# Cat’s claw (Uncaria tomentosa)

*Spanish *u a de gato*; *saventaro*; ‘life-giving vine of Peru’; *Uncaria tomentosa* (Willd. ex Schult.) DC.; in pharmacy *Uncariae tomentosae cortex**

**Known today as.** *Uncaria tomentosa*, of the family Rubiaceae, a thick woody vine of the Amazon rain forest and other tropical parts of South and Central America, scrambling up to twenty or thirty metres. Its hook-like thorns, set along the vine, resemble the claws of a cat. The drug is the bark of the stem or root. The European Medicines Agency’s assessment report warns that the names cat’s claw and *u a de gato* are used for several plants in tropical America, and that the related *Uncaria guianensis*, lower-growing and easier to find, is a common adulterant. Its characteristic constituents are oxindole alkaloids, with quinovic acid glycosides and proanthocyanidins.

Kind: Plant

> **Caution.** Only few and mild side effects have been reported. A single case report suggested that it may not be wise to combine it with medicines broken down by the liver enzyme CYP3A4. Its safety in pregnancy, breast-feeding, and under eighteen has not been established. LiverTox finds that it has not been implicated in liver injury.

## What was it used for?

A Peruvian remedy for inflammation. The assessment report records that Peruvian tribes, the Ash ninka with the longest recorded history of its use, took it as an anti-inflammatory, a contraceptive, and an emmenagogue, and for gastric ulcer, diarrhoea, asthma, wounds, arthritis, and cancer, and that it was traditionally avoided in pregnancy, breast-feeding, and for children. Since the early 1990s it has been used in Peru and Europe as an adjunct in cancer and AIDS.

## What does modern science say?

The European Medicines Agency’s herbal committee declined to adopt a monograph on the bark (public statement of 2015): preparations had been in medicinal use in the European Union for more than fifteen but less than thirty years, and the requirements for well-established use were not met. Its assessment report found the preclinical data diverse and noted that most studies did not specify which bark was used. LiverTox, revised in 2019, finds the evidence for its efficacy in people mixed: small controlled trials suggested some benefit for pain in rheumatoid arthritis and osteoarthritis, while other studies were inconclusive.

## Pharmacognosy and toxicology

- **oxindole alkaloids**: the characteristic constituents
- **quinovic acid glycosides**: 
- **proanthocyanidins**: 

**Mechanism.** Not established in the sources read for this entry.

**Standing.** There is no European monograph: the European Medicines Agency’s herbal committee declined to adopt one (public statement of 2015).

## What did the older authorities say?

**The European Medicines Agency’s assessment report (2015).** The plant was first described in 1830 and first studied in Peru by the German biologist Brell in 1950. In the 1970s the Austrian Klaus Keplinger began the scientific work that led to extracts sold in Austria and Germany and to four United States patents on its oxindole alkaloids; the research and business that followed so overharvested the vine that it declined in the Peruvian rainforests.

## Sources

- European Medicines Agency, Committee on Herbal Medicinal Products. *Public statement on Uncariae tomentosae cortex (Cat's Claw)*. EMA/HMPC/588732/2014, 24 November 2015.
- European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Uncariae tomentosae cortex*. EMA/HMPC/259598/2014, 24 November 2015.
- LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, “CatsClaw.” National Institute of Diabetes and Digestive and Kidney Diseases, updated 2019. NCBI Bookshelf.
- European Medicines Agency, Committee on Herbal Medicinal Products. *Public statement on Uncariae tomentosae cortex (Cat's Claw)*. EMA/HMPC/588732/2014, 24 November 2015.
- European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Uncariae tomentosae cortex*. EMA/HMPC/259598/2014, 24 November 2015.
- LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, “CatsClaw.” National Institute of Diabetes and Digestive and Kidney Diseases, updated 2019. NCBI Bookshelf.

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*Cat’s claw.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-17. The Thinking Press. https://thethinkingpress.org/materia-medica/cat-s-claw

Historical description, not medical advice.