Cat's Claw



Cat's claw, also known as una de gato, belongs to the genus Uncaria and is indigenous to the Amazon rainforest and other tropical areas of South and Central America. Uncaria plants are woody vines with characteristic curved thorns, which resemble cat claws, on their stems. The species most widely used for medicinal purposes in Western countries is Uncaria tomentosa, but a related species, U. guianensis, is also employed. Other species are popular in Asia.

Uses:

Cat's claw preparations have been employed by native populations of the upper Amazon basin for generations to treat a myriad of health problems. The Peruvian Ashaninka Indians view the vine as "life giving." Cat's claw is traditionally used to treat arthritis and rheumatism, ulcers and other disorders of the gastrointestinal tract, asthma, wounds, gonorrhea, dysentery, and tumors; to help recover from childbirth; and as a contraceptive (in large doses). In North America and Europe, cat's claw is currently promoted for similar uses, with an emphasis on stimulating the immune system to treat disorders such as cancer, viral diseases (including AIDS), gastrointestinal illnesses, and inflammatory disorders. Anecdotal reports abound describing the healing properties of cat's claw preparations for many serious or chronic medical conditions.

Pharmacology:

Active chemical constituents from the roots, bark, and other parts of the plant include pentacyclic and tetra­cyclic oxindole alkaloids, quinovic acid glycosides, polyhydroxy­lated triterpenes, and several steroidal components (such as heta-sitosterol). Peruvian Indian healers can reportedly identify plants that have the most healing properties, which may be of a :;pecific botanic chemotype that contains more pentacyclic (rather Ihan tetracyclic) alkaloids. These constituents, as well as whole extracts, have been investigated in a variety of experiments to assess their proposed immunomodulatory, anti-inflammatory, and anticancer properties.

Contrasting effects on the immune/inflammatory system are found in vitro. Aqueous bark extracts inhibit the inflammatory response by suppressing TNF-alpha production. 6 In contrast, higher concentrations induce IL-1 and IL-6 production, at least in rat alveolar macrophagesJ Although isolated pentacyclic oxindole al­kaloids enhance phagocytic activity and affect the proliferation of human lymphocytes, the tetracyclic alkaloids antagonize this ac­tivity on lymphocytes. In animal studies, extracts are reported to increase induced lymphocyte proliferation in splenocytes, in­crease peripheral white blood cell (WBC) counts, and enhance recovery of chemotherapy-induced leukopenia. Quinovic acid glycosides reduce an experimental inflammatory response, and oral administration attenuates indomethacin-induced intestinal in­flammation in animal models.

Preliminary investigations of cat's claw extracts have dem­onstrated potential anticancer activity. Specific extracts appear to have cytoprotective antioxidant properties, and enhance repair of DNA breaks in irradiated rats. They inhibit specific leukemia and lymphoma cell lines by inducing apoptosis and cell death.

Among miscellaneous in vitro studies, extracts have been found to inhibit stomatitis virus, to noncompetitively bind to estro­gen receptors, and to inhibit the cytochrome P450 3A4 iso­zyme.14-16 Tetracyclic oxindole alkaloids and other constituents from Uncaria species used in Asia are reported to have CNS (sedative, anticonvulsant) and cardiovascular (hypotensive, anti­thrombotic) properties in animal models. These effects have not been studied in South American species of Uncaria.

Pharmacologic studies in humans are limited. In both a case report and a randomized, double-blind study of 24 subjects, smokers given U. tomentosa reportedly had decreased muta­genic activity of their urine. In another study, four healthy volun­teers took a 350-mg capsule of a purified water-soluble extract (called C-M ED-1 00) daily for 6 weeks. 9 An increase in WBCs was reported, but this was not clinically significant (mean increase from 6.6 to 7.18 x 10 3 ).

Clinical Trials:

No complete clinical trials have been pub­lished. One uncontrolled clinical trial has been partially described in a review article. 4 Thirteen subjects with HIV infection who re­fused other therapies were given 20 mg/day of a U. tomentosa root extract (containing 12 mg/g of pentacyclic oxindole alkaloids) for a period ranging from 2.2 to 5 months. The total leukocyte count and T4/T8 ratio were not altered. The relative and absolute lymphocyte count increased slightly (from 24% to 33.7%), which was statistically significant. In a double-blind, randomized, con­trolled trial that was unpublished but reported in company litera­ture, 40 patients with rheumatoid arthritis were given three 20-mg capsules daily of Krallendorn (by Immodal Pharmaka), a popular European cat's claw extract, or placebo for 6 months. 18 Two of three primary outcomes were reportedly improved in the treat­ment group, including objective evaluations of number and sever­ity of tender joints (p < 0.05).

Adverse Effects:

Cat's claw is generally considered to be safe and well tolerated, although data is limited. No side effects were reported in the few human studies, and no adverse effects were found in rodent toxicity studies.Screening laboratory analyses were not affected in the 6-month clinical trial in rheumatoid arthritis patients.Mild lymphocytosis, erythrocytosis, constipation, diarrhea, and hyperuricemia have been anecdotally reported by European researchers.

Interactions:

In one in vitro study, cat's claw inhibited activity of the 3A4 isozyme of cytochrome P450, a common drug metabolizing enzyme. This has not been validated in vivo, and no drug interactions have been reported.

Cautions:

Based on in vitro studies, European researchers believe that products containing the tetracyclic oxindole alkaloids (TOAs) may be detrimental or can attenuate the beneficial immunologic effects of the pentacyclic alkaloids. They recommend that these products not be used for transplant patients, or for other conditions in which "immune-stimulation" may be detrimental. A case report of reversible acute renal failure (possibly due to allergic interstitial nephritis) was associated with ingestion of a cat's claw supplement in a patient with systemic lupus erythematosus (SLE).Although this may represent an idiosyncratic reaction, it would be prudent for patients with SLE to avoid this herb,and caution should be advised to other patients with autoimmune disorders.

Because of cat's claw's traditional use as a contraceptive, it is not recommended during pregnancy. Its safety while breast feeding is not known.

Preparations & Doses:

Traditionally, cat's claw vine bark is boiled in water and the decoction is drunk daily. Commercial preparations are available from a number of Peruvian, European, ,and U.S.-managed companies. Preparations are usually available in 200- to 500-mg capsules of U. tomentosa, although concentrated extracts are available. Some manufacturers standardize their product to contain a specific amount of oxindole alkaloids and polyphenols, and advertise that they are free of TOAs. Krallendorn (by Immodal Pharmaka, Austria), one of the original cat's claw products evaluated and used in Europe, is marketed in the U.S. as Saventaro (by Enzymatic Therapy/PhytoPharmica). It is a standardized root extract and stated to be free of TOAs. The suggested dose is one 20-mg capsule t.i.d. for the first 10 days, then one capsule daily thereafter, although in the clinical trial of rheumatoid arthritis patients the t.i.d. dose was administered for 6 months.

Dosage recommendations vary widely among different products and are generally empirical. Tea preparations are also available, predominantly used for treating gastrointestinal ailments such as gastritis, peptic ulcer disease, colitis, diverticulitis, hemorrhoids, and "leaky bowel syndrome.

Summary Evaluation:

The current popularity of cat's claw is based primarily on traditional use, anecdotes, and preliminary in vitro and animal studies. Reported clinical benefits have not been objectively evaluated in published peer-reviewed studies, and the plethora of positive claims is most likely exaggerated. Extracts and chemical con-stituents have active pharmacologic properties in vitro and in animal experiments that warrant clinical investigation, but there is little objective evidence that cat's claw preparations reliably bene­fit any medical disorder. Cat's claw appears to be safe for most people (without autoimmune disorders), and it has no known side effects.