Review of Usnic Acid and Usnea Barbata Toxicity

Abstract

Usnic acid is a prominent secondary lichen metabolite that has been used for various purposes worldwide. Crude extracts of usnic acid or pure usnic acid have been marketed in the United States as dietary supplements to aid in weight loss. The US Food and Drug Administration (FDA) received 21 reports of liver toxicity related to the ingestion of dietary supplements that contain usnic acid. This prompted the FDA to issue a warning about one such supplement, LipoKinetix, in 2001 (http://www.cfsan.fda.gov/~dms/ds-lipo.html). Subsequently, usnic acid and Usnea barbata lichen were nominated by the National Toxicology Program (NTP) for toxicity evaluations. At present, a toxicological evaluation of usnic acid is being conducted by the NTP. This review focuses on the recent findings of usnic acid-induced toxicities and their underlying mechanisms of action.

Keywords:

• Weight loss dietary supplement
• usnic acid and Usnea barbata toxicity

This article is not an official guidance or policy statement of US Food and Drug Administration (FDA). No official support or endorsement by the US FDA is intended or should be inferred. This research was supported in part by Interagency Agreement (IAG 224-07-007) between the National Center for Toxicological Research/US FDA and the National Institute for Environmental Health Sciences/National Toxicology Program.