Preparation of a polymethoxyflavone-rich fraction (PRF) of Citrus sunki Hort. ex Tanaka and its antiproliferative effects

The peel of Citrus sunki is a rich source of polymethoxyflavones (PMFs). In this study, a PMF-rich fraction (PRF) was obtained from the peels of C. sunki by hot-water extraction and subsequent fractionation with n-hexane. Six PMFs and two demethylated PMFs were isolated by semi-preparative HPLC, and their structures were identified by 1H NMR and 13C NMR. To define the synergistic effects of PRF, the PRF and its eight individual components were assessed for antiproliferative activity using HL-60 cells. The PRF showed greater growth inhibitory activity (IC50 value = 25.14 μg/ml), compared with its individual components. Flow cytometric analysis confirmed that the PRF significantly increased the percentage of sub-G1 cells (30.1% at 25 μg/ml). Our study provides an efficient method for preparing a PRF for use as a functional food ingredient.