THE REDUCING POWER AND DPPH FREE RADICAL SCAVENGING ACTIVITY OF POLYPHENOLS FROM ETHANOL EXTRACT OF ALLIUM CEPA L. LEAVES AND PEEL

Abstract

Abstract
Onions have a wide range of uses in the chemical and food industries including increasing product, as ingredients in food, substrate for enzyme production, and as colourant in some dishes. The study evaluated the tannin, flavonoids, and phenolic contents of the ethanol extract of onion peel and leaves as well as the 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity and reducing power. The total antioxidant capacity, flavonoids, tannins, and phenol contents of the extracts were assessed using standard methods. The In-vitro antioxidant activities (reducing power activity and DPPH free radical scavenging activity) were also estimated using standard methods. The results showed that the total phenol and tannins content of the onion leaf extracts (258.00±6.00 and 254.70±6.03) was significantly higher (p<0.05) compared to the onion peel extract (110.70±1.20 and 67.33±4.04). Conversely, the total flavonoid content of the onion peel extract (1.30±0.02) was significantly higher (p<0.05) relative to the onion leaves extract (0.38±0.02). One-way ANOVA revealed a non-significant (p>0.05) increase in the total antioxidant activity of onion leaf extract (0.63±0.03) compared to the onion peel extract (0.53±0.03). Conclusively, the ethanol extract of onion leaves and peel contains varying amounts of tannins, phenols and flavonoids with strong antioxidant properties. These compounds can be extracted from onion leaves and peels that are usually discarded to serve as antioxidants for improving livestock and human health