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Cat's Claw

Scientific Name(s): Uncaria guianensis (Aubl.) Gmel., Uncaria tomentosa (Willd.) DC
Common Name(s): C-Med 100, Cat's claw, Cortex Uncariae, Life-giving vine of Peru, Reparagen, Samento, Uña de gato

Medically reviewed by Last updated on Nov 20, 2023.

Clinical Overview


Despite multiple purported effects, controlled clinical trials are lacking.


One gram of root bark given 2 to 3 times daily is a typical dose, while 20 to 30 mg of a root bark extract has been recommended. Clinical trials are generally lacking to support appropriate dosages. A standardized extract containing 8% to 10% carboxy alkyl esters and less than 0.5% oxindole alkaloids has been used in clinical studies in doses of 250 to 300 mg.


Cat's claw products should be avoided before and after surgery, as well as by those using immunosuppressant therapy and in children due to lack of safety data.


Information regarding safety and efficacy during pregnancy and lactation is lacking.


See Drug Interactions section.

Adverse Reactions

Although reports of adverse effects are rare, GI complaints (nausea, diarrhea, stomach discomfort), renal effects, neuropathy, and an increased risk of bleeding with anticoagulant therapy are possible.


Historical ethnomedicinal evidence and current use by consumers suggest low toxicity; however, toxicological studies are limited.

Scientific Family


Cat's claw 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 mainly in tropical regions of Southeast Asia, the Asian continent, and South America. There are 34 reported species of Uncaria.

U. tomentosa and U. guianensis species are found in South America and are lianas, or high-climbing, twining, woody vines growing up to 305 m in length and several centimeters in diameter. Both species are known in Peru as uña de gato (Spanish for cat's claw). 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.

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. The related species Uncaria rhynchophylla is more commonly used in China.PLANTS 2011, WHO 2007, Heitzman 2005


Cat's claw has had a history of folkloric use in South America for wound healing and for treating arthritis, gastric ulcers, intestinal disorders, and some skin disorders and tumors. The part used medicinally is the inner bark of the vine or root. In Peru, a boiled decoction of U. guianensis is used as an anti-inflammatory, antirheumatic, and contraceptive agent, as well as for treating gastric ulcers and tumors, gonorrhea (by the Bora tribe), dysentery (by the Indian populations of Colombia and Guiana), and cancers of the urinary tract in women. The Ashanica Indians believe that samento (U. tomentosa) has life-giving properties and ingest a cup of the decoction every 1 to 2 weeks to ward off disease, treat bone pain, and cleanse the kidneys. Other reported uses include treatment for abscesses, asthma, chemotherapy adverse effects, fever, hemorrhage, rheumatism, skin impurities, urinary tract inflammation, weakness, and wounds, as well as for disease prevention and recovery from childbirth.

Demand for the bark has been partially attributed to European reports of its clinical use with zidovudine in AIDS treatment. The demand for the bark in the United States is based on its purported use as a tea in treating diverticulitis, hemorrhoids, peptic ulcers, colitis, gastritis, parasites, and "leaky gut syndrome." There are, however, no controlled clinical trials to support these uses.WHO 2007, Keplinger 1999, Duke 1994


Many reports exist on the chemical composition of the various Uncaria species and differentiations of the compounds found in different plant parts; reviews have also been published. More than 150 chemical compounds have been isolated from the genus, with approximately 50 chemical entities attributed to U. tomentosa, some of which possibly novel to that species.

Two different chemotypes of U. tomentosa have been described, while U. guianensis and U. rhynchophylla have also been extensively studied. No official standardization exists, and commercially available preparations may consist of mixed plant sources despite claiming to be "100% pure." Inter-batch variations have been reported.

Key compounds common to the genus are primarily the indole and oxindole alkaloids, pentacyclic triterpenoids, and flavonoids. Alkaloids found in most of the species include hirsuteine, hirsutine, mitraphylline, and rhychophylline. The terpenoids include cytotoxic phenolic acid esters, uncarric acids, and glycosides, while other novel compounds include quinovic acids, sterols, and coumarins.Heitzman 2005, Kitajima 2003, Laus 2004, Erowele 2009, Hemingway 1974

Uses and Pharmacology


Cat's claw is a potent inhibitor of production of the pro-inflammatory cytokine tumor necrosis factor (TNF)-alpha in vitro. The anti-inflammatory activity appears to involve suppression of TNF-alpha synthesis, as well as the secretion of nitric oxide and interleukins.(Sandoval 2009, Zeng 2009, Kim 2010, Allen-Hall 2010) The antioxidant activity associated with the phenolic and flavonoid content does not appear to be related to inhibition of nuclear factor kappaB (NF-kB) because quinic acid esters have no inherent antioxidant potential, but inhibit NF-kB.(Zeng 2009, Amaral 2009)

Animal data

The pentacyclic oxindole alkaloids were possibly associated with the anti-inflammatory activity of 2 extracts from U. tomentosa when tested in mouse paw edema(Aguilar 2002); however, CNS pathways such as serotonin receptors may also be involved.(Jürgensen 2005) Induced lung inflammation was reduced in mice pretreated with U. tomentosa bark extract,(Cisneros 2005) while inflammatory-induced bone loss was attenuated partially due to a reduction in neutrophil migration and myeloperoxidase production in a periodontitis rat model.(Lima 2020)

Clinical data

Limited clinical studies suggest an anti-inflammatory action of cat's claw in osteoarthritis.(Hardin 2007, Mehta 2007) A small trial (N = 45) found improved subjective measures of pain with cat's claw; however, other objective measures were not significantly altered. Adverse effects were comparable with placebo.(Piscoya 2001) In another small randomized trial (N = 40), U. tomentosa extract resulted in a reduction in the number of painful joints in patients with rheumatoid arthritis compared with placebo.(Mur 2002) A 2010 systematic review identified 4 randomized controlled trials that studied cat’s claw for osteo- or rheumatoid arthritis; 2 of the trials used the herb in combination with other herbs. Of the 2 using only cat’s claw, one is cited above and the second additional randomized clinical trial was a double-blind trial conducted in 45 men with osteoarthritis of the knee. Administration of 100 mg cat’s claw extract for 4 weeks led to significant improvements in pain with activity as well as both patient- and physician-assessed pain scores compared to placebo (P<0.001).(Rosenbaum 2010)

Antimicrobial activity

In vitro data

Alkaloidal extracts of U. tomentosa have shown in vitro antiviral activity against the vesicular stomatitis virus, rhinovirus, Dengue virus, and herpes simplex virus type 1.(Aquino 1989, Reis 2008, Yepes-Perez 2021) U. tomentosa extract has also demonstrated activity against SARS-CoV-2 in human airway epithelial cells that express high levels of ACE-2 receptors. At 25 mcg/mL, the extract inhibited 92.7% of SARS-CoV-2 growth (P<0.0001) while the positive control, chloroquine, showed 100% inhibition at 50 mcM (P<0.0001). Additionally, U. tomentosa extract significantly reduced the cytopathic effect of the virus by up to 98.6% (P=0.02). In silico modelling identified specific constituents of the extract that are capable of binding strongly to SARS-CoV-2 spike protein thereby blocking its attachment to ACE-2 receptors as well as disruptive actions at the SARS-CoV-2 /ACE-2 binding interface.(Yepes-Perez 2021, Yepes-Perez 2020)

Antibacterial activity has been demonstrated in vitro to human oral pathogens, such as S. mutans and S. aureus, but not C. albicans or P. aeruginosa.(Ccahuana-Vasquez 2007)


Experimental studies have shown antiproliferative (antimitotic) and apoptotic activity of extracts of U. tomentosa. Cell lines evaluated include human leukemic(Anter 2011, Pilarski 2007); lymphoma(Heitzman 2005, Laus 2004); lung, cervical, and colon carcinoma(Pilarski 2010); as well as neuroblastoma and glioma.(García Prado 2007) A protective effect was demonstrated in vitro against ultraviolet damage of skin cells.(Mammone 2006) Different preparations of U. tomentosa contain different alkaloids and result in varying cellular responses that may be related to antioxidant action on signaling pathways.(Heitzman 2005, Laus 2004, Anter 2011, Mammone 2006, Gurrola-Díaz 2011) Extracts of U. guianensis and U. rhynchophylla containing uncarine triterpenes have also been evaluated for their cytotoxic effects.(Laus 2004, Bae 2010)

Animal data

Studies in animal rodent models have shown a reduction in tumor growth with use of extracts of U. tomentosa.(Pilarski 2010)

Clinical data

Clinical studies are limited. One ex vivo study using human leukemic cells obtained from children demonstrated an increased survival when exposed to extracts of U. tomentosa; therefore, caution is advised.(Styczynski 2006) One phase 2 prospective open-label study investigated the safety and efficacy of dry root bark extract of U. tomentosa on adults with advanced solid tumors and no alternative therapeutic options. After 8 weeks of 100 mg 3 times daily, the average overall quality of life, social functioning, and fatigue improved significantly (P=0.041, P=0.034, and P=0.049, respectively); however, no tumor response to the medication was observed.(de Paula 2015)

Cardiovascular effects

Older data from in vitro and animal studies suggested hypotensive, diuretic, and vasorelaxant activity of rhynchophylline, mytraphylline, and gambirine.(Hemingway 1974, Harada 1979, Harada 1976, Mok 1992) However, clinical studies are lacking.

CNS effects

Animal and in vitro data

Although the mechanism of action remains unclear, pteropodine and isopteropodine may increase the affinity of agonists or act as positive modulators of muscarinic M1 and 5-HT2 receptors, improving impaired cognitive processes.(Kang 2002) In vitro binding of mitraphylline to amyloid protein(Frackowiak 2006) and an apparent improvement in functioning in amyloid precursor protein transgenic mice by Yokukansan (a combination preparation containing Uncaria hook)(Fujiwara 2011) suggest investigative potential as Alzheimer disease therapeutic agents. Yokukansan and U. rynchophylla have been evaluated for other CNS effects, including epilepsy.(de Caires 2010, Tang 2010, Lo 2010, Kawakami 2011)

In murine models of aging, administration of cat's claw for 1 year as well as 1 month significantly improved some cognitive tests (eg, escape latency) compared to controls in middle-aged rats. However, overall spatial memory was similar between groups. Levels of acetylcholinesterase were found to be significantly lower in the cerebral cortex of animals treated for 1 month as well as 1 year with cat's claw compared to untreated controls.(Castilhos 2020)

Denture stomatitis

Clinical data

A systematic review of studies that investigated topical application of natural products compared to conventional antifungals for treatment of denture stomatitis identified one double-blind, randomized, controlled trial that administered cat’s claw (N=48). After 14 days, the severity of denture stomatitis as well as the fungal load decreased in both groups with no significant difference between 2% cat’s claw gel and miconazole.(Ignacio Silveira 2021)

Estrogen effects

Animal data

Studies are conflicting on the effect of U. tomentosa extracts on estrogen receptors.(Budán 2011) In rats with induced endometriosis, cat's claw preparations decreased the volume of foci and exerted possible anti-inflammatory and immune-modulatory activity.(Nogueira Neto 2011)


In vitro data

All individual alkaloids of U. tomentosa, with the exception of rhynchophylline and mitraphylline, have immunostimulant properties(Wagner 1985) and the ability to enhance phagocytosis in vitro. Researchers have shown that pteropodine and isopteropodine have immune-stimulating effects.(Jones 1994)

Clinical data

Controlled clinical trials are lacking; however, an uncontrolled study suggested a positive effect on lymphocytes in HIV-positive individuals.(Erowele 2009)

Other uses

Body mass index, energy expenditure, fasting blood glucose, blood insulin levels, liver insulin signaling, as well as hepatic collogen deposition and lipid content improved significantly (P<0.05 for each) with administration of cat’s claw compared to controls in experimental NAFLD in 2 murine models of obesity (ie, high-fat diet, genetically obese).(Araujo 2018)

Prophylactic administration of cat's claw improved fipronil-induced hepatotoxicity in a murine model of chronic insecticide exposure. Cat's claw led to significant improvements in total antioxidant capacity, total cholesterol, and activation of hepatic NF-kappaB as well as liver histology that approached that of controls.(Elgawish 2019)

In a periodontitis rat model, cat’s claw extract improved inflammatory-induced bone loss via reductions in bone resorption, attachment loss, and osteoclasogenesis without altering liver or kidney indices. In addition to attenuating osteoclast formation, a reduction in myeloperoxidase indicated a significantly lower migration of neutrophils to the gingival tissue.(Lima 2020)


One gram of root bark given 2 to 3 times daily is a typical dose, while 20 to 30 mg of a root bark extract has been recommended.WHO 2007 Clinical trials are generally lacking to support appropriate dosages. A standardized extract based on a particular chemotype of this species containing 8% to 10% carboxy alkyl esters and less than 0.5% oxindole alkaloids has been used in clinical studies in doses of 250 to 300 mg.Lehmann-Willenbrock 1988, Sheng 2001

Pregnancy / Lactation

Information regarding safety and efficacy during pregnancy and lactation is lacking. U. tomentosa has traditionally been used as an emmenagogue.WHO 2007, Erowele 2009


Atazanavir: Cat's claw may increase the serum concentration of atazanavir. Monitor therapy.(Lopez Galera 2008)

Blood pressure lowering agents: Herbal products with blood pressure lowering effects may enhance the hypotensive effect of blood pressure lowering agents. Monitor therapy.(Askarpour 2019, Boushehri 2020, Ismail 2021, Lan 2015, Zhang 2020)

Herbal products with blood pressure lowering effects: Herbal products with blood pressure lowering effects may enhance the hypotensive effect of other herbal products with blood pressure lowering effects. Monitor therapy.(Askarpour 2019, Boushehri 2020, Ismail 2021, Lan 2015, Zhang 2020)

Ritonavir: Cat's claw may increase the serum concentration of ritonavir. Monitor therapy.(Lopez Galera 2008)

Saquinavir: Cat's claw may increase the serum concentration of saquinavir. Monitor therapy.(Lopez Galera 2008)

Adverse Reactions

Case reports of adverse events are rare, although information is lacking. The American Herbal Products Association rates Uncaria preparations as class 4 (lack of data to support safety).(Erowele 2009, Piscoya 2001)

Possible adverse effects include GI complaints (nausea, diarrhea, stomach discomfort), renal effects (a case report of acute renal failure exists), hormonal effects (in vitro data suggest extracts may interact with estrogen-receptor binding sites), neuropathy (a case report of worsened Parkinson disease symptoms exists),(Cosentino 2008) and an increased risk of bleeding with anticoagulant therapy.(Cosentino 2008, Ernst 2003, Erowele 2009, Vogel 2005) A case of silicate nephrolithiasis was reported in a 38-year-old woman with a history of Lyme disease, osteoarthritis, gallstones, and irritable bowel syndrome who had been taking several dietary supplements for a few years. Three of the supplements contained silica dioxide as an ingredient, one of which was cat’s claw. Her symptoms of flank pain and gravel-like urine sediment resolved upon discontinuation of her supplements and recurred upon restarting them.(Flythe 2009) Cat's claw present in several multi-ingredient nutritional supplements was hypothesized as being a facilitator to inducing serotonin syndrome in a 37-year-old female. However, her complex medical history that involved multiple medications for anxiety, depression, GI, sinusitis, and headaches accompanied by her recent weight loss routine that entailed consuming nutritional supplements instead of eating prevents certainty of the role of cat's claw.(Ragsdell 2021)

It is recommended that Uncaria-containing products be avoided before and after surgery, by those using immunosuppressant therapy, and in children due to lack of safety data.(Erowele 2009)

Data collected between 2004 and 2013 from 8 US centers in the Drug-induced Liver Injury Network revealed that 15.5% (130) of hepatotoxicity cases were caused by herbals and dietary supplements, whereas 85% (709) of cases were related to prescription medications. Of the 130 cases of liver injury related to supplements, 65% were from non-bodybuilding supplements and occurred most often in Hispanics/Latinos compared with non-Hispanic whites and non-Hispanic blacks. Liver transplant was also more frequent with toxicity from non-bodybuilding supplements (13%) than with conventional medications (3%) (P<0.001). Overall, the proportion of severe liver injury cases was significantly higher for supplements than for conventional medications (P=0.02). Of the 217 supplement products implicated in liver injury, 175 had identifiable ingredients, of which cat's claw was among the 32 (18%) single-ingredient products.(Navarro 2014)


Historical ethnomedicinal evidence and current use by consumers suggest low toxicity; however, toxicological studies are limited. In rats, the median lethal dose 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 adverse effects observed at a repeated dose of 350 mg/day for 6 consecutive weeks.WHO 2007, Williams 2001, Sheng 2000, Valerio 2005

Index Terms



This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.

This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.

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