Herbal Monograph
Cat's Claw
Uncaria tomentosa (Willd. ex Schult.) DC.
Rubiaceae (Gentianales)
Amazonian immunomodulating vine with potent anti-inflammatory and DNA repair-enhancing properties, distinguished by...
Overview
Plant Description
Cat's Claw is a large, woody, perennial liana (climbing vine) that can reach lengths of up to 30 meters (100 feet), ascending into the upper canopy of tropical rainforest by means of distinctive curved, claw-like thorns (recurved spines) that arise from the leaf axils. These paired thorns, which strongly resemble the retractable claws of a cat, give the plant both its common English name and its Spanish name 'Uña de Gato' (claw of the cat). The stem is woody, cylindrical, and up to 20 cm in diameter in mature specimens, with a characteristic fibrous, reddish-brown bark. The inner bark (cortex) is the primary medicinal part and is pale yellowish-brown when freshly stripped. Leaves are simple, opposite, and stipulate; oblong to oblong-ovate or elliptic, measuring 7.5-17 cm long and 5-12 cm wide, with entire margins, acute to rarely acuminate apex, and round to cordate base. The upper leaf surface is glabrous and glossy dark green; the lower surface is pubescent (tomentose) -- the species epithet 'tomentosa' refers to this characteristic woolly-hairy undersurface. Inflorescences are globular, axillary, pedunculate capitula (head-like clusters) approximately 2 cm in diameter, bearing numerous small, tubular, yellowish-white to cream-colored flowers with 5-lobed corollas. The fruit is a spindle-shaped capsule containing numerous small, winged seeds adapted for wind dispersal. The root system produces large, woody taproots and lateral roots that also contain the medicinally active alkaloids and are harvested in some traditions, though bark harvesting from stems is less destructive and now preferred for sustainability.
Habitat
Uncaria tomentosa is a species of primary tropical rainforest, though it also occurs in disturbed forest margins, secondary forest edges, and riparian zones. It thrives in the warm, humid lowlands of the Amazon basin and adjacent tropical forests at elevations from sea level to approximately 800 meters (2,600 feet). The vine requires the support of tall forest trees and is most commonly found growing on mature hardwoods in the forest understory and mid-canopy. It prefers well-drained, acidic to neutral soils with high organic matter content, consistent with the lateritic and alluvial soils of Amazonian lowlands. Rainfall requirements are high, typically 2,000-4,000 mm annually, with sustained humidity. The species is shade-tolerant as a juvenile but reaches full photosynthetic potential when its canopy emerges into brighter light zones of the upper forest. Wild-harvested populations have declined in some regions due to overexploitation, prompting sustainability concerns and cultivation initiatives.
Distribution
Native to the tropical rainforests of Central and South America, with the center of distribution and greatest abundance in the Peruvian Amazon basin, particularly in the departments of Junín, Ucayali, Loreto, Madre de Dios, Huánuco, and San Martín. The species range extends across the Amazon basin into Brazil (Acre, Amazonas), Colombia (Putumayo, Amazonas, Caquetá), Ecuador (eastern lowlands), Bolivia (Beni, Pando), Venezuela, Guyana, Suriname, French Guiana, and Trinidad. In Central America, populations occur in Panama, Costa Rica, Nicaragua, Honduras, Guatemala, and Belize, typically in lowland wet forests. Peru remains the primary source of both wild-harvested and cultivated Cat's Claw for the international herbal market, with the majority of commercial bark originating from the Selva Central (central jungle) region. The Asháninka indigenous territory in the Perené and Ene river valleys of Junín department is a historically significant harvest area.
Parts Used
Inner bark (cortex) of stem and branches
Preferred: Dried inner bark for decoction; hydroalcoholic extract; dried powdered bark capsules; standardized extract (POA content)
The inner bark (secondary phloem and cortical tissues) is the primary medicinal part used in both traditional Amazonian medicine and modern herbal commerce. This is the part listed in the European Medicines Agency (EMA) assessment report and referenced in clinical trials. It contains the full spectrum of oxindole alkaloids (both pentacyclic and tetracyclic types), quinovic acid glycosides, proanthocyanidins, and other bioactive compounds. The inner bark is distinguished from the outer bark by its lighter color (yellowish-brown vs. reddish-brown) and more fibrous texture. Traditional Amazonian preparation involves decoction of the inner bark for extended periods. Most commercial Cat's Claw products are manufactured from inner bark.
Root bark
Preferred: Historically used as decoction; now largely replaced by stem bark in commerce
Root bark was the original part used in some Asháninka traditional preparations and contains higher concentrations of oxindole alkaloids than stem bark in some analyses. However, root bark harvesting kills or severely damages the plant and is now strongly discouraged for sustainability reasons. Most herbal authorities and conservation organizations recommend exclusive use of stem bark. Some older ethnobotanical literature references root bark specifically. The alkaloid profile of root bark may differ quantitatively (though not qualitatively) from stem bark.
Leaves
Preferred: Dried leaf for infusion or extraction; not yet widely standardized for commercial use
Leaves have been investigated as a potentially sustainable alternative source of oxindole alkaloids, as they can be harvested without damaging the vine. Leaf alkaloid content varies seasonally but can be comparable to bark in some analyses. Leaves also contain significant quantities of flavonoids, phenolic acids, and proanthocyanidins. Some commercial preparations use leaf material, though bark remains the standard. The EMA assessment report does not cover leaf preparations. Research suggests leaves may have higher proportions of certain POAs (particularly mitraphylline and isomitraphylline) compared to bark.
Key Constituents
Pentacyclic oxindole alkaloids (POAs)
The pentacyclic oxindole alkaloids (POAs) are considered the primary immunostimulating constituents of Cat's Claw and the pharmacological basis for its use as an immune-supporting herb. The six principal POAs (isopteropodine, pteropodine, mitraphylline, isomitraphylline, uncarine F, and speciophylline) collectively enhance immune function through multiple mechanisms: increasing phagocytic activity of macrophages and granulocytes, enhancing natural killer cell activity, stimulating lymphocyte proliferation, and modulating cytokine production. CRITICALLY, these immunostimulating effects are attributed specifically to the pentacyclic (five-ring) oxindole alkaloids, NOT the tetracyclic forms. The POA content and profile are the primary quality markers for immunomodulatory Cat's Claw products. The Mur et al. (2002) rheumatoid arthritis trial specifically used a POA-chemotype extract. Three distinct chemotypes have been identified in wild U. tomentosa populations based on their oxindole alkaloid profile: Chemotype I (POA-dominant with cis D/E ring junction), Chemotype II (POA-dominant with trans D/E ring junction, showing higher selectivity against cancer cells), and Chemotype III (TOA-dominant). Only Chemotypes I and II are considered appropriate for immunomodulatory use. Total oxindole alkaloid content in dried bark typically ranges from 0.2-0.8% by weight, with POAs constituting 60-90% of the total in POA-chemotype plants.
Tetracyclic oxindole alkaloids (TOAs)
The tetracyclic oxindole alkaloids (TOAs) have distinct and, in some respects, opposing pharmacological effects compared to the pentacyclic oxindole alkaloids (POAs). While TOAs demonstrate valuable antihypertensive, neuroprotective, and anti-inflammatory properties in their own right, their presence in Cat's Claw preparations intended for immunomodulation is considered undesirable. Reinhard (1999) and subsequent researchers demonstrated that TOAs can antagonize the immunostimulating effects of POAs on dendritic cell function and lymphocyte activation. This finding has profound implications for Cat's Claw product quality: plants of the TOA-dominant Chemotype III, or poorly characterized wild-harvested material containing significant TOA content, may fail to deliver the expected immunomodulatory benefits and may actually inhibit immune function. This has led to the development of 'TOA-free' or 'POA-dominant' standardized extracts (such as the extract used in the Mur 2002 RA trial), where manufacturing processes selectively remove or minimize TOA content. However, for cardiovascular and neuroprotective applications (particularly in the TCM tradition using U. rhynchophylla), TOAs are the desired active constituents. The POA/TOA distinction is perhaps the most critical quality and efficacy consideration in Cat's Claw therapeutics.
Quinovic acid glycosides (triterpene glycosides)
Quinovic acid glycosides represent an important but often overlooked class of bioactive compounds in Cat's Claw. They contribute significantly to the anti-inflammatory and antiviral properties of the plant, independent of the oxindole alkaloid content. This is clinically relevant because it means that even alkaloid-depleted preparations (such as the water-soluble C-Med-100/AC-11 extract used in the Sheng DNA repair studies) retain meaningful biological activity. The quinovic acid glycosides demonstrate anti-inflammatory effects through TNF-alpha inhibition and NF-kB pathway modulation. Their antiviral activity against RNA viruses (vesicular stomatitis virus, rhinovirus) has been demonstrated in vitro, supporting traditional use of Cat's Claw for infections.
Proanthocyanidins and polyphenols
The proanthocyanidin and polyphenol fraction of Cat's Claw is a major contributor to its antioxidant and anti-inflammatory properties. Crucially, Sandoval et al. (2002) demonstrated that the anti-inflammatory and antioxidant activities of Cat's Claw and U. guianensis are independent of their alkaloid content, highlighting the therapeutic importance of the non-alkaloid polyphenolic constituents. Proanthocyanidins scavenge reactive oxygen and nitrogen species, inhibit lipid peroxidation, modulate inflammatory enzyme activity (COX, LOX), and demonstrate cytoprotective effects in gastrointestinal epithelial cells. This polyphenol-mediated antioxidant and anti-inflammatory activity likely explains the traditional use of Cat's Claw bark decoctions for gastrointestinal complaints and systemic inflammation, even in preparations where alkaloid extraction may be suboptimal.
Plant sterols (phytosterols)
The phytosterol content of Cat's Claw contributes modestly to its anti-inflammatory and immunomodulatory profile. Beta-sitosterol and stigmasterol have independently demonstrated anti-inflammatory effects through prostaglandin synthesis inhibition and immune cell modulation. While not as pharmacologically distinctive as the oxindole alkaloids or quinovic acid glycosides, the phytosterols provide additional anti-inflammatory support consistent with the plant's traditional use for inflammatory conditions.
Additional constituents
The additional non-alkaloid and minor alkaloid constituents of Cat's Claw underscore the complexity of this plant's pharmacology and the inadequacy of reducing its activity solely to oxindole alkaloids. The carboxyl alkyl esters (CAEs) are particularly noteworthy as the basis for the DNA repair-enhancing activity documented by Sheng et al., representing a distinct mechanism of action from the immunomodulating POAs. The presence of multiple classes of anti-inflammatory compounds (quinovic acid glycosides, proanthocyanidins, phytosterols, ursolic/oleanolic acids, phenolic acids) explains the robust anti-inflammatory activity observed even in alkaloid-depleted preparations. This multi-constituent activity profile is consistent with traditional preparation by prolonged decoction, which extracts the full spectrum of water-soluble and partially soluble bioactive compounds.
Herbal Actions
Modulates and balances immune function
The hallmark pharmacological action of Cat's Claw, specifically attributed to the pentacyclic oxindole alkaloids (POAs) in POA-chemotype preparations. POAs enhance phagocytic activity of macrophages and granulocytes, increase natural killer (NK) cell activity, stimulate lymphocyte proliferation, and modulate cytokine production including IL-1, IL-6, and TNF-alpha. Unlike simple immunostimulants, Cat's Claw demonstrates bidirectional immunomodulation: enhancing suppressed immune function while also demonstrating anti-inflammatory effects that temper overactive immune responses. This dual action is supported by the Mur et al. (2002) rheumatoid arthritis trial, where a POA-chemotype extract reduced joint inflammation in an autoimmune context while other studies show immune-enhancing effects in immunosuppressed states. The Sheng et al. studies demonstrated enhanced white blood cell counts and improved DNA repair capacity in healthy volunteers, supporting immune tonic activity. CRITICAL caveat: immunomodulatory effects are chemotype-dependent; TOA-dominant preparations may not provide the same immune benefits and may actually antagonize POA-mediated immune enhancement.
[2, 6, 7, 8, 11]Reduces inflammation
Potent anti-inflammatory activity demonstrated through multiple pathways and confirmed in both in vitro, in vivo, and clinical studies. The primary mechanism involves inhibition of TNF-alpha production through NF-kB pathway suppression. Aguilar et al. (2002) demonstrated that U. tomentosa acts as a potent TNF-alpha inhibitor through NF-kB-dependent mechanisms. Sandoval et al. (2000, 2002) showed that Cat's Claw inhibits TNF-alpha production and scavenges free radicals, and that anti-inflammatory and antioxidant activities are independent of alkaloid content, implicating quinovic acid glycosides and proanthocyanidins as additional anti-inflammatory agents. A 2024 systematic review and meta-analysis of in vivo studies confirmed significant reduction in NF-kB across multiple studies using aqueous and hydroethanolic extracts. Clinical evidence includes the Piscoya et al. (2001) OA trial (U. guianensis) showing reduced pain and inflammation, and the Mur et al. (2002) RA trial showing reduced joint pain and swelling.
[5, 6, 10, 11, 12]Prevents or slows oxidative damage to cells
Significant antioxidant activity attributable primarily to the proanthocyanidin, polyphenol, and phenolic acid content of bark extracts. Demonstrated free radical scavenging activity against superoxide, hydroxyl, peroxyl, and peroxynitrite radicals. Sandoval et al. (2000) showed that Cat's Claw is a remarkably potent inhibitor of TNF-alpha production AND an effective antioxidant, with free radical scavenging contributing to cytoprotective effects. Antioxidant activity is efficiently extracted by aqueous decoction and is independent of alkaloid content. The proanthocyanidin fraction shows particularly high ORAC (oxygen radical absorbance capacity) values. Antioxidant effects contribute to the overall anti-inflammatory, cytoprotective, and antimutagenic properties of Cat's Claw.
[10, 11]Cat's Claw extracts, particularly the aqueous C-Med-100/AC-11 preparation standardized to carboxyl alkyl esters (CAEs), demonstrate significant enhancement of DNA repair mechanisms. Sheng et al. (2000) showed that C-Med-100 enhanced repair of both single-strand and double-strand DNA breaks after irradiation in animal models. A subsequent human volunteer study (Sheng et al. 2001) demonstrated statistically significant decreases in DNA damage and increases in DNA repair in supplemented groups (250-350 mg/day) compared to non-supplemented controls. A further study (Sheng et al. 2005) confirmed that a water-soluble extract from U. tomentosa is a potent enhancer of DNA repair in primary organ cultures of human skin. This DNA repair-enhancing activity is distinct from simple antioxidant free radical scavenging and involves active upregulation of DNA repair enzyme pathways. These findings have implications for cancer prevention, anti-aging, and protection against mutagenic environmental exposures.
[7, 8, 9]Antiviral activity has been demonstrated in vitro for several constituent classes. Quinovic acid glycosides from U. tomentosa showed activity against vesicular stomatitis virus (VSV) and rhinovirus in early studies (Aquino et al. 1989). The mechanisms likely involve both direct antiviral effects (interference with viral replication) and indirect effects through immune enhancement (increased NK cell activity, enhanced interferon production). Traditional use in Amazonian medicine for febrile illness and infections is consistent with antiviral activity, though clinical trials specifically assessing antiviral efficacy in human viral infections are lacking.
[13]Lowers blood pressure
Mild blood pressure-lowering activity attributable primarily to the tetracyclic oxindole alkaloids (TOAs) rhynchophylline and isorhynchophylline, which demonstrate calcium channel blocking and vasodilatory effects. This pharmacology is better characterized for the related East Asian species U. rhynchophylla (Gou Teng), which is used specifically for hypertension in TCM. In U. tomentosa, the hypotensive effect is clinically mild and considered a secondary or incidental property rather than a primary therapeutic target. The hirsutine and hirsuteine indole alkaloids also contribute to vasodilatory and anti-arrhythmic effects. This activity is most relevant as a safety consideration in patients taking antihypertensive medications (potential additive effect) and is most pronounced in TOA-rich preparations.
[1]Therapeutic Indications
Immune System
Immune support and immune deficiency states
Cat's Claw (POA chemotype) is primarily indicated as an immune tonic for supporting overall immune function, particularly in conditions of immune deficiency or suppression. The pentacyclic oxindole alkaloids enhance phagocytosis, NK cell activity, and lymphocyte proliferation. Sheng et al. (2000, 2001) demonstrated increased white blood cell counts and enhanced DNA repair in healthy volunteers taking C-Med-100 extract. The Mur et al. (2002) trial indirectly supports immunomodulatory activity. Traditional Asháninka use as a general health tonic and recovery aid is consistent with immune support. Preparations should be standardized to POA content or verified as POA-chemotype for immunomodulatory indications. TOA-free preparations are preferred by some practitioners.
[6, 7, 8]Cancer (adjunctive immune support during chemotherapy)
Cat's Claw is used in integrative oncology practice as adjunctive immune support during conventional cancer treatment, based on its immunomodulating and DNA repair-enhancing properties. Sheng et al. (2000) showed that C-Med-100 treatment enhanced recovery from chemotherapy-induced leukopenia in a rat model, suggesting protective effects against myelosuppression. In vitro studies demonstrate selective cytotoxicity against various cancer cell lines (breast cancer, Ewing's sarcoma, glioblastoma, leukemia, prostate cancer), with POA-rich extracts (particularly Chemotype II with trans D/E ring junction) showing the highest selectivity against malignant cells. Mitraphylline has shown IC50 values lower than some standard chemotherapeutic agents in certain in vitro models. However, clinical evidence is very limited. Cat's Claw should NOT be used as a primary cancer treatment. Its role is strictly adjunctive: supporting immune function, potentially reducing chemotherapy side effects, and providing antioxidant cytoprotection. Patients on immunosuppressive chemotherapy should consult their oncologist before use, as immune enhancement could theoretically interfere with certain treatment protocols.
[7, 9]Upper respiratory tract infections
Traditional Amazonian use includes treatment of fevers, infections, and respiratory complaints. The immunomodulating effects (enhanced NK cell activity, increased phagocytosis, improved white blood cell counts) combined with demonstrated in vitro antiviral activity against rhinovirus provide mechanistic support for use in upper respiratory infections. However, no clinical trials specifically evaluating Cat's Claw for URI treatment or prevention have been published. Use is based on traditional evidence, immune-enhancing mechanisms, and extrapolation from immunological studies.
[7, 13]DNA damage and mutagenesis (chemoprotective and antimutagenic use)
A unique and well-documented indication for Cat's Claw based on the Sheng et al. studies of the C-Med-100/AC-11 aqueous extract. DNA repair enhancement has been demonstrated in animal models (irradiation-induced DNA damage) and confirmed in a human volunteer study (250-350 mg/day for 8 weeks). The extract enhanced repair of both single-strand and double-strand DNA breaks and improved DNA repair in human skin organ cultures. This activity is attributed to the carboxyl alkyl ester (CAE) fraction rather than oxindole alkaloids. The implications include potential for cancer prevention, protection against environmental mutagens, and anti-aging applications. This is a modern research-derived indication without direct traditional precedent, though the traditional use as a general tonic for health maintenance could be considered broadly consistent.
[7, 8, 9]Convalescence and post-illness recovery
The Asháninka and other Amazonian peoples traditionally used Cat's Claw bark decoctions for recovery from illness, childbirth, and debility. The immune-enhancing, anti-inflammatory, and antioxidant properties provide mechanistic support for this traditional use as a convalescent tonic. The increase in white blood cell counts observed in the Sheng et al. human study is consistent with immune reconstitution during recovery. No specific clinical trials address this indication, but the overall pharmacological profile supports use as a post-illness recovery tonic, particularly where immune function may be compromised.
[1, 8]Musculoskeletal System
Osteoarthritis (particularly knee osteoarthritis)
The strongest clinical evidence for Cat's Claw in a specific condition comes from the Piscoya et al. (2001) randomized, double-blind, placebo-controlled trial of freeze-dried U. guianensis bark in 45 patients with knee osteoarthritis. Four weeks of treatment significantly reduced pain associated with activity (P < 0.05) and improved medical and patient assessment scores, with benefits observed within the first week. Pain at rest and knee circumference were not significantly reduced in this short trial. The anti-inflammatory mechanism was attributed to TNF-alpha inhibition and, to a lesser extent, PGE2 suppression. Cat's Claw was well tolerated with no deleterious effects on blood or liver function. Note: this trial used U. guianensis rather than U. tomentosa, but both species share anti-inflammatory constituent profiles. Traditional use for bone pain, joint inflammation, and arthritis among Amazonian peoples supports this indication.
[5, 10]Rheumatoid arthritis
Mur et al. (2002) conducted a 52-week, two-phase randomized double-blind trial of a POA-chemotype U. tomentosa extract (60 mg/day) in 40 patients with active rheumatoid arthritis receiving concurrent sulfasalazine or hydroxychloroquine. After 24 weeks, the extract group showed significantly greater reduction in painful joints compared to placebo (53.2% vs 24.1%, P = 0.044). In the second open-label phase, patients who switched from placebo to extract also experienced significant reductions in painful joints (P = 0.003), swollen joints (P = 0.007), and Ritchie Index (P = 0.004). The extract was well tolerated. This is promising preliminary evidence supporting Cat's Claw as adjunctive therapy in RA, but the study was small (n=40), used a specific POA-chemotype extract, and patients were on concurrent DMARDs. Larger confirmatory trials are needed. The immunomodulatory mechanism is particularly relevant in RA, as Cat's Claw may help rebalance overactive immune responses while reducing inflammatory cytokines.
[6]General musculoskeletal inflammation and pain
Traditional Amazonian use encompasses bone pain, muscle inflammation, and generalized rheumatic complaints. The multi-target anti-inflammatory mechanisms (NF-kB inhibition, TNF-alpha suppression, COX/LOX modulation, antioxidant cytoprotection) provide broad-spectrum support for musculoskeletal inflammatory conditions beyond the specific arthritis indications studied in clinical trials. The Asháninka use for bone pain and rheumatism is well documented in ethnobotanical literature.
[1, 11]Digestive System
Gastrointestinal inflammation (gastritis, gastric ulcers, Crohn's disease, IBD)
Cat's Claw has a strong traditional reputation in Amazonian medicine for treating gastrointestinal conditions including stomach ulcers, gastritis, and intestinal inflammation. The Asháninka traditionally used bark decoctions for gastric ulcers and intestinal complaints. The pharmacological basis for this traditional use is supported by demonstrated TNF-alpha inhibition, NF-kB suppression, antioxidant cytoprotection of GI epithelial cells, and the tannin-rich proanthocyanidin content that provides astringent and mucosal-protective effects. In vitro studies show that Cat's Claw extracts protect gastric epithelial cells from oxidative damage. However, no controlled clinical trials specifically evaluating Cat's Claw for GI conditions have been published. An open-label pilot study by Sandoval-Chacon et al. suggested benefit in Crohn's disease patients, but this was not a randomized controlled trial. GI use remains supported primarily by traditional evidence and mechanistic plausibility.
[1, 10]Intestinal dysbiosis and parasitic infections
Traditional Amazonian use includes treatment of dysentery, diarrhea, and intestinal parasites. The tannin (proanthocyanidin) content provides astringent and antimicrobial effects in the GI tract. The immunomodulating properties may also contribute to improved mucosal immune defense against GI pathogens. Clinical evidence for antiparasitic or antimicrobial activity in human GI infections is lacking.
[1]Cardiovascular System
Mild hypertension (adjunctive, incidental benefit)
The tetracyclic oxindole alkaloids (rhynchophylline, isorhynchophylline) demonstrate calcium channel blocking and vasodilatory activity, contributing to mild blood pressure-lowering effects. This pharmacology is far better characterized for the related TCM species U. rhynchophylla (Gou Teng), which is used specifically for hypertension. In U. tomentosa, hypotensive effects are clinically mild and incidental rather than a primary therapeutic target. TOA-rich preparations would theoretically have greater hypotensive effects than POA-dominant preparations. Not recommended as primary antihypertensive therapy.
[1]Urinary System
Urinary tract inflammation and infections
The Asháninka traditionally used Cat's Claw bark decoctions for inflammation of the urinary tract and as a kidney cleanser. The anti-inflammatory and immunomodulating properties provide mechanistic plausibility, and the diuretic/kidney-cleansing traditional use may reflect mild effects on urinary tract inflammation. No clinical studies specifically address this indication. Use is based entirely on traditional evidence.
[1]Energetics
Temperature
cool
Moisture
slightly dry
Taste
Tissue States
heat/excitation, damp/stagnation, cold/depression (immune deficiency)
Cat's Claw does not have a classical TCM or Ayurvedic energetic classification, as it is an Amazonian plant outside those traditional systems. In Western herbal energetics, it is generally characterized as cool to neutral in temperature and slightly drying in moisture, reflecting its bitter and astringent taste profile. The pronounced bitter quality (from oxindole alkaloids and other constituents) indicates a clearing, anti-inflammatory, and stimulating action on secretory and immune function. The astringent quality (from the high proanthocyanidin/tannin content) contributes to tissue-toning and mucosal-protective effects. Cat's Claw addresses heat/excitation tissue states (inflammatory conditions -- arthritis, GI inflammation, systemic inflammation), damp/stagnation states (immune stagnation, chronic infections, congested lymphatics), and paradoxically also cold/depression states (immune deficiency, debility, convalescence) through its immunomodulating rather than simple immunostimulating activity. This bidirectional capacity -- cooling inflammation while warming depressed immune function -- is characteristic of true immunomodulators and aligns with the adaptogenic concept, though Cat's Claw is not traditionally classified as an adaptogen per se. CAVEAT: Herbal energetics are interpretive frameworks within Western herbalism and are not standardized across all practitioners. Amazonian ethnomedicine has its own distinct conceptual framework (hot/cold, spiritual/physical) that does not map directly onto Western or Asian energetic systems.
Traditional Uses
Asháninka and Amazonian indigenous medicine (Peru)
- Central medicinal plant of the Asháninka people of the Peruvian Selva Central, used for over 2,000 years
- Inner bark decoction for treating deep wounds, bone pain, and inflammation of the urinary tract
- Treatment of asthma, arthritis, rheumatism, and generalized inflammation
- Recovery from childbirth and as a tonic for reproductive health
- Kidney cleansing and treatment of urinary tract infections
- Treatment of gastric ulcers and intestinal inflammation
- General health tonic for disease prevention and immune support
- Traditional contraceptive use (high doses of root bark) -- the basis for modern pregnancy contraindication
- Treatment of tumors and cancerous growths (traditional interpretation)
- Used by Asháninka spiritual healers (sheripiari) to regulate the connection between physical and spiritual being
"The Asháninka (also spelled Campa Asháninka) of the Peruvian central jungle have the longest recorded history of Cat's Claw use, spanning over 2,000 years. Their medicinal system recognizes three categories of healers, and U. tomentosa holds a privileged position as a plant used by the sheripiari (spiritual healer/priest) to mediate between physical and spiritual health. Keplinger (1999) documented extensive Asháninka ethnomedicinal use. The Asháninka call the plant 'samento' and use decoctions of the inner bark for an extraordinarily wide range of conditions. Notably, the traditional use in high doses as a contraceptive led directly to the modern precautionary contraindication in pregnancy. Other Amazonian tribes including the Aguaruna, Cashibo, Conibo, and Shipibo share overlapping traditional uses, with emphasis on fever, inflammation, GI complaints, and general debility."
[1]
South American folk medicine (broader Amazonian and Andean traditions)
- Bark decoction as a general anti-inflammatory for joint pain, muscle pain, and swelling
- Treatment of fevers, malaria, and infectious disease
- Wound healing (external application of bark decoction as wash)
- Treatment of dysentery, diarrhea, and intestinal parasites
- Male and female reproductive tonic
- Blood purifier and detoxifying agent
- Treatment of skin conditions and abscesses
- Used in combination with other Amazonian medicinal plants in traditional formulas
"Beyond the Asháninka heartland, Cat's Claw entered broader South American folk medicine as knowledge spread through trade networks, colonial-era documentation, and modern ethnobotanical research. Jesuit missionaries in the 16th century documented indigenous use of the plant for gastrointestinal disorders, fevers, and skin infections. The Spanish common name 'Uña de Gato' became widely recognized across Peru, Brazil, Colombia, and other South American countries. In folk medicine, the bark decoction is prepared by extended boiling (often 3 or more hours) and consumed multiple times daily for chronic conditions. The plant is considered a potent 'limpiador' (cleanser) in many folk traditions."
[1]
Modern Western herbal medicine
- Immune support and immune modulation (primary modern indication)
- Anti-inflammatory for osteoarthritis and rheumatoid arthritis
- Adjunctive support during cancer treatment
- Antiviral immune support for recurrent infections
- DNA repair and antimutagenic agent (based on C-Med-100/AC-11 research)
- Gastrointestinal anti-inflammatory (IBD, Crohn's disease, gastritis)
- General anti-inflammatory tonic
"Cat's Claw entered Western herbal and integrative medicine practice primarily through the work of Austrian researcher Klaus Keplinger, who investigated the plant beginning in the 1970s after learning of its use from Asháninka healers. Keplinger's research, patents, and publications brought Cat's Claw to international attention, leading to rapid commercial development in the 1990s. The Austrian pharmacognosist's work identified the oxindole alkaloids and their immunomodulatory effects, establishing the scientific foundation for modern use. Cat's Claw became one of the best-selling herbal supplements in the United States and Europe by the late 1990s. Current Western herbal practice emphasizes the POA-chemotype distinction and tends to focus on immunomodulatory and anti-inflammatory applications supported by clinical trial evidence."
Modern Research
Freeze-dried Cat's Claw (U. guianensis) for knee osteoarthritis
Randomized, double-blind, placebo-controlled trial of freeze-dried U. guianensis bark in 45 patients with symptomatic osteoarthritis of the knee over 4 weeks, assessing pain, joint function, and safety.
Findings: Pain associated with physical activity was significantly reduced in the Cat's Claw group compared to placebo. Medical assessment scores and patient self-assessment scores were also significantly improved. Benefits were observed within the first week of therapy. Pain at rest or at night and knee circumference were not significantly reduced during this brief trial period. Cat's Claw had no deleterious effects on blood or liver function parameters, and no significant side effects were observed compared to placebo. The anti-inflammatory mechanism was attributed to inhibition of TNF-alpha production and, to a lesser extent, PGE2 reduction.
Limitations: Short treatment duration (4 weeks). Moderate sample size (n=45, 30 active, 15 placebo). Used U. guianensis rather than U. tomentosa (though both share anti-inflammatory properties). Did not assess alkaloid chemotype. Single-center study conducted in Peru. Freeze-dried bark preparation; results may not generalize to all Cat's Claw products.
[5]
POA-chemotype extract for rheumatoid arthritis
Randomized, double-blind, placebo-controlled, two-phase trial of a POA-chemotype U. tomentosa extract (60 mg/day) in 40 patients with active rheumatoid arthritis receiving concurrent DMARDs (sulfasalazine or hydroxychloroquine) over 52 weeks.
Findings: Phase 1 (24 weeks, double-blind): Treatment with POA-chemotype extract resulted in a 53.2% reduction in the number of painful joints compared to 24.1% reduction with placebo (P = 0.044). Phase 2 (28 weeks, open-label, all patients on extract): Patients who switched from placebo to the extract experienced significant reductions in painful joints (P = 0.003), swollen joints (P = 0.007), and Ritchie Index (P = 0.004) compared to their values after 24 weeks of placebo. The extract was well tolerated with no serious adverse effects. Dyspepsia and pruritus were the most common minor side effects. Laboratory values did not change significantly.
Limitations: Small sample size (n=40). All patients were on concurrent DMARD therapy, so the effect of Cat's Claw alone cannot be isolated. Used a specific proprietary POA-chemotype extract; results may not generalize to other preparations. Relatively low dose (60 mg/day of extract). Phase 2 was open-label, introducing potential bias. Single-center study in Austria.
[6]
Enhanced DNA repair and immune function with C-Med-100 aqueous extract
Preclinical and early clinical investigation of C-Med-100 (an aqueous extract of U. tomentosa standardized to carboxyl alkyl esters, later renamed AC-11) for DNA repair enhancement and immune function in animal models and human volunteers.
Findings: In female rats, C-Med-100 (0-80 mg/kg for 8 weeks) significantly increased lymphocyte proliferation and elevated white blood cell counts at the highest doses. Repair of DNA single-strand and double-strand breaks 3 hours after irradiation was significantly improved in C-Med-100 treated animals compared to controls. In a human volunteer study, C-Med-100 (5 mg/kg daily for 6 weeks in 4 healthy adult males) produced no toxicity and significantly elevated white blood cell counts. These findings established the DNA repair-enhancing and immunostimulatory properties of the alkaloid-free aqueous extract.
Limitations: Small human sample size (n=4 in the pilot study). Animal model data may not directly translate to human clinical outcomes. C-Med-100 is a specific proprietary extract; results are specific to this preparation. Healthy volunteer study; effects in disease states not assessed. Short study duration.
[7]
DNA repair enhancement in human volunteers with C-Med-100/AC-11
Controlled human volunteer study assessing the effects of C-Med-100/AC-11 supplementation (250 and 350 mg/day) on DNA damage and DNA repair markers over 8 weeks.
Findings: Statistically significant decreases in DNA damage and concomitant increases in DNA repair were observed in supplemented groups at both 250 and 350 mg/day compared to non-supplemented controls. The DNA repair enhancement was dose-dependent. These findings confirmed the animal model data in humans and established a clinically relevant dose range for the DNA repair-enhancing effect. No adverse effects were reported at either dose level.
Limitations: Non-randomized, open-label study design. Limited sample size. Healthy volunteers only; applicability to disease states uncertain. Specific proprietary extract (C-Med-100/AC-11) may not represent all Cat's Claw products. Surrogate biomarker endpoints (DNA damage/repair assays) rather than clinical disease outcomes.
[8]
Water-soluble extract enhances DNA repair in human skin organ cultures
In vitro study examining the effects of a water-soluble U. tomentosa extract on DNA repair in primary organ cultures of human skin after UV-induced damage.
Findings: The water-soluble Cat's Claw extract demonstrated potent enhancement of DNA repair in human skin organ cultures exposed to UV radiation. The extract increased both the rate and extent of DNA repair of UV-induced photodamage. The findings suggest potential applications in photoprotection, skin cancer prevention, and anti-aging skincare, and confirm the DNA repair-enhancing activity observed in the earlier animal and human studies.
Limitations: In vitro organ culture model; topical or systemic delivery in vivo not assessed. Specific extract preparation. Clinical relevance for skin cancer prevention or photoaging requires human clinical trials.
[9]
Cat's Claw inhibits TNF-alpha production and scavenges free radicals
In vitro investigation of Cat's Claw extracts as TNF-alpha inhibitors and free radical scavengers, elucidating the dual anti-inflammatory and antioxidant mechanisms underlying cytoprotective effects.
Findings: Cat's Claw bark extract demonstrated potent inhibition of TNF-alpha production in LPS-stimulated macrophages, identifying it as a remarkably effective TNF-alpha inhibitor among tested herbal agents. Additionally, the extract showed significant free radical scavenging activity against superoxide and hydroxyl radicals. These dual mechanisms (anti-cytokine + antioxidant) contribute to cytoprotective effects on gastric epithelial cells and other cell types. The study established the mechanistic basis for Cat's Claw's anti-inflammatory activity and its traditional use for gastrointestinal inflammation.
Limitations: In vitro study; concentrations used may not reflect achievable in vivo tissue levels. Single commercial extract tested. TNF-alpha inhibition in cultured cells does not necessarily predict clinical anti-inflammatory efficacy.
[10]
Anti-inflammatory and antioxidant activities independent of alkaloid content
Comparative study of U. tomentosa and U. guianensis extracts demonstrating that anti-inflammatory and antioxidant activities are independent of their oxindole alkaloid content.
Findings: Both U. tomentosa and U. guianensis demonstrated significant anti-inflammatory (TNF-alpha inhibition) and antioxidant (free radical scavenging) activities. Critically, these activities were independent of the oxindole alkaloid content of the extracts. Alkaloid-depleted fractions retained full anti-inflammatory and antioxidant potency, implicating non-alkaloid constituents (quinovic acid glycosides, proanthocyanidins, phenolic acids) as major contributors to these effects. This finding has important implications for quality control and product standardization: Cat's Claw products need not be alkaloid-rich to deliver anti-inflammatory and antioxidant benefits, though alkaloid content remains important for immunomodulatory effects specifically.
Limitations: In vitro study. Does not diminish the importance of alkaloids for immunomodulatory indications specifically. The specific non-alkaloid compounds responsible were not individually isolated and tested in this study.
[11]
Uncaria tomentosa acts as a potent TNF-alpha inhibitor through NF-kB
Mechanistic study investigating the molecular pathway by which U. tomentosa inhibits TNF-alpha production, identifying NF-kB as the central mediator.
Findings: Treatment of monocyte-like THP-1 cells with U. tomentosa extract inhibited LPS-dependent activation of specific NF-kB (p50/p65) and AP-1 transcription factor components. The extract inhibited production of the pro-inflammatory cytokine TNF-alpha while augmenting production of IL-1-beta, demonstrating differential cytokine modulation. NF-kB mediated the differential secretion of TNF-alpha and IL-1-beta resulting from Cat's Claw treatment. This study established NF-kB inhibition as the primary molecular mechanism for Cat's Claw's anti-inflammatory activity, placing it in the same mechanistic category as pharmaceutical NF-kB inhibitors.
Limitations: In vitro monocyte cell line model. Clinical translation of NF-kB inhibition to disease outcomes requires clinical trial validation. Single extract preparation tested. Dose-response relationships for NF-kB inhibition in vivo not established.
[12]
Systematic review and meta-analysis of anti-inflammatory/immunomodulatory activities (in vivo)
Systematic review and meta-analysis of in vivo studies evaluating the anti-inflammatory and/or immunomodulatory activities of U. tomentosa extracts, published in Frontiers in Pharmacology (2024).
Findings: The meta-analysis found that aqueous and hydroethanolic U. tomentosa extracts produced significant reductions in NF-kB activity across multiple in vivo studies. Anti-inflammatory effects were consistent across different animal models and extract types. Immunomodulatory effects were confirmed, supporting both immune-enhancing and anti-inflammatory applications. The review highlighted the multi-target pharmacology of Cat's Claw, with effects on NF-kB, TNF-alpha, IL-1, IL-6, COX-2, and oxidative stress markers.
Limitations: Meta-analysis of animal (in vivo) studies only; human clinical data analyzed separately. Heterogeneity in extract preparations, doses, and endpoints across included studies. Publication bias possible. Animal model outcomes do not always translate to human clinical efficacy.
[14]
Identification of PXR activators from Uncaria species (CYP3A4 induction)
Investigation identifying pregnane X receptor (PXR) activators in both U. rhynchophylla (Gou Teng) and U. tomentosa (Cat's Claw), with implications for CYP3A4-mediated drug interactions.
Findings: Both Uncaria species contained compounds that activate the pregnane X receptor (PXR), a nuclear receptor that regulates CYP3A4 gene expression. PXR activation by Uncaria constituents leads to induction of CYP3A4, which could increase the metabolism of CYP3A4 substrate drugs. This mechanism is in addition to the previously documented direct inhibition of CYP3A4 enzyme activity by Cat's Claw, creating a complex interaction profile: acute exposure may inhibit CYP3A4 (raising drug levels) while chronic exposure may induce CYP3A4 expression (lowering drug levels). Specific oxindole alkaloids and other constituents were identified as PXR ligands.
Limitations: In vitro cell-based PXR activation assay. Clinical significance of PXR activation by Cat's Claw at typical oral doses requires pharmacokinetic studies in humans. The dual inhibition/induction profile complicates prediction of net clinical effect on drug metabolism.
[15]
Preparations & Dosage
Decoction
Strength: Standard: 3-5 g dried bark per 250 mL water (approximately 1:50-1:80). Concentrated traditional: 20-30 g per liter, reduced by one-third (approximately 1:25-1:30 final concentration).
Use dried inner bark of U. tomentosa, cut into small pieces or coarsely powdered. Place 1-2 teaspoons (approximately 3-5 g) of dried bark per cup (250 mL) of cold water. Bring to a boil, then reduce to a low simmer and decoct for 15-45 minutes. For a more concentrated therapeutic preparation (traditional Asháninka method), use 20-30 g of bark per liter of water and simmer for 2-3 hours until the volume is reduced by approximately one-third. Strain through cloth or fine mesh. The resulting liquid is amber to dark brown with a distinctly bitter and slightly astringent taste. Adding a small amount of lemon juice or vinegar (approximately 1/2 teaspoon per cup) during boiling may help extract alkaloids more efficiently while reducing tannin content.
Standard decoction (15-minute simmer): 1 cup (250 mL) two to three times daily. Concentrated decoction (2-3 hour traditional method): 60-80 mL (approximately 1/4 cup) two to three times daily.
Two to three times daily, preferably between meals
Acute conditions: 2-4 weeks. Chronic inflammatory conditions: 8-12 weeks or longer under practitioner guidance. Traditional use supports extended daily consumption. Reassess therapeutic need periodically.
Not recommended for children under 12 years due to insufficient pediatric safety data. Adolescents (12-18): half adult dose under practitioner supervision.
Decoction is the traditional Amazonian preparation method and remains the most appropriate for extracting the water-soluble constituents of the woody inner bark, including proanthocyanidins, quinovic acid glycosides, phenolic acids, and carboxyl alkyl esters. However, hot water decoction extracts oxindole alkaloids less efficiently than hydroalcoholic preparations. The prolonged boiling time used in traditional Asháninka preparation (2-3 hours) achieves more complete extraction than shorter decoction times. The bitter taste is normal and indicates the presence of bioactive constituents. Decoctions can be refrigerated for up to 48 hours. For immunomodulatory applications where alkaloid content is important, tincture or standardized extract may be preferred over simple decoction.
[1]
Tincture
Strength: 1:5, 45-60% ethanol (dried inner bark). Some manufacturers use 1:3 or 1:4 ratios for a more concentrated product.
Use dried, finely chopped or coarsely powdered inner bark. Standard maceration method: Combine bark with 45-60% ethanol (or equivalent vodka/grain alcohol dilution) at a 1:5 ratio by weight (e.g., 200 g dried bark per 1 liter of menstruum). Place in an airtight glass jar, seal, and macerate for 4-6 weeks in a cool, dark location with daily agitation (shaking). After maceration, press through cheesecloth and filter through unbleached muslin or coffee filter. The resulting tincture should be amber to dark reddish-brown with a pronounced bitter taste.
2-4 mL (40-80 drops) two to three times daily
Two to three times daily, taken diluted in a small amount of water
May be used for extended periods for chronic conditions. Reassess periodically.
Not recommended for children due to alcohol content and lack of pediatric safety data
Tincture preparation provides more efficient extraction of the oxindole alkaloids (both POAs and TOAs) compared to water decoction alone, as these alkaloids have moderate lipophilicity that benefits from hydroalcoholic extraction. The 45-60% ethanol range is sufficient for alkaloid extraction while also extracting water-soluble polyphenols and glycosides. Tincture is a convenient dosage form for long-term use. For immunomodulatory indications, practitioners should be aware that standard tinctures extract both POAs and TOAs; they do not provide the selective POA-chemotype preparations used in the Mur et al. clinical trial. The alcohol content means tinctures are not appropriate for patients avoiding alcohol, patients with liver disease, or children.
[1]
Capsule / Powder
Strength: Crude bark powder: 400-500 mg per capsule. Dry extract: typically 4:1 to 10:1 concentration ratio. Alkaloid-standardized products specify POA or total alkaloid content.
Dried inner bark, finely powdered (ground to pass through a 40-60 mesh sieve), filled into vegetarian or gelatin capsules. Standard capsule size: 400-500 mg of powdered bark per capsule. Alternatively, concentrated dry extract powder (typically standardized to 3-5% total alkaloids or to specific POA content) encapsulated.
Crude bark powder: 1-2 g (2-4 capsules of 500 mg) two to three times daily, total daily dose 3-6 g. Concentrated dry extract: 300-500 mg two to three times daily, depending on concentration ratio.
Two to three times daily, taken with water, preferably with meals to reduce potential GI discomfort
May be used long-term as a daily supplement. Clinical trials have used treatment periods of 4-52 weeks.
Not recommended for children under 12
Capsules are the most common commercial dosage form for Cat's Claw. Product quality varies enormously in the commercial market. Key quality considerations: (1) Species identification -- ensure the product is U. tomentosa, not U. guianensis or other Uncaria species, unless U. guianensis is specifically desired for anti-inflammatory use. (2) Chemotype -- for immunomodulatory applications, products should specify POA-chemotype or POA-dominant alkaloid profile. (3) Plant part -- inner bark is the standard; some products may contain root bark or leaf material. (4) Standardization -- products may be standardized to total alkaloid content (typically 3-5%), POA content specifically, or carboxyl alkyl ester content (as in AC-11 products). (5) Third-party testing for identity, potency, and contaminants is recommended.
Standardized Extract
Strength: POA extract: highly concentrated, approximately 60 mg daily dose in clinical trial. AC-11: standardized to 8-10% CAEs. General: DER typically 4:1 to 15:1; standardized to 3-5% total oxindole alkaloids.
Commercially prepared standardized extracts are available in several distinct formulations reflecting different therapeutic targets: (1) POA-chemotype extract -- standardized to pentacyclic oxindole alkaloid content, specifically manufactured to minimize TOA content. The extract used in the Mur et al. (2002) RA trial was of this type (60 mg/day). (2) C-Med-100/AC-11 extract -- aqueous extract standardized to 8-10% carboxyl alkyl esters (CAEs), alkaloid-free or very low alkaloid content. Used in the Sheng et al. DNA repair studies. (3) General standardized bark extract -- standardized to total alkaloid content (typically 3-5% oxindole alkaloids) without specific chemotype selection.
POA-chemotype extract: 20-60 mg daily (as per Mur et al. clinical trial: 60 mg/day). AC-11/C-Med-100 extract: 250-350 mg daily (as per Sheng et al. human studies). General standardized extract: 300-500 mg two to three times daily. Maximum alkaloid dose: 10-30 mg per day of total oxindole alkaloids.
One to three times daily depending on extract type and concentration
Mur et al. trial used 24-52 weeks. Sheng et al. used 6-8 weeks. May be used long-term.
Not established in standardized extract form for children
Standardized extracts represent the most reproducible and clinically validated form of Cat's Claw. The critical distinction between POA-chemotype extracts, AC-11/CAE extracts, and general alkaloid-standardized extracts must be understood: each has a different therapeutic rationale and different evidence base. POA-chemotype extracts are specifically for immunomodulatory and anti-inflammatory applications (RA, immune support). AC-11 extracts are specifically for DNA repair enhancement and antimutagenic applications. General standardized extracts provide the broad-spectrum activity of whole bark. Products labeled 'TOA-free' indicate specific manufacturing steps to remove tetracyclic oxindole alkaloids, which is relevant for immunomodulatory but not anti-inflammatory applications. The EMA assessment report covers bark preparations but has not adopted a formal European Union herbal monograph due to insufficient evidence for the required 30-year traditional use period in Europe.
Infusion (Tea)
Strength: 1-2 teaspoons (approximately 2-4 g) powdered bark per cup (250 mL) of boiling water
While decoction is the traditional and preferred preparation for the woody inner bark, a simple infusion (tea) can be prepared from finely powdered bark or commercially available Cat's Claw tea bags. Place 1-2 teaspoons of finely powdered bark or 1 tea bag in a cup. Pour boiling water over the bark, cover, and steep for 10-15 minutes. Strain and drink. Infusion extracts water-soluble constituents (phenolic acids, proanthocyanidins, some glycosides) but is less efficient than prolonged decoction for extracting alkaloids and triterpenoid glycosides from the woody bark matrix.
1 cup two to three times daily
Two to three times daily
May be used daily as a health-supporting tea. For therapeutic use, decoction or extract forms are preferred.
Not recommended for children under 12
Infusion is a less potent preparation than decoction for Cat's Claw due to the woody nature of the inner bark, which requires prolonged simmering for thorough extraction. However, a hot infusion of finely powdered bark or commercially prepared tea bags provides a convenient, mild daily preparation with appreciable polyphenol and phenolic acid content. This form is most appropriate for general wellness and mild immune support rather than therapeutic treatment of specific conditions. For clinical indications such as arthritis or cancer adjunctive support, decoction, tincture, or standardized extract forms are strongly preferred.
[1]
Safety & Interactions
Class 4
Insufficient data available for classification (AHPA Botanical Safety Handbook)
Contraindications
Cat's Claw is contraindicated during pregnancy based on traditional Asháninka use of high-dose root bark decoctions as a contraceptive agent. The mechanism is not fully elucidated but may involve uterotonic effects, hormonal modulation, or embryotoxicity. No controlled studies in pregnant women have been conducted, and the traditional contraceptive use constitutes a clear signal of reproductive risk. The AHPA, EMA, NCCIH, and essentially all herbal safety authorities agree on this contraindication. Women attempting to conceive should also avoid Cat's Claw given the traditional contraceptive use.
Insufficient safety data for use during lactation. Oxindole alkaloids and other bioactive constituents may be excreted in breast milk with unknown effects on the nursing infant. Given the lack of data and the absolute contraindication in pregnancy, avoidance during lactation is recommended as a precautionary measure.
The immunostimulating properties of POA-chemotype Cat's Claw (enhanced NK cell activity, increased T-cell proliferation, stimulated phagocytosis) could theoretically counteract immunosuppressive medications used to prevent organ rejection (cyclosporine, tacrolimus, mycophenolate, etc.) or to manage autoimmune conditions. Use of immunostimulating herbs in transplant recipients carries the theoretical risk of precipitating acute rejection. This is a firm contraindication across herbal safety authorities.
Cat's Claw should be discontinued at least 2 weeks before elective surgery due to: (1) immunomodulatory effects that could interfere with perioperative immune function; (2) potential antiplatelet effects (though these are less well-documented than for some other herbs); and (3) CYP3A4 interaction potential that could affect metabolism of anesthetic and perioperative medications. This is consistent with general guidance for herbal product discontinuation before surgery.
Cat's Claw is not recommended for children under 3 years of age due to complete absence of safety data in this population. The developing immune system of young children may respond unpredictably to the potent immunomodulatory alkaloids. For children aged 3-12, use only under practitioner supervision with appropriately reduced doses.
Drug Interactions
| Drug / Class | Severity | Mechanism |
|---|---|---|
| CYP3A4 substrate medications (e.g., protease inhibitors: atazanavir, ritonavir, saquinavir; some statins: atorvastatin, simvastatin; calcium channel blockers: amlodipine, nifedipine; benzodiazepines: midazolam, alprazolam; immunosuppressants: cyclosporine, tacrolimus) (CYP3A4 substrates) | moderate | Cat's Claw has been shown to inhibit CYP3A4 enzyme activity in vitro with IC50 values less than 1% full strength concentration, making it one of the most potent herbal CYP3A4 inhibitors tested. Additionally, Liu et al. (2023) demonstrated that Uncaria species activate the pregnane X receptor (PXR), which regulates CYP3A4 gene expression, suggesting potential for CYP3A4 induction with chronic use. Acute inhibition of CYP3A4 would be expected to INCREASE serum levels of CYP3A4 substrate drugs, while chronic PXR activation could DECREASE levels through enzyme induction. The net clinical effect may depend on duration of concurrent use. |
| Cyclosporine, tacrolimus, mycophenolate, and other immunosuppressants (Immunosuppressants) | moderate | Dual interaction mechanism: (1) Pharmacodynamic opposition -- Cat's Claw POAs stimulate immune function (enhanced NK cells, T-cell proliferation, phagocytosis) which could counteract the immunosuppressive effects of these medications. (2) Pharmacokinetic interaction -- CYP3A4 inhibition could increase serum levels of cyclosporine and tacrolimus (both CYP3A4 substrates), potentially causing toxicity. The combination of pharmacodynamic opposition and pharmacokinetic increase creates a complex and unpredictable interaction profile. |
| Warfarin, heparin, and other anticoagulants; aspirin and antiplatelet agents (Anticoagulants and antiplatelet agents) | theoretical | Theoretical additive effect on bleeding risk. Some sources cite antiplatelet effects for Cat's Claw, though this is less well-documented than for herbs like garlic, ginkgo, or reishi. The primary concern is precautionary. Additionally, warfarin is metabolized by CYP enzymes, and Cat's Claw CYP3A4 inhibition could potentially affect warfarin metabolism, though warfarin is primarily metabolized by CYP2C9. |
| Antihypertensive medications (ACE inhibitors, ARBs, calcium channel blockers, beta-blockers) (Antihypertensives) | minor | Additive blood pressure-lowering effect. The tetracyclic oxindole alkaloids (rhynchophylline, isorhynchophylline) demonstrate calcium channel blocking and vasodilatory activity, contributing to mild hypotensive effects. Combined use with pharmaceutical antihypertensives could theoretically result in enhanced blood pressure reduction. |
| Antiretroviral medications for HIV (particularly protease inhibitors and NNRTIs) (Antiretrovirals) | moderate | CYP3A4 inhibition leading to increased serum levels of protease inhibitors (atazanavir, ritonavir, saquinavir, darunavir, lopinavir) and some non-nucleoside reverse transcriptase inhibitors (NNRTIs). The clinical case report of a 45-year-old HIV-positive woman demonstrated dramatic increases in protease inhibitor levels when taking Cat's Claw concurrently. |
Pregnancy & Lactation
Pregnancy
unsafe
Lactation
insufficient data
Cat's Claw is CONTRAINDICATED in pregnancy based on well-documented traditional Asháninka use of high-dose root bark decoctions as a contraceptive and abortifacient agent. While the specific mechanism of contraceptive/abortifacient activity has not been fully elucidated in modern pharmacological studies, the consistent traditional use for this purpose across multiple indigenous groups constitutes a strong safety signal. No controlled reproductive toxicity studies in animals or humans have been published. All major herbal safety authorities (AHPA, EMA, NCCIH, Botanical Safety Handbook) agree on the contraindication in pregnancy. Women of childbearing potential should be counseled about this risk. For lactation, no specific data on excretion of Cat's Claw constituents in breast milk are available. Given the pregnancy contraindication and the potent immunomodulatory alkaloids, avoidance during breastfeeding is recommended as a precautionary measure.
Adverse Effects
References
Monograph Sources
- [1] Keplinger K, Laus G, Wurm M, Dierich MP, Teppner H. Uncaria tomentosa (Willd.) DC.--ethnomedicinal use and new pharmacological, toxicological and botanical results. J Ethnopharmacol (1999) ; 64 : 23-34 . DOI: 10.1016/S0378-8741(98)00096-8 . PMID: 10075119
- [2] Reinhard KH. Uncaria tomentosa (Willd.) D.C.: Cat's claw, Uña de Gato, or Saventaro. J Altern Complement Med (1999) ; 5 : 143-151 . DOI: 10.1089/acm.1999.5.143 . PMID: 10328635
- [3] Heitzman ME, Neto CC, Winiarz E, Vaisberg AJ, Hammond GB. Ethnobotany, phytochemistry and pharmacology of Uncaria (Rubiaceae). Phytochemistry (2005) ; 66 : 5-29 . DOI: 10.1016/j.phytochem.2004.10.022 . PMID: 15649507
- [4] European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). Assessment report on Uncaria tomentosa (Willd. ex Schult.) DC., cortex. EMA/HMPC/259600/2012 (2015)
Clinical Studies
- [5] Piscoya J, Rodriguez Z, Bustamante SA, Okuhama NN, Miller MJ, Sandoval M. Efficacy and safety of freeze-dried cat's claw in osteoarthritis of the knee: mechanisms of action of the species Uncaria guianensis. Inflamm Res (2001) ; 50 : 442-448 . DOI: 10.1007/PL00000268 . PMID: 11603848
- [6] Mur E, Hartig F, Eibl G, Schirmer M. Randomized double blind trial of an extract from the pentacyclic alkaloid-chemotype of Uncaria tomentosa for the treatment of rheumatoid arthritis. J Rheumatol (2002) ; 29 : 678-681 . PMID: 11950006
- [7] Sheng Y, Pero RW, Amiri A, Bryngelsson C. Enhanced DNA repair, immune function and reduced toxicity of C-MED-100, a novel aqueous extract from Uncaria tomentosa. J Ethnopharmacol (2000) ; 69 : 115-126 . DOI: 10.1016/S0378-8741(99)00070-7 . PMID: 10687868
- [8] Sheng Y, Li L, Holmgren K, Pero RW. DNA repair enhancement of aqueous extracts of Uncaria tomentosa in a human volunteer study. Phytomedicine (2001) ; 8 : 275-282 . DOI: 10.1078/0944-7113-00045 . PMID: 11515717
- [9] Sheng Y, Åkesson C, Holmgren K, Bryngelsson C, Giamapa V, Pero RW. An active ingredient of Cat's Claw water extracts: identification and efficacy of quinic acid. J Ethnopharmacol (2005) ; 96 : 577-584 . DOI: 10.1016/j.jep.2004.10.002 . PMID: 15619580
Traditional Texts
- [10] Sandoval M, Okuhama NN, Zhang XJ, Condezo LA, Lao J, Angeles FM, Musah RA, Bobrowski P, Miller MJ. Cat's claw inhibits TNFalpha production and scavenges free radicals: role in cytoprotection. Free Radic Biol Med (2000) ; 29 : 71-78 . DOI: 10.1016/S0891-5849(00)00327-0 . PMID: 10962207
- [11] Sandoval M, Okuhama NN, Clark M, Angeles FM, Lao J, Bobrowski P, Miller MJ. Anti-inflammatory and antioxidant activities of cat's claw (Uncaria tomentosa and Uncaria guianensis) are independent of their alkaloid content. Phytomedicine (2002) ; 9 : 325-337 . DOI: 10.1078/0944-7113-00117 . PMID: 12120814
- [12] Aguilar JL, Rojas P, Marcelo A, Plaza A, Bauer R, Reininger E, Klaas CA, Merfort I. Anti-inflammatory activity of two different extracts of Uncaria tomentosa (Rubiaceae). J Ethnopharmacol (2002) ; 81 : 271-276 . DOI: 10.1016/S0378-8741(02)00093-4 . PMID: 12065162
- [13] Aquino R, De Feo V, De Simone F, Pizza C, Cirino G. Plant metabolites. Structure and in vitro antiviral activity of quinovic acid glycosides from Uncaria tomentosa and Guettarda platypoda. J Nat Prod (1989) ; 52 : 679-685 . DOI: 10.1021/np50064a002 . PMID: 2553871
- [14] Rodrigues BLC, et al.. Anti-inflammatory and/or immunomodulatory activities of Uncaria tomentosa (cat's claw) extracts: A systematic review and meta-analysis of in vivo studies. Front Pharmacol (2024) ; 15 : 1378408 . DOI: 10.3389/fphar.2024.1378408
- [15] Liu J, et al.. Identification of PXR activators from Uncaria rhynchophylla (Gou Teng) and Uncaria tomentosa (Cat's Claw). Drug Metab Dispos (2023) ; 51 : 629-637 . DOI: 10.1124/dmd.122.001092 . PMID: 36797057
Pharmacopeias & Reviews
- [16] ESCOP (European Scientific Cooperative on Phytotherapy). Uncariae tomentosae cortex (Cat's Claw Bark). ESCOP Monographs: The Scientific Foundation for Herbal Medicinal Products, 2nd edition supplement (2003)
- [17] World Health Organization. WHO monographs on selected medicinal plants, Volume 3: Cortex Uncariae. World Health Organization, Geneva (2007)
Last updated: 2026-03-02 | Status: review
Unlock the Full Materia Medica
This monograph is part of our complete evidence-based herbal reference. Enter your email to get free, unlimited access to all of our monographs.
No spam, ever. Unsubscribe anytime.
You're In!
You now have full access to all of our herbal monographs.