Orange Peel: Low Cost Agro-waste for the Extraction of Polyphenols by Statistical Approach and Biological Activities

Abstract

Food waste is an excellent source of various bioactive secondary metabolites. In addition, food waste is a global issue, and more research is being focused on the conversion of value-adding products from food waste, especially fruits. In this study, bioactive polyphenols were extracted from orange peels. The parameters that affect the extraction of polyphenols from orange peels were optimized using response surface methodology. Ethanol was used to extract bioactive polyphenols, and the extraction time (min), extraction temperature, and ethanol concentration (%) were analyzed. Orange peels are an excellent source of polyphenols, and the yield was increased under optimized extraction conditions (p<0.05). The polyphenol content increased twofold (38.4 mg GAE/g) under the optimized extraction conditions (53% ethanol, 51 degrees centigrade and 96 min extraction time). Crude polyphenols exhibited significant antibacterial activity against Bacillus subtilis (19±1 mm zone of inhibition), followed by Staphylococcus aureus (17±2 mm zone of inhibition) (p<0.05). In addition, orange peel extract exhibited antifungal activity against A. flavus and C. albicans. The ethanol extract exhibited DPPH activity (1.61±0.03 mg GAE/100 g) and ABTS reducing power (1.48±0.01 mg GAE/100 g). The polyphenol compounds exhibited antibiofilm activity against biofilm-producing Bacillus subtilis and increased in a dose-dependent manner (p<0.05).