Assessment of kavalactones in kava beverage products and aqueous infusions

Kava (Piper methysticum Forst. f. ) is traditionally used as a beverage for relaxation in social occasions in South Pacific islands. This study was conducted to develop analytical methods for assessing kavalactone content in functional beverage products containing kava, as well as beverages prepared from kava roots by a traditional method involving infusion (mild extraction) with water. Samples of fruit-flavored beverages were prepared by solid-phase or liquid-liquid extraction to remove interfering substances and the major kavalactones (methysticin, dihydromethysticin, kavain, dihydrokavain, yangonin, and desmethoxyyangonin) were separated and identified by GC-FID and GC/EI-MS. A difference in kavalactone content was observed between the 2 commercial beverage products (37.03 compared with 0.044 mg per serving in 240 mL). Kava beverages prepared fresh by water infusion contained much higher levels of kavalactones than the commercial products as determined by a high-performance liquid chromatographic procedure. The results also demonstrated the isomerization of yangonin (Y) in an acidic aqueous solution with exposure to light, with the presence of cis-Y in a fruit-flavored beverage containing kava. The implications of the isomerization of Y on quality and safety aspects have yet to be evaluated. The analytical methods developed in this study are potentially applicable to kavalactone analysis in various nonalcoholic, noncarbonated beverages.