Effect of UV-A on the linolenic acid micelles.

UV-A produced a dose-dependent linear increase of peroxidation in linolenic acid micelles as detected by the assay of (i) conjugated dienes, (ii) hydroperoxides, (iii) malondialdehyde (MDA), and (iv) the fluorescent adduct formed by the reaction of MDA with the amino acid, glycine. While sodium formate, dimethyl sulfoxide, superoxide dismutase, and ethylenediamine-tetraacetic acid produced no significant inhibition, some generally used singlet oxygen quenchers, beta-carotene, dimethylfuran, L-histidine, and sodium azide, caused significant inhibition of the UV-A-induced peroxidation of the linolenic acid micelles. alpha-Tocopherol and butylated hydroxytoluene produced more than 90% inhibition of the UV-A-induced peroxidation. ESR spectrometry revealed the formation of 2,2,6,6-tetramethylpiperidine oxide in the UV-A-irradiated aqueous solution of 2,2,6,6-tetramethylpiperidine. The involvement of singlet oxygen (1O2) in the UV-A-induced peroxidation of linolenic acid micelles is discussed.