Evaluation of Flavonoids and Monoterpenes in the Sour Citrus Fruit, “Bushukan”

Abstract

This study determines the flavonoid composition of “bushukan”, a citrus fruit mainly cultivated in the Hata district of Kochi, Japan. The fruit was harvested in August, September, and December, and flavonoids in the flavedo, albedo, and juice were measured. In September, fruits were harvested from three different fields. Flavonoid contents of the comparative “naoshichi” and kabosu (Citrus sphaerocarpa) fruits were also measured. “Bushukan” was found to contain the flavanones hesperidin, narirutin, and naringin, and the polymethoxyflavones nobiletin and tangeretin. Narirutin and naringin contents were notably higher in “Bushukan” compared with naoshichi and kabosu. “Bushukan” harvested in August had the highest compositions of these flavonoids. Flavonoid content variance between crop fields was small. The contents of aromatic components, limonene and myrcene, in the flavedo were also measured. Myrcene content in “bushukan” was the highest, especially in fruits harvested in September. The suppression effect of flavedo extract on the degranulation in RBL-2H3 cells was evaluated. The flavedo extract of “Bushukan” which was harvested in August and September showed the suppression effect.