The protection of polyunsaturated fatty acids in micellar systems against UVB-induced photo-oxidation by procyanidins from Vitis vinifera L., and the protective synergy with vitamin E

The protective effect of procyanidins (catechin oligomers) from Vitis vinifera seeds on the UVB-promoted photo-oxygenation of polyunsaturated fatty acids (PUFAs) (linoleic, linolenic and arachidonic acids, 35 mM) has been studied in 0.5 mM sodium dodecylsulfate micelles exposed to UVB radiation (1-8 J cm-2) and determined qualitatively by Fourier transform infrared spectroscopy (FT-IR) and quantitatively by UV spectroscopy (conjugated dienes and total lipid hydroperoxides). Procyanidins (1-10 muM) strongly and dose-dependently inhibit the formation of PUFA hydroperoxides (IC50 = 4-6 muM), with a potency comparable to that of vitamin E. In these micellar systems, a strong co-operative interaction (synergistic effect) between procyanidins and vitamin E (1:1 molar ratio) in PUFA protection was demonstrated; this, as shown by electron spin resonance (ESR) studies, is a result of the ability of procyanidins to regenerate alpha-tocopherol from the alpha-tocopheroxyl radical (generated by a UV Solar Simulator), through a hydrogen transfer mechanism. HPLC monitoring of vitamin E in PUFAs micelles oxidatively stressed by UVB, confirms that procyanidins save vitamin E from consumption. All these findings, if properly extrapolated to an in vivo situation, indicate that this class of radical scavengers can be used as adjuvants of physical/chemical sunscreens in skin protection from photodamage.