Investigation and Identification of Antioxidative Flavonols, Quercetin and Kaempferol Glycosides in the Unused Parts of 10 Types of Food Plants Commonly Consumed in Japan.

The antioxidative flavonols, quercetin and kaempferol in the unused parts of 10 types of food plants commonly consumed in Japan were determined by paper chromatography and ultraviolet spectroscopy. The purpose was to determine a whether these portions might be usable as an antioxidant to protect foodstuffs from oxidation. The leaves of burdock and moroheiya and used tea leaves were found to contain an abundance of quercetin glycosides. These were isolated and identified as quercetin 3-O-ramnoglucoside (substance 1(Tables 1,2))(burdock), quercetin 3-O-ramnoside (substance 5)(moroheiya), and quercetin 3-O-glucoside (substance 4)(used tea leaves). The leaves of persimmon and peach trees contained a large amount of kaempferol glycosides, and these were isolated and identified as kaempferol 3-O-glucoside (substance 2(Tables 1,2))(persimmon), and kaempferol 3,7-O-glycoside-(substance 3)(peach tree). Among the flavonols, quercetin 3-O-glucoside (substance 1) from the leaves of burdock, and kaempferol 3,7-O-glycoside (substances 3 and 10) from the leaves of peach tree and ume (Japanese apricot) tree are the first reported here. Our data will provide a basis for the possible utilization of the leaves of burdock, persimmon and peach trees, and used tea leaves as antioxidants to protect foodstuffs from oxidation.