Flavonoids as potential protective agents against photo-oxidative skin damage

Flavonoids, a group of phenolic compounds widely occurring in the plant kingdom, have been reported to possess strong antioxidant activity. This preliminary study was designed to estimate the potential utility of topically applied flavonoids to prevent photooxidative stress in the skin. With this aim we have evaluated the protective effect of three flavonoids (quercetin, hesperetin and naringenin), chosen according to their structural characteristics, against UV radiation-induced peroxidation on phosphatidylcholine (PC) vesicles as a model membrane. Furthermore human skin permeation of these flavonoids was measured, given that a suitable percutaneous absorption is an essential requirement for satisfactory topically applied photoprotective agents. The flavonoids tested in our study proved to protect efficiently PC liposomes from UV radiation-induced peroxidation, probably by scavenging oxygen free radicals generated by UV irradiations; their antilipoperoxidative activity can be classified as follows: quercetin > hesperetin > naringenin. In addition, naringenin, hesperetin and, at a very lower degree, quercetin were able to permeate through the stratum corneum (which is the main barrier against the penetration of exogenous substances through the skin) and, so, to penetrate into deeper skin layers. Taken together, these findings suggest that topically applied flavonoids could be excellent candidates for successful employment as protective agents in certain skin diseases caused, initiated or exacerbated by sunlight irradiation. Copyright (C) 1996 Elsevier Science B.V.