Simultaneous HPLC-DAD analysis of four methylated flavonols in Amomum koenigii

Four bioactive methylated flavonols isolated from Amomum koenigii J.F. Gmelin, 3,7-dihydroxy-5,3',4'-trimethoxyflavone (1), 5-hydroxy-3,7,4'-trimethoxyflavone (2), 3,7-dihydroxy-5,4'-dimethoxyflavone (3), and 5-hydroxy-3,7,3',4'-tetramethoxyflavone (retusin, 4), have been analyzed by HPLC–DAD on a 4.6 mm × 150 mm, 5-µm particle, C8 column with an acetonitrile–aqueous acetic acid gradient as mobile phase. UV detection was at 360 nm. The method was validated in detail. The results indicated that the total amounts of these four constituents in the seeds were 0.776–0.829%, higher than in the pericarp. Retusin was the major constituent with a maximum content of approximately 0.50% in the seeds. This method is useful for quality control of the crude drug.