Health Care Professional Information

Scientific Name
Uncaria tomentosa
Common Name

Una de gato, life-giving vine of Peru, hawk’s claw

Clinical Summary

Cat's claw is a vine native to South America, the bark of which has been used in traditional medicine to treat diseases. It is also a very popular immune-enhancing supplement. In vitro studies show that the alkaloids from Cat's claw enhance phagocytosis, display immunomodulatory properties, alleviate inflammation, and possess anti-viral activity (1) (2) (3) (4) (5).

Cat's claw demonstrated anticancer effects against several cancer cell lines (6) (7) (17) (18). However, no human studies have been conducted to evaluate its efficacy.
Reported adverse reactions include hypotension and diarrhea. An additive effect with anticoagulants or hypotensives is possible (8).

Purported Uses
  • Cancer treatment
  • GI disorders
  • AIDS
  • Inflammation
  • Oxindole alkaloids: Isopteropodine, pteropodine, rhynchophylline, mytraphylline, speciphylline
  • Indole alkaloidal glucosides: Cadambine, 3-dihydrocadambine, and 3-isodihydrocadambine
  • Hirsutine
  • Quinovic acid glycosides
  • Tannins
  • Polyphenols
  • Catechins
  • Beta sitosterol
    (9) (10)
Mechanism of Action

The oxindole alkaloids are claimed to have immunostimulating properties in vitro, increasing phagocytotic activity and synthesis of WBCs (4) and enhancing T-helper cell function (1). The major alkaloid, rhynchophylline, is claimed to be anti-hypertensive; it relaxes the endothelial cells of blood vessels, dilates peripheral blood vessels, inhibits sympathetic nervous system activities, and lowers the heart rate and blood cholesterol. The alkaloid mytraphylline has diuretic properties, and hirsutine inhibits urinary bladder contractions and possesses local anesthetic (4) (11) (12). The anti-inflammatory activity may be caused by the inhibition of TNF-alpha production (2) (3). Uncaria tomentosa water extracts have been shown to enhance DNA repair after chemical-induced damage (13).

Adverse Reactions

Common: May cause diarrhea and lower blood pressure.
Case report: Acute renal failure was observed in a patient with systemic lupus erythematosus (SLE) (14).
Case report: Worsening of motor signs in a 38-year-old patient with Parkinson disease has been reported after oral intake of cat's claw extract. But the symptoms improved following withdrawal of cat's claw use (16).

Herb-Drug Interactions

Cytochrome P450 substrates: Cat's claw inhibits CYP3A4 in vitro indicating that it may increase the serum levels of drugs such as nonnucleoside reverse-transcriptase inhibitors, cyclosporine, and some benzodiazepines (8).
Protease Inhibitors: Cat's claw was shown to increase the serum concentrations of atazanavir, ritonavir and saquinavir (15).

Literature Summary and Critique

The safety and efficacy of Cat's claw have not been evaluated in humans.

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  1. Riva L, et al. The antiproliferative effects of Uncaria tomentosa extracts and fractions on the growth of breast cancer cell line. Anticancer Res 2001;21:2457-61.
  2. Sandoval M, et al. Cat's claw inhibits TNFalpha production and scavenges free radicals: role in cytoprotection. Free Radic Biol Med 2000;29:71-8.
  3. Sandoval M, et al. Anti-inflammatory and antioxidant activities of cat's claw (Uncaria tomentosa and Uncaria guianensis) are independent of their alkaloid content. Phytomedicine 2002;9:325-37.
  4. Sheng Y, Bryngelsson C, Pero R. Enhanced DNA repair, immune function and reduced toxicity of C-MED-100, a novel aqueous extract from Uncaria tomentosa. J Ethnopharmacol 2000;69:115-26.
  5. Reis SR, Valente LM, Sampaio AL, et al. Immunomodulating and antiviral activities of Uncaria tomentosa on human monocytes infected with Dengue Virus-2. Int Immunopharmacol. Mar 2008;8(3):468-476.
  6. Garcia Prado E, Garcia Gimenez MD, De la Puerta Vazquez R, Espartero Sanchez JL, Saenz Rodriguez MT. Antiproliferative effects of mitraphylline, a pentacyclic oxindole alkaloid of Uncaria tomentosa on human glioma and neuroblastoma cell lines. Phytomedicine. Apr 2007;14(4):280-284.
  7. Pilarski R, Poczekaj-Kostrzewska M, Ciesiolka D, Szyfter K, Gulewicz K. Antiproliferative activity of various Uncaria tomentosa preparations on HL-60 promyelocytic leukemia cells. Pharmacol Rep. Sep-Oct 2007;59(5):565-572.
  8. Scott GN, Elmer GW. Update on natural product-drug interactions. Am J Health-Syst Pharm 2002;59:339-47.
  9. Hemingway SR, Phillipson JD. Proceedings: alkaloids from south American species of Uncaria (Rubiaceae). J Pharm Pharmacol 1974;26(suppl):113.
  10. Wirth C, et al. Pharmacologically active procyanidines from the bark of Uncaria tomentose. Phytomedicine 1997;4:265-6.
  11. Aquino R, et al. Plant metabolites: New compounds and anti-inflammatory activity of Uncaria tomentosa. J Nat Prod 1991;54:453-9.
  12. Rizzi R, et al. Mutagenic and antimutagenic activities of Uncaria tomentosa and its extracts. J Ethnopharmacol 1993;38:63-77.
  13. Sheng Y, et al. DNA repair of aqueous extracts of Uncaria tomentosa in a human volunteer study. Phytomedicine 2001;8:275-82.
  14. Hilepo JN, et al. Acute renal failure caused by 'cat's claw' herbal remedy in a patient with systemic lupus erythematosus. Nephron 1997;77:361.
  15. López Galera RM, Ribera Pascuet E, et al. Interaction between cat's claw and protease inhibitors atazanavir, ritonavir and saquinavir. Eur J Clin Pharmacol. 2008 Dec;64(12):1235-6.
  16. Cosentino C, Torres L. Reversible worsening of Parkinson disease motor symptoms after oral intake of Uncaria tomentosa (cat's claw). Clin Neuropharmacol. 2008 Sep-Oct;31(5):293-4.
  17. Rinner B, Li ZX, Haas H, et al. Antiproliferative and pro-apoptotic effects of Uncaria tomentosa in human medullary thyroid carcinoma cells. Anticancer Res. 2009 Nov;29(11):4519-28.
  18. García Giménez D, García Prado E, Sáenz Rodríguez T, et al. Cytotoxic effect of the pentacyclic oxindole alkaloid mitraphylline isolated from Uncaria tomentosa bark on human Ewing sarcoma and breast cancer cell lines. Planta Med. 2010 Feb;76(2):133-6.

Consumer Information

How It Works

Bottom Line: Cat's claw may stimulate the body's immune system but it has not been shown to be an effective treatment for cancer or HIV.

In laboratory experiments, compounds found in cat's claw stimulate the activity of specific immune cells (phagocytes and T-helper cells). It also lowers blood pressure by relaxing the cells that line blood vessels and inhibiting the excitatory effect that the sympathetic nervous system (the “fight or flight” response) has on the heart and blood vessels. These extracts are also able to 1) slow some of the processes that cause inflammation and 2) enhance the repair of DNA in the laboratory setting. However, it is not known if these effects occur in the human body.

Purported Uses
  • To treat cancer
    Cat's claw inhibits the growth of certain cancer cells in the labs. Human data are lacking.
  • To treat gastrointestinal disorders
    Laboratory studies suggest that cat's claw may reduce inflammation. This has not been studied in humans.
  • To treat HIV and AIDS
    Laboratory studies suggest that cat's claw can stimulate the activity of specific immune cells. Human studies are needed.
Do Not Take If
  • You are taking medication to lower your blood pressure (Cat's claw can have additive effects).
  • You are taking warfarin or other blood thinners (Cat's claw may increase the risk of bruising and bleeding).
  • You are taking drugs that are substrates of Cytochrome P450 3A4 (Cat's claw may increase the risk of side effects of these drugs).
  • You are taking Protease Inhibitors (Cat's claw was shown to increase the serum concentrations of atazanavir, ritonavir and saquinavir and can increase their side effects).
Side Effects
  • Diarrhea
  • Low blood pressure
  • Case report: Acute renal failure was observed in a patient with systemic lupus erythematosus (SLE).
    Case report: Worsening of motor signs in a 38-year-old patient with Parkinson disease has been reported after oral intake of cat's claw extract. But the symptoms improved following withdrawal of cat's claw use.
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