The rise in solar ultraviolet radiation on the earth's surface has led to a depletion of stratospheric ozone over recent decades, thus accelerating the need to protect human skin against the harmful effects of UV radiation such as erythema, edema, hyperpigmentation, photoaging, and skin cancer. There are many different ways to protect skin against UV radiation's harmful effects. The most popular way to reduce the amount of UV radiation penetrating the skin is topical application of sunscreen products that contain UV absorbing or reflecting active molecules. Based on their protection mechanism, the active molecules in sunscreens are broadly divided into inorganic and organic agents. Inorganic sunscreens reflect and scatter UV and visible radiation, while organic sunscreens absorb UV radiation and then re-emit energy as heat or light. These synthetic molecules have limited concentration according to regulation concern. Several natural compounds with UV absorption property have been used to substitute for or to reduce the quantity of synthetic sunscreen agents. In addition to UV absorption property, most natural compounds were found to act as antioxidants, anti-inflammatory, and immunomodulatory agents, which provide further protection against the damaging effects of UV radiation exposure. Compounds derived from natural sources have gained considerable attention for use in sunscreen products and have bolstered the market trend toward natural cosmetics. This adds to the importance of there being a wide selection of active molecules in sunscreen formulations. This paper summarizes a number of natural products derived from propolis, plants, algae, and lichens that have shown potential photoprotection properties against UV radiation exposure-induced skin damage.

SynopsisCarboxymethyl chitosan is a chitosan derivative of the most intensively investigated due to its water solubility in wider pH range compared with the parent compound, thus extended its use in various applications. In this review, different preparation conditions, which resulting in the N-and O-carboxylated chitosan, diverse degree of substitution and water solubility are recapitulated. Five important features of carboxymethyl chitosan from recent studies, which are moisture absorption-retention, anti-microbial properties, antioxidant capacities, delivery system and emulsion stabilization, have been centred and emphasized for cosmetic utilization. Additionally, cytotoxicity information has been inclusively incorporated to ensure its safety in application.R esum e Le carboxym ethyl chitosan est un des plus etudi es d eriv es de chitosan en raison de sa solubilit e dans l'eau dans la gamme de pH la plus large par rapport a la mol ecule m ere; ainsi son utilisation s'est etendue dans diverses applications. Dans cette revue, les diff erentes conditions de pr eparation qui en r esultent dans le chitosan N et Ocarboxyl e, le degr e divers de substitution et leur solubilit es dans l'eau sont r ecapitul es. Cinq caract eristiques importantes de carboxym ethylchitosan d' etudes r ecentes, qui sont l'absorption ou r etention d'humidit e, les propri et es antimicrobiennes, les capacit es anti-oxydantes, le syst eme de vectorisation et de stabilisation des emulsions, ont et e evalu es pour l'utilisation cosm etique. En outre, les informations de cytotoxicit e ont et e incorpor ees pour assurer sa s ecurit e dans les applications.

The dioxo tungsten(VI) and molybdenum(VI) complexes WCl2(O)2(OPMePh2)2, WCl2(O)2dppmO2, and MoCl2(O)2dppmO2, the oxoperoxo compounds WCl2(O)(O2)(OPMePh2)2, WCl2(O)(O2)dppmO2, and MoCl2(O)(O2)dppmO2, and the oxodiperoxo complexes, W(O)(O2)2dppmO2 and Mo(O)(O2)2dppmO2 have been prepared and characterized by IR spectroscopy, 31P NMR spectroscopy, elemental analysis, and X-ray crystallography. The structural and X-ray crystallographic data of compounds WCl2(O)2(OPMePh2)2, WCl2(O)(O2)(OPMePh2)2, MoCl2(O)2dppmO2.4H10O, WCl2(O)2dppmO2, Mo(O)(O2)2dppmO2, and W(O)(O2)2dppmO2 are also detailed. All complexes were studied as catalysts for cis-cyclooctene epoxidation in the presence of tert-butyl hydroperoxide (TBHP) or H2O2 as an oxidant. The Mo-based catalysts showed a superior reactivity over W-based catalysts in the TBHP system. On the other hand, in the H2O2 system, the W-based catalysts (accomplishing nearly 100% epoxidation of cyclooctene in 6 h) are more reactive than the Mo catalysts (<45% under some conditions). Various solvent systems have been investigated, and ethanol is the most suitable solvent for the H2O2 system.

Overexposure to ultraviolet (UV) radiation can cause a number of skin disorders such as erythema, edema, hyperpigmentation, immunosuppression, photoaging, and skin cancer. Since the level of UV radiation is increasing as a result of depletion of the stratospheric ozone and climate change, the protection of human skin against the harmful effects of UV radiation is an urgent need. Topical application of sunscreens is a strategy to protect the deleterious effect of UV radiation on the skin. Sunscreens today contain one or several synthetic UV filter molecules which protect the UV radiation exposed on the epidermis. These molecules are broadly divided into physical and chemical agents. Physical sunscreens reflect and scatter UVB, UVA and visible radiation. Chemical sunscreens act by absorbing ultraviolet radiation and re-emitting chemical energy as heat or light. Several synthetic UV filter molecules are available in the market but they have limited use because these active molecules may create adverse effects on human skin. Some information on possible photon induced reaction such as photoirritation, photosensitization and contact dermatitis by sunscreen products containing synthetic organic sunscreen agents. To overcome these side effects, naturally occurring compounds have gained considerable attention as photoprotective agents. Flavonoids, a group of natural occurring compounds, act as catalysts in the light phase of photosynthesis and as stress protectants in plant cells by scavenging reactive oxygen species (ROS). Natural flavonoids have the potential photoprotection because of their UV absorbing, their ability to act as direct and indirect antioxidants as well as anti-inflammatory and immunomodulatory agents which provide exciting platforms for the development of photoprotection. This review summarizes the structure and potential photoprotection activity of several natural flavonoids.

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