Effects of molecular configurations of food colorants on their efficacies as photosensitizers in lipid oxidation

Effects of twelve commercially available synthetic food colorants, including tartrazine, rose bengal, brilliant blue FCF, new coccin, amaranth, erythrosine B, phloxine B, indigo carmine, acid red, fast green FCF, allura red AC and sunset yellow FCF, on photosensitized oxidation of methyl linoleate (MeLe) were investigated. Rose bengal, erythrosine B and phloxine B accelerated oxidation of MeLe under light exposure and their pro-oxidative effects were concentration-dependent. Light exposure of MeLe with added colorants induced generation of hydroperoxide isomers, including 10-cis,trans- and 12-cis,trans-MeLe hydroperoxide, suggesting that the food colorants served as photosensitizers under the present conditions. The addition of α-tocopherol or β-carotene effectively suppressed the oxidation of MeLe, and their antioxidative effects were concentration-dependent. Neither α-tocopherol nor β-carotene altered the distributions of hydroperoxide isomers of MeLe. This study showed that the food colorants containing a xanthene skeleton increased their potential as photosensitizers with increase in both the number and atomic mass of halogen substituents on the xanthene skeleton.