Photoprotection

A pele é o maior órgão do corpo humano e possui funções importantes de proteção para o organismo. Por ser o órgão mais externo, a pele está frequentemente exposta a inúmeras agressões, como à radiação ultravioleta (UV). A fim de proteger o corpo dos malefícios da radiação solar, indica-se o uso de protetores solares. A informação da necessidade do uso de fotoprotetores é amplamente propagada à população, porém pouco se fala sobre possíveis toxicidades associadas ao seu uso, incluindo em situações em que quando a pele não se apresenta íntegra, cenário comum entre diferentes populações, tais como crianças, atletas e portadores de doenças de pele. Protetores solares são formulações que possuem, em sua composição, filtros físicos e/ou químicos, os quais atuam espalhando, refletindo ou absorvendo a radiação solar. Por seu uso crônico e diário, foram levantadas preocupações a respeito de suas possíveis toxicidades. Os principais riscos identificados incluíram desenvolvimento de melanoma, deficiência de vitamina D, efeitos cutâneos, alterações na penetração dérmica e absorção sistêmica, efeitos no desenvolvimento fetal e neonatal, danos ao DNA e fotocarcinogênese, alterações no sistêmica endócrino, efeitos neurotóxicos e efeitos inalatórios. A avaliação destes, porém, é muitas vezes inconclusiva pela existência de informações limitadas e observação, em sua maioria, em cenário in vitro e in vivo utilizando animais, por um curto período e utilizando concentrações muito mais elevadas do que aquelas encontradas nas formulações hoje disponíveis. De forma geral, apesar das possíveis toxicidades identificadas, os benefícios dos filtros solares ainda superam seus riscos. Diversas estratégias e alternativas estão sendo desenvolvidas a fim de ampliar o espectro de ação de fotoprotetores e melhorar sua segurança, considerando individualidades de seus consumidores.

Green coffee oil and modified starch were recently found to have an enhanced protection effect against UV radiation. Therefore, this work aimed to develop an innovative sunscreen formulation based on Pickering emulsions concept, i.e., surfactant-free emulsions stabilized by physical UV filters associated natural oils as a key strategy for prevention against UV-induced skin damage. The Pickering emulsions of different compositions were characterized in terms of pH, mechanical, physical and microbiological stability by a thorough pharmaceutical control. In addition, the sun protection factor (SPF) as well as the in vitro and in vivo biological properties of the final formulations, including Episkin®, HRIPT and sunscreen water resistance. Formulation studies demonstrated the addition of physical UV filters was beneficial, leading to the inclusion of ZnO and TiO2 to ensure a high SPF against UVA and UVB, respectively. Although starch particles presented no intrinsic photoprotection prop...

Analysis of the partitioning of absorbed light energy within PSII into fractions utilised by PSII photochemistry (ΦPSII), thermally dissipated via ΔpH- and zeaxanthin-dependent energy quenching (ΦNPQ) and constitutive non-photochemical energy losses (Φf,D) was performed in control and cold-stressed maize (Zea mays L.) leaves. The estimated energy partitioning of absorbed light to various pathways indicated that the fraction of ΦPSII was twofold lower, whereas the proportion of thermally dissipated energy through ΦNPQ was only 30% higher, in cold-stressed plants compared with control plants. In contrast, Φf,D, the fraction of absorbed light energy dissipated by additional quenching mechanism(s), was twofold higher in cold-stressed leaves. Thermoluminescence measurements revealed that the changes in energy partitioning were accompanied by narrowing of the temperature gap (ΔTM) between S2/3QB− and S2QA− charge recombinations in cold-stressed leaves to 8°C compared with 14.4°C in contro...

Objectives: Various treatment options are available for the management of photosensitivity. The objective of this review is to evaluate the use of botanicals rich in antioxidants for photosensitivity reduction.
Design: Embase and Ovid/MEDLINE databases were searched for clinical studies evaluating antioxidants from botanical sources in the management of photosensitivity.
Results: Of 339 citations, 10 met the inclusion criteria. Four studies evaluated Polypodium leucotomos, two evaluated Camelia sinensis, while Hamamelis, Pistacia vera L., Citrus sinensis varieties Moro, Tarocco and Sanguinello, and Capparis spinosa were investigated in one study each. Five studies evaluated oral supplementation, four evaluated topical formulations, and one study evaluated both oral and topical antioxidants. Main results were summarized.
Conclusions: There is some evidence that antioxidants derived from botanical sources may be beneficial in reducing skin erythema and photosensitivity. However, the studies included in this review have methodological limitations and large scale randomized, placebo controlled trials are needed to further evaluate the efficacy and safety of botanical antioxidants in photosensitivity reduction.

Context: The incidence of solar ultraviolet radiation (UV) on Earth has increased due to diminish of the ozone layer. This enviromental agent is highly genotoxic causing numerous damage in DNA molecule. Nowadays there is a growing interest in the search of compounds capable to minimize these effects. In particular, phytocompounds have been tested as excelent candidates for their antigenotoxic properties.

Aims: To evaluate the protective effect of the aqueous extract of Pinus caribaea (EPC) against the damage induced by the UVB and UVC radiation.

Methods: The cell-free plasmid DNA assay was employed. The forms of plasmid were separated electrophoretically in agarose gel. For genotoxic and photoprotective evaluation of P. caribaea, different concentrations of the extract (0.1 – 2.0 mg/mL) and exposure times were evaluated. The CPD lesions were detected enzymatically. Additionally, the transmittance of the aqueous extract against 254 nm and 312 nm was measured.

Results: None of the concentrations were genotoxic in 30 min of treatment, for superior times a clastogenic effect was observed. The EPC despite inhibiting the activity of the enzyme T4 endo V, impedes photolesions formation in DNA at concentrations ≥ 0.1 mg/mL.

Conclusions: The EPC has photoprotective properties, this effect could be related with its antioxidants and absorptives capacities.

At present, there is a need and demand for the development of safe, cheap and effective topical herbal formulations as sun screens. In this context, this study was initiated to evaluate the sunscreen potential of a Sri Lankan salt marshy plant, Salicornia brachiata Roxb (Family: Amaranthaceae; formally Family: Chenopodiaceae) in vitro using a UV spectroscopic technique and Mansur equation. Sun Protection Factor (SPF) value was ascertained (which is an index of sun protection activity) using a methanolic extract having a concentration of 2.0 mgmL-1. Methanol soluble fraction of Dermatone® (2.0 mgmL-1), a well known sunscreen cream, was used as the reference agent. The results showed that the plant extract has a markedly high absorbance values (3.0-3.2) at 290-320 nm range with a SPF value of 30.89 (which is a novel finding) whilst the reference agent exhibited a SPF value of 34.23. Phytochemical analysis of the extract showed the presence of flavonoids, tannins, phenols and steroids. It is concluded that a safe, cheap and efficacious topical sun screen formulation could be developed from salt marshy plant S. brachiata.

Increasing global population demands the doubling of crop production by 2050. Advancements in agricultural techniques make it possible to increase the rate of crop improvement, though utilization of molecular tools to identify traits related to yield and stress tolerance is poor. The development of effective physiological selection criteria that are fast and non-destructive, particularly those related to yield and stress tolerance, will help in developing improved crop cultivars. In plant stress physiology, established chlorophyll fluorescence parameters , such as the efficiency of photosystem II (Ф PSII), photosystem I electron transport rate (PSI ETR), and non-photochemical quenching (NPQ), have received attention. The pho-toprotective processes conferred by NPQ serve fundamental roles in maintaining plant fitness and sustainable yields where their importance in predicting crop performance and yield under normal or stressful environments has been widely recognized. In this review, we focus on two informative parameters,-q E and q I ,-which are components of NPQ that have been ignored by most photosynthesis-measuring systems. We argue for adding these parameters to photosynthesis machines as calculating them later can be cumbersome and their inclusion will help plant breeders and non-specialists in phenotyping using chlorophyll fluorescence.

Ten days after withholding water from bean (Phaseolus vulgaris L. cv. Contender) plants net photosynthetic CO2 uptake by leaves declined and no net CO2 uptake occurred after 15d. A similar decline in stomatal conductance also occurred over this 15-d period. Leaf relative water content and tugor pressure remained very similar to that measured on control plants during most of the experimental period. The decline of net CO2 uptake by leaves during dehydration is attributed to stomatal closure since CO2-dependent O2 evolution measured on the same leaves at saturating light and CO2 concentration always remained identical to that of control plants. Dehydration of the leaves had no effect on the quantum yield of CO2-dependent O2 evolution during the experimental period. Leaves from dehydrating plants maintained in normal (21% O2 + 350 μmol·mol-1 CO2) air exhibited a substantial rate of photosynthetic activity (about 38% of that measured at saturation light and CO2 concentration) associated with O2 reduction. Decreasing the oxygen content of the air from 21% to 2% in order to inhibit photorespiration produced a decrease in the linear electron transport rate by ca. 65% However, inhibiting photosynthetic O2 reduction during high-light treatment did not increase the extent of photoinhibition of photosystem II photochemistry and did not change the amount of violaxanthin converted to zeaxanthin. It is concluded that photorespiration does not protect the photosynthetic apparatus against high-light damage during drought conditions. Thermal deactivation of energy in the photosystem II antennae appears to be the main protective mechanism against deleterious effects of high light.

Abstract Ten days after withholding water from bean (Phaseolus vulgaris L. cv. Contender) plants net photosynthetic CO 2 uptake by leaves declined and no net CO 2 uptake occurred after 15d. A similar decline in stomatal conductance also occurred over this 15-d period. Leaf relative water content and tugor pressure remained very similar to that measured on control plants during most of the experimental period. The decline of net CO 2 uptake by leaves during dehydration is attributed to stomatal closure since CO 2-dependent O 2 ...

Increasing global population demands the doubling of crop production by 2050. Advancements in agricultural techniques make it possible to increase the rate of crop improvement, though utilization of molecular tools to identify traits related to yield and stress tolerance is poor. The development of effective physiological selection criteria that are fast and non-destructive, particularly those related to yield and stress tolerance, will help in developing improved crop cultivars. In plant stress physiology, established chlorophyll fluorescence parameters , such as the efficiency of photosystem II (Ф PSII), photosystem I electron transport rate (PSI ETR), and non-photochemical quenching (NPQ), have received attention. The pho-toprotective processes conferred by NPQ serve fundamental roles in maintaining plant fitness and sustainable yields where their importance in predicting crop performance and yield under normal or stressful environments has been widely recognized. In this review, we focus on two informative parameters,-q E and q I ,-which are components of NPQ that have been ignored by most photosynthesis-measuring systems. We argue for adding these parameters to photosynthesis machines as calculating them later can be cumbersome and their inclusion will help plant breeders and non-specialists in phenotyping using chlorophyll fluorescence.

The authors declare that they have no conflict of interest. Abbreviations: Fm-maximal fluorescence yield of the dark-adapted state; F 0 m-maximum fluorescence at the dark-adapted state; Fm'-maximum fluorescence in the light; F r m-Fm in the presence of slowly relaxing quenching; NPQ-nonphotochemical quenching; NPQf-fast nonphotochemical quenching; NPQs-slow nonphotochemical quenching; qE-fast component of NPQ; qI-slow component of NPQ; qT-state transitions; qZ-zeaxanthin dependent quenching.

Exposure of control (non-hardened) Arabidopsis leaves for 2 h at high irradiance at 5 degrees C resulted in a 55% decrease in photosystem II (PSII) photochemical efficiency as indicated by F(v)/F(m). In contrast, cold-acclimated leaves exposed to the same conditions showed only a 22% decrease in F(v)/F(m). Thermoluminescence was used to assess the possible role(s) of PSII recombination events in this differential resistance to photoinhibition. Thermoluminescence measurements of PSII revealed that S(2)Q(A)(-) recombination was shifted to higher temperatures, whereas the characteristic temperature of the S(2)Q(B)(-) recombination was shifted to lower temperatures in cold-acclimated plants. These shifts in recombination temperatures indicate higher activation energy for the S(2)Q(A)(-) redox pair and lower activation energy for the S(2)Q(B)(-) redox pair. This results in an increase in the free-energy gap between P680(+)Q(A)(-) and P680(+)Pheo(-) and a narrowing of the free energy gap between primary and secondary electron-accepting quinones in PSII electron acceptors. We propose that these effects result in an increased population of reduced primary electron-accepting quinone in PSII, facilitating non-radiative P680(+)Q(A)(-) radical pair recombination. Enhanced reaction center quenching was confirmed using in vivo chlorophyll fluorescence-quenching analysis. The enhanced dissipation of excess light energy within the reaction center of PSII, in part, accounts for the observed increase in resistance to high-light stress in cold-acclimated Arabidopsis plants.