In Vitro Chlorophyll Degradation Involved in Flavonoid Radical Formed by Chlorophyll-degrading Peroxidase in Flavedo Extract of Citrus nagato-yuzukichi Fruit

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