Cat’s claw is a medicinal herb traditionally used to stimulate the immune system. Research has shown it boosts immune function, reduces inflammation, and helps with chemotherapy. Read on to discover the health benefits and adverse effects associated with this herb.

What is Cat’s Claw?

Cat’s claw (Uncaria tomentosa) is a medicinal plant that grows in the Amazonian rainforest and other tropical areas in Central and South America. The use of the herb dates back to the Inca civilization. Indigenous cultures of South America used cat’s claw for inflammation, cancer, viral infections, ulcers, and to stimulate the immune system [1, 2].

It gets its name from its thorns, which resemble the claws of cats.

Cat’s claw can refer to Uncaria tomentosa and Uncaria guianensis [3, 4].

Most commercial preparations such teas, tablets, and capsules contain U. tomentosa [2].

There are two different types of cat’s claw, and they contain different active compounds and have different medicinal properties. One contains more pentacyclic oxindole alkaloids (POAs) and the other more tetracyclic oxindole alkaloids (TOAs) [3, 4].

TOAs act on the central nervous system (brain and spinal cord), whereas POAs affect the immune system [5].

TOAs cancel out the effects of POAs. Therefore it is important when purchasing and consuming cat’s claw extracts to be sure that they have been tested for TOA and POA levels [5].

Differences between the two types are conveyed in the chemical structure. Pentacyclic alkaloids are found in the vine bark while tetracyclic alkaloids are found in the leaves and stem of the plant [6, 7].

Main Beneficial Compounds of Cat’s Claw

Cat’s claw is rich in three major groups of chemical compounds: alkaloids, terpenoids, and flavonoids [4].

Specific compounds found in cat’s claw include:

  • Mitraphylline is an alkaloid usually found in older leaves and has anticancer effects, causing cell death in sarcoma and breast cancer cells [48].
  • Rhynchophylline is an alkaloid isolated from the bark, which helps with convulsions, lightheadedness, numbness, and hypertension [910].
  • Isopteropodine is an alkaloid isolated from the leaves and has antimicrobial properties against (Gram-positive) bacteria [9 11].
  • Uncarine (C, D, and E) are a family of alkaloids found in the leaves, which have anti-cancer properties, inducing cell death in leukemia cells [412].
  • Hirsutine is an alkaloid found in the young leaves, which has antihypertensive properties, relaxing blood vessels and reducing overall blood pressure [413].
  • Uncaric acid is a triterpene extracted from the bark and is effective against Mycobacterium tuberculosis (H37Rv strain) [1415].
  • Quinovic acid is an acid triterpene compound extracted from the bark that reduces heart rate [1617].
  • Quinic acid has antioxidant properties, enhances DNA repair, and has neuroprotective effects in the brain [181920].
  • Procyanidins is a flavonoid (phenolic compounds found in the leaves, stems, bark, and wood of U. tomentosa), which has antioxidant, anti-inflammatory, and anticancer properties [2122].

Mechanisms of Action

Cat’s claw:

  • Decreases inflammatory molecules TNF-α and NF-κB [23242523].
  • Blocks the release of iNos, an enzyme that creates free radicals as part of the immune response [26].
  • Blocks the release of COX-1 and COX-2, enzymes that play crucial roles in inflammation and pain [27, 28].

Health Benefits

1) Can Help with Chemotherapy

In rats who received chemotherapy, cat’s claw increased white blood cell count and helped repair damaged DNA [29].

In a study of 40 breast cancer patients undergoing chemotherapy, 300 mg cat’s claw extract prevented a decrease in white blood cells (neutropenia) and repaired DNA damage [30].

However, in another study of 43 colorectal cancer patients undergoing chemotherapy, 300 mg of cat’s claw extract did not affect white or red blood cell counts [31].

Cat’s claw also stimulates the growth of progenitor cells in mice, which can replace damaged cells and reduce the damaging effects of chemotherapy [32].

2) Helps Treat Arthritis

Cat’s claw’s anti-inflammatory effects have been commonly used to treat both rheumatoid arthritis and osteoarthritis. The different compounds in cat’s claw act together to achieve these effects [33].

Mitraphylline blocks the release of inflammatory molecules such as IL-1, IL-4, and IL-17, and TNF-alpha [34].

Other pentacyclic oxindole alkaloids cause the release of a currently unidentified immune regulating factor that reduces arthritic joint pain [3536].

Quinic acid decreases inflammatory molecules like NF-κB [182537].

Cat’s claw extract (Vincaria) increased IGF-1 levels in human cartilage cells, which might help to maintain cartilage health and prevent cartilage breakdown [38].

Cat’s claw blocks IL-1β and other inflammatory molecules that suppress IGF-1 production [39, 40].

In one study of 40 rheumatoid arthritis patients, cat’s claw combined with conventional arthritis treatments (sulfasalazine/hydroxychloroquine) reduced tender and painful joints [36].

In another study of 45 patients with osteoarthritis, one week of cat’s claw reduced pain associated with activity compared to placebo [41].

3) Helps with Stomach and Gut Inflammation

Cat’s claw can cleanse the digestive tract and may help treat inflammatory gut disorders including [42]:

  • Crohn’s disease
  • Colitis
  • Gastritis
  • Diverticulitis
  • Stomach ulcers
  • Leaky gut

Cat’s claw protected against stomach inflammation in rats and prevented TNF-α production and cell death [25].

Bacterial toxins also cause the release of inflammatory molecules like NF-κB and TNF-α. Cat’s claw blocks the release of these inflammatory molecules [43, 34].

Inflammation of the gut is also caused by toxic free radicals (peroxynitrite). Cat’s claw not only acts as a powerful antioxidant against free radicals but also reduces cell death caused by gut bacterial toxins [44].

4) May Help with High Blood Pressure

Cat’s claw inhibits platelet aggregation and blood clot formation, decreasing overall blood pressure and increasing circulation. It also inhibits the formation of plaques and blood clots in the heart, brain, and blood vessels [45].

Cat’s claw contains a compound called hirsutine that reduces blood pressure [4, 13].

Hirsutine acts as a calcium channel blocker in the heart and blood vessels, which slows down heart rate and relaxes the blood vessels [46].

5) Fights the Herpes Virus

Cat’s claw prevented immune cells from being infected with Dengue Virus and reduced inflammatory cytokines TNF-alpha and IFN-alpha [47].

The extracts prevented the spread of the herpes virus by preventing it from attaching to cells [48].

In a study of 31 volunteers with cold sores (herpes labialis), cat’s claw was more effective in reducing symptoms such as swelling, skin reddening, and pain compared to prescription antiviral drug Acyclovir [49].

6) Can Protect Against Type 1 Diabetes

Cat’s claw has positive effects in the treatment of diabetes [50].

Type 1 diabetes is a chronic autoimmune disorder, where the immune system destroys the cells in the pancreas that make insulin [51].

Cat’s claw reduced blood sugar levels and inflammation and prevented diabetes in mice given whose insulin-releasing cells were damaged [52].

7) May Help Fight Cancer

Cat’s claw directly inhibited the growth of human breast cancer cells [53].

Cat’s claw extracts inhibited the growth of and increased programmed cell death in leukemia cells [12].

8) Boosts the Immune System

Cat’s claw enhances the immune system by increasing the levels of key immune cells (T helper and B cells) and the activity of granulocytes [54, 55, 56, 57].

9) Protects Red Blood Cells

Cat’s claw protected red blood cells (RBCs) from damage due to toxins and reduced oxidative stress [58].

Cat’s claw prevented cell death and oxidative stress in RBCs exposed to pesticides [59, 60].

10) Is Anti-inflammatory

Procyanidins and other polyphenols in cat’s claw scavenge and remove oxidative radicals in cell studies [61].

Cat’s claw also prevented the production of the inflammatory cytokine TNF-α and prevented programmed cell death in cell studies [25].

Side Effects and Precautions, Limitations & Dosage

Cat’s claw is generally considered safe and effective as a complement to chemotherapy [30].

Pregnant women should avoid using cat’s claw because of the herb’s potential to cause abortion [2].

When cat’s claw was used in combination with some HIV treatments like protease inhibitors (atazanavir, ritonavir, and saquinavir), it increased their toxicity [62].

Common side effects include [63]:

  • Dizziness
  • Upset stomach
  • Skin rash
  • Nausea
  • Diarrhea

1) May Worsen Autoimmune Diseases

Cat’s claw enhances the immune response by increasing the activities of immune cells [64].

Enhancing the immune system can increase the symptoms of autoimmune disorders [65, 64].

2) May Increase Bleeding

Clotting is essential for preventing blood loss and allowing tissue repair [66].

Cat’s claw decreased molecules that activate clotting (IL-1α, 1β, 4, 17, and TNF) [34].

This may increase the risk of bruising or bleeding [47].


Few high-quality clinical trials with cat’s claw have been conducted in humans and more studies are needed to confirm its health benefits [2].


Clinical trials have used between 80 – 350 mg of cat’s claw extract. These extracts usually contain a certain amount of pentacyclic oxindole alkaloids, rather than tetracyclic oxindole alkaloids.

Experiences with Cat’s Claw

According to one doctor, “In my experience on approximately 150 patients during the last four years… I have seen Uncaria tomentosa break through severe intestinal derangements that no other available products can touch.”

One user noted that cat’s claw increased the severity of their headache and fatigue, which they linked to a die-off effect.

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About the Author

Will Hunter

BA (Psychology)
Will received his BA in Psychology from the University of California, Los Angeles. 
Will's main passion is learning how to optimize physical and mental performance through diet, supplement, and lifestyle interventions. He focuses on systems thinking to leverage technology and information and help you get the most out of your body and brain.

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