The methoxyflavones in Citrus reticulata Blanco cv. ponkan and their antiproliferative activity against cancer cells

The major polymethoxyflavones in the fruit (ponkan) peels of Citrus reticulata Blanco cv. ponkan were identified as isosinensetin, sinensetin, nobiletin and tetramethyl-o-scutellarein by a combined separation using high-speed countercurrent chromatography and preparative high performance liquid chromatography, and structure elucidation by electrospray ionisation mass spectrometry (ESI-MS) and ¹H and ¹³C nuclear magnetic resonance (NMR). The antiproliferative activity of the four compounds against four cancer cell lines (A549, HL-60, MCF-7 and HO8910) showed that isosinensetin had a lower IC₅₀ value for MCF-7 and HO8910 cancer cell lines. Determination of polymethoxyflavones in ponkan peels from different cultivation regions displayed relatively steady contents of the four compounds and a higher content of isosinensetin, which suggested that ponkan peels are excellent sources of functional polymethoxyflavones that may help prevent female cancers, such as ovarian cancer and breast cancer.