Wikipedia pisze:

One group of scholars say that organic solvents introduce compounds that may affect the liver into the standardized product; these compounds are not extracted by water and consequently largely absent from kava prepared with water. For instance, when compared with water extraction, organic solvents extract vastly larger amounts of flavokavains, compounds associated with adverse reactions to kava that are present in very low concentrations in noble kava, but significant in non-noble.

Also "chemical solvents used do not extract the same compounds as the natural water extracts in traditional use. The extraction process may exclude important modifying constituents soluble only in water". In particular, it has been noted that, unlike traditional, water-based preparations, products obtained with the use of organic solvents do not contain glutathione, an important liver-protecting compound. Another group of researchers noted: "The extraction process (aqueous vs. acetone in the two types of preparations) is responsible for the difference in toxicity as extraction of glutathione in addition to the kava lactones is important to provide protection against hepatotoxicity".