Written by Klara Rombauts, Italo M Cesari and the CAM-Cancer Consortium.
Updated March 9, 2017

Cat's claw (Uncaria spp)

Does it work?

Clinical trials

No controlled clinical trials investigating cat’s claw as an anticancer agent are available.

Two randomized clinical trials focusing on the reduction of side effects caused by chemotherapy are available 25,26. Both trials using an ethanolic extract of cat’s claw were published by the same group. The treatment consisted of oral tablets containing 300 mg of U. tomentosa dried ethanolic extract on top of chemotherapy. The control group received chemotherapy only. In the first trial (n=43), in this population and at the dose used, cat’s claw dry extract was not effective in reducing the most prevalent adverse events caused by treatment with 5-fluorouracil and oxaliplatin in colorectal cancer patients 25. In the second trial, cat’s claw was able to reduce neutropenia caused by a regimen consisting of fluorouracil, doxorubicin and cyclophosphamide and was also able to restore cellular DNA damage in the treatment of breast cancer. Cat’s claw showed no effect on antioxidant activity and on immune response. The dose of extract used in both trials was not tested in a dose-finding study but was based on the dose used in other (not cancer-related) clinical trials (discussed in the ‘Is it safe?’ section below (34-36)). Since these trials used an aqueous extract, different phytochemicals were extracted so there is no rationale to use this dose. It is unknown if the optimal dose was used in these trials.

One uncontrolled trial of 51 patients with advanced solid tumours assessed the effects of a 100mg dose of a dry extract of cat’s claw three times daily 39. Some improvements in overall quality of life, social functioning and fatigue were reported. None of the biochemical or inflammatory parameters assessed changed significantly and no tumour response was detected.

Case series/studies

Although a large number of case reports are available on the internet, none have been published in peer-reviewed journals.


Klara Rombauts, Italo M Cesari, CAM-Cancer Consortium. Cat's claw (Uncaria spp) [online document]. http://cam-cancer.org/The-Summaries/Herbal-products/Cat-s-claw-Uncaria-spp. March 9, 2017.

Document history

Revised in March 2017 by Barbara Wider.

Assessed as up to date in September 2014 by Barbara Wider.
Summary first published in February 2013, authored by Klara Rombauts and Italo M Cesari.


  1. Keplinger K, Laus G, Wurm M, Dierich MP, Teppner H. Uncaria tomentosa (Willd.) DC. ethnomedicinal use and new pharmacological, toxicological and botanical results. J. Ethnopharmacol. 1999;64(1):23–24.
  2. Reinhard KH. Uncaria tomentosa (Willd.) D.C.: cat’s claw, uña de gato, or sevéntaro. J Alternative Complementary Med. 1999;5(2):143–151.
  3. Dr. Duke's Phytochemical and Ethnobotanical Databases. Uncaria tomentosa. [internet]. Available at https://phytochem.nal.usda.gov/phytochem/plants/show/2064?et=, accessed 9th March 2017.
  4. Laus G, Brossner D, Keplinger K. Alkaloids of peruvian Uncaria tomentosa. Phytochemistry. 1997;45:855-860.
  5. Sandoval M, Charbonnet RM, Okuhama NN, Roberts J, Krenova Z, Trentacosti AM, Miller MJ. Cat´s claw inhibits TNF-alpha production and scavenges free radicals: role in cytoprotection. Free Radic Biol Med. 2000;29(1):71-8.
  6. Kitajima M, Hashimoto K, Takamaya H, Shakai SI. A new gluco indole alkaloid from Peruvian Uncaria tomentosa. Chem Pharm Bull (Tokyo). 2000;48(10):1410-2.
  7. Kitajima M, Hashimoto K, Yokoya M, Takayama H, Sandoval M, Aimi N. Two new nor-triterpene gycosides from Peruvian "Una de gato" (Uncaria tomentosa). J. Nat. Prod. 2003;66(2):320-323.
  8. Ganzera M, Muhammad I, Khan RA, Khan IA. Improved method for determination of oxindole alkaloids Uncaria tomentosa by high performance liquid chromatography. Planta Med. 2001;67:447-450.
  9. Montoro P, Carbone V, Quiroz J, De Simone F, Pizza C. Identification and quantification of components in extracts of Uncaria tomentosa by HPLC-ES/MS. Phytochemistry. 2004;158(1):55-64.
  10. Gattuso M, Di Sapio O, Gattuso S, Pereyra EL. Morphoanatomical studies of Uncaria tomentosa and Uncaria guianensis bark and leaves. Phytomedicine. 2004;11(2-3):213-23.
  11. Heitzman ME, Neto CC, Winiarz E, Vaisberg AJ, Hammond GB. Ethnobotany, phytochemistry and pharmacology of Uncaria (Rubiaceae). Phytochemistry 2005;66(1):5-29.
  12. Obregon Vilches LE (1995). Cat's claw, Uncaria genus. Botanical, chemical and pharmacological studies of Uncaria tomentosa (Willd.) D.C. (Rubiaceae) and Uncaria guinensis (Aubl.) Gmel. Lima (Perú): Instituto de Fitoterapia Andina, 144 p.
  13. Tropical Plant Database: Cat’s Claw (Uncaria tomentosa). [Internet] Available from: http://www.rain-tree.com/catclaw.htm#, accessed 9th March 2017.
  14. Valerio LG Jr, Gonzales GF. Toxicological aspects of the South American herbs cat’s claw (Uncaria tomentosa) and Maca (Lepidium meyenni): A critical synopsis. Toxicol Rev 2005;24(1): 1-25.
  15. Natural Medicines Comprehensive Database. Cat’s Claw [internet] Available from: http://naturaldatabase.therapeuticresearch.com, accessed 9th March 2017.
  16. Wirth C, Wagner H. Pharmacologically active procyanidines from the bark of Uncaria tomentosa. Phytomedicine. 1997;4:265-266.
  17. Pilarski R, Zielinski H, Ciesiotka D, Gulewicz K. Antioxidant activity of ethanolic and aqueous extracts of Uncaria tomentosa (Willd.) DC. Ethnopharmacol. 2006;104: 18-23.
  18. Sheng Y, Bryngelsson C, Pero WR. Enhanced DNA repair, immune function and reduced toxicity of C-MED-100 tm, a novel aqueous extract from Uncaria tomentosa. J. Ethnopharmacol. 2000;69:115-126.
  19. De Martino L, Silva-Martinot JL, Franceschelli S, Leone A, Pizza C, De Feo V. Proapoptotic effect of Uncaria tomentosa extracts. J. Ethnopharmacol. 2006;107(1):91-4.
  20. Caballero M, Arsenak M, Abad MJ, Cesari IM, Taylor PG. Effect of 3 plant extracts on B16-BL6 melanoma cell growth and metastasis in C57BL/6 mice. Acta Científica Venezolana. 2005;55:21-27.
  21. Fazio A, Ballen D, Cesari IM, Abad M, Arsenak M, Taylor P. An ethanolic extract of Uncaria tomentosa reduces inflammation and B16-BL6 melanoma growth in C57BL/6 mice. Bol Latinoam Caribe Plant Med Arom 2008;7(4): 217-225.
  22. Sandoval-Chacon M, Thompson JH, Zhang XJ, Liu X, Mannick EE, Sadowska-Krowicka H, Charbonnet RM, Clark DA, Miller MJ. Antiinflamatory actions of cat´s claw: the role of NF-kappaB. Aliment Pharmacol Ther. 1998;12(12):1279-1289.
  23. Akesson C, Lindgreen H, Pero RW, Leanderson T, Ivars F. An extract of Uncaria tomentosa inhibiting cell division and NF-B activity without inducing cell death. Int Immunpharmacol. 2003;3(13-14):1889-900.
  24. Dreifuss AA, Bastos-Pereira AL, Avila TV, da Silva Soley B, Rivero AJ, Aguilar JL, Acco A. Antitumoral and antioxidant effects of a hydroalcoholic extract of cat’s claw (Uncaria tomentosa) (Willd. Ex Roem. & Schult) in an in vivo carcinosarcoma model. J Ethnopharmacol. 2010;130:127–133.
  25. Farias ILG, Araújo MCS, Farias JG, Rossato LV, Elsenbach LI, Dalmora SL, Flores NMP, Durigon M, Cruz IBM, Morsch VM, Schetinger MRC. Uncaria tomentosa for reducing side effects caused by chemotherapy in CRC patients: Clinical trial. Evidence-Based Complementary and Alternative Medicine Vol. 2012, Article ID 892182: 8 pages.
  26. Araújo MCS, Farias ILG, Gutierres J, Dalmora SL, Flores N, Farias J, Cruz I, Chiesa J, Morsch VM, Schetinger MRC (2012). Uncaria tomentosa – Adjuvant Treatment for Breast Cancer: Clinical trial. Evidence-Based Complementary and Alternative Medicine Vol. 2012, Article ID 676984: 8 pages.
  27. Sheng Y, Pero RW, Amiri A, Bryngelsson C. Induction of apoptosis and inhibition of proliferation in human tumor cells treated with extracts of Uncaria tomentosa. Anticancer Res. 1998;18(5A):3363-8.
  28. Pilarski R, Filip B, Wietrzyk J, Kuras M, Gulewicz K. Anticancer activity of the Uncaria tomentosa DC. preparations with different oxindole alkaloid composition. Phytomedicine. 2010;17:1133–1139.
  29. 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. 2001;4A:2457-61.
  30. Bacher N, Tiefenthaler M, Sturm S, Stuppner H, Ausserlechner M, Kofler R. Oxindole alkaloids from Uncaria tomentosa induce apoptosis in proliferating, G0/G1-arrested and bcl-2-expressing acute lymphoblastic leukaemia cells. Br J Haematol. 2006;132:615-622.
  31. Erowele GI, Kalejaiye AO. Pharmacology and therapeutic uses of cat’s claw. Am. J. Health-Syst. Pharm. 2009;66:992-995.
  32. 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. 2007;14:280-284.
  33. García Giménez D, García Prado E, Sáenz Rodríguez T, Fernández Arche A, De la Puerta R. 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. 2010;76(2):133-6.
  34. Sheng Y, Li L, Holmgren K, Pero RW. DNA repair enhancement of aqueous extracts of Uncaria tomentosa in a human volunteer study. Phytomedicine. 2001;8(4):275-82.
  35. Lamm S, Sheng Y, Pero RW. Persistent response to pneumococcal vaccine in individuals supplemented with a novel water soluble extract of Uncaria tomentosa, C-Med-100. Phytomedicine. 2001;8(4):267-274.
  36. Piscoya J, Rodriguez Z, Bustamante SA, Okuhama NN, Miller MJ, Sandoval M. Efficacy and safety of freeze-dried cat's claw in osteoarthritis of the knee: mechanisms of action of the species Uncaria guianensis. Inflamm Res 2001;50(9): 442-8.
  37. Bright-Gbebry et al. Use of multivitamins, folic acid and herbal supplements among breast cancer survivors: the black women’s health study. BMC Complementary and Alternative Medicine 2011;11:30
  38. Rinner B et al. Antiproliferative and pro-apoptotic effects of Uncaria tomentosa in human medullary thyroid carcinoma cells. Anticancer Res. 2009;29(11):4519-28.
  39. de Paula LC, Fonseca F, Perazzo F, Cruz FM, Cubero D, Trufelli DC, Martins SP, Santi PX, da Silva EA, Del Giglio A. Uncaria tomentosa (cat's claw) improves quality of life in patients with advanced solid tumors. J Altern Complement Med. 2015;21(1):22-30.