Phenolic and antioxidant evaluation of the aqueous and ethanol extracts of unripe Citrus reticulata peels

Abstract

Citrus reticulata is a widely consumed citrus fruit in Nigeria, but its potential as a source of alternative medicine has been poorly explored. The present study, therefore attempts to evaluate the phenolic, tannin, flavonoids and proanthocyanidin contents as well as the free radical scavenging activity of the aqueous and ethanol extracts of the peels of unripe Citrus reticulata and was carried out using standard methods. Results from the quantitative phytochemical analysis revealed that the total phenols for both the aqueous and ethanol extracts were 52.50±0.21 and 23.750 ± 0.271 mg GAE/g extract, tannins 29.60±0.25 and 13.006± 0.326mg TAE/g extract, flavonoids 22.96±5.05 and 04.207 ± 5.803 mg QE/g extract and proanthocyanidin 332.75±16.42 and 127.750± 11.755mg AAE/g extract respectively. There was a concentration- dependent increase in the scavenging activity of 1,1–diphenyl–2–picrylhydrazyl (DPPH) radical, Ferric Reducing Antioxidant Power (FRAP), nitric oxide reducing power. The results suggest that the extracts of unripe peels of Citrus reticulata possess appreciable antioxidant activity due to the presence of important phytochemicals, which may be of high nutraceutical and pharmaceutical importance.

Keywords: Citrus reticulata, Phenols, Flavonoids, Proanthocyanidin, Antioxidant