Chemical composition, antioxidant, antibacterial and tyrosinase inhibition activities of extracts from Newhall navel orange (Citrus sinensis Osbeck cv. Newhall) peel.

Newhall navel orange (Citrus sinensis Osbeck cv. Newhall) is the major navel orange cultivar planted in China. Currently, almost all Newhall navel orange peels produced here are discarded, which are not only harmful to the environment but also a total waste of resource. Therefore, it is very important and necessary to carry out researches exploring the utilization potential of this resource.The 95% ethanol extract (EE) of Newhall orange peel was prepared and fractionated into three subextracts as PEE (petroleum ether extract), EtOAcE (ethyl acetate extract), and WE (water extract) by simple liquid/liquid extractions. These four extracts were then subjected to antioxidant, antibacterial, and tyrosinase inhibition assay. Interestingly, EtOAcE was significantly superior to all other three extracts, exhibiting the best biological effects tested. Furthermore, TPC (total polyphenol content), TFC (total flavonoid content), and primary individual flavonoids of these four extracts were analysed and compared, which were followed by PCA (principal component analysis) and Pearson's correlation test. The result indicates that the primary bioactive compounds responsible for the biological effects of the EtOAcE are of sinensetin, 4',5,6,7-tetramethoxyflavone, nobiletin, 3,3',4',5,6,7-hexamethoxyflavone, and narirutin. In view of its easy preparation and potent biological effects, EtOAcE might demonstrate great application potential in various industrial areas.This study successfully identified EtOAcE as a potent naturally occurring antioxidant, antibacterial, and tyrosinase inhibitory agents, which might contribute to the value-added utilization of Newhall navel orange peel in food, cosmetic, and pharmaceutical industries. This article is protected by copyright. All rights reserved.