Herbal products for liver diseases: a therapeutic challenge for the new millennium.

Use of herbal drugs in the treatment of liver diseases has a long tradition, especially in Eastern medicine. Standardization has been a problem, and randomized, placebo-controlled clinical trials to support efficacy are lacking. Some herbal extracts promoted for gastrointestinal or biliary disorders contain potent hepatotoxic alkaloids and are harmful. However, some of these extracts have yielded molecules, often related to flavonoids, with proven antioxidative, antifibrotic, antiviral, or anticarcinogenic properties, including glycyrrhizin, phyllanthin, silibinin, picroside, and baicalein, which derive from licorice root, Phyllanthus amarus, milk thistle, Picrorhiza kurroa, and sho-saiko-to, respectively, that can serve as primary compounds for the development of specific hepatotropic drugs.