Electrospray high performance liquid chromatography mass spectrometry in phytochemical analysis of kava (Piper methysticum) extract

HPLC coupled with electrospray (ES) MS was used to study a chloroform extract from kava roots (Piper methysticum). A total of thirteen kavalactones and flavokavains were identified. Seven major kavalactones, methysticin (4), dihydromethysticin (5), kavain (6), 7,8-dihydrokavain (7), 5,6-dehydrokavain (8), 5,6-dehydromethysticin (9) and yangonin (10), were easily recognized in the extract by their [M + H](+) or [M + Na](+) ions, UV spectra, and retention times, compared with those of standard compounds. Six minor constituents were isolated as our own reference compounds. These constituents were identified by their [M + H](+) or [M + Na](+) ions, UV spectra and NMR data as 11-hydroxy-12-methoxydihydrokavain (1), 7,8-dihydro-5-hydroxy-kavain (2), 11,12-dimethoxydihydrokavain (3), and flavokavains A, B and C (19, 20, 21). HPLC-ES-MS appears to be a suitable technique for identification of kavalactones and kavachalcones in the kava extract. The method also provides direct guidance for identification of other trace constituents from kava extracts.