Kava Does Not Display Metabolic Toxicity in a Homogeneous Cellular Assay

Abstract

To determine whether kava (Kava kava, ‘Awa, Yaqona, Piper methysticum Forst.), the popular herbal product associated recently with possible human hepatotoxicity, is bioactivated by cytochrome P450 enzymes to cytotoxic metabolites, three kava lactones (methysticin, yangonin, and desmethoxyyangonin) and an ethanolic extract of dried kava root were incubated over time in culture with MCL-5 cells, a human lymphoblastoid cell line that has been stably transfected with five human P450’s (CYP 1A1, 1A2, 2A6, 2E1, and 3A4) and human epoxide hydrolase. Incubations were performed concurrently with a control cell line (cH2) that is derived from the same parental line as MCL-5, but transfected with two empty vectors. The kava compounds displayed varying degrees of toxicity (IC₅₀ values ranged from 50 to > 100 μM) to the MCL-5 and cH2 cell lines; however, both cell lines were equally sensitive to the test compounds. These results suggest that the parent compound for each of the four test compounds was primarily responsible for the observed cell toxicity and that CYP 1A1, 1A2, 2A6, 2E1, and 3A4 or epoxide hydroxylase did not appear to be involved. Thus, in vitro kava does not appear to be activated to toxic metabolites by enzymes known to be important in metabolic toxicity.

References

• 1 Lebot V, Merlin M D, Lindstrom L. Kava: The Pacific drug. Psychoactive plants of the world. New Haven; Yale University Press 1992 vii: 255
• 2 Norton S A, Ruze P. Kava dermopathy.  J Am Acad Dermatol. 1994;  31 89-97
• 3 Stickel F, Baumuller H M, Seitz K, Vasilakis D, Seitz G, Seitz H K. et al . Hepatitis induced by Kava (Piper methysticum rhizoma).  J Hepatol . 2003;  39 62-7
• 4 Russmann S, Lauterburg B H, Helbling A. Kava hepatotoxicity.  Ann Intern Med. 2001;  135 68-9
• 5 From the Centers for Disease Control and P revention. Hepatic toxicity possibly associated with kava-containing products - United States, Germany, and Switzerland, 1999 - 2002.  JAMA. 2003;  289 36-7
• 6 Schmidt P, Boehncke W H. Delayed-type hypersensitivity reaction to kava-kava extract.  Contact Dermatitis . 2000;  42 363-4
• 7 Singh Y N, Devkota A K. Aqueous kava extracts do not affect liver function tests in rats.  Planta Medica. 2003;  69 496-9
• 8 Mathews J M, Etheridge A S, Black S R. Inhibition of human cytochrome P450 activities by kava extract and kavalactones.  Drug Metab Dispos. 2002;  30 1153-7
• 9 Unger M, Holzgrabe U, Jacobsen W, Cummins C, Benet L Z. Inhibition of cytochrome P450 3A4 by extracts and kavalactones of Piper methysticum (Kava-Kava).  Planta Medica. 2002;  68 1055-8
• 10 Johnson B M, Qiu S X, Zhang S, Zhang F, Burdette J E, Yu L. et al . Identification of novel electrophilic metabolites of Piper methysticum Forst. (Kava).  Chem Res Toxicol. 2003;  16 733-40
• 11 White K D, Hartman N, Strong J, Musser S M. Metabolism of kava pyrones to glutathione reactive metabolites. Abstract. 51st American Society of Mass Spectroscopy, July 8 - 12, 2003 Montreal, Canada;
• 12 Guarino R D, Xia H, Parikh S, Patten C, Crespi C, Dike L. A rapid homogenous method for metabolic toxicity screening. Poster. Eurolab Automation 2001
• 13 Zou L, Harkey M R, Henderson G L, Sakai Y, Li A P. Human P450 inhibitory potential of Kava (Kava-kava, 'Awa, Yaqona, Piper methysticum). Phytomedicine 2004: in press
• 14 Lebot V, Levesque J. Genetic control of kavalactone chemotypes in Piper methysticum cultivars.  Phytochemistry. 1996;  43 397-403
• 15 Malsch U, Kieser M. Efficacy of kava-kava in the treatment of non-psychotic anxiety, following pretreatment with benzodiazepines.  Psychopharmacology (Berl). 2001;  157 277-83
• 16 Kubatova A, Miller D J, Hawthorne S B. Comparison of subcritical water and organic solvents for extracting kava lactones from kava root.  J Chromatogr . 2001;  923 187-94
• 17 Crespi C L, Gonzalez F J, Steimel D T, Turner T R, Gelboin H V, Penman B W. et al . A metabolically competent human cell line expressing five cDNAs encoding procarcinogen-activating enzymes: application to mutagenicity testing.  Chem Res Toxicol. 1991;  4 566-72
• 18 Wodnicka M, Guarino R D, Hemperly J J, Timmins M R, Stitt D, Pitner J B. Novel fluorescent technology platform for high throughput cytotoxicity and proliferation assays.  J Biomol Screen. 2000;  5 141-52