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. KeywordsWeight loss dietary supplement; usnic acid and Usnea barbata toxicity

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In 1994, the Dietary Supplement Health and Education Act (DSHEA) amended the Federal Food, Drug, and Cosmetic Act (FDC Act) to set up a distinct regulatory framework for what we now call dietary supplements. The DSHEA was passed with the intent of striking a balance between providing consumers access to safe dietary supplements to help maintain or improve their health and giving the US Food and Drug Administration (FDA) authority to regulate and take action against manufacturers of supplements or supplement ingredients that present safety problems, are presented with false or misleading claims, or are adulterated or misbranded. This article will present FDA's recent experience in collecting and evaluating dietary supplement adverse event data for the purpose of assuring the public that the dietary supplements they purchase are safe.

CellulonTM fiber, a cellulose produced by a bacterial fermentation process employing a strain of Acetobacter aceti subsp. xylinum, was tested for genotoxicity in four assays: (1) microbial reverse mutation assay in Salmonella typhimurium (Ames assay), (2) an assay for chromosomal aberrations in Chinese hamster ovary (CHO) cells, (3) an assay for induction of unscheduled DNA synthesis (UDS) in rat primary hepatocytes, and (4) the CHO/HGPRT forward mutation assay. Each assay was conducted at a wide range of dose levels, both with and without metabolic activation (assay 1, 2, and 4). Test results gave no indication that Cellulon fiber possessed any genotoxic potential. The pyrogenicity of five batches of Cellulon fiber was tested in the Limulus Amebocyte Lysate assay, gel-clot method. Test results were negative for the presence of gram-negative bacterial endotoxin. The primary eye and dermal irritation potential of Cellulon fiber were examined in New Zealand White rabbits. The Draize method was employed to evaluate and grade ocular and dermal irritation as a result of test material administration. Test results indicated that Cellulon fiber is a minor ocular irritant up to 1 hour postadministration. However, the resultant irritation was considered to be mechanical and related to the dry, granular form of the test material. In addition, test results indicated that Cellulon fiber is not a dermal irritant in the rabbit. The acute oral toxicity of Cellulon fiber was determined in Sprague-Dawley rats, and the LD50 was found to be greater than 2000 mg/kg of body weight. The subchronic toxicity of Cellulon fiber was examined in Sprague-Dawley rats fed diets containing 0, 5, and 10% Cellulon fiber or microcrystalline cellulose for 13 weeks. No dose-related effects on survival, growth, hematology, blood chemistry, organ weights, or pathologic lesions were observed. The results of these studies indicate that Cellulon fiber and microcrystalline cellulose are toxicologically equivalent and that Cellulon fiber does not possess genotoxic potential, is nonpyrogenic, and that animals are not adversely affected by acute or subchronic exposure to Cellulon fiber.

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