Varietal Differences in Quercetin Contents and Antioxidant Capacities of Onions

Contents of quercetin glucosides, antioxidant capacities (ORAC method), and total polyphenol contents were compared among 9 cultivars of onions harvested in Hokkaido, Japan. The contents of quercetin glucosides ranged from 31.24 +/- 2.15 to 133.7 +/- 8.88 mu mol/100 g fresh weight. ORAC values and total polyphenol contents ranged from 878.1 +/- 44.7 to 2 075.6 +/- 168.6 mu mol Trolox equivalent/100 g fresh weight, and 22.65 +/- 1.41 to 48.44 +/- 1.35 mg gallic acid equivalent/100 g fresh weight, respectively. Tsukikou 24 showed the highest quercetin content, ORAC value, and total polyphenol contents. Tsukikou 24 was the richest in quercetin derivatives among the onion cultivars; hence, it is suggested that its extract showed the highest antioxidant capacity.