Used in the rainforest for over 2,000 years by indigenous tribes, cat's claw has anti-inflammatory, cytotoxic, and antiviral properties. Traditional indications include sexually-transmitted diseases, arthritis, gastritis, contraception (a reported three-year hiatus in fertility), and cancer. Purported attributes drew attention from the Westernized world: in 1997, it was on the top-10 list of herb sales in natural food stores in the U.S.

In 1989 the methods for extracting the immune-stimulant oxindole alkaloid constituents in cat's claw root bark were patented. Primarily the work of Hildebert Wagner at the Institute for Pharmaceutical Biology, Munich, and Klaus Keplinger at Innsbruck University, studies revealed that cat's claw was antiviral in the feline crown virus, the lamb Maed visna virus, human herpesvirus, and effective against neurobronchitis and allergies. Injections of the alkaloids raised T-4 lymphocyte counts, and cat's claw preparations stimulated enhanced phagocytosis, and reduced both the progression of the AIDS virus and side effects of the therapies used to treat AIDS patients. It also reduced the side effects of radiation in cancer therapy.

Today, very few studies of cat's claw in humans exist. International research institutes and manufacturing companies currently conduct studies on the pharmacokinetics and mechanisms of action for cat's claw and its isolated constituents. Results of placebo-controlled, phase II trials using cat's claw in the treatment of patients with HIV and rheumatoid arthritis have not yet been published.

Cat's claw is a climbing shrub with woody, thick vines. Growing as high as 100 feet in the Amazon rainforest and tropical countries in South America and Central America, the vines have curved, claw-like thorns where leaves meet the stem. Inside the stem is a bitter-tasting, water-like liquid reportedly drunk as refreshment to relieve fatigue.

Two Uncaria species are called cat's claw, which are differentiated by their flowers: U. tomentosa has yellow-white flowers; U. guianensis, reddish-orange flowers. Phytochemically, U. guianensis contains tetracyclic oxindoles not found in the therapeutically superior U. tomentosa.

The root bark is the source of medicine. Because harvesting the root destroys the plant, the inner bark of the vine may be used as well. It is unclear whether this is an equal substitute.

• Roots
• Bark
• Vine
• Inner bark

• Pentacyclic oxindole alkaloids (alloisopteropodine, alloteropdine, isomitraphylline, isorhynchophylline, mitraphylline, rhynchophylline)
• Tannins (epicatechin and procyanidins)
• Quinovic acid glycosides
• Polyhydroxylated triterpenes

Crude bark as tea or in tablets; aqueous-alcohol extracts standardized to oxindole alkaloids, in liquid form or dried encapsulations

Traditional: anti-inflammatory, antiviral; used for arthritis, dysentery, gastric ulcer, diabetes, cancer, menstrual disorders, convalescence, general debility, gonorrhea, cirrhosis

Conditions: acne, asthma, arthritis, bone pain, cancer, depression, fungus, fistulas, gastritis, gastric ulcer, hemorrhoids, herpes, inflammation of the urinary tract, immune system disorders, menstrual irregularities, neuralgias, rheumatism, shingles, wounds

Clinical applications (pursuant to future research): disorders of the digestive tract; hypertension, and heart disease; HIV, AIDS, and cancers; drug or radiation side effects; allergy, herpes, shingles, arthritis, tumors, cysts, and to treat reduced physical and mental stamina

Cat's claw has immune-stimulant, anti-inflammatory, and antimutagenic actions.

Pentacyclic oxindole alkaloids stimulate phagocytosis and activate T-lymphocytes and macrophages. Quinovic acid glycosides act as an antiviral against rhinovirus type 1B and vesicular stomatitis virus. The oxindoles suppress growth in tumor cell lines; five are antileukemic. Root and bark extracts are antitumor.

In one study, mutagenic metabolites normally formed in the urine of smokers were absent following dosing with cat's claw.

Anti-inflammatory actions may be due to the quinovic acid glycosides, which demonstrate 46% to 69% inhibition of inflammation in vivo and in vitro. The sterols beta-sitosterol, stigmasterol, and campesterol are moderately anti-inflammatory.

Cat's claw may reduce side effects from chemotherapy, including hair loss, weight loss, nausea, secondary infections, and skin problems. Cat's claw may also have cardiovascular effects: Oxindole alkaloids rhynchophylline, hirsutime, and mitraphylline are hypotensive and vasodilative.

Rhynchophylline inhibits platelet aggregation, prevents blood clots, relaxes endothelial blood vessels, dilates peripheral blood vessels, lowers heart rate, and lowers blood cholesterol.

Traditional use for treating conditions listed above:

• 3 to 25 g dried bark as tea or tablets
• 20 to 30 g finely chopped bark, boiled in a liter of water for 20 to 30 minutes. Take liquid tid.

Conventional use for treating mild stomach pains, sore throats, and colds; immune function; and minor injuries:

• Tea: 1 g root bark to 250 ml water, boil for 10 to 15 minutes, cool, and strain. Drink 1 cup, tid.
• Tincture: 1 to 2 ml bid to tid.
• Dry, encapsulated, standardized extract: 20 to 60 mg daily

Nontoxic in traditional lore. Loose stools or diarrhea have been noted. The American Herbal Products Association (AHPA) safety rating: class 4 (indicating lack of data). Tannin content cautionary. More research could change this safety rating.

At this time, cat's claw should not be used in skin graft or organ transplant patients. Its use in patients with HIV, AIDS, and tuberculosis is controversial. Not for children under 3, or during pregnancy or breast-feeding.

Cat's claw extract inhibited the cytochrome P450 enzyme system in vitro (Budzinski et al. 2000). Specific interactions between this herb and conventional medications metabolized via the P450 system have not been documented to date. The National Center for Complementary and Alternative Medicine (NCCAM) is funding research to further evaluate interactions between botanicals and drugs (Council for Responsible Nutrition 2000).

In rat studies, cat's claw tea given orally decreased indomethacin-induced enteritis (Sandoval-Chacon et al. 1998). Cat's claw may protect patients from gastrointestinal damage associated with nonsteroidal anti-inflammatory drugs.

U.S. FDA: Dietary supplement.

German Commission E: Not included in phytomedicinal monographs.

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Aquino R, De Simone F, Vincieri FF, Pizza C, Gacs-Baitz C. New polyhydroxylated triterpenes from Uncaria tomentosa. J Nat Prod. 1990;53:559-564.

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Budzinski JW, Foster BC, Vandenhoek S, Arnason JT. An in vitro evaluation of human cytochrome P450 3A4 inhibition by selected commercial herbal extracts and tinctures. Phytomed. 2000;7(4):273-282.

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Sandoval-Chacon M, et al. Anti-inflammatory actions of cat's claw: the role of NF-kappaB. Aliment Pharmacol Ther. 1998;12:1279-1289.

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