Composition and content of flavonol glycosides in broccoli florets (Brassica olearacea) and their fate during cooking

Abstract

The two main flavonol glycosides present in broccoli florets were identified as quercetin 3-O-sophoroside and kaempferol 3-O-sophoroside. Three minor glucosides of quercetin and kaempferol were also detected, namely isoquercitrin, kaempferol 3-O-glucoside and a kaempferol diglucoside. The sophorosides of quercetin and kaempferol were present in raw florets at a level of 65 mg kg−1 and 166 mg kg−1 fresh weight, respectively. The total content of quercetin and kaempferol glycosides expressed as aglycone was 43 and 94 μg g−1 fresh weight, respectively, and these agree with other recently published data. During the cooking process only 14–28% of the individual glucosides were retained in the cooked tissue, the remainder being largely leached into the cooking water with only a small loss attributed to the formation of the respective aglycones. © 1998 SCI.