Antioxidant and taste properties of fresh onion (Allium cepa L.) leaves

We characterized the antioxidant properties and taste quality of fresh onion leaves compared with those of welsh onion (Allium fistulosum L.) (green-leafed small variety), which taste similar. In fresh onion leaves, the total oxygen radical absorbance capacity value and 1, 1-diphenyl-2-picrylhydrazyl free radical-scavenging activity were the same as in welsh onion. However, the total quercetin concentrations in fresh onion leaves were markedly higher than in welsh onion. The concentrations of total vitamin C, beta-carotene, and chlorophylls were almost the same in the fresh onion leaves and welsh onion. In addition, the sourness and bitterness of taste responses and Brix for fresh onion leaves were higher and lower, respectively, than for welsh onion. The 5 '-guanylate concentration was higher in fresh onion leaves than in welsh onion, and some free amino acids, citric acid and total organic acid concentrations were lower in fresh onion leaves than in welsh onion. These results indicate that fresh onion leaves are good dietary sources of some antioxidants, such as quercetin, vitamin C, beta-carotene, and chlorophylls. In addition, the taste of fresh onion leaves is sour and lower bitterness and sweetness than welsh onion, which is due to differences in some taste profile components.