By Alessio Di Domenico
Master’s Degree in Food Science and Bachelor’s Degree in Food Technologies
Università Degli Studi di Firenze, Italy

Last updated Thursday, January 28, 2021

The Amazon rainforest, the largest rainforest on earth, is richer in plant life than any other place in the world. Targeted by pharmaceutical companies for over a century as a land of exploration for source materials of new drugs, the Amazon rainforest is also a treasure trove of botanicals for the herbal supplement industry. Among the many Amazon botanicals that have come to light in recent years, Uña de Gato (Uncaria tomentosa), which means “cat’s claw” in Spanish, is one of the most promising of all.

Cat’s claw is a large vine that grows in the Amazon River basin and has been used in South American traditional medicine for centuries, its name referring to the curved thorns found along its woody vines that resemble cat’s claws. Cat’s claw includes two species, Uncaria tomentosa and Uncaria guinaensis, and the extract is usually made from their root bark most commonly from U. tomentosa. Cat’s claw is used as an analgesic and antiinflammatory agent to treat gastrointestinal, rheumatologic and other chronic inflammatory conditions (LiverTox), as a potential alternative natural solution for preventing and reducing both brain plaques and tangles (3) and a complementary and/or alternative medicine for COVID-19 treatment (4). Constituents of cat’s claw extracts include 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 and beta sitosterol. In vitro, extracts of cat’s claw have immune modulatory, antiviral and antimutagenic activities. The active ingredients of cat’s claw extracts are not completely well defined. Their anti-inflammatory action in cell culture studies seems to be represented by the oxindole alkaloids. On the other hand, the polyphenols and catechins present in the cortex have antioxidant actions. In humans, the evidence for the effectiveness of cat’s claw extracts has been mixed. While small controlled studies have suggested a beneficial effect on pain in chronic rheumatoids and osteoarthritis, other studies have been inconclusive, as improvements in clinical symptoms are similar to those with placebo or comparator arms. However, cat’s claw is widely used and is claimed to have anti-inflammatory and analgesic effects and is often given in combination with other dietary supplements (such as glucosamine and chondroitin) or with conventional therapies. Despite being widely used, cat’s claw has not been implicated in cases of clinically apparent liver injury and, in prospective studies, has had no effect on serum enzyme levels. In vitro studies have demonstrated antioxidant activity of cat’s claw extracts which may be hepatoprotective. Because cat’s claw inhibits microsomal CYP 3A4 activity, it has a potential to cause herb-drug interactions and raise the levels of other drugs that are metabolized by CYP 3A4 (LiverTox). Capsules, extracts, tinctures, decoctions, and teas produced from cat’s claw are commercially available. As a capsule, 250–1000 mg daily has been taken by mouth in divided doses. Up to 25 g of the raw bark has been used in decoctions, although this is based on traditional administration practices. Cat’s claw is also available in preparations for the skin, but no specific dose has been shown to be safe or effective.

Few adverse effects have been reported, and most are believed to be rare. Some adverse effects are theoretical and have not yet been reported in humans. Some possible adverse effects include stomach discomfort, nausea, diarrhea, slow or altered heartbeats, kidney disease, acute kidney failure, neuropathy, decreased estrogen or progesterone levels, and increased risk of bleeding (National Center for Complementary and Alternative Medicines). Although traditional knowledge suggests that cat’s claw is safe and nontoxic, the American Herbal Products Association (AHPA) has given cat’s claw a class-4 safety rating, which indicates a lack of scientific data to consider the herb safe. In addition, AHPA does indicate that the tannin content of cat’s claw may cause some abdominal pain or gastrointestinal problems, including diarrhea. Cat’s claw should not be used by individuals with skin grafts or tuberculosis or by those receiving organ transplants. The safety of cat’s claw has not been established in pregnant or breastfeeding women or in children. Because of the lack of toxicity data, the use of cat’s claw during pregnancy or lactation should be avoided. Cat’s claw does have immunostimulant properties, which may interfere with immunosuppressive therapy and it has also been contraindicated in patients receiving anticoagulants and in those with coagulation disorders because of the inhibitory effects of rhynchophylline on platelet aggregation (2).

Cat’s claw has been used widely in folk medicine for years, but its formulations are frequently used for their medicinal activity with minimal adverse effects. However, because of the lack of adequate clinical trials, more studies are needed to establish a place in therapy for cat’s claw (1).

Bibliography

  1. Erowele GI, Kalejaiye AO. Pharmacology and therapeutic uses of cat’s claw. Am J Health Syst Pharm. 2009 Jun 1;66(11):992-5. doi: 10.2146/ajhp080443. PMID: 19451609.
  2. Jin RM, Chen CX, Li YK, Xu PK. [Effect of rhyncophylline on platelet aggregation and experimental thrombosis]. Yao Xue Xue Bao. 1991;26(4):246-9. Chinese. PMID: 1957668.
  3. Snow AD, Castillo GM, Nguyen BP, Choi PY, Cummings JA, Cam J, Hu Q, Lake T, Pan W, Kastin AJ, Kirschner DA, Wood SG, Rockenstein E, Masliah E, Lorimer S, Tanzi RE, Larsen L. The Amazon rain forest plant Uncaria tomentosa (cat’s claw) and its specific proanthocyanidin constituents are potent inhibitors and reducers of both brain plaques and tangles. Sci Rep. 2019 Feb 6;9(1):561. doi: 10.1038/s41598-019-38645-0. PMID: 30728442; PMCID: PMC6365538.
  4. Yepes-Pérez AF, Herrera-Calderon O, Quintero-Saumeth J. Uncaria tomentosa (cat’s claw): a promising herbal medicine against SARS-CoV-2/ACE-2 junction and SARS-CoV-2 spike protein based on molecular modeling. J Biomol Struct Dyn. 2020 Oct 29:1-17. doi: 10.1080/07391102.2020.1837676. Epub ahead of print. PMID: 33118480; PMCID: PMC7657399.

Sitography

  1. American Herbal Products Association. Cats claw. www.ajc.com/health/altmed/shared/health/alt_medicine/ConsHerbs/CatsClawch.html (accessed 2009 Mar 31).
  2. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury [Internet]. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases; 2012-. Cat’s Claw. [Updated 2019 Feb 18]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK548323/
  3. National Center for Complementary and Alternative Medicines. Herbs at a glance. Cat’s claw. http://nccam.nih.gov/health/catclaw/#uses (accessed 2008 Jul 29).