Preparative isolation and purification of polymethoxylated flavones from Tangerine peel using high-speed counter-current chromatography.

Several polymethoxylated flavones including nobiletin, 3,5,6,7,8,3',4'-heptamethoxyflavone, tangeretin and 5-hydroxy-6,7,8,3',4'-pentamethoxyflavone were separated from Tangerine peel (Juhong in Chinese) by high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (1:0.8:1:1, v/v). Then, 26 mg of nobiletin, 6 mg of 3,5,6,7,8,3',4'-heptamethoxyflavone, 35 mg of tangeretin and 11 mg of 5-hydroxy-6,7,8,3',4'-pentamethoxyflavone could be obtained from 150 mg crude extracts and their purities were 98.6%, 95.9%, 99.8% and 96.8%, respectively. All these constituents were identified by EI-MS and 1H NMR.