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 various conditions such as gastric and inflammatory disorders (1). It is also a very popular immune-enhancing supplement.

In vitro studies show that constituents from cat’s claw enhance phagocytosis, display immunomodulatory properties, alleviate inflammation, and possess antiviral and antimutagenic activities (1) (2) (3) (4) (5) (6). It has also been shown to modulate DNA repair in human skin (7).

Cat's claw demonstrated anticancer effects against several cancer cell lines (8) (9) (10) (11). An in vivo study also indicates anti-neoplastic effects in a breast tumor model (12). Another animal model suggests it may stimulate healthy hematopoietic tissue cells and reduce chemotherapy side effects such as neutropenia (13). A purified extract has modest benefit in patients with active rheumatoid arthritis (14), but confirmatory studies are lacking. Another small study indicates that cat’s claw may reduce chemotherapy side effects in breast cancer patients (15), but more studies are needed.

Pediatric leukemic cells exposed to U. tomentosa extract demonstrated an increased survival of these cells (16).

Purported Uses
  • AIDS
  • Arthritis
  • Cancer treatment
  • Chemotherapy side effects
  • GI disorders
  • Inflammation
  • Oxindole alkaloids: Isopteropodine, pteropodine, rhynchophylline, mytraphylline, speciophylline, uncarine F, uncarine E
  • Indole alkaloidal glucosides: Cadambine, 3-dihydrocadambine, and 3-isodihydrocadambine
  • Quinovic acid glycosides
  • Tannins
  • Polyphenols
  • Catechins
  • Beta sitosterol
    (1) (6) (17) (18) (19) (20)
Mechanism of Action

The oxindole alkaloids are claimed to have immunostimulating properties in vitro, increasing phagocytotic activity and synthesis of WBCs (5) and enhancing T-helper cell function(2). Inhibition of TNF-alpha production (3) (4) has both been linked to observed anti-inflammatory activities. Mitraphylline isolated from cat’s claw was also identified as possessing anti-inflammatory effects by inhibiting the release of interleukins 1α, 1β, 4, 17, and TNF-α (21).

U. tomentosa water extracts have been shown to enhance DNA repair after chemical-induced damage (22). Protection against oxidative DNA damage following UVB exposure may occur via enhanced base excision repair and inherent antioxidant effects (23). The biphasic manner in which U. tomentosa modulates anxiety, initially inducing and then reversing these effects after long-term administration, is attributed to the presence of many alkaloids and flavonols (18).

Quinovic acid glycosides purified fraction of U. tomentosa inhibits the growth of human bladder cancer cell lines by inducing apoptosis through modulation of NF-κB (20). Cat’s claw also inhibits lactate dehydrogenase-A, an enzyme that is highly expressed in diverse human malignant and treatment-resistant tumors with clinically poor outcomes (24). In vivo studies demonstrate antineoplastic effects against breast tumors due to modulation of oxidative stress and synergy among constituents with antioxidant properties, rather than alkaloid activity (12).


Should be avoided perioperatively and for those on immunosuppressant therapy (25).

Adverse Reactions

GI complaints: nausea, diarrhea, stomach discomfort (25)

Case reports
Acute renal failure: In a patient with systemic lupus erythematosus (SLE) (26).
Worsening motor signs: In a 38-year-old patient with Parkinson’s disease after oral intake of cat's claw extract, with symptom improvement after cessation and withdrawal (27).

Herb-Drug Interactions

Anticoagulants, antihypertensives: May increase effects of cardiovascular drugs, including increased risk of bleeding (25) (28).
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 (29).
Protease inhibitors: Cat's claw was shown to increase the serum concentrations of atazanavir, ritonavir and saquinavir (30).

Literature Summary and Critique

Santos Araujo Mdo C, et al. Uncaria tomentosa-Adjuvant Treatment for Breast Cancer: Clinical Trial. Evid Based Complement Alternat Med. 2012;2012:676984.
In this interventional study, 40 women with Stage 2 invasive ductal carcinoma who underwent complete resection and were beginning adjuvant doxorubicin-based chemotherapy were randomized to also receive either U. tomentosa 300 mg dry extract daily or no supplementation. These two groups were also compared with an additional group of 20 age-matched healthy controls who did not receive any medication or have any chronic disease. Blood samples were collected before each of 6 chemotherapy cycles, and hematologic and immunologic parameters, antioxidant enzymes, and oxidative stress were analyzed. The addition of U. tomentosa to the chemotherapy regimen appeared to reduce cellular DNA damage and chemotherapy-induced neutropenia. By the last cycle of chemotherapy, leukocyte and neutrophil counts in the group receiving supplementation were double that of the non-supplementation group. The supplementation group also had white blood cell and neutrophil counts that remained close to healthy control reference values. In immune response evaluations of CD4+  and CD8+ T cells and IL-6 levels, no significant between-group differences were noted. Because chemotherapy-induced neutropenia can result in treatment delays and dose reductions, this may have potential as an adjuvant therapy, but larger placebo-controlled trials are needed to confirm safety as well as effectiveness.

Dosage (Inside MSKCC Only)
This field is only visible to only OneMSK users.
  1. 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. doi: 10.1016/j.intimp.2007.11.010
  2. Riva L, Coradini D, Di Fronzo G, et al. The antiproliferative effects of Uncaria tomentosa extracts and fractions on the growth of breast cancer cell line. Anticancer Res. Jul-Aug 2001;21(4A):2457-2461.
  3. Sandoval M, Charbonnet RM, Okuhama NN, et al. Cat's claw inhibits TNFalpha production and scavenges free radicals: role in cytoprotection. Free Radic Biol Med. Jul 1 2000;29(1):71-78.
  4. Sandoval M, Okuhama NN, Zhang XJ, et al. Anti-inflammatory and antioxidant activities of cat's claw (Uncaria tomentosa and Uncaria guianensis) are independent of their alkaloid content. Phytomedicine. May 2002;9(4):325-337.
  5. Sheng Y, Bryngelsson C, Pero RW. Enhanced DNA repair, immune function and reduced toxicity of C-MED-100, a novel aqueous extract from Uncaria tomentosa. J Ethnopharmacol. Feb 2000;69(2):115-126.
  6. Caon T, Kaiser S, Feltrin C, et al. Antimutagenic and antiherpetic activities of different preparations from Uncaria tomentosa (cat's claw). Food Chem Toxicol. Apr 2014;66:30-35. doi: 10.1016/j.fct.2014.01.013
  7. Mammone T, Akesson C, Gan D, et al. A water soluble extract from Uncaria tomentosa (Cat's Claw) is a potent enhancer of DNA repair in primary organ cultures of human skin. Phytother Res. Mar 2006;20(3):178-183. doi: 10.1002/ptr.1827
  8. Garcia Prado E, Garcia Gimenez MD, De la Puerta Vazquez R, et al. 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. doi: 10.1016/j.phymed.2006.12.023
  9. Pilarski R, Poczekaj-Kostrzewska M, Ciesiolka D, et al. Antiproliferative activity of various Uncaria tomentosa preparations on HL-60 promyelocytic leukemia cells. Pharmacol Rep. Sep-Oct 2007;59(5):565-572.
  10. Rinner B, Li ZX, Haas H, et al. Antiproliferative and pro-apoptotic effects of Uncaria tomentosa in human medullary thyroid carcinoma cells. Anticancer Res. Nov 2009;29(11):4519-4528.
  11. Garcia Gimenez D, Garcia Prado E, Saenz Rodriguez T, et al. Cytotoxic effect of the pentacyclic oxindole alkaloid mitraphylline isolated from Uncaria tomentosa bark on human Ewing's sarcoma and breast cancer cell lines. Planta Med. Feb 2010;76(2):133-136. doi: 10.1055/s-0029-1186048
  12. Dreifuss AA, Bastos-Pereira AL, Fabossi IA, et al. Uncaria tomentosa exerts extensive anti-neoplastic effects against the Walker-256 tumour by modulating oxidative stress and not by alkaloid activity. PLoS One. 2013;8(2):e54618. doi: 10.1371/journal.pone.0054618
  13. Farias I, do Carmo Araujo M, Zimmermann ES, et al. Uncaria tomentosa stimulates the proliferation of myeloid progenitor cells. J Ethnopharmacol. Sep 1 2011;137(1):856-863. doi: 10.1016/j.jep.2011.07.011
  14. Mur E, Hartig F, Eibl G, et al. Randomized double blind trial of an extract from the pentacyclic alkaloid-chemotype of Uncaria tomentosa for the treatment of rheumatoid arthritis. J Rheumatol. Apr 2002;29(4):678-681.
  15. Santos Araujo Mdo C, Farias IL, Gutierres J, et al. Uncaria tomentosa-adjuvant treatment for breast cancer: clinical trial. Evid Based Complement Alternat Med. 2012;2012:676984. doi: 10.1155/2012/676984
  16. Styczynski J, Wysocki M. Alternative medicine remedies might stimulate viability of leukemic cells. Pediatr Blood Cancer. Jan 2006;46(1):94-98. doi: 10.1002/pbc.20513
  17. Hemingway SR, Phillipson JD. Proceedings: Alkaloids from S. American species of Uncaria (Rubiaceae). J Pharm Pharmacol. Dec 1974;26 Suppl:113P.
  18. Bigliani MC, Rosso MC, Zunino PM, et al. Anxiogenic-like effects of Uncaria tomentosa (Willd.) DC. aqueous extract in an elevated plus maze test in mice: a preliminary study. Nat Prod Res. 2013;27(18):1682-1685. doi: 10.1080/14786419.2012.761617
  19. Kaiser S, Dietrich F, de Resende PE, et al. Cat's claw oxindole alkaloid isomerization induced by cell incubation and cytotoxic activity against T24 and RT4 human bladder cancer cell lines. Planta Med. Oct 2013;79(15):1413-1420. doi: 10.1055/s-0033-1350742
  20. Dietrich F, Kaiser S, Rockenbach L, et al. Quinovic acid glycosides purified fraction from Uncaria tomentosa induces cell death by apoptosis in the T24 human bladder cancer cell line. Food Chem Toxicol. May 2014;67:222-229. doi: 10.1016/j.fct.2014.02.037
  21. Rojas-Duran R, Gonzalez-Aspajo G, Ruiz-Martel C, et al. Anti-inflammatory activity of Mitraphylline isolated from Uncaria tomentosa bark. J Ethnopharmacol. Oct 11 2012;143(3):801-804. doi: 10.1016/j.jep.2012.07.015
  22. Sheng Y, Li L, Holmgren K, et al. DNA repair enhancement of aqueous extracts of Uncaria tomentosa in a human volunteer study. Phytomedicine. Jul 2001;8(4):275-282. doi: 10.1078/0944-7113-00045
  23. Emanuel P, Scheinfeld N. A review of DNA repair and possible DNA-repair adjuvants and selected natural anti-oxidants. Dermatol Online J. 2007;13(3):10.
  24. Deiab S, Mazzio E, Messeha S, et al. High-Throughput Screening to Identify Plant Derived Human LDH-A Inhibitors. European J Med Plants. 2013;3(4):603-615.
  25. Erowele GI, Kalejaiye AO. Pharmacology and therapeutic uses of cat's claw. Am J Health Syst Pharm. Jun 1 2009;66(11):992-995. doi: 10.2146/ajhp080443
  26. Hilepo JN, Bellucci AG, Mossey RT. Acute renal failure caused by 'cat's claw' herbal remedy in a patient with systemic lupus erythematosus. Nephron. 1997;77(3):361.
  27. Cosentino C, Torres L. Reversible worsening of Parkinson disease motor symptoms after oral intake of Uncaria tomentosa (cat's claw). Clin Neuropharmacol. Sep-Oct 2008;31(5):293-294. doi: 10.1097/WNF.0b013e31815a5eef
  28. Vogel JH, Bolling SF, Costello RB, et al. Integrating complementary medicine into cardiovascular medicine. A report of the American College of Cardiology Foundation Task Force on Clinical Expert Consensus Documents (Writing Committee to Develop an Expert Consensus Document on Complementary and Integrative Medicine). J Am Coll Cardiol. Jul 5 2005;46(1):184-221. doi: 10.1016/j.jacc.2005.05.031
  29. Scott GN, Elmer GW. Update on natural product—drug interactions. Am J Health Syst Pharm. Feb 15 2002;59(4):339-347.
  30. Lopez Galera RM, Ribera Pascuet E, Esteban Mur JI, et al. Interaction between cat's claw and protease inhibitors atazanavir, ritonavir and saquinavir. Eur J Clin Pharmacol. Dec 2008;64(12):1235-1236. doi: 10.1007/s00228-008-0551-1

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 known as phagocytes and T-helper cells. Cat’s claw may also be able to slow some of the processes that cause inflammation, enhance DNA repair, and may reduce certain chemotherapy side effects. However, most of these effects are observed in lab studies, with only a few small studies in humans reported.

Purported Uses
  • To treat arthritis
    A small study using a highly purified extract of a particular chemical makeup suggested modest benefit in patients with active rheumatoid arthritis, but larger well-designed studies are needed to confirm this.
  • To reduce cancer-treatment side effects
    A small study suggests that Cat's claw may protect against abnormally low counts of white blood cells in patients receiving certain cancer treatments, but more studies are needed to prove safety and effectiveness.
  • 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.
Research Evidence

Cancer-treatment side effects
A small study evaluated whether Cat’s claw may be helpful to prevent chemotherapy side effects. Forty women with breast cancer who underwent surgery and were starting a doxorubicin-based chemotherapy were randomly assigned to also receive either Cat’s claw extract daily or no supplementation. The two groups were also compared with an additional group of 20 healthy subjects of similar ages. Blood samples were collected before each of 6 chemotherapy cycles and analyzed. Researchers found that Cat’s claw supplementation reduced the incidence of very low white blood cell counts caused by chemotherapy. They also noted these counts were similar to those in the healthy subject group. Since chemotherapy-induced side effects like these can result in treatment delays and dose reductions, Cat’s claw may have potential as support therapy along with certain kinds of chemotherapy, but larger studies are needed to confirm both safety and effectiveness.

Do Not Take If
  • 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.
  • You are taking immune suppressants: Cat's claw may stimulate immune cells, which may make these drugs less effective.
  • You are having surgery: Due to the potential for increased bleeding and lack of safety data.
Side Effects

Nausea, diarrhea, stomach discomfort. Case reports of kidney failure in a patient with lupus, and worsening movement in a patient with Parkinson’s disease.

Special Point

Caution is advised for cancer patients outside of participation in a clinical study, because pediatric leukemia cells in the lab exposed to cat’s claw actually survived longer than those that weren’t exposed.

E-mail your questions and comments to