymine dimers when irradiated with DNA in vitro, but also photosensitize double stranded supercoiled DNA making it prone to single-strand break formation. Both these lesions, if unrepaired, may contribute to mutagenesis, carcinogenesis, inherited disease and eventually cell death. The purpose of this investigation was to determine if a group of benzophenone-derived sunscreen agents has the ability to photosensitize the cleavage of DNA, whereby supercoiled DNA is converted to the relaxed circular and linear forms. The group of UV absorbers investigated in this study included benzophenone-4, benzophenone-3 , 2,4 dihydroxybenzophenone (or benzophenone-l), 2,2'-dihydroxy-4,4'-dimethoxy benzophenone sulphonic acid (or trade name Uvinul DS49) and 2-phenylbenzimidazole-5-sulphonic acid (or trade name Eusolex 232). For comparison the parent compound benzophenone and the NSAID ketoprofen, a well-known photocleaver, were also studied. Buffered aqueous solutions of the benzophenones were irradiated in the presence of DNA at wavelengths greater than 300 nm with an Osram 500 W/2 high-pressure mercury lamp in conjunction with a 10 mm thick Pyrex filter. The irradiated samples were analysed for DNA cleavage by agarose gel electrophoresis and for DNA binding by fluorescence spectroscopy. The photostability of the UV absorbers was also investigated. In addition, computational studies were conducted to obtain the lowest energy geometrical structures of these UV absorbers and hence determine if intercalation of these UV absorbers with DNA was possible. From the photostability experiments conducted, it is apparent that the benzophenone-based UV absorbers were stable to photodecomposition when irradiated with UV light. They behaved in a manner different from their parent compound benzophenone, and from ketoprofen, where substantial photodegradation occurred upon UV irradiation. This is indicative of the rapid photoreactivity of the benzophenone backbone. The relative photostability of the UV absorbers was not anticipated and was attributed to the substituents present on the benzophenone backbone. The agarose gel electrophoresis experiments however clearly showed that benzophenone, ketoprofen, benzophenone-l, Uvinul DS49 and Eusolex 232 cleave ?X174 DNA when irradiated with UV light at wavelengths greater than 300 nm, while benzophenone-3 and benzophenone-4 did not. For these UV absorbers with the exception of benzophenone-3 and benzophenone-4, the number of single strand breaks in the DNA increased compared to when it was irradiated in their absence. In addition, the supercoiled DNA was converted to the relaxed circular and linear forms, the latter of which was undetected in the absence of the UV absorbers. Binding of benzophenone, ketoprofen, benzophenone-l and Uvinul DS49 to calf thymus DNA was also detected by the fluorescence spectroscopy technique. However, this was not observed for Eusolex 232, benzophenone-3 and benzophenone-4, since they did not compete with ethidium bromide for DNA binding sites. Where DNA cleavage did occur, the mechanism of this interaction had to be determined hence the motivation for the computational studies. From computational studies using PM3 semi- empirical calculations, it was determined that the benzophenone-based UV absorbers investigated, apart from Eusolex 232, displayed non-planar geometrical structures. This indicated that DNA intercalation of these sunscreen agents with DNA would at best be very limited, since only one half of the molecule could possibly interact with the bases of DNA. For benzophenone, ketoprofen, benzophenone-l and Uvinul DS49, photosensitised type I and type II processes involving triplet energy transfer reactions has been identified in literature as being responsible for DNA cleavage. It was determined by ab initio calculations that Eusolex 232 exists in a planar structure unlike the other UV absorbers mentioned above that were non- planar. It was concluded that although Eusolex 232 has the ability to intercalate with the base pairs of DNA, it does not do so, as shown by its lack of binding to calf thymus DNA by the fluorescence spectroscopy study. Literature alludes to photooxidation by singlet oxygen in single stranded DNA via the type II reaction and type I electron transfer reactions in double stranded DNA as the mechanism responsible for DNA cleavage induced by Eusolex 232. / Thesis (M.Sc.)-University of Natal, Durban, 2003.

Ultraviolet radiation (UVR) is known to be highly mutagenic. What types of DNA lesions that are induced by different UVR wavelengths are still a matter of debate. UVR induces mutagenesis mostly by the formation of photoproducts and the induction of reactive oxygen species (ROS). ROS can give rise to mutations via oxidation of nucleotides in the DNA or the nucleotide pool. Oxidized nucleotides in the nucleotide pool can thereby be incorporated into the DNA during replication and ultimately give rise to mutations. MTH1 however, dephosphorylates oxidized nucleotides in the nucleotide pool, in particular 8-oxo-dGTP and 2-OH-dATP, and inhibits their incorporation into the DNA.The aim of the present study was to investigate the role of MTH1 in mutagenesis and cytogenetic damage induced by UVR in a human lymphoblastoid TK6 cell line. The clonogenic survival, mutant frequency and micronucleus frequency were measured following exposure to UVA, UVB and UVC in MTH1-knockdown and wild-type TK6 cells. As a biomarker for oxidative damage the level of intracellular and extracellular 8-oxo-dG was measured in TK6 cells exposed to UVA. The mutational spectra of UVA-induced mutations at the thymidine kinase gene in MTH1-knockdown and wild-type TK6 cells were investigated.The results show that MTH1 protects against UVA and UVB mutagenesis significantly. MTH1, however, has been shown to offer no protection against UVR-induced cytogenetic damage and is therefore suggested to mainly inhibit mutagenesis. The mutational spectra show that GC&gt;AT and AT&gt;GC transitions are the dominant mutation types in cells exposed to UVA.In conclusion, MTH1 protects TK6 cells against mutagenesis induced by longer wavelengths of UVR. This indicates that the nucleotide pool is a significant target in mutagenesis for longer wavelengths of UVR. The type of mutations induced by UVA, GC&gt;AT and AT&gt;GC, can be formed by the incorporation of 2-OH-dATP from nucleotide pool into the DNA. UVA is therefore suggested to induce mutations by induction of oxidized nucleotides such as 2-OH-dATP. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

Marine phytoplankton are known to produce UV-absorbing compounds (UVACs) for protection against UV radiation. To assess whether the same strategy applies to sea ice-associated algal communities, MAAs were measured in algae associated with surface melt ponds, sea ice, sea ice−water interface, and underlying seawater in a coastal bay of the Canadian Arctic Archipelago during the 2011 spring melt transition. Six UVACs were detected as the spring melt progressed, namely shinorine, palythine, and porphyra-334 and three unknowns (U1, U2 and U3). U1 was most likely palythene, another MAA. The molecular identities of the other two UVACs, U2 and U3, which have an absorption maximum of 363 and 300 nm, respectively, remain to be structurally elucidated. The results confirm that Arctic sea ice-associated algal communities are capable of producing photoprotectants and that spatial and temporal variations in MAA and other UVAC synthesis are affected by snow cover and UV radiation exposure. / May 2016

Background: Sun exposure is strongly associated with skin cancer. Sun protection to reduce harmful effects of sun exposure, including skin cancer, is encouraged. However, sun sensitivity, a possible confounder of the association between sun exposure and sun protection, is often overlooked. Objectives: This study examined how sun exposure and sun protection behaviors among indoor workers vary between sun sensitive and less sun sensitive individuals. Methods: Diaries over 45 days (August and September of 2009) from indoor workers in the Midwest were examined. Diaries included daily sun exposure, sun protection, and sun sensitivity. Sun sensitivity was measured by determination of fair and non-fair complexion, categorized based on inability to tan and tendency to sunburn. Sun exposure was compared between fair and non-fair complexion. Total exposure (sunrise to sunset) was examined, along with exposure between 10 am and 4 pm, and long exposure between 10 am and 4 pm (at least 60 minutes). Percentages of time in the sun spent practicing sun protection were reported by study participants with fair and non-fair complexion. Logistic regression was used to determine odds ratios between fair complexion and mean sun exposure and mean sun protection times. Results: Fair complexioned individuals spent less time in the sun than non-fair complexioned individuals. In addition, fair complexioned individuals spent greater percentages of time practicing sun protection behaviors while they were in the sun. They were more likely to practice sun protection behaviors related to sunscreen application and protective clothing, notably, wearing a long-sleeved shirt.Conclusion: Fair complexioned individuals spend less time in the sun and practice more sun protective behaviors than non-fair complexioned individuals. These interrelations between sun sensitivity, sun protection and amount of sun exposure suggest that controlling for potential confounding when examining one of these factors and skin cancer may be challenging.

Pseudomonas syringae produz núcleos de gelo biológicos de grande eficiência. Bioaerossóis destas células tem potencial de participar na glaciação de nuvens, podendo influenciar a precipitação. Foram estudadas como as condições as quais P. syringae está sujeita em suspensão na atmosfera afetam sua sobrevivência e sua atividade de nucleação de gelo. Duas cepas foram testadas, e ambas apresentaram baixa tolerância ao UV-C e ao UV-B, mas exibiram uma maior resistência quando expostas a um espectro semelhante ao encontrado no ambiente. A atividade de congelamento de uma das cepas (pv. syringae) não foi afetada pelo UV, enquanto que para a outra (pv. garcae) houve uma redução moderada. Em resposta à dessecação, pv. garcae foi substancialmente mais resistente que pv. syringae. Isto também afetou a nucleação de gelo das cepas. Em ensaios adicionais, estas bactérias foram expostas em um voo de balão estratosférico, e a uma simulação em laboratório das condições no topo da troposfera. Nestes dois experimentos, sobreviventes protegidos do UV foram recuperados. / Pseudomonas syringae produces biological ice nuclei of great efficiency. Bioaerosols of these cells have the potential to take part in cloud glaciation, possibly influencing the precipitation. It was studied how the conditions to which P. syringae is subjected while in suspension in the atmosphere affect its survival and its ice nucleation activity. Two strains were tested, and both showed a low tolerance to UV-C and UV-B, but exhibited a higher resistance when exposed to a spectrum similar to the one found in the environment. The freezing activity of one of the strains (pv. syringae) was not affected by the UV, while that for the other (pv. garcae) there was a moderate reduction. In response to desiccation, pv. garcae was substantially more resistant than pv. syringae. This also affected the ice nucleation by the strains. In additional assays, these bacteria were exposed in a stratospheric balloon flight, and to a laboratory simulation of the conditions at the top of the troposphere. After these two experiments, survivors protected from the UV were recovered.

Neste estudo foi avaliado o potencial tóxico de diferentes desinfetantes (cloro, ácido peracético, radiação ultravioleta e ozônio) utilizados na desinfecção de esgotos sanitários. Para tanto, foram realizados ensaios de desinfecção (em diversas concentrações e tempos de contato) com o esgoto doméstico originário da estação de tratamento de esgotos da cidade de Araraquara (SP) e, posteriormente, ensaios de toxicidade a fim de verificar possíveis efeitos agudos e crônicos nos seguintes organismos-teste: Daphnia similis, Ceriodaphnia silvestrii, Chironomus xanthus, Danio rerio e Allium cepa. Todos os desinfetantes, nas condições experimentais testadas, foram capazes de produzir efeitos deletérios aos organismos-teste utilizados nesta pesquisa. O cloro foi considerado o desinfetante mais tóxico, sendo seguido pelo ozônio, ácido peracético e radiação UV. Verificou-se ainda que quando o efluente não desinfetado foi tóxico aos organismos-alvo, sua toxidez foi potencializada com a adição dos diferentes agentes desinfetantes. Os resultados obtidos neste estudo sugerem que a utilização do cloro para desinfecção de esgotos sanitários, sem prévia descloração, deve ser revista, em face da eficiência satisfatória de inativação de bactérias proporcionada por outros agentes de desinfecção potencialmente menos tóxicos (tais como o ácido peracético e a radiação UV). / In this study, it was evaluated the toxic potential of different disinfectant agents (chlorine, peracetic acid, ultraviolet radiation and ozone) used in the disinfection of urban wastewater. For so much, disinfection assays were accomplished (in several concentrations and contact times) with the domestic sewage from Araraquara city (SP) and toxicity bioassays were developed in order to verify possible acute and chronic effects in the following test-organisms: Daphnia similis, Ceriodaphnia silvestrii, Chironomus xanthus, Danio rerio and Allium cepa. All the disinfectants, in the tested experimental conditions, were capable to produce harmful effects to the test-organisms used in this research. Chlorine was considered the most toxic disinfectant, being followed by ozone, peracetic acid and UV radiation. It was noticed that when the effluent, by itself, was toxic to the test-organism, its toxicity was increased with the different disinfecting agents\' addition. The results obtained in this study suggest that the use of chlorine as a wastewater disinfectant, without previous dechlorination, should be reviewed, because it was observed that other disinfection agents (such as peracetic acid and UV radiation) were able to promote satisfactory levels of bacteria inactivation for potentially less toxicity.

A luz ultravioleta (UV) induz no DNA dímeros de pirimidina ciclobutano (CPDs) e pirimidina (6-4) pirimidona fotoprodutos (6-4PPs). Fotoliases revertem estas lesões, mas estão ausentes em mamíferos placentários que contam com a via de reparo por excisão de nucleotídeos para removê-las. O objetivo deste trabalho é investigar os papéis específicos de CPDs e 6-4PPs nas respostas epiteliais à UV. Camundongos deficientes em reparo de DNA, expressando CPD- ou 6-4PP-fotoliase, foram expostos aguda ou cronicamente à luz UV, sendo avaliados morte e divisão celular, hiperplasia, expressão de p53 e melanogênese. Resultados sugerem que a remoção ubíqua de CPD em animais XPA leva à melanogênese que suprime hiperplasia. O mesmo não é observado quando 6-4PPs são removidas em queratinócitos basais de animais XPA ou quando qualquer fotolesão é removida de queratinócitos basais em animais CSA. Este trabalho revela a importância da natureza, concentração e localização das fotolesões, esclarecendo a participação de CPDs e 6-4PPs nas consequências desses danos na pele de mamíferos. / Ultraviolet (UV) light induces two lesions in DNA: cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs). Photolyases convert these lesions to monomers but are absent in placental mammals who count on the nucleotide excision repair pathway to remove photolesions. The aim of this work is to investigate the specific roles of CPDs and 6-4PPs on epithelial responses to UV. DNA repair deficient mice, expressing either CPD- or 6-4PP-photolyase, were acute or chronically UV exposed and apoptosis, cell proliferation, hyperplasia, p53 overexpression and melanogenesis were evaluated. Data suggests that ubiquitous CPD removal in XPA mice leads to increased melanogenesis, which suppresses hyperplasia. This is not observed when 6-4PPs are removed from basal keratinocytes in XPA mice or when either lesion is removed from basal keratinocytes in CSA mice. This work points out the importance of the nature, amount and location of photolesions, shedding light on the participation of CPDs and 6-4PPs in mammalian skin responses to UV light.

Polihidroxialcanoatos (PHA) produzidos por Pseudomonas sp. LFM046 a partir de carboidratos e ácido propiônico contem monômeros com número ímpar e par de carbonos, representando um bom modelo para o estudo do metabolismo de propionato. Genes relacionados ao ciclo do 2-metilcitrato foram encontrados em todas as espécies de Pseudomonas compondo um operon prpRBCAcnMprpFD. Genes da via do metilmalonil-CoA não foram encontrados em Pseudomonas. Genes da <font face=\"Symbol\">a-oxidação de propionato foram encontrados apenas em P. aeruginosa. A análise de um mutante prp obtido por inserção de transposon revelou que estava mutado no gene prpB, relacionado ao ciclo do 2-metilcitrato. A análise de mutantes obtidos por radiação ultravioleta revelou que dois devem estar afetados em via menos relevante para o metabolismo de propionato e outros dois na ativação desse ácido orgânico. Experimentos com propionato marcado (1C13) demonstraram que as vias do oxobutirato, do metimalonil-CoA e do 2-hidroxiglutarato não devem contribuir para o metabolismo de propionato em Pseudomonas sp. LFM046. / Polyhydroxyalkanoates (PHA) produced by Pseudomonas sp. LFM046 from carbohydrates and propionic acid contains monomers with odd and even number of carbons, representing a good model to study the propionate metabolism. Genes related to 2-methycytrate cycle were found in all Pseudomonas species organized in an operon prpRCAAcnMprpFD. Genes related to the methylmalonyl-CoA pathway were not found in Pseudomonas. Genes related to the propionic <font face=\"Symbol\">a-oxidation were found only in P. aeruginosa. Analysis of a prp mutant obtained by transposon insertion revealead that it was mutated in prpB gene, related to the 2-methylcytrate cycle. The analysis of mutants obtained using ultraviolet radiation showed that two should be affected in less relevant propionate metabolism pathways and other two in the activation of this organic acid. Experiments with labeled propionate (113C) demonstrated that the oxobutyrate, methylmalonil-CoA and 2-hydroxyglutarate pathways should not contribute to the propionate metabolism in Pseudomonas sp. LFM046.