Quantitative analysis of hydroxylated polymethoxyflavones by high-performance liquid chromatography.

Since the hydroxylated polymethoxyflavones were isolated from orange and other citrus peels, they have been found to exhibit potent anti-cancer and anti-inflammatory activities. Hydroxylated polymethoxyflavones, especially 5-demethylnobiletin and 5-hydroxy-3,6,7,8,3',4'-hexamethoxyflavone, exert more potent activities than their counterpart polymethoxyflavones (PMFs). These findings have led to a new era of exploration of hydroxylated polymethoxyflavones and PMFs from the citrus genus for their potential application in nutraceutical, pharmaceuticals and functional foods. A practical and efficient analytical method for quantitatively characterizing the composition of PMFs has only recently been developed, and has applications both in academic research laboratories and quality controls. However, chemical analyses of the hydroxylated polymethoxyflavones have not been previously described. This paper reports the quantitative analysis of six 5-demethylated PMFs in various commercial orange peel extracts, using high-performance liquid chromatography with UV detection.