Cat's Claw

Cat's claw is the common name for Uncaria tomentosa, a large woody vine, or liana, of the family Rubiaceae that grows in the Amazon basin and other tropical parts of Central and South America ^[1]. Its name, echoed in the Spanish uña de gato, comes from the curved, claw-shaped thorns that line its stems and help it climb; the vine can reach great lengths as it grows up through the forest canopy ^[1]. A closely related species, Uncaria guianensis, is also sold under the same common name ^[4].

The bark and root of cat's claw have a long history in the traditional medicine of Peru and neighboring countries, where a decoction has been taken for a wide range of complaints, including arthritis and rheumatism, inflammation, infections, gastric ulcers, and general weakness ^[1]. This ethnomedicinal reputation is what first drew scientific and commercial interest to the plant ^[1].

Chemically, cat's claw is a rich source of natural products. Its most characteristic constituents are oxindole alkaloids, alongside quinovic acid glycosides, polyphenols such as proanthocyanidins, and various triterpenes and sterols ^[2]. Importantly, the plant occurs as two distinct chemotypes that differ in their alkaloids: one contains mainly pentacyclic oxindole alkaloids, which act on the immune system, while the other contains tetracyclic oxindole alkaloids that act on the central nervous system and can even oppose the effects of the pentacyclic type, so the two forms are considered unsuitable to mix for medicinal use ^[3].

Modern research has focused on the anti-inflammatory, antioxidant, and immune-modulating actions of cat's claw ^[2]. Laboratory studies show that extracts scavenge free radicals and suppress inflammatory signals, notably the cytokine TNF-alpha, and a small controlled trial in people with osteoarthritis of the knee reported reduced pain during activity within the first weeks of treatment, with few side effects ^[1][4]. Despite these encouraging findings, reviewers caution that rigorous, large-scale clinical evidence for treating specific human diseases is still lacking ^[1].

Cat's claw is sold as a dietary supplement, in the form of capsules, tablets, teas, and liquid extracts, rather than as an approved medicine. Because it can influence the immune system and other body systems, it is noted for potential interactions with numerous prescription drugs, including immunosuppressants, blood thinners, and blood-pressure medicines, and it is generally advised that people on such treatments, as well as those who are pregnant, use it only with medical guidance ^[1].

Usually well tolerated, with occasional GI upset or headache. Because it modulates the immune system, people with autoimmune disease or on immunosuppressants should be cautious, and it may interact with blood pressure or anticoagulant medication. Avoid in pregnancy.