This study investigated the antioxidant and cytotoxic effect of oxidized lutein using human cervical carcinoma cell lines (HeLa). Liposome contained phosphatidylcholine (20 micromol) in Tris-HCl buffer and lutein (200 micromol) was exposed to sunlight for 100 min. Photo-oxidized lutein products were characterized by LC-MS (APCI(+)) and studied for their antioxidant property and apoptosis in terms of cell viability, glutathione and malondialdehyde (MDA) levels. Photo-oxidized lutein fragmented ions were identified as 523 (M+ + H+-3CH3), 476 (M+ + H+-6CH3), 551 (M+ + H+-H2O) and its isomers as 13-Z lutein, 13'-Z lutein, 13-Z zeaxanthin, all-E zeaxanthin, 9-Z lutein, 9'-Z lutein. Free radical scavenging activity of oxidized lutein was higher by 45.9% (IC(50), 3.71 microg) than lutein (IC(50), 5.28 microg). Oxidized lutein lowered the lipid peroxidation by 20.7% than lutein. The viability of HeLa cells, glutathione and MDA levels were decreased by 64%, 40% and 18% than lutein. To conclude, oxidized lutein may be highly reactive, since oxidation results in radical ions, which can combine with similar reactive oxidative species that could lead to higher antioxidant effect. This may be true in this study that antioxidant property of oxidized lutein was higher than lutein that correlates with free radical scavenging activity and cytotoxic effects on HeLa cells.