Roots and extracts of the kava plant have been used in herbal medicine to treat sleep disturbances, stress and anxiety, although reported cases of liver toxicity led to many countries restricting its sale. The detection of the presence of kava in many medicinal products requires the use of methods capable of identifying the kavalactones with high certainty. Here we describe the use of FT-ICR-MS for the characterisation of six kavalactones (kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin and desmethoxyyangonin) utilising accurate mass measurement for the determination of their elemental formulae and product ion MS (both SORI-CID and IRMPD) for structural confirmation. HPLC-FT-ICR-MS with a dual spray system for internal calibration of mass spectra was employed for accurate mass measurement and the determination of elemental formulae of the kavalactones in both standards and a root extract to confirm the presence of the kavalactones in the root powder. Mass accuracy of < 1 ppm was achieved. For structural confirmation, the IRMPD and SORI-CID spectra of the kavalactones in standards and a kava root powder extract were compared. Accurate mass measurement of the product ions was also conducted by external calibration and the elemental formula determined to aid with structural confirmation. The presence of the same fragment ions detected in the standards as in the extract further confirmed the presence of the kavalactones in the kava root powder with high certainty.

Keywords: FT-ICR-MS, SORI-CID, IRMPD, structural characterisation, accurate mass measurement, HPLC-FT-ICR-MS, kava (piper methysticum), dual spray