Peroxidation of soybean phosphatidylcholine liposomes photoinduced by pterin

MARIANA VIGNONI; ANGEL CATALA; ANDRÉS H. THOMAS

Cordoba

Congreso; 16th International Congress on Photobiology; 2014

Lipid peroxidation process is thought to be involved in many physiological and pathological events [1]. Many model membranes can be used to learn more about issues that cannot be studied in biological membranes. Sonicated liposomes prepared with soybean phosphatidylcholine (SoyPC) were submitted to lipid peroxidation, under air atmosphere at room temperature, with pterin (Ptr) as initiator. Pterins are heterocyclic compounds widespread in nature and have been previously identified as good photosensitizers under UVA irradiation [2,3]. In this work, we have investigated the ability of Ptr (50-250μM), the parent compound of oxidized pterins, to photosensitize the oxidation of SoyPC in aqueous solutions under UVA irradiation. Conjugated dienes and trienes, determined by absorption at 234 and 270 nm respectively were measured as a function of time. Peroxidation of SoyPC (260 µM) resulted in an increase in conjugated dienes production, reaching a maximum at around 50 min and then decreasing. When lipid peroxidation was performed in the absence of Ptr a significant smaller production of conjugated dienes, after a lag of e.a. 30 min, was observed. Also, mass spectrometry measurements were performed to identify peroxidation products. As a conclusion, steady UVA irradiation of solutions containing Ptr and SoyPC led to the lipid peroxidation of polyunsaturated fatty acids, whereas the Ptr concentration remained unchanged. Ptr showed a clearly enhanced effect on peroxidation rate and steady state concentration of oxidation products. This model constitutes a useful system to study formation of lipid peroxidation intermediaries and products in an aqueous environment to determine the effect of Ptr as photoinducers. [1] A. Catalá, Chemistry and Physics of Lipids, 2009, 157, 1. [2] G. Petroselli, M. L. Dántola, F. M. Cabrerizo, A. L. Capparelli, C. Lorente, E. Oliveros, A. H. Thomas, J. Am. Chem. Soc., 2008, 130, 3001. [3] A. H. Thomas, C. Lorente, K. Roitman, M. M. Morales,M. L. Dántola, J. Photochem. Photobiol. B, 2013, 120, 52.