HPLC analysis of flavokavins and kavapyrones from Piper methysticum Forst.

A simultaneous HPLC separation of the six major kavapyrones and the flavokavins A–C in an ethanolic extract of Piper methysticum was carried out on a Symmetry C18 column. For quantitative determinations of the flavokavins, calibration curves with correlation coefficients between 0.9986 and 0.9998 were established. Detection limit for each flavokavin of 0.5 ng per injection was measured at 355 nm. The precision of the HPLC analysis was verified by six determinations of the content of flavokavins in the kava extract. Flavokavins A–C contents of 0.62 ± 0.01 mg/100 mg, 0.34 ± 0.01 mg/100 mg and 0.14 ± 0.003 mg/100 mg ethanolic kava extract was found, respectively. From the corresponding relative standard deviation of 1.53, 1.99 and 2.30% the confidential interval (P = 95) of the mean value was calculated for each flavokavin. The accuracy of the method was proven by recoveries between 99.2 ± 0.3% and 101.1 ± 0.4% for the flavokavins A–C.