Stability of meoru (Vitis coignetiea) anthocyanins under photochemically produced singlet oxygen by riboflavin

Abstract

This study investigated the stability of meoru (wild vine grape) anthocyanins in the aqueous solution under singlet oxygen. Freeze-dried meoru (1 kg) contained 179.98 mg anthocyanins including delphinidin-3-glucoside, malvidin-3,5-diglucoside, cyanidin-3,5-diglucoside, malvidin-3-glucoside, and cyanidin-3-glucoside. Malvidin-3,5-diglucoside and cyanidin-3-glucoside were the meoru anthocyanins at the highest and the lowest concentration, respectively. Little decrease in total anthocyanins in the aqueous solution was observed in the dark with or without riboflavin, or with light without riboflavin. Singlet oxygen degraded the meoru anthocyanins in the aqueous solution, which suggested chemical quenching of singlet oxygen by the anthocyanins. Degradation of the meoru anthocyanins was structure-dependent; diglucoside anthocyanins were more stable than monoglucoside. And malvidin glucoside was more stable than delphinidin or cyanidin glucoside, which suggested the number of hydroxy groups in the structure was partly related with the anthocyanin stability under singlet oxygen. This is the first report on anthocyanins stability affected by its structure under singlet oxygen.