Extraction and Characterization of Antioxidant from Orange Peels

Antioxidants are substances which are able to prevent or inhibit oxidation processes in human body as well as in food products. Natural antioxidants have gained considerable interest in recent years for their role in preventing the auto oxidation of fats, oils and fat containing food products by replacing synthetic antioxidants. In this study, orange peel was selected as a source of natural antioxidant. The aim of this study was to investigate the antioxidant yield and antioxidant activity of two different varieties of orange peels namely Washington and Valencia using maceration extraction method with ethanol-water mixture binary solvent. Extraction yield was checked at different levels of extraction conditions. The extraction yield obtained ranged from 18-29% for Washington and 14.4-25.9% for Valencia. From the model regression equation developed, the linear terms of temperature, concentration and time had positive effect on response yield. The quadratic terms (pure and interaction quadratic terms) had negative effect on extraction yield except AB interaction for Valencia extract. Concentration had a more weighty linear effect on yield as compared to extraction temperature and time. Response yield was positively affected by linear terms and negatively affected by quadratic terms for Washington extract. From the linear effects, concentration had the highest positive effect on yield; and from quadratic effects, C2 had the highest negative effect. Antioxidant potential was examined by measuring total phenolic content (TPC), total flavonoid content (TFC), 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (RSA) using spectrophotometer. The total phenol content ranged from 29.24 to 135.22 mg GAE/g extract for Washington and 61.94 to 182.58 mg GAE/g extract for Valencia. The total flavonoid content of Washington extract was 22.120 mg CAT/g extract and for Valencia, it was 25.456 mg CAT/g extract. DDPH radical inhibition activity ranged from 47.07 to 92.80 % for Washington and 55.91 to 93.40% for Valencia. Hence, Valencia extract has more potent in free radical inhibiting activity. Antioxidant potential of the extract was also examined by IC50 (concentration of extract or sample at which 50% of free radicals were inhibited). It was determined using linear regression. The IC50 value for Washington and Valencia, it was 1.1269mg/ml and 0.6731mg/ml respectively. The lower IC50 value the more potent antioxidant activity. Hence, Valencia extract has more potential in antioxidant activity than Washington extract. Keywords: Citrus sinensis, Orange peel, Total phenol content, Total flavonoid content, Antioxidant activity, DPPH free radical scavenging activity.