Studies On The Isolation Of Chemical Components In Ponkan Peels And Their Antioxidant Activity

China is rich in citrus resource and the second largest country of citrus fruit production. During domestic citrus fruit processing, a large amount of by-product such as the peels was produced. Therefore it was essential to develop the utilization way of functional peels.Epidemiological studies and animal tests show that the citrus fruit is rich in flavonoids, carotenoids, limonin, and other types of substances with bioactive function including antioxidant activity, anti-cancer, anti-inflammatory, anti-bacterial and anti-allergic, etc. So it was expected to utilize the bioactive constituents citrus fruit for functional food. The present study focuses the extraction, isolation and antioxidant activity of chemical components in the peels ponkan belong to citrus fruits.Ponkan peels was extracted with 90% ethanol, partitioned with petroleum ether, ethyl acetate, chloroform and n-butanol after the extraction solution was concentrated to yield petroleum ether extract, ethyl acetate extract, chloroform extract and n-butanol extract which were used for separation of chemical components.Ethyl acetate extract was separated with high-speed countercurrent chromatography(HSCCC) with a solvent system composed of petroleum ether -ethyl acetate -mathanol-water (1: 1: 1: 1.5, V/V). In each separation, a HSCCC instrument with 400ml-column was loaded 2 g of ethyl acetate extract resulting in 27.5 mg of component A, 43.1 mg of component B, and 20.7 mg of 5,6,7,8,3',4'-hexamethoxyflavone (nobiletin) with a purity more than 98%. Components A, B were separated by preparative HPLC to yield 5,7,8,3',4'-pentamethoxyflavone (12.5mg), 5,6,7,3',4'-pentamethoxyflavone (sinensetin ) (11.9mg ) and 5,7,8, 4'-tetramethoxyflavone (12.3mg).2 g of butanol extract was separated with HSCCC to yield a component which was subjected to preparative HPLC separation resulting 28.3mg of synephrine with a purity of over 98%.The chemical of the five compounds were identified by ESI-MS and NMR spectra. The antioxidant activity of the petroleum ether extract, ethyl acetateextract, chloroform extract, n-butanol extract and the five compounds were assayed by scavenging rate of DPPH free radical and O₂^- free radical. The Results showed that only ethyl acetate extract and n-butanol extract possess higher antioxidant activity, the other extracts and compounds showed lower antioxidant activity. The ethyl acetate extract and n-butanol extract gave about 75% antioxidant activity of Vc at a concentration of 80ug/ml.The research results of this paper will provide scientific basis and technological support since many literatures show methoxyflavones possess bioactivity of anit-cancer and synephrine possess bioactivities of lowering fat and blood pressure.