Cat's claw grabs popular attention

Finding its roots in Amazonian folk medicine, two species of cat's claw are now finding their place in modern natural medicine, being used for such health concerns as arthritis, intastinal disorders, and cancer.

An Amazonian downpour had left the streets of Iquitos, Peru glistening in the morning light. A steady drizzle continued, but we headed to the Saturday market, despite the rain. It was the first day of the American Botanical Council and the Texas Pharmacy Foundation's annual week-long sojourn to the Peruvian Amazon, organized to educate pharmacists and other participants on the medicinal plants of Amazonia.

Looking for cat's claw...

Naturally, we were interested in finding herb vendors in the market, and we particularly hoped to see cat's claw. And we did. Bundles of the reddish-brown bark, about a foot long and as large as you could clasp in your hand, were offered throughout the market. Cat's claw was in fact the most abundant herb in the marketplace, except for cayenne peppers and garlic. It soon became clear that the current popularity of the herb in the American market was driven by its stellar reputation as a folk medicine in its native haunts of the Amazon.

I have to admit to approaching this herb with a good deal of skepticism. In various magazines and promotional literature, it has been touted as a cure for just about anything. A friend stopped by my office offering her personal testimonial of success in using the herb to treat Crohn's disease (a serious form of intestinal inflammation), with which she suffered. She claimed that while taking the product, her symptoms disappeared. The manager of the herb section at the local natural food shop had also told me how it had helped her relieve an as-yet-undiagnosed pain she experienced in her extremities. I began to wonder if both were experiencing a glorified placebo effect, or if there was really something behind the use of this botanical. The inhabitants of the primary rainforest of the upper Amazon, both urban and rural populations, rely on the herb for numerous conditions, as they have for hundreds of years. It has only been in the 1990s, however, that cat's claw has emerged as one of the top tropical Amazonian herbs in the American marketplace.

A high-climbing, twining, woody vine in the Amazon

On the flight from Miami to Iquitos, I sat with Jim Duke. Dr. Duke was priming me for my first trip to the Amazon, a trip he has made dozens of time. Having retired as head of the USDA's Germplasm Resources Laboratory just two weeks before our trip, he was ready for a jaunt to the Amazon, his home away from home. Duke explained that cat's claw, as it is known in English, or una de gato as it is called in Spanish, is a tropical member of the madder family that botanists call a liana -- a high-climbing, twining, woody vine -- which can sometimes stretch from the forest floor to the canopy more than twelve stories above. A single vine, he believed, when fully grown, could weigh upwards of one ton. The genus Uncaria includes 34 species found throughout the tropics, primarily in Asia, Africa and South America. Two species are found in South America including Uncaria tomentosa and Uncaria guianensis, Duke explained.

Duke, along with a Peruvian ethnobotanist colleague, Rodolfo Vasquez, had recently completed their book Amazonian Ethnobotanical Dictionary (CRC Press, 1994). All royalties to Duke and Vasquez's book will go to the Amazonian Center for Environmental Education and Research (ACEER). ACEER is a non-profit organization located in the Amazon Biosphere Reserve, a protected wilderness area encompassing 250,000 acres of pristine primary rainforest. It was here at ACEER a few days after our arrival that Duke showed me the young cat's claw plant (as pictured on the first page of this article).

In their Dictionary, Duke and Vasquez write that a bark decoction of U. guianensis is used in Piura as an anti-inflammatory, antirheumatic, as well as a contraceptive. It is also used for treating gastric ulcers and tumors. The Boras use the bark for the treatment of gonorrhea. In Columbia and Guyana, Indian groups use it for the treatment of dysentery, a disease characterized by severe diarrhea.

Two species offered for the most health-care uses

U. guianensis has been used as a folk medicine for intestinal ailments, and to promote healing of wounds. The plant also has a reputation as a folk cancer remedy for cancer of the urinary tract, particularly in women.

U. tomentosa, which is apparently most abundant in Peru, is generally used interchangeably with U. guianensis. Other uses enumerated for U. tomentosa include the treatment of: gastric ulcers; arthritis; intestinal disorders; certain skin diseases; and various tumors. Both U. tomentosa and U. guianensis are widely used as folk medicines in the Amazon. U. guianensis is collected in large quantities in South America for shipment to the European market, while U. tomentosa has evolved as the species of choice in the American market.

Why the current world-wide interest in cat's claw?

The excitement can be traced to a book called Witch Doctor's Apprentic: Hunting for Medicinal Plants in the Amazon (1990, Third Edition, Citadel Press, New York) by Nicole Maxwell. Before this book fueled interest in the plant, it was simply another obscure research subject that intrigued scientists from time to time. In Maxwell's book, she reveals that the National Cancer Institute had some encouraging results in screening the plant for potential antitumor activity in the 1970s. Funding for the National Cancer Institute's plant screening program ended in 1980 (before starting up again in the mid-1980s). Reports of success as a folk remedy for cancer, especially in South America, continued, leading to further scientific research on the plant group. Much of that research has been conducted in Germany, Austria, and Italy.

1974: one of the first chemical studies on cat's claw

In 1974, a research group in London conducted one of the first chemical studies on cat's claw. Looking at both South American species, they found a number of major alkaloids from the stems and leaves of both species. During the same time period, an Italian research group also isolated various compounds from cat's claw. They found some of the same alkaloids as did the London group, along with an alkaloid identified as uncarine F. Interested in the fact that the plant was widely used as a folk cancer remedy in the Amazon, they conducted preliminary screening and found that proanthocyanidins in the plant may be responsible for some of the claimed anti-tumor activity.

In 1985, researchers at the Institute for Pharmaceutical Biology at the University of Munich published their findings on cat's claw's chemical and pharmacological research. They developed a method for identifying several alkaloids from U. tomentosa, including six oxindole alkaloids. They also tested the compounds in the carbon clearance test, a method of measuring the immunostimulating potential of compounds by measuring the rate at which carbon particles are cleared from the blood by the immune system. They found that the alkaloids isopteropodin, pteropodin, isomitraphyllin, and isorychnophyllin had a pronounced immunostimulating effect in laboratory experiments. Further research revealed that yet another alkaloid, alloisopteropodine, had strong immunostimulating effects as well.

Meanwhile, researchers in Naples continued their work on cat's claw, looking for more compounds with biological activity. They found a group of chemicals called quinovic glycosides. Interested in potential antiviral activity, the researchers conducted a battery of tests and found that some of these compounds had what they described as insignificant antiviral activity. In later studies, however, they were able to correlate significant anti-inflammatory activity to this group of compounds. In a 1993 paper, these researchers also found that U. tomentosa extracts may have potential antimutagenic activity (the process of preventing normal cells from mutating to cancerous ones) as well as possible antioxidant activity.

Working closely with colleagues in Munich, a research group in Innsbruck, Austria, which has investigated the potential use of cat's claw compounds in stimulating the immune system, looked at the pharmacology of cat's claw alkaloids against various cancer cell lines. They individually tested six different alkaloids individually to see if they could hold back the production of leukemia cells by stimulating the targeting (specialization) of such white blood cells as granulocytes (in HL 60 leukemia) and macrophages (in U-937 lymphoma). Five of the six compounds were found to be active. Uncarine F showed the greatest potential, as it had a capacity to selectively inhibit leukemia-affected cells, while not affecting normal cells. The authors concluded that uncarine F is a candidate worthy of further research as a possible treatment for acute leukemia treatment in humans.

In terms of its reputation as a folk remedy in the Amazon, few plants native to that region are thought of as highly as cat's claw by the people who live there. In the American herb market, cat's claw is definitely a new, yet rising, star. When focusing on cat's claw from a scientific perspective, we can see that it is only during the last decade that scientists have begun to understand what makes cat's claw work. Research to date has isolated several dozen chemical compounds in a number of chemical classes. Anti-inflammatory, immunostimulating, and anti-tumor activities have been attributed to various compounds suggesting a possible scientific explanation for its myriad of folk uses and stellar reputation. In the next decade, increased scientific interest will be focused on the plant as it gains popularity in the medicinal herb market

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