Flavonoid content of several vegetables and their antioxidant activity

Several vegetables were selected to study their flavonoid contents and anti oxidant activities. The results showed that both green and purple leaves of sweet potatoes (185.01 and 426.82 mg kg(-1) respectively) and the outer le aves of onion (264.03 mg kg(-1)) possessed higher amounts of flavonoids, an d more than 85% of free radical scavenging activities were evaluated by usi ng 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide and hydroxyl radicals. In addition, green leaves of sweet potatoes and the outer leaves of onion s howed higher reducing power and higher antioxidant activity in a Linoleic a cid system as compared to cabbage, spinach, potato and crown daisy. Blanchi ng of green leaves of sweet potatoes for 30-60 s retained more flavonoids a nd higher free radical scavenging activities as compared to more than 1 min of blanching. The storage test showed that green leaves of sweet potatoes stored at 4-10 degrees C maintained better quality than those stored at roo m temperature. (C) 2000 Society of Chemical Industry.