Spectroscopic detection of photoproducts in lecithin model system after 8-methoxypsoralen plus UV-A treatment

Photoreactions of 8-methoxypsoralen (8-MOP) in the presence of synthetic lecithins esterified at the β-position with linoleic/oleic and γ-palmitic acid (PCd2/d1pal) have been studied. Following UV-A (320–400 nm) irradiation, the photoproducts separated by thin-layer chromatography are analysed by UV absorption spectroscopy, nuclear magnetic resonance and mass spectroscopy. The new isolated products are lecithin double cyclobutane adducts, PC–(8-MOP)2, fatty acid–8-MOP split adducts from phosphatidylcholine and lecithin adducts with photo-oxidized 8-MOP. The photolysis performed in the presence of 8-MOP is related to the previously reported lecithin cyclobutane adducts with psoralen. A hypothetical scheme of lecithin photolysis under PUVA (psoralen+UV-A) treatment is proposed. We suggest that photolysis of lecithin may have a significant role in the chain of reactions triggered in cell membrane submitted to PUVA treatment.