(Willd. ex Schult.) DC.
Uncaria tomentosa is a woody vine found in the tropical jungles of South and Central America. In several languages it is known as cat’s claw because of its claw-shaped thorns (English cat’s claw, although that name is also used for other plants; Spanish uña de gato). It is also known as vilcacora; Polish journalist Roman Warszewski claims the invention of the latter name by combining the qechua words ‘vilca’ + ‘cora’.
It is used in herbalism for a variety of ailments.
Uncaria tomentosa is a liana deriving its name from hook-like thorns that resemble the claws of a cat. U. tomentosa can grow up to 30 m (100 ft) tall, climbing by means of these thorns. The leaves are elliptic with a smooth edge, and grow in opposite whorls of two. Cat’s claw is indigenous to the Amazon rainforest, with its habitat being restricted primarily to the tropical areas of South and Central America.
There are two species of cat’s claw commonly used in North America and Europe, Uncaria tomentosa and Uncaria guianensis, each having different properties and uses. The two are frequently confused but U. tomentosa is the more heavily researched for medicinal use and immune modulation, while U. guianensis may be more useful for osteoarthritis. U. tomentosa is further divided into two chemotypes with different properties and active compounds, a fact ignored by most manufacturers that can have significant implications on both its use as an alternative medicine and in clinical trials to prove or disprove its efficacy. Another species, Uncaria rhynchophylla, has usage in Chinese medicine, and several unrelated species bear the same nickname.
According to the American Cancer Society, cat’s claw is often promoted for its health benefits and has become a popular herbal supplement in the United States and Europe. However, they state:
Available scientific evidence does not support claims that this herb can treat cancer or other diseases in people. Animal and laboratory studies may show promise, but further studies are necessary to find out whether the results apply to humans. Until clinical trials in humans are completed, the true value of cat’s claw remains uncertain.
Some studies on its effect on rheumatoid arthritis reported modest results, which need confirmation in standardized trials.
The indigenous peoples of South America have used cat’s claw for centuries in the belief it is a treatment for various disorders.
Individuals allergic to plants in the Rubiaceae family and different species of Uncaria may be more likely to have allergic reactions to cat’s claw. Reactions can include itching, rash and allergic inflammation of the kidneys. In one case study, kidney failure occurred in a patient with Lupus erythematosus. The patient’s kidney failure improved after stopping the herbal remedy.
There are other plants which are known as cat’s claw (or uña de gato) in Mexico and Latin America; however, they are entirely different plants, belonging to neither the Uncaria genus, nor to the Rubiaceae family. Some of the Mexican uña de gato varieties are known to have toxic properties.