title: In vitro cytotoxicity of nonpolar constituents from different parts of kava plant (Piper methysticum).
abstract: Kava (Piper methysticum), a perennial shrub native to the South Pacific islands, has been used to relieve anxiety. Recently, several cases of severe hepatotoxicity have been reported from the consumption of dietary supplements containing kava. It is unclear whether the kava constituents, kavalactones, are responsible for the associated hepatotoxicity. To investigate the key components responsible for the liver toxicity, bioassay-guided fractionation was carried out in this study. Kava roots, leaves, and stem peelings were extracted with methanol, and the resulting residues were subjected to partition with a different polarity of solvents (hexane, ethyl acetate, n-butanol, and water) for evaluation of their cytotoxicity on HepG2 cells based on the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and lactate dehydrogenase and aspartate aminotransferase enzyme leakage assays. Organic solvent fractions displayed a much stronger cytotoxicity than water fractions for all parts of kava. The hexane fraction of the root exhibited stronger cytotoxic effects than fractions of root extracted with other solvents or extracts from the other parts of kava. Further investigations using bioassay-directed isolation and analysis of the hexane fraction indicated that the compound responsible for the cytotoxicity was flavokavain B. The identity of the compound was confirmed by (1)H and (13) C NMR and MS techniques.
authors.affiliation: National Center for Toxicological Research, U.S. Food and Drug Administration, HFT-230, 3900 NCTR Road, Jefferson, Arkansas 72079, USA. jjhoo@kangwon.ac.kr
authors.forename: Jin-Woo
authors.initials: JW
authors.lastname: Jhoo
authors.forename: James P
authors.initials: JP
authors.lastname: Freeman
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Heinze
authors.forename: Joanna D
authors.initials: JD
authors.lastname: Moody
authors.forename: Laura K
authors.initials: LK
authors.lastname: Schnackenberg
authors.forename: Richard D
authors.initials: RD
authors.lastname: Beger
authors.forename: Klaus
authors.initials: K
authors.lastname: Dragull
authors.forename: Chung-Shih
authors.initials: CS
authors.lastname: Tang
authors.forename: Catharina Y W
authors.initials: CY
authors.lastname: Ang
mesh_terms: D001219:Aspartate Aminotransferases / Q000378:metabolism; D002460:Cell Line; D056486:Chemical and Drug Induced Liver Injury; D005419:Flavonoids / Q000633:toxicity; D020901:Kava / Q000737:chemistry* / Q000633:toxicity*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D000432:Methanol; D010936:Plant Extracts / Q000633:toxicity*; D018515:Plant Leaves / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry; D018547:Plant Stems / Q000737:chemistry; D012997:Solvents
chemical_list: D005419:Flavonoids; D010936:Plant Extracts; D012997:Solvents; C452039:flavokawain B; D007770:L-Lactate Dehydrogenase; D001219:Aspartate Aminotransferases; D000432:Methanol