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.