Impact of kava cultivar, plant part and extraction medium on in-vitro cytotoxicity of kava (Piper methysticum) in HepG2 and Hep3B cells

Preparations from kava (Piper methysticum G. Forst.) have been banned based on the suspicion of adverse liver effects. To date, no convincing proof has been given to substantiate the danger of a relevant toxicity.

We systematically tested kava extracts prepared with acetone or ethanol from two different cultivars, both used for kava extract production: Ava Laau from Samoa, a “noble kava“, and Palisi from Vanuatu, a “Tudei kava“ (“two-day“ lasting effect). We also tested the influence of aerial parts (stem peelings) on toxicity.

Methods: Extracts were prepared and characterized by the working group of Prof. Nahrstedt at the University of Münster (Germany). Kava plant material was obtained from cultivations. Extracts were tested in HepG2 and Hep3B liver cells, using the MTT test, the Rezasurin blue assay, quantification of LDH leakage and measurements of intracellular ATP and GSH contents.

Results: Only gradual differences in cytotoxicity were found. The sequence of toxicity for ethanolic extracts was roots (noble) < peelings (noble) ≤ roots (Tudei) < peelings (Tudei). In the case of extracts prepared with acetone the toxicity of the Tudei-material was partly reversed: peelings (Tudei) < roots (Tudei). In no case were the EC₅₀ values in a relevant dosage range (1250 to >5000µg/mL for roots, 800 to >5000µg/mL for peelings in the MTT test and rezasurin blue assay, with the highest toxicity found with Tudei peelings in the rezasurin blue test in Hep 3B cells).

Conclusions: No hint on relevant liver cell toxicity was found in this battery of in vitro models.