by Varro Tyler, Ph.D., Sc.D.*

Cat's claw and Uña de Gato are common names for Uncaria tomentosa, a climbing vine in Peru. Cat's claw is named for the plant's numerous curved thorns, which resemble long claws. The Ashaninka Indians of Peru have long valued the plant's root as a cure-all for almost every ailment, and in the U.S., persons of Hispanic origin view it as a useful medicine

Until recently, American cat's claw products' effectiveness was uncertain. Research in Austria has revealed the reason. There are two Uncaria tomentosa chemotypes, that is, plants that appear identical but have very different chemical properties. One of these contains pentacyclic oxindole alkaloids (POAs) which are vital to the herb's activity; the other contains tetracyclic oxindole alkaloids (TOAs), which negate the POAs' beneficial properties.

Most cat's claw products marketed in the U.S. are indiscriminate mixtures of both chemotypes with uncertain activity. To be certain that a preparation is active, it is mandatory that it be certified as TOA-free; only then can utility be assured.

Several in-vitro studies have shown that POA-containing cat's claw products activate both T-lymphocytes and B-lymphocytes and also increase the phagocyte performance rate of the granulocytes and of cells in the reticul-endothelial system. At the same time, the proliferation of transformed and activated T-lymphoblasts and B-lymphoblasts is inhibited. These immunomodulating effects play an essential role in the clinical use of cat's claw. The herb is believed to accelerate wound healing and to enhance cartilage restoration in joint disorders. It is therefore recommended as an adjunct in the treatment of rheumatic and arthritic conditions.

A preliminary randomized, double-blind clinical trial in 40 patients supports this indication, and a number of case studies also show promise for treating various immunodeficiency states, autoimmunological diseases, allergic diseases, tumors, gastrointestinal inflammation, and even viral and bacterial infections. The latter activity is due, at least in part, to quinovic acid glycosides contained in cat's claw. Additional clinical studies will be required to verify these initial results, but the outcomes to date are hopeful.

In summary, cat's claw products that contain POAs but are TOA-free have been found to act as effective immunomodulators. As such, the preparations have demonstrated utility in treating various rheumatic and arthritic conditions. The use of cat's claw for several other conditions appears promising, but additional studies are required.


1. Reinhard K-H, Uncaria tomentosa (Willd.) D.C.: Cat's Claw, Uña de Gato. J Alt Comp Med 1999; 5:143-151.

2. Keplinger K, Laus G, Wurm M, Dierich MP, Teppner H., Uncaria tomentosa (Willd.) D.C.-Ethnomedical Use and New Pharmacological, Toxicological and Botanical Results. J Ethnopharmacol 1999; 64:23-34.

* Varro E. Tyler, Ph.D., Sc.D., is a leading expert on plant-derived medicine. He is Dean Emeritus of the Purdue University School of Pharmacy and Pharmacal Sciences. He's also the author of more than 300 scientific articles and 20 books, including The Honest Herbal and Herbs of Choice: The Therapeutic Use of Phytomedicinals.