Dark oxidation of unsaturated lipids by the photo-oxidized 8-methoxypsoralen.

8-Methoxypsoralen (8-MOP) in ethanol, acetone, benzene, or CC14 is photo-oxidized under UV-irradiation (320-400 nm). Photo-oxidized 8-MOP (O2-8-MOP) is stable in the organic solvents, but it is destructed in water or in liposome suspension. The destruction rate constants are 0.04 s(-1) in water and 0.004 s(-1) in liposome membranes as estimated by the kinetics of the chemiluminescence accompanying the destruction. In course of O2-8-MOP destruction the residues of phospholipid unsaturated fatty acids are oxidized . Generation of the singlet oxygen (1 delta g) by excited 8-MOP is observed neither nor in ethanol. Quantum yield of 1 delta g) formation in CCl4 is less than 3%. A pattern is proposed for 8-MOP-sensitized oxidation of unsaturated lipids proceeding without direct attack of lipids by singlet oxygen.