Flavonoid composition and antioxidant activities of Chinese local pummelo (Citrus grandis Osbeck.) varieties

China is one of the most important diversity centres of the genus Citrus L. and is particularly rich in pummelo germplasm. In this study, the flavonoids in the peels and pulps of 28 Chinese local pummelos and four grapefruits were determined by optimised Ultra Performance Liquid Chromatography (UPLC), and their antioxidant capacities were evaluated using 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH), ferric reducing/antioxidant power (FRAP) and superoxide anion methods. We found that naringin was the predominant flavonoid in pummelo, while naringin and neohesperidin were the predominant flavonoids in grapefruit. The fruit peels of Citrus paradisi cvs. Rio Red and Cocktail had the highest contents of naringin (9871.69 mg/kg FW) and neohesperidin (7011.15 mg/kg FW), respectively. Overall, C. paradisi cvs. Cocktail, Rio Red and Changshanhuyou, Citrus grandis cvs. 28-19, Chandler, and Hongxinyou contained more flavonoids and exhibited higher antioxidant capacities and are potentially good sources of phytochemicals and natural antioxidants.