Determination of Flavonoid Contents and Evaluation of in vitro Antioxidant Activities of the Extract of Selected Citrus Fruit Peel

Abstract

Flavonoids capture and neutralize the oxidative agents, and quench free radicals. The peel which represents almost one half of the fruit mass has been found to be the main sources of total phenols and flavonoids in the citrus fruit. In present study, flavonoid content and in vitro antioxidant activities of ethanol extracts from some selected citrus fruit peels grown in Ethiopia were determined. Colorimetric aluminum chloride was used for flavonoid content determination. In vitro antioxidant properties of the citrus fruit peels were determined by measuring DPPH and Nitric Oxide radical scavenging activity, and reducing power. The study result showed that lemon peel contained significantly the highest flavonoid content (8.88 ± 0.621 mg of quercetin equivalent/g of extract) at 100 µg/ml concentration. When compared to vitamin C used as standard, lemon peel extract showed significantly higher DPPH radical scavenging of 75.60 ± 2.4 %. Lime peel extract showed highest (0.38 ± 0.01) reducing power activity at 1000 µg/mL concentrations. Strong linear correlations was observed between flavonoid contents of selected citrus peel extract and DPPH free radical scavenging activity (r = 0.975, p = 0.025). Overall, in vitro antioxidant potential of citrus fruit peels extract grown in Ethiopia was confirmed and correlation between in vitro antioxidant activity and flavonoid content of citrus peel extract showed different trends. Further analysis is required to purify specific structure of flavonoid components of citrus fruit peel from Ethiopian cultivar using advanced purification techniques.