Antioxidant Capacity, Phenolic and Flavonoid Content in Stalks and Leaves of Three Allium Species

The study compared the total phenolic content (TPC), total flavonoid content (TFC), and scavenging capacity (IC50) of leaves and stalks/bulbs of lokio (Allium chinense G. Don), an underutilised allium species, and compared them with two commercially popular onions, i.e., spring onion (Allium fistulosum L.) and green onion (Allium ascalonicum L.). Extracts of the three alliums exhibited distinct antioxidant capacity, and significant differences existed in TPC, TFC, and IC50 among the three species. The allium stalk/bulb contained significantly higher TPC, TFC, and IC50 than its green leaf counterparts, with a strong correlation (r = 0.9064). It was observed that the TPC of the bulb/stalk of A. chinense (20.20 mg/g GAE FW) was higher as compared to A. fistulosum (19.97 mg/g GAE FW) and A. ascalonicum (19.62 mg/g GAE FW). Meanwhile, in terms of TFC, the bulb of A. ascalonicum contained the highest (5.06 mg/g QE FW), followed by A. chinense (3.63 mg/g QE FW) and A. fistulosum (1.70 mg/g QE FW). Among the three alliums, A. chinense had the highest antioxidant capacity, as indicated by a lower IC50 in the white stalks (97.40 ppm), followed by A. ascalonicum (98.21 ppm) and A. fistulosum (100.80 ppm). This study also revealed strong correlations (r > 0.90) between TPC, TFC, and the antioxidant capacity of tested allium. The results of the current assessment would be useful for future studies and applications of lokio (Allium chinense G. Don) as an alternative to popular spring onion and green onion in food, nutraceuticals, and cosmetic product development.