Pipermethystine

Pipermethystine is a toxic alkaloid present in the aerial (aboveground) portions of the kava plant. It is not a kavalactone, containing no lactone structure. Correctly prepared kava root products will contain almost no pipermethystine.

Toxicity
Pipermethystine is known to induce hepatoxicity in humans, and was first believed to be the cause of liver failure in individuals consuming kava supplements, but not in proper root powder or fresh root, which is consumed in Polynesia traditionally. Later analyses of the implicated drug materials and products revealed that medical Kava extracts contain less than 45 ppm of this alkaloid, while the leaves contain about 0.2% (2000ppm). Based on this retrospective study, pipermethystine is an unlikely cause for the observed hepatotoxicity of commercial Kava preparations.