Given that flavonoids are known for their ultraviolet (UV)B photoprotective properties in plants that contain them, we chose to study quercetin (1) and rutin (2) as agents that could potentially be used in sunscreen products. These two substances proved to behave in similar ways. When incorporated in oil-in-water emulsions, at a concentration of 10% (w/w), 1 and 2 give sun protection factor (SPF) values similar to that of homosalate, a standard substance. These two flavonoids also provided a non-negligible level of photoprotection in the UVA range. When used in association with titanium dioxide, the SPF obtained was around 30.

Depigmentation and skin lightening products, which have been in use for ages in Asian countries where skin whiteness is a major esthetic criterion, are now also highly valued by Western populations, who expose themselves excessively to the sun and develop skin spots as a consequence. After discussing the various possible mechanisms of depigmentation, the different molecules that can be used as well as the status of the products containing them will now be presented. Hydroquinone and derivatives thereof, retinoids, alpha-and beta-hydroxy acids, ascorbic acid, divalent ion chelators, kojic acid, azelaic acid, as well as diverse herbal extracts are described in terms of their efficacy and safety. Since a genuine effect (without toxic effects) is difficult to obtain, prevention by using sunscreen products is always preferable.

In diatoms, the main photosynthetic pigments are chlorophylls a and c, fucoxanthin, diadinoxanthin and diatoxanthin. The marine pennate diatom Haslea ostrearia has long been known for producing, in addition to these generic pigments, a water-soluble blue pigment, marennine. This pigment, responsible for the greening of oysters in western France, presents different biological activities: allelopathic, antioxidant, antibacterial, antiviral, and growth-inhibiting. A method to extract and purify marennine has been developed, but its chemical structure could hitherto not be resolved. For decades, H. ostrearia was the only organism known to produce marennine, and can be found worldwide. Our knowledge about H. ostrearia-like diatom biodiversity has recently been extended with the discovery of several new species of blue diatoms, the recently described H. karadagensis, H. silbo sp. inedit. and H. provincialis sp. inedit. These blue diatoms produce different marennine-like pigments, which belong to the same chemical family and present similar biological activities. Aside from being a potential source of natural blue pigments, H. ostrearia-like diatoms thus present a commercial potential for aquaculture, cosmetics, food and health industries.

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