Flavonoids in sanboukan, a citrus fruit,and its antioxidative activity

Abstract

　The characteristics of flavonoids in sanboukan, a citrus fruit, produced mainly in the Wakayama region were examined in this study. Flavonoids (eriocitrin, neoeriocitrin, narirutin, naringin, hesperidin, neohesperidin, didymin, poncirin, 6, 8-C-diglucosylapigenin, diosmin, sinensetin, nobiletin, 6-dimethoxynobiletin, tangeretin, and 6-dimethoxytangeretin) in the peel and juice of sanboukan, related varieties (yutaka-no-takarakan, amanatsu), and others (houraikan, dekopon, unsyu-mikan) were determined using HPLC and examined by analysis of principal component. Eriocitrin, narirutin, hesperidin, and 6, 8-C-diglucosylapigenin were shown to be characteristic substances in the peel of sanboukan, and eriocitrin was a characteristic substance in the juice. 6, 8-C-Diglucosylapigenin was newly shown to be abundant in the peel and juice of sanboukan in this study. Eriocitrin exhibited the highest antioxidative activity of the flavonoids of sanboukan fruit by measurement of the scavenging activity of the DPPH radical. The peel of sanboukan exhibited significantly high antioxidative activity in comparison with other citrus peels. This high activity was suggested to be related to the high total content of flavonoids and to the eriocitrin. The albedo, mesocarp of the fruit, was shown to contain abundant characteristic flavonoids of sanboukan peel. The flavedo, epicarp of the fruit, exhibited the highest levels of antioxidative activity in the structural portions of the fruit (flavedo, albedo, segment epidermis tissue, juice vesicle tissue, and seed).