In vitro chlorophyll degradation involved in flavonoid radical formed by chlorophyll-degrading peroxidase in flavedo extract of Citrus nagato-yuzukichi fruit

摘要

Effects of flavonoid radical formed by a chlorophyll (Ch1)-degrading peroxidase in the flavedo extract of the green sour citrus, Nagato-yuzukichi (Citrus nagato-yuzukichi hort. ex Y. Tanaka) fruit on in vitro Ch1 degradation were determined. Adding hydrogen peroxide accelerated the Ch1 breakdown by the flavedo extract which included flavonoids and a Ch1-degrading peroxidase. During Ch1 degradation, naringin, hesperidin, and neohesperidin were rapidly oxidized, but only naringin was involved in Ch1 degradation by Ch1(-) degrading peroxidase. This enzymatic degradation in the flavedo extract was suppressed by the addition of scavengers of radical and superoxide anions. The superoxide formed by a xanthine-xanthine oxidase system and a superoxide dismutase, however, had little effect on Ch1 degradation. MnCl2, which is a superoxide anion scavenger, also inhibited the flavonoid oxidation. These findings indicate that the naringin radical formed by a Ch1-degrading peroxidase in the flavedo could be related to Ch1 degradation.