Cat's Claw
Uncaria tomentosa (Willd.) DC and Uncaria guianensis (Aubl.) Gmel. Family: Rubiaceae
Cat's claw , life-giving vine of Peru , samento , uña de gato 1,  , 2
 
Clinical Overview
Uses
Various species have been used as an astringent and anti-inflammatory agent, for GI and cancer treatment, as a contraceptive, general tonic, and for other uses. Studies have verified some anti-inflammatory, anticancer, and immunostimulant properties. The major alkaloid rhynchophylline has hypotensive effects. Because of potential immunostimulating effects, cat's claw should not be used in patients scheduled for organ transplants, skin grafts, or immunosuppressive therapy, and in patients with autoimmune disorders. However, no clinical trials have been conducted.

Dosing
One gram of root bark given 2 to 3 times/day is a typical dose, while 20 to 30 mg of a root bark extract has been recommended. A standardized extract containing 8% to 10% carboxy alkyl esters and less than 0.5% oxindole alkaloids has been used for clinical trials as an immunostimulant in doses of 250 to 300 mg.

Contraindications
None well documented.

Pregnancy/Lactation
Cat's claw should not be used during pregnancy and lactation.

Interactions
Cat's claw may potentiate the action of antihypertensive drugs. Because of potential immunostimulating effects, it would be prudent to avoid cat's claw in patients receiving immunosuppressive therapy.

Adverse Reactions
Low incidence.

Toxicology
Historical ethnomedicinal evidence and current use by health care consumers suggest low toxicity. In rats, the LD50 of a single dose of a water extract of U. tomentosa was determined to be greater than 8 g/kg. In humans, there were no toxic side effects observed at a repeated dose of 350 mg/day for 6 consecutive weeks.

 
Botany
Cat's claw, or uña de gato (Spanish), is a tropical vine of the madder family (Rubiaceae). The name describes the small, curved-back spines on the stem at the leaf juncture. The genus Uncaria is found throughout the tropics, mainly in Southeast Asia, the Asian continent, and South America. 2
U. tomentosa (Willd.) DC and U. guianensis (Aubl.) (Gmel.), are found in South America. These species are lianas or high climbing, twining, woody vines growing up to 305 m in altitude and several centimeters in diameter. Both species are known in Peru as uña de gato. 1,  , 2,  , 3,  , 4
There are 34 reported species of Uncaria . One Asian species, known as gambir or pole catechu ( Uncaria gambir ) (Hunter) Roxb., is a widely used tanning agent that also has had a long history of medicinal use as an astringent and antidiarrheal. 5
 
History
U. guianensis has had folkloric use in South America for wound healing and for treating intestinal ailments. Large amounts of U. guianensis are collected in South America for the European market, while American sources prefer U. tomentosa . By 1997, over 50 dietary supplement manufacturers offered cat's claw products in the United States. 2,  , 3,  , 4
The part used medicinally is in the inner bark of the vine. In Peru, a boiled decoction of U. guianensis is used therapeutically as an anti-inflammatory, antirheumatic, and contraceptive agent, as well as in treating gastric ulcers and tumors, gonorrhea (by the Bora tribe), dysentery (by the Indian groups of Colombia and Guiana), and cancers of the urinary tract in women. 1,  , 4
The center of the U. tomentosa range is in Peru. Its uses are similar to those of U. guianensis and include treatment of arthritis, gastric ulcers, intestinal disorders, and some skin problems and tumors. 4
The Ashanica Indians believe that samento (also U. tomentosa ) has “life-giving” properties and use a cup of the decoction each week or two to ward off disease, treat bone pain, and cleanse the kidneys. 5
Some of the demand for the bark has been attributed to European reports on its clinical use with zidovudine in AIDS treatment. The demand for the bark in the United States is based on the purported usefulness of its tea in treating diverticulitis, hemorrhoids, peptic ulcers, colitis, gastritis, parasites, and leaky bowel syndrome. 5 There are no clinical data available to support these uses.
Other reported therapeutic uses include treatment for abscesses, asthma, chemotherapy side effects, fever, hemorrhage, rheumatism, skin impurities, urinary tract inflammation, weakness, and wounds, and for disease prevention and recovery from childbirth. 2 There are no clinical data available to support these uses.
 
Chemistry
Over 17 alkaloids have been identified in U. tomentosa . There are 2 chemotypes of U. tomentosa , each containing different alkaloids. One contains pentacyclic oxindoles, which affect the immune system, and the other contains tetracyclic oxindoles, which affect the nervous system. Medicinally, the tetracyclic oxindole alkaloids exert an antagonistic effect on the action of pentacyclic oxindole alkaloids. Pentacyclic oxindoles include pteropodine, isopteropodine, speciophylline, uncarine F, mitraphylline, and isomitraphylline. Tetracyclic oxindoles include rhynchophylline, isorhynchophylline, corynoxeine, and isocorynoxeine. 2,  , 6,  , 7,  , 8
Nine quinovic acid glycosides, which contain various sugar moieties, have been isolated from U. tomentosa . Two nor-triterpene glycosides, tomentosides A and B, have been isolated. 9,  , 10,  , 11,  , 12
The sterols beta-sitosterol, stigmasterol, and campesterol have been isolated from cat's claw. 2
Several studies on the chemistry of the genus Uncaria have been undertaken. Research on the Thai species includes the isolation and identification of 4 pentacyclic oxindole alkaloids, isopteropodine, pteropodine, speciophylline, and uncarine F, from the leaves of Uncaria homomalla , 13 as well as the alkaloids 3-isoajmalicine, 19-epi-3-isoajmalicine, mitraphylline, and uncarine B from the leaves of Uncaria attenuata . 14
Other studies include reports on 3 indole alkaloidal glucosides (cadambine, 3-alpha-dihydrocadambine, and 3-beta-isodihydrocadambine) from the Asian crude drug chotoko (the dried climbing hooks of Uncaria ) 15 ; alkaloids of Uncaria ferrea 16 ; alkaloids of Uncaria rhynchophylla 17 ; 3 polyhydroxylated triterpenes from U. tomentosa 18 ; the alkaloid gambirine from Uncaria callophylla 19,  ; and the gluco indole alkaloid 3,4-dehydro-5-carboxystrictosidine. 20
Several of these constituents have verified some of the pharmacological activities reported for the crude extract of the bark used in folkloric preparations.
 
Uses and Pharmacology
Both species, U. tomentosa and U. guianensis , have been used in the form of a bark decoction for a wide range of disorders, including gastric ulcers, inflammation, rheumatism, and tumors, and as a contraceptive. U. guianensis has been used to treat dysentery, gonorrhea, and cancer of the urinary tract in women. 3
Anti-inflammatory and immunostimulating effects   Reviews and scientific studies by the National Cancer Institute have led to verification of some of the anticancer and immunostimulant properties. 4
Animal data   The pentacyclic oxindole alkaloids may be associated with the anti-inflammatory activity of 2 extracts from U. tomentosa when tested in mouse paw edema. 21
Clinical data   Reports have demonstrated Uncaria 's role in improving immunity in cancer patients, 5,  as well as its antimutagenic properties. 17 Plant extracts and fractions of U. tomentosa exhibit a protective antimutagenic property in vitro and a decreased mutagenicity in a smoker who had ingested a decoction of the plant for 15 days. 22
All of the individual alkaloids of U. tomentosa , with the exception of rhynchophylline and mitraphylline, have immunostimulant properties 23,  and the ability to enhance phagocytosis in vitro. Other researchers have shown pteropodine and isopteropodine to have immunostimulating effects. 5
The anti-inflammatory activity of cat's claw in treating osteoarthritis of the knee was studied in 1 clinical trial involving 45 patients. Subjective measures from patient assessment scores indicated pain associated with activity was significantly reduced. However, knee pain at rest or at night and knee circumference were not significantly reduced. Side effects were comparable to placebo. 24
Forty patients undergoing sulfasalazine or hydroxychloroquine treatment for rheumatoid arthritis were enrolled in a randomized, 52-week, 2-phase study. Phase 1 of the study lasted 24 weeks, and patients were treated with an U. tomentosa extract or placebo. Phase 2 of the study lasted 28 weeks, and patients were treated only with an U. tomentosa extract. Treatment during phase 1 resulted in a reduction of the number of painful joints compared with placebo (53.2% vs 24.1%; P = 0.044). Treatment during phase 2 resulted in a reduction in the number of painful ( P = 0.003) and swollen joints ( P = 0.007) compared with the values of placebo. 25
Because of potential immunostimulating effects, cat's claw should not be used in patients scheduled for organ transplants, skin grafts, or immunosuppressive therapy, or in patients with autoimmune disorders.
In vitro   Cat's claw is a potent inhibitor of tumor necrosis factor (TNF) alpha (a marker used in chronic inflammation) production in vitro. The anti-inflammatory activity appears to involve suppression of TNF alpha synthesis. 26
Cardiovascular and neurological effects
Animal data   The major alkaloid rhynchophylline has been shown to be antihypertensive, to relax the blood vessels of endothelial cells, dilate peripheral blood vessels, inhibit sympathetic nervous system activities, and lower the heart rate and blood cholesterol. 5,  , 27,  The alkaloid mytraphylline has diuretic properties, 5,  while the alkaloid hirsutine inhibits urinary bladder contractions and possesses local anesthetic properties. 5,  , 28
At higher dosages, hirsutine showed a “curare-like” ability on neuromuscular transmission. 5,  , 29,  Chotoko has hypotensive properties. 15 The alkaloid gambirine isolated from U. callophylla has cardiovascular properties. 19 An IV injection of this alkaloid (dose range, 0.2 to 10 mg/kg) in normotensive rats produced a dose-related decline in systolic and diastolic blood pressure.
Although the mechanism of action remains unclear, pteropodine and isopteropodine may increase the affinity of agonists or act as positive modulators of muscarinic M(1) and 5-HT(2) receptors and thus may improve impaired cognitive processes. 30
Clinical data   Research reveals no clinical data regarding the use of cat's claw as an antihypertensive or antihyperlipidemic agent.
Antiviral activity   Six quinovic acid glycosides in U. tomentosa have antiviral activity in vitro against the vesicular stomatitis virus (VSV). The inhibitory effect against VSV infection was observed at MIC50 of 20 to 60 mg/L. 2,  , 10,  , 18
 
Administration & Dosage
One gram of root bark given 2 to 3 times/day is a typical dose, while 20 to 30 mg of a root bark extract has been recommended. A standardized extract based on a particular chemotype of this species (C-Med-100,   Krallendorn , Immodal Pharmaka GmbH) containing 8% to 10% carboxy alkyl esters and less than 0.5% oxindole alkaloids has been used for clinical trials as an immunostimulant in doses of 250 to 300 mg. 31,  , 32
 
Pregnancy/Lactation
Cat's claw should not be used during pregnancy and lactation.
 
Interactions
Cat's claw may also potentiate the action of antihypertensive drugs. 1 Because of potential immunostimulating effects, it would be prudent to avoid cat's claw in patients receiving immunosuppressive therapy.
 
Adverse Reactions
Low incidence of side effects.
 
Toxicology
Historical ethnomedicinal evidence and current use by health care consumers suggest low toxicity. In rats, the LD50 of a single dose of a water extract of U. tomentosa was determined to be greater than 8 g/kg. In humans, there were no toxic side effects observed at a repeated dose of 350 mg/day for 6 consecutive weeks. 1,  , 33
 
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