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Kava (Piper methysticum) and kavalactones were recently suspected to be the cause of drug induced hepatitis. Our in vitro screening was aimed on the detection of cytotoxic effects of differently produced kava extracts and isolated kavalactones
in liver cells. Methods: Kava root powder, an ethanolic full extract, an acetonic special extract and the six major kavalactones (kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin and desmethoxyyangonin) were tested in primary cultured rat hepatocytes and human HepG2 cells using cytotoxicity assays including the MTT test.

Results: The tested kava extracts were essentially non-toxic in the relevant dosage range. Kavalactones showed a differential behaviour with concentration-dependent toxicity only detectable in primary cultured rat hepatocytes, but not in human HepG2 cells (EC₅₀ >200 µg/ml). In rat hepatocytes, only kavain and methysticin (EC₅₀ 45 respectively 63 µg/ml) displayed noteworthy effects.

Conclusions: In this in vitro model, neither the tested kava extracts nor the individual kavalactones displayed relevant liver cell toxicity. The results argue against the suspicion of potentially severe hepatotoxicity of kava products.

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Poster: 53^rd Annual Congress of the Society for Medicinal Plant Research, Florence (Italy), August 21-25, 2005