Ultraviolet A-induced peroxidation of phosphatidylcholine in unilamellar liposomes.

Unilamellar liposomes of 1-palmitoyl-2-linoleoyl-3-sn-phosphatidylcholine (PLPC) were exposed to ultraviolet A (UVA) light at 37 degrees C. The UVA-induced PLPC peroxidation was inhibited by free radical scavengers, while singlet oxygen quenchers showed slight inhibition. When pre-existing hydroperoxides were reduced, UVA irradiation could not initiate the lipid peroxidation. The UVA-induced reaction of PLPC hydroperoxides with alpha-tocopherol produced addition products. The results indicate that UVA irradiation might dissociate hydroperoxides to alkoxyl and peroxyl radicals which stimulate lipid peroxidation.