Characteristics of flavonol glycosides in bean (Phaseolus vulgaris L.) seed coats

Seed coats of coloured dry beans contain biologically active compounds. Flavonol glycosides were identified from acetone extracts of seed coats of black beans, pinto beans, and red kidney beans and evaluated for antioxidant activity. High Performance Liquid Chromatography - Mass Spectrometry/Mass Spectrometry (HPLC-MS/MS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging capacity were used to measure flavonols and antioxidant capacity, respectively. The main flavonol glycosides in black beans were the 3-O-glycosides of kaempferol, quercetin and myricetin; pinto beans contained kaempferol 3-O-glycosides, while red kidney beans contained quercetin 3-O-glycoside and quercetin 3-O-rutinoside (rutin). A flavonol triglycoside was identified in dark red kidney bean. Despite differences in total flavonol content, extracts from Eclipse, (black bean) and Windbreaker (pinto bean) had the significantly higher antioxidant activities than other bean seed coats. Results suggest seed coats of Windbreaker and Eclipse may have potential as functional food ingredients, though benefits may not be simply due to flavonols.