Cat's Claw

Cat’s claw has been used by Amazonian Indigenous peoples, among them the Aguaruna, Asháninka, Cashibo, Conibo and Shipibo, for at least two thousand years ^{5,29,30,33Reference 5Sandoval et al. · 2002In vitroAnti-inflammatory and antioxidant activities of cat’s claw are independent of their alkaloid content — in vitroView study →Reference 29Heitzman et al. · 2005ReviewEthnobotany, phytochemistry and pharmacology of Uncaria (Rubiaceae) — reviewView study →Reference 30Keplinger et al. · 1999ReviewUncaria tomentosa — ethnomedicinal use and new pharmacological, toxicological and botanical results — reviewView study →Reference 33Taylor · 2005The healing power of rainforest herbs: A guide to understanding and using herbal medicinals}. The part used is the inner bark of the vine, and the root, both decocted.

The Asháninka of Peru have the longest recorded history with the plant. They use it for asthma, urinary-tract inflammation, arthritis, rheumatism and bone pain, for recovery after childbirth, as a kidney cleanser, as a vulnerary for deep wounds, and for general inflammation, gastric ulcers and cancer ^{30,33Reference 30Keplinger et al. · 1999ReviewUncaria tomentosa — ethnomedicinal use and new pharmacological, toxicological and botanical results — reviewView study →Reference 33Taylor · 2005The healing power of rainforest herbs: A guide to understanding and using herbal medicinals}.

Other Peruvian traditions add tumours, diabetes, haemorrhage, menstrual irregularity, cirrhosis, fever, abscesses, gastritis and viral illness, along with a general role as a normaliser of the body ^{29,30,33Reference 29Heitzman et al. · 2005ReviewEthnobotany, phytochemistry and pharmacology of Uncaria (Rubiaceae) — reviewView study →Reference 30Keplinger et al. · 1999ReviewUncaria tomentosa — ethnomedicinal use and new pharmacological, toxicological and botanical results — reviewView study →Reference 33Taylor · 2005The healing power of rainforest herbs: A guide to understanding and using herbal medicinals}.

Several Peruvian peoples have also used cat’s claw as a contraceptive, at doses far larger than a capsule. The Asháninka preparation reduces 5–6 kg of root, boiled in water, down to about 250 mL, taken during menstruation over three months, with reported sterility lasting three to four years afterwards ^{33Reference 33Taylor · 2005The healing power of rainforest herbs: A guide to understanding and using herbal medicinals}.

Chinese medicine uses a related Asian species, Uncaria rhynchophylla, as the drug Gou Teng.

Gou Teng clears heat, expels wind and extinguishes internal wind, calms and anchors the shen, settles tremors and anchors the yang ^{34Reference 34Hempen et al. · 2009A materia medica for Chinese medicine: plants, minerals, and animal products}. It is given for headache, irritability, red eyes, vertigo, fever, dizziness and seizures, and is regarded as acceptable in pregnancy ^{34Reference 34Hempen et al. · 2009A materia medica for Chinese medicine: plants, minerals, and animal products}.

In modern use it is given for tremor, seizure and epilepsy, and for central nervous complaints generally ^{35Reference 35Shim et al. · 2009In vitroEffects of the hook of Uncaria rhynchophylla on neurotoxicity in the 6-hydroxydopamine model of Parkinson’s disease — in vitro/animal (U. rhynchophylla)}.

The standard preparation is 6–15 g decocted for about ten minutes. The decoction is kept short because prolonged boiling destroys the indole alkaloids ^{34Reference 34Hempen et al. · 2009A materia medica for Chinese medicine: plants, minerals, and animal products}.

A 4-week randomized placebo-controlled trial in knee osteoarthritis (n=45) using freeze-dried Uncaria guianensis found significant reductions in pain with activity within the first week, with no effect on liver or blood parameters ^{1Reference 1Piscoya et al. · 2001RCTEfficacy and safety of freeze-dried cat’s claw in osteoarthritis of the knee — randomised controlled trialView study →}.

A 52-week randomized, partly double-blind trial in rheumatoid arthritis (n=40, on background sulfasalazine or hydroxychloroquine) using a purified pentacyclic-chemotype U. tomentosa extract reported a modest reduction in tender joints versus placebo (53% vs 24%) ^{2Reference 2Mur et al. · 2002RCTRandomized double blind trial of an extract from the pentacyclic alkaloid-chemotype of Uncaria tomentosa for the treatment of rheumatoid arthritis — randomised controlled trialView study →}.

Mechanistically, the anti-inflammatory effect is well mapped in vitro and in animals to inhibition of NF-κB and downstream TNF-α, IL-1β and PGE2 ^{3,4,5Reference 3Sandoval-Chacón et al. · 1998In vitroAntiinflammatory actions of cat’s claw: the role of NF-κB — in vitro/animalView study →Reference 4Allen-Hall et al. · 2010In vitroUncaria tomentosa acts as a potent TNF-α inhibitor through NF-κB — in vitroView study →Reference 5Sandoval et al. · 2002In vitroAnti-inflammatory and antioxidant activities of cat’s claw are independent of their alkaloid content — in vitroView study →}, and a whole-bark extract protected mice from ozone-induced lung inflammation ^{6Reference 6Cisneros et al. · 2005AnimalAn Uncaria tomentosa (cat’s claw) extract protects mice against ozone-induced lung inflammation — animal modelView study →}.

This activity appears largely independent of alkaloid content, pointing to the quinovic acid glycosides and antioxidant phenolics rather than the oxindoles ^{5Reference 5Sandoval et al. · 2002In vitroAnti-inflammatory and antioxidant activities of cat’s claw are independent of their alkaloid content — in vitroView study →}.

Gap: a 2017 systematic review found the osteoarthritis evidence too low-quality to confirm benefit over control ^{7Reference 7Del Grossi Moura et al. · 2017Meta-analysisOral herbal medicines marketed in Brazil for the treatment of osteoarthritis — systematic review and meta-analysisView study →}. Both trials are small and single-site, each used its own standardised preparation, and neither has been replicated.

Most of the immune research used one proprietary hot-water extract, C-Med-100 (marketed as Saventaro), in very small volunteer studies. A randomized human study (n=12) found supplementation for 8 weeks significantly increased DNA repair and reduced DNA damage after a hydrogen-peroxide challenge ^{8Reference 8Sheng et al. · 2001RCTDNA repair enhancement of aqueous extracts of Uncaria tomentosa in a human volunteer study — randomisedView study →}, and a controlled study showed a more durable antibody response to pneumococcal vaccine with a reduced decay in titres at 5 months ^{9Reference 9Lamm et al. · 2001RCTPersistent response to pneumococcal vaccine in individuals supplemented with C-Med-100 — randomised controlled trialView study →}.

Supporting animal and ex vivo work shows myeloid/white-cell stimulation, prolonged lymphocyte survival and enhanced DNA repair in skin organ cultures ^{11,12,13,14,31Reference 11Sheng et al. · 2000Enhanced DNA repair, immune function and reduced toxicity of C-MED-100 — animal and humanView study →Reference 12Sheng et al. · 2000AnimalTreatment of chemotherapy-induced leukopenia in a rat model with aqueous extract from Uncaria tomentosa — animal modelView study →Reference 13Farias et al. · 2011In vitroUncaria tomentosa stimulates the proliferation of myeloid progenitor cells — in vitroView study →Reference 14Åkesson et al. · 2003In vitroAn extract of Uncaria tomentosa inhibiting cell division and NF-κB activity without inducing cell death — in vitroView study →Reference 31Mammone et al. · 2006In vitroA water-soluble extract from Uncaria tomentosa is a potent enhancer of DNA repair in primary organ cultures of human skin — in vitroView study →}, and the water-extract’s active component has been narrowed to quinic acid rather than the alkaloids ^{32Reference 32Åkesson et al. · 2005In vitroQuinic acid is a biologically active component of the Uncaria tomentosa extract C-Med-100 — in vitroView study →}.

In an oncology setting, a randomized adjuvant trial in stage-II breast cancer (n≈40) found 300 mg/day dry extract alongside FAC chemotherapy reduced neutropenia and restored DNA damage markers ^{10Reference 10Santos Araújo et al. · 2012Clinical trialUncaria tomentosa — adjuvant treatment for breast cancer — clinical trialView study →}.

Gap: nearly all of this belongs to one proprietary water extract, in cohorts of 12 to 40, several from the same group. Generic cat’s claw products are not C-Med-100, and no trial tested whether any of it prevents an infection.

Cat’s claw is a consistent free-radical scavenger in vitro. Ethanolic and aqueous bark extracts show dose-dependent antioxidant activity attributed to tannins, catechins and procyanidins ^{15Reference 15Pilarski et al. · 2006In vitroAntioxidant activity of ethanolic and aqueous extracts of Uncaria tomentosa — in vitroView study →}, and DPPH scavenging is comparable between U. tomentosa and U. guianensis ^{1Reference 1Piscoya et al. · 2001RCTEfficacy and safety of freeze-dried cat’s claw in osteoarthritis of the knee — randomised controlled trialView study →}.

Repeatedly, whole hydroalcoholic extracts outperform fractions enriched in either alkaloid or non-alkaloid components, which the authors read as intra-plant synergy ^{5,16Reference 5Sandoval et al. · 2002In vitroAnti-inflammatory and antioxidant activities of cat’s claw are independent of their alkaloid content — in vitroView study →Reference 16Dreifuss et al. · 2013AnimalUncaria tomentosa exerts extensive anti-neoplastic effects against the Walker-256 tumour by modulating oxidative stress and not by alkaloid activity — animal modelView study →}.

In the Walker-256 rat tumor model this antioxidant capacity — not alkaloid content — tracked with the anti-neoplastic effect ^{16,17Reference 16Dreifuss et al. · 2013AnimalUncaria tomentosa exerts extensive anti-neoplastic effects against the Walker-256 tumour by modulating oxidative stress and not by alkaloid activity — animal modelView study →Reference 17Dreifuss et al. · 2010AnimalAntitumoral and antioxidant effects of a hydroalcoholic extract of cat’s claw — animal modelView study →}.

All of it is in vitro or animal. No human study has measured an oxidative-stress endpoint.

Preclinical anticancer data are broad but entirely non-clinical for tumor response. Oxindole alkaloids from U. tomentosa induce apoptosis in acute lymphoblastic leukemia cells, including bcl-2-expressing and G0/G1-arrested cells ^{18Reference 18Bacher et al. · 2006In vitroOxindole alkaloids from Uncaria tomentosa induce apoptosis in proliferating, G0/G1-arrested and bcl-2-expressing acute lymphoblastic leukaemia cells — in vitroView study →}.

Mitraphylline is cytotoxic to Ewing’s sarcoma, breast, glioma and neuroblastoma lines ^{19,20Reference 19García Giménez et al. · 2010In vitroCytotoxic effect of the pentacyclic oxindole alkaloid mitraphylline on human Ewing’s sarcoma and breast cancer cell lines — in vitroView study →Reference 20García Prado et al. · 2007In vitroAntiproliferative effects of mitraphylline on human glioma and neuroblastoma cell lines — in vitroView study →}.

Whole extracts slow the Walker-256 tumor in rats via oxidative-stress modulation ^{16,17Reference 16Dreifuss et al. · 2013AnimalUncaria tomentosa exerts extensive anti-neoplastic effects against the Walker-256 tumour by modulating oxidative stress and not by alkaloid activity — animal modelView study →Reference 17Dreifuss et al. · 2010AnimalAntitumoral and antioxidant effects of a hydroalcoholic extract of cat’s claw — animal modelView study →}.

The only human data are supportive rather than curative: the breast-cancer adjuvant trial reduced chemotherapy toxicity, not tumor burden ^{10Reference 10Santos Araújo et al. · 2012Clinical trialUncaria tomentosa — adjuvant treatment for breast cancer — clinical trialView study →}. Gap: no human trial has tested cat’s claw against a tumour, only alongside chemotherapy for its side effects. The herb also inhibits CYP3A4, which clears many chemotherapy drugs ^{26,27Reference 26Budzinski et al. · 2000In vitroAn in vitro evaluation of human cytochrome P450 3A4 inhibition by selected commercial herbal extracts and tinctures — in vitroView study →Reference 27López Galera et al. · 2008Case reportInteraction between cat’s claw and protease inhibitors atazanavir, ritonavir and saquinavir — case reportView study →}.

Antiviral evidence is preclinical and mechanism-focused. In human monocytes infected with Dengue Virus-2, a hydroalcoholic extract and its pentacyclic-alkaloid fraction reduced the proportion of infected cells and dampened TNF-α and IFN-α ^{21Reference 21Reis et al. · 2008In vitroImmunomodulating and antiviral activities of Uncaria tomentosa on human monocytes infected with Dengue Virus-2 — in vitroView study →}, and the alkaloidal fraction reduced endothelial permeability, IL-8 and viral NS1 production in a dengue model ^{22Reference 22Lima-Junior et al. · 2013In vitroUncaria tomentosa alkaloidal fraction reduces paracellular permeability, IL-8 and NS1 production on dengue-infected endothelial cells — in vitroView study →}. The traditional and popular use against HIV, herpes and other viral infections is not supported by human trials — and one clinical case report shows cat’s claw raising HIV protease-inhibitor drug levels (a pharmacokinetic interaction, not an antiviral effect) ^{27Reference 27López Galera et al. · 2008Case reportInteraction between cat’s claw and protease inhibitors atazanavir, ritonavir and saquinavir — case reportView study →}, consistent with its potent CYP3A4 inhibition in vitro ^{26Reference 26Budzinski et al. · 2000In vitroAn in vitro evaluation of human cytochrome P450 3A4 inhibition by selected commercial herbal extracts and tinctures — in vitroView study →} and PXR activation ^{28Reference 28Lei et al. · 2023In vitroIdentification of PXR activators from Uncaria rhynchophylla and Uncaria tomentosa — in vitroView study →}.

No human antiviral trial exists. The in-vitro dengue work is the strongest finding; the HIV, herpes and EBV uses are traditional.

The neuroprotective and Alzheimer’s literature attached to “cat’s claw” is mostly about a different plant — the Chinese species Uncaria rhynchophylla, not the Amazonian U. tomentosa. In that species, extracts inhibit β-amyloid fibril aggregation and can disassemble preformed fibrils ^{23Reference 23Fujiwara et al. · 2006In vitroUncaria rhynchophylla has potent antiaggregation effects on Alzheimer’s β-amyloid proteins — in vitroView study →}, and bioassay-guided work identified rhynchophylline and isorhynchophylline as the compounds that reduce β-amyloid-induced cell death, calcium overload and tau hyperphosphorylation in PC12 cells ^{24Reference 24Xian et al. · 2012In vitroBioassay-guided isolation of neuroprotective compounds from Uncaria rhynchophylla against β-amyloid-induced neurotoxicity — in vitroView study →}.

These alkaloids do also occur in U. tomentosa, but at different ratios and with no human cognitive data for either species.

Gap: nearly all of this work used U. rhynchophylla, a Chinese species with a different traditional use.

The cardiovascular claims rest on old, constituent-level pharmacology. Alkaloids of Uncaria hooks — rhynchophylline, hirsutine and related compounds — produce hypotensive and vasodilatory effects in isolated-tissue and animal preparations ^{25Reference 25Endo et al. · 1983In vitroHypotensive principles of Uncaria hooks — in vitro/animalView study →}. These findings again derive largely from the Asian Uncaria species used in Chinese medicine for hypertension-related conditions.

The work is in vitro and animal, decades old, and mostly in non-Amazonian species. There is no human blood-pressure trial of cat’s claw.

Tolerability. Cat’s claw is generally well tolerated in short human trials, with no significant changes to blood, liver or kidney parameters over 4–52 weeks and only minor, mostly gastrointestinal, side effects ^{1,2,8Reference 1Piscoya et al. · 2001RCTEfficacy and safety of freeze-dried cat’s claw in osteoarthritis of the knee — randomised controlled trialView study →Reference 2Mur et al. · 2002RCTRandomized double blind trial of an extract from the pentacyclic alkaloid-chemotype of Uncaria tomentosa for the treatment of rheumatoid arthritis — randomised controlled trialView study →Reference 8Sheng et al. · 2001RCTDNA repair enhancement of aqueous extracts of Uncaria tomentosa in a human volunteer study — randomisedView study →}. Large single doses (3–4 g) can cause transient gastrointestinal upset that usually settles with continued use.

CYP3A4 interactions. Cat’s claw inhibits CYP3A4 in vitro, one of the most potent herbal inhibitors tested ^{26Reference 26Budzinski et al. · 2000In vitroAn in vitro evaluation of human cytochrome P450 3A4 inhibition by selected commercial herbal extracts and tinctures — in vitroView study →}. A clinical case report describes it raising blood levels of the HIV protease inhibitors atazanavir, ritonavir and saquinavir ^{27Reference 27López Galera et al. · 2008Case reportInteraction between cat’s claw and protease inhibitors atazanavir, ritonavir and saquinavir — case reportView study →}, and the same mechanism could affect many CYP3A4-metabolised drugs. This matters most for anyone taking antiretroviral or other prescription medication.

Immunosuppressant therapy. Because it stimulates immune activity, cat’s claw is generally avoided alongside immunosuppressant therapy and around organ, bone-marrow or skin-graft transplantation, where it could increase the risk of rejection or counteract the medication.

Blood thinners. Its reported anticoagulant and antiplatelet activity calls for care with warfarin and other blood thinners, and for stopping at least a week before surgery.

The CYP3A4 inhibition and the protease-inhibitor case report are documented. The warfarin and immunosuppressant cautions are inferred from pharmacology and traditional practice rather than from trials.