Inhibition of UVA and UVB radiation-induced lipid oxidation by quercetin.

The flavonol quercetin is believed to provide protection against ultraviolet (UV)-induced damage to plants. As part of our investigations into the potential for quercetin to protect skin against UV-induced damage, we have measured the ability of quercetin to inhibit UV-induced lipid peroxidation in vitro in liposomes. Quercetin, which absorbs UV radiation at 255 and 365 nm, was determined to be a stronger inhibitor of lipid oxidation induced by UVB (3.7 radicals scavenged per molecule) than by lipid oxidation induced by UVA (1.9 radicals scavenged per molecule). The values for inhibition of UVB-induced lipid oxidation by quercetin are comparable to those when 2,2'-azobis(2-amidinopropane) was used as an oxidizing system (four radicals scavenged per molecule). The protective effect of quercetin appears to be mainly the result of scavenging of UV-generated radical species, although this may be decreased slightly in the UVA as a result of its absorption at 365 nm.