Antioxidant effect of inorganic ions on UVC and UVB induced lipid peroxidation

Phosphate buffer suspensions of unilamellar liposomes of phosphatidylcholine were irradiated with UVC (254 nm) and UVB (300 nm) light. The irradiation provoked lipid peroxidation and liposome lysis with release of entrapped glucose-6-phosphate. At the same intensity of absorbed light, the photochemical effect at 254 nm is higher than at 300 nm. The addition of copper(II) and manganese(II) reduced both the peroxidation and the lysis. The copper showed an inhibitory effect only on the process provoked by the 254 nm irradiation, whereas the manganese was efficient both at 254 and 300 nm. The results are interpreted with a mechanism of peroxidation and quenching, involving photoformation of peroxyl radicals that are scavenged by manganese(II) and copper(I), with consequent breaking of the radical chain and reduction of the peroxidation rate. The copper(I), which is the active species, can be formed only at 254 nm by electron capture. The experimental data fit the kinetic equations obtained by the proposed mechanism by means of computer software.