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 humans.
In laboratory experiments, compounds found in cat's claw have been shown to stimulate the activity of specific immune cells (phagocytes and T-helper cells). Cat's claw extracts may lower 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 may inhibit the growth of certain cancer cells in the labs. It has not been shown to be an effective cancer treatment.
To treat gastrointestinal disorders
Laboratory studies suggest that cat's claw may reduce inflammation, but there is no proof from clinical trials that cat's claw can treat gastrointestinal problems in humans.
To treat HIV and AIDS
Laboratory studies suggest that cat's claw can stimulate the activity of specific immune cells, but there is no proof from clinical trials that cat's claw can treat HIV or AIDS.
Research Evidence
No clinical trials have tested the safety or effectiveness of cat's claw in humans.
Warnings
Cat's claw is suspected to inhibit the liver enzyme cytochrome P450 3A4. This enzyme is necessary for metabolizing several drugs and eliminating them from the body. Therefore cat's claw might slow this important activity and raise the blood levels of drugs such as protease inhibitors, nonnucleoside reverse-transcriptase inhibitors, cyclosporine, some benzodiazepines, and many others. Patients should ask their doctor if cat's claw might interfere with the metabolism of any medication they are taking.
This product is regulated by the F.D.A. as a dietary supplement. Unlike approved drugs, supplements are not required to be manufactured under specific standardized conditions. This product may not contain the labeled amount or may be contaminated. In addition, it may not have been tested for safety or effectiveness.
Do Not Take If
You are taking medication to lower your blood pressure (Cat's claw might lower blood pressure even lower).
Are taking warfarin or other blood thinners (Cat's claw may increase the risk of bruising and bleeding).
Side Effects
Diarrhea
Low blood pressure
One patient with systemic lupus erythematosus (SLE) experienced acute kidney failure after using cat's claw.
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 this plant 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 is also thought to have anticancer activities and lab results demonstrated growth inhibitory effects on glioma and neuroblastoma cells as well as promyelocytic leukemia cells
(6) (7). However, no human studies have been conducted to evaluate efficacy.
Reported adverse reactions include hypotension and diarrhea. An additive effect with anticoagulants or hypotensives is possible; therefore caution should be exercised
(8).
Purported uses
Cancer treatment
GI disorders
HIV and AIDS
Inflammation
Constituents
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 in a patient with systemic lupus erythematosus (SLE)
(14)
Herb-Drug Interactions
Antihypertensives: Cat's claw may have an additive or synergistic hypotensive effect.
Anticoagulants / Antiplatelets: Cat's claw may have an additive anticoagulant effect.
CYP3A4: In vitro, cat's claw inhibits CYP3A4, indicating that it may theoretically increase the serum levels of drugs such as protease inhibitors, nonnucleoside reverse-transcriptase inhibitors, cyclosporine, some benzodiazepines, and others.
(8)
Literature Summary and Critique
Animal and in vitro data exist in cancer, immunostimulant, inflammation, and antiviral studies. Human studies are lacking, and further research is needed.
References
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.
