Uncaria

Otros Nombres

AgylophoraCat's clawCatechuCatechu pallidumChinese UncariaChōtōkōCinchona kattukambarDiao Gou TengFish hook vineGambeerGambierGambirGarabatoGarbato cashaGou TengGoutengHawk's clawHooked UncariaJotodeungKagi-kazuraKancuKynsiliaanitNauclea aculeataNauclea gambirNauclea rhynchophyllaNauclea sinensisNauclea tomentosaOuroupariaOurouparia gambirOurouparia rhynchophyllaOurouparia tomentosaParaguayoRamulus Uncariae cum UncisRestiariaSamentoSaventaroTambor huascaTerra japonicaToroñUña de gatoUña de gavilanUña huascaUncaria acidaUncaria angolensisUncaria attenuataUncaria barbataUncaria bernaysiiUncaria borneensisUncaria callophyllaUncaria canescensUncaria cordataUncaria domatiiferaUncaria ellipticaUncaria gambirUncaria guianensisUncaria hirsutaUncaria homomallaUncaria laevigataUncaria lancifoliaUncaria lanosaUncaria longifloraUncaria macrophyllaUncaria ovataUncaria perrottetiiUncaria rhynchophyllaUncaria roxburghianaUncaria scandensUncaria sessilifructusUncaria sinensisUncaria sterrophyllaUncaria surinamensisUncaria tomentosaUncaria velutinaUncaria wangiiUrupariaUruparia gambirVincaria儿茶钩藤华钩藤大叶钩藤白儿茶釣鉤藤鈎藤屬钓钩藤钩藤属

Sinopsis

Uncaria: A Comprehensive Reference

1. Identity and Botanical Overview

Uncaria is a genus of flowering plants in the family Rubiaceae (the coffee family), comprising woody climbing lianas, shrubs, and vines distributed across tropical regions of South America, Southeast Asia, and parts of Africa. Uncaria species are endemic to many parts of Southeast Asia, Africa, and South America and are widely used in traditional medicine for various applications. The genus is characterized by distinctive recurved hook-like thorns or modified branches that allow the plants to climb host trees, and it is from this morphological feature that the most commercially important species derives its common name.

Over 150 compounds have been isolated and identified from the Uncaria genus. More than 200 chemical constituents, including indole alkaloids, triterpenes, flavonoids and phenylpropanoids, have been isolated from the genus Uncaria. The three most scientifically and commercially significant species are described below.

1.1 Uncaria tomentosa (Willd. ex Schult.) DC. — Cat's Claw / Uña de Gato

Uncaria tomentosa, commonly known as cat's claw, is a tropical medicinal vine of the Rubiaceae family. Its common name derives from the Spanish term Uña de Gato, which identifies the small, curved-back thorns on the stem at the leaf junction. It is widely distributed in the Amazon rainforest and other areas of South and Central America. The plant is recognized by its curved, claw-like thorns at the base of its leaves. Its leaves are opposite, elliptical, and glossy green, measuring approximately 6–12 cm long, and its flowers are small and yellowish, forming globular heads. Native to the Amazon rainforest and tropical areas of South and Central America, particularly Peru, Colombia, and Brazil, it thrives in humid, well-drained soils along riverbanks and forest edges.

Cat's claw is an herbal medicine derived from the bark of the Uncaria tomentosa vine, which is used for its anti-inflammatory and immune-modulating effects in the treatment of fever, fatigue, muscle and joint aches, and the symptoms of chronic inflammatory conditions. Cat's claw includes two species, Uncaria tomentosa and Uncaria guianensis, and the extract is usually made from their root bark, most commonly from U. tomentosa.

The plant is also known by other vernacular names including Samento, Saventaro, Tambor Huasca, Uña Huasca, Paraguayo, and Garabato.

1.2 Uncaria rhynchophylla (Miq.) Jacks. — Gou-teng / Gouteng

Uncaria rhynchophylla (Miq.) Jacks, a member of the Rubiaceae family, is commonly known as Gou-teng in Chinese medicine and is used in traditional Chinese medicine practice for the treatment of convulsions, hypertension, epilepsy, eclampsia, and other cerebral diseases. Uncaria rhynchophylla is a climbing shrub of the Rubiaceae family and has been a foundational remedy in traditional Chinese medicine for over 1,500 years, long used to treat neurological disorders, hypertension, and inflammatory conditions associated with "Liver Wind" and "Liver Yang Rising."

1.3 Uncaria gambir (Hunter) Roxb. — Gambir / Pale Catechu

Uncaria gambir, commonly known as gambir, is a woody climbing shrub or liana in the Rubiaceae family, native to Southeast Asia. Gambier is an extract derived from the leaves of Uncaria gambir, a climbing shrub native to tropical Southeast Asia. It is produced in Indonesia and Malaysia, where it was an important trade item into the late nineteenth century, and can be used as a tanning agent, a brown dye, a food additive, and as herbal medicine. Also known as pale catechu, white catechu, or Japan Earth, it is often confused with other forms of catechu.

1.4 Other Notable Species

Thirty-four Uncaria species have been reported, including U. guianensis and U. tomentosa, which are found in South America. The most studied Uncaria species are U. gambir, U. nervosa, U. longiflora, U. tomentosa, U. cordata, U. macrophylla, U. rhynchophylla, and U. hirsuta.

1.5 Common Preparations and Dosage Forms

Several formulations of cat's claw (e.g., tinctures, decoctions, capsules, extracts, and teas) are available in the market. The inner bark of cat's claw is used to make liquid extracts, capsules, and teas. Preparations of cat's claw can also be applied to the skin. The dried hooks of U. rhynchophylla are the parts used in TCM formulas, while the bark and root bark of U. tomentosa are the primary commercial sources in Western supplement markets. The extract known as gambier or pale catechu, derived from U. gambir, is obtained by boiling and evaporating the leaves and young twigs, yielding a product rich in polyphenols.

2. Traditional and Historical Use

2.1 Uncaria tomentosa — Amazonian Tradition

Uncaria tomentosa is a Rubiaceae used for at least 2,000 years among some Peruvian tribes, especially the Asháninka. Cat's claw has been used medicinally by the Aguaruna, Ashaninka, Cashibo, Conibo, and Shipibo tribes of Peru for at least 2,000 years, and the Ashaninka Indian tribe in central Peru has the longest recorded history of use of the plant.

A decoction of U. tomentosa bark, root, and leaves is used traditionally for different health problems, including arthritis, weakness, viral infections, skin disorders, abscesses, allergies, asthma, cancer, fevers, gastric ulcers, hemorrhages, inflammations, menstrual irregularity, rheumatism, urinary tract inflammation, and wounds.

The Ashaninka use cat's claw to treat asthma, inflammations of the urinary tract, arthritis, rheumatism, and bone pain; to recover from childbirth; as a kidney cleanser; to cure deep wounds; and to control inflammation and gastric ulcers. Indigenous tribes in Piura use cat's claw to treat tumors, inflammations, rheumatism, and gastric ulcers.

Ethnic groups in the Peruvian Amazon — such as the Ashaninka, Aguaruna, Huambisa, Jivaro, Shipibo-Conibo, Bora, Mashiguenga, Campa, and Piro tribes — have utilized cat's claw for centuries to treat conditions including arthritis, allergies, asthma, diabetes, cancer, and bacterial and viral infections.

The traditional preparation method was principally a bark decoction. The bark and roots were prepared as a decoction to treat various ailments. The plant entered Western botanical and scientific awareness in the 20th century, and its phytochemical study expanded rapidly from the 1970s onward.

2.2 Uncaria rhynchophylla — Traditional Chinese Medicine

Uncaria rhynchophylla has been a foundational remedy in traditional Chinese medicine for over 1,500 years, and has long been used to treat neurological disorders, hypertension, and inflammatory conditions associated with "Liver Wind" and "Liver Yang Rising." U. rhynchophylla possesses many medicinal values in traditional Chinese medicine, including arresting convulsions, treating gastric problems, reducing body heat, and suppressing liver hyperfunction. Clinically in TCM, it has a role in treating hypertension, dizziness, epilepsy, and cardiovascular diseases.

The dried hooks of some Uncaria species have been integral components in traditional oriental medicines, and generally have been used as spasmolytics, analgesics, and sedatives for symptoms associated with nervous disorders. One of the earlier phytochemical reports on Uncaria was published in 1928 and revealed the isolation of rhynchophylline from U. rhynchophylla.

Yi-Gan-San, a traditional prescription consisting of U. rhynchophylla, Bupleurum chinense, Angelica sinensis, Ligusticum wallichii, and Poria cocos, can improve various behavioral and psychological symptoms of dementia and has also shown neuroprotective effects on many neurodegenerative disorders.

2.3 Uncaria gambir — Southeast Asian Tradition

Gambier production began as a traditional occupation in the Malay archipelago. By the middle of the seventeenth century, it was established in Sumatra, the western parts of Java, and the Malay peninsula. It was initially used as medicine and chewed with betel, and local Chinese also began to use gambier to tan hides. The traditional use is for chewing betel. Traditionally, gambier has been used for the treatment of various ailments such as wounds, ulcers, fevers, headaches, gastrointestinal illness, microbial infections, hypertension, and nervous disorders.

Traditionally, gambir is used as a mixture of medicines, namely for burns, headaches, diarrhoea, dysentery, canker sores, and skin pain medication.

3. Key Constituents and Active Compounds

3.1 Uncaria tomentosa

U. tomentosa is rich in many phytoconstituents such as oxindole and indole alkaloids, glycosides, organic acids, proanthocyanidins, sterols, and triterpenes. Phytochemical studies have shown the presence of a wide range of bioactive compounds in various parts of U. tomentosa (bark, leaves, stem, and others), including alkaloids of the indole and oxindole type; triterpenes based on ursolic, oleanolic, or quinovic acid; glycosides, sterols and phenolic compounds; phenolic acids; and flavan-3-ol related compounds like proanthocyanidins.

The plant is rich in bioactive compounds including pentacyclic (POA) and tetracyclic (TOA) oxindole alkaloids, triterpenes, quinic acid esters, polyphenols (phenolic acids and proanthocyanidins), flavonoids, quinones, and glycosides.

Of the known constituents, indole alkaloids are regarded as the main bioactive constituents and are responsible for the broad spectrum of biological properties reported for Uncaria species. Reports indicate that the tetracyclic oxindole alkaloids present in Uncaria mainly act on the central nervous system, whereas pentacyclic oxindole alkaloids affect the cellular immune system.

Among numerous U. tomentosa compounds, mitraphylline is considered the major alkaloid present in this plant and it might be at least partially responsible for the anti-inflammatory activity of Uncaria bark extracts. In most studies, its anti-inflammatory activity has been attributed to tetracyclic and pentacyclic oxindole alkaloids; however, currently available pharmacological data indicate that this biological activity is due to the synergistic action of several compounds present in this species.

Four oxindole alkaloids — isopteropodine, pteropodine, isomitraphylline, and isorhynchophylline — were demonstrated to potentiate phagocytosis by white blood cells.

Specific proanthocyanidins, i.e., epicatechin dimers and variants thereof, are newly identified polyphenolic components within Uncaria tomentosa that possess both plaque- and tangle-reducing and inhibitory activity.

3.2 Uncaria rhynchophylla

U. rhynchophylla's major active components are alkaloids, terpenoids, and flavonoids. The plant primarily contains monoterpenoid indole alkaloids, triterpenoids, flavonoids, and phenolics. Major compounds identified from U. rhynchophylla include corynoxine B, corynoxine, rhynchophylline, and isorhynchophylline.

Tetracyclic oxindole alkaloids are regarded as the main bioactive constituents acting on the CNS. Rhynchophylline, the most prominent tetracyclic alkaloid isolated from U. rhynchophylla, has been the subject of particularly intensive research for neuroprotective properties. Rhynchophylline, a neuroprotective agent isolated from the traditional Chinese medicinal herb U. rhynchophylla, has been reported to cause a drastic acceleration of slow inactivation of delayed rectifiers in neuroblastoma cells and Kv1.2 channels.

3.3 Uncaria gambir

The plant is primarily valued for its astringent extract, known as gambier or pale catechu, obtained by boiling and evaporating the leaves and young twigs, yielding a product rich in polyphenols such as catechins (comprising 80–90% of the extract), along with flavonoids, tannins, alkaloids like gambirine, terpenoids, and saponins. The gambier extract is mainly composed of catechin-tanic acid (a tannin) and catechin (a flavan-3-ol). Commercially produced gambier may range in catechin content from less than 20% to more than 40% depending on quality.

Phytochemically, U. gambir contains catechin compounds, catechic acid, pyrocatechol, quercetin, tannins, flavonoids, gambirin alkaloid compounds, fluorescence gambir, tannin gambir, wax, rhynchophylline, isorhynchophylline, gambirdin, isogambirdine, and auroparin.

4. Mechanisms of Action

4.1 NF-κB Inhibition and Anti-inflammatory Signaling

U. tomentosa preparations have been found to show various anti-inflammatory effects such as inhibiting the production of the inflammatory cytokine TNF-α and the activation of the nuclear transcription factor NF-κB. Treatment with Uncaria tomentosa inhibited the LPS-dependent activation of specific NF-κB and AP-1 components. From a mechanistic standpoint, Uncaria tomentosa has been found to affect tumor growth by inhibiting the Wnt or NF-κB/TNF-α signaling pathways.

4.2 Immunomodulation

Immunomodulating, anti-inflammatory, and anticancer properties of Uncaria tomentosa have been suggested and attributed mainly to the presence of tetracyclic or pentacyclic oxindole alkaloids. However, the synergic action of different compounds occurring in extracts and modulation of redox processes may significantly influence the anticancer activity of Uncaria tomentosa.

4.3 DNA Repair Enhancement

It has been reported that the water-soluble extract of the Uncaria species enhances DNA repair in both rats and humans, wherein the DNA repair process removes DNA damages in the nucleus, which inhibits cell replication and immune function. A specific water-soluble extract proprietary fraction designated C-MED-100 has been the focus of this line of research. NF-κB inhibition by such extracts may effectively kill tumor cells by forcing them out of replication via apoptosis; NF-κB also sends signals to inflammatory cells instructing them to produce cytokines, thereby stimulating phagocytic cells to kill invading infectious agents. Inhibiting NF-κB has anti-inflammatory properties because it prevents over-reaction of the inflammatory process.

4.4 Pro-apoptotic Activity in Cancer Cells

Extract of U. tomentosa has been found to be cytotoxic against cancer cells and to induce oxidative stress in cancer cells but not in normal cells. In cancer cells, the extract activates effector caspase-3 and caspase-7, which execute apoptosis. Additionally, a reduction in the NF-κB active form has been observed in cancer but not in normal cells, and inhibition of NF-κB activity may prevent cancer cell resistance to chemotherapy.

4.5 Neuroprotective Mechanisms (Uncaria rhynchophylla)

Goutengsan, a Chinese herbal formula containing U. rhynchophylla, has shown a protective role against Aβ-induced cell damage; major compounds identified from the Goutengsan extraction — including rhynchophylline, isorhynchophylline, corynoxeine, and isocorynoxeine — also showed a protective role. This extraction has shown a neuroprotective role in Alzheimer's disease with significant inhibition of Aβ aggregation and accumulation in the cortex and subiculum, alleviating synaptic and neuronal loss and improving impaired hippocampal neurogenesis.

Based on a network pharmacology analysis, 90 anti-AD targets related to alkaloids were identified, of which 28 were significantly correlated with Aβ and tau pathology.

5. Scientific Evidence by Area of Use

5.1 Inflammatory and Rheumatic Conditions

Osteoarthritis (OA)

Forty-five patients with osteoarthritis of the knee were recruited in a clinical trial; 30 were treated with freeze-dried U. guianensis, and 15 with placebo. Among the 45 patients with painful osteoarthritis of the knee treated with cat's claw (100 mg once daily) or placebo for 4 weeks, pain scores decreased more with cat's claw, but night-time pain and swelling did not change; cat's claw was well tolerated and there were no serious adverse events or changes in serum ALT and AST values during treatment. The main benefit associated with treatment was the relief of exercise-related pain.

This was a small, single-center, short-duration trial (4 weeks) using U. guianensis, not U. tomentosa — a species distinction that limits direct extrapolation. Evidence from this study is preliminary.

Rheumatoid Arthritis (RA)

In a trial to evaluate safety and clinical efficacy of a plant extract from the pentacyclic chemotype of Uncaria tomentosa (UT) in patients with active rheumatoid arthritis (RA), forty patients undergoing sulfasalazine or hydroxychloroquine treatment were enrolled in a randomized 52-week, 2-phase study. During the first phase (24 weeks, double-blind, placebo-controlled), patients were treated with UT extract or placebo. Twenty-four weeks of treatment with the UT extract resulted in a reduction of the number of painful joints compared to placebo (by 53.2% vs. 24.1%; p = 0.044). Patients receiving the UT extract only during the second phase experienced a reduction in the number of painful (p = 0.003) and swollen joints (p = 0.007) and the Ritchie Index (p = 0.004) compared to the values after 24 weeks of placebo.

In a randomized trial of cat's claw (30 mg daily) vs. placebo in 40 patients with rheumatoid arthritis, adverse events were uncommon and minor, the most common being dyspepsia and pruritus; laboratory results did not change. This single trial is relatively small and the patient population was concurrently receiving conventional DMARDs, limiting the ability to attribute effects solely to cat's claw. Evidence is suggestive but not conclusive.

Preclinical (Animal) Evidence for Inflammation

A systematic review and meta-analysis of preclinical studies published before July 2023, identified in PubMed, Embase, and Scopus, was conducted using four independent reviewers. The effects of U. tomentosa on inflammatory diseases and inflammatory mediators were extracted. Standardized mean differences and 95% CIs were estimated using RevMan 5.4 (Cochrane Collaboration), and the protocol was registered in PROSPERO. Twenty-four of 523 studies were included.

In this systematic review and meta-analysis, U. tomentosa decreased the levels of IL-6 and NF-κB but not of IL-1, IL-10, or TNF-α in animal models of inflammatory diseases. These models included asthma, diabetes, arthritis, obesity, gastric ulcers, and intestinal diseases. Six studies showed that the aqueous extract tended to increase IL-6, whereas hydroethanolic extracts significantly reduced IL-6 levels (SMD: −0.72, 95% CI: −1.15, −0.29, p = 0.001). There was a high risk of bias regarding sample size calculation, missing outcome data (excluded animals), and possible conflicts of interest, and a moderate risk of bias for temperature control, number of animals appropriate to the model, and compliance with animal welfare regulations. These findings support anti-inflammatory potential but do not substitute for robust human clinical trials.

5.2 Anticancer Activity

Evidence for anticancer activity of U. tomentosa is predominantly in vitro (cell culture studies), with very limited human data.

A 2025 systematic review found that the most promising in vitro findings were observed for crude aqueous bark extracts against squamous cell carcinoma and pentacyclic oxindole alkaloid (POA)-rich extracts against prostate cancer and leukemia. In contrast, tetracyclic oxindole alkaloid (TOA)- and proanthocyanidin (PAC)-rich fractions showed limited cytotoxicity. Most extracts were non-toxic to normal cells, except for the crude aqueous bark extract, which exhibited cytotoxicity in keratinocytes.

U. tomentosa has potential as a source of selective anticancer agents, particularly through crude aqueous bark and POA-rich extracts. The observed cytotoxic effects vary considerably depending on the extraction method and chemical composition, underscoring the need for standardization in future studies. Further standardized studies and mechanistic investigations are required to validate its therapeutic potential for cancer treatment.

On the clinical side, a randomized clinical trial was conducted to evaluate the effectiveness of Uncaria tomentosa in minimizing the side effects of chemotherapy and improving the antioxidant status of colorectal cancer (CRC) patients. Patients (43) undergoing adjuvant/palliative chemotherapy with FOLFOX4 were split into two groups: the UT group received chemotherapy plus 300 mg of Uncaria tomentosa daily, and the control group received only FOLFOX4. The use of 300 mg of Uncaria tomentosa daily during 6 cycles of FOLFOX4 did not change the analyzed parameters, and no toxic effects were observed. This study was small and did not demonstrate a significant clinical benefit in terms of side-effect reduction or immunological parameters. Overall, anticancer evidence in humans is at a very early and preliminary stage.

5.3 Neurodegenerative Disease

Alzheimer's Disease and Cognitive Protection

Research on U. tomentosa in Alzheimer's disease (AD) is largely preclinical. Specific proanthocyanidins within Uncaria tomentosa — namely, epicatechin dimers and variants thereof — possess both plaque- and tangle-reducing and inhibitory activity. A specific and natural plant extract (PTI-00703 cat's claw) from a specific Peruvian source was identified as a potent inhibitor and reducer of both beta-amyloid fibrils (the main component of "plaques") and tau protein paired helical filaments/fibrils (the main component of "tangles"). These findings are in vitro and in transgenic animal models; no human clinical trial results are available for this application.

For U. rhynchophylla, Uncaria rhynchophylla, named Gouteng in Chinese, has been reported to have an effective neuroprotective role in neurodegenerative diseases. Major compounds including corynoxine B, corynoxine, rhynchophylline, and isorhynchophylline have been summarized for pharmacological effects and signaling pathways in neurodegenerative diseases. U. rhynchophylla and its major components have multiple beneficial pharmacological effects on the CNS; further studies are warranted to fully illustrate the underlying molecular mechanisms, pharmacokinetics, and toxicological profiles before clinical application can be established. Human clinical evidence for this application remains lacking.

5.4 Antiviral Activity

Biological activities of U. tomentosa have been examined against various microorganisms and parasites, including pathogenic bacteria, viruses, and Plasmodium, Babesia, and Theileria parasites. Published in vitro data and limited animal studies exist, but controlled human clinical trials on antiviral efficacy are absent from the scientific record. This area should be considered exploratory only.

5.5 Antimicrobial and Antioxidant Activity

U. tomentosa has been found to be effective as an immune system rejuvenator, antioxidant, antimicrobial, and anti-inflammatory agent. Various studies have shown that extracts and compounds obtained from U. gambir have medical uses for their antioxidant, antibacterial, anti-helminthic, anticancer, antifungal, anti-inflammatory, anti-hyperglycemic, anti-hyperuricemic, anti-lipid peroxidation, and antihyperlipidemic properties. The bulk of this evidence is from in vitro and animal studies; robust human evidence is lacking.

6. Body Systems and Associated Health Areas

Musculoskeletal / Rheumatological: The Rubiaceae species U. guianensis and U. tomentosa are clinically evaluated in the treatment of rheumatic diseases. The primary human evidence base covers osteoarthritis and rheumatoid arthritis.
Immune System: Uncaria tomentosa has immunomodulatory properties. Pentacyclic oxindole alkaloids are associated with cellular immune system modulation.
Central Nervous System: The protective effects of U. rhynchophylla and its major components on the central nervous system have become a focus of research in recent decades.
Gastrointestinal: Traditional use across multiple cultures encompasses gastric ulcers, gastritis, diarrhea, and dysentery, particularly for U. tomentosa and U. gambir.
Cardiovascular / Antihypertensive: The genus Uncaria from the Rubiaceae family is a significant plant source of active alkaloids with anti-hypertensive, sedative, anti-Alzheimer's disease, anti-drug addiction, and anti-inflammatory effects.
Oncology (Adjunct / Investigational): Preclinical and limited clinical investigation into cytotoxic and chemoprotective roles, particularly for POA-rich fractions.
Antimicrobial / Antiviral: In vitro activity documented against various pathogens; human evidence is absent.

7. Dosages Reported in Studies

Dosages vary significantly by species, extract type, chemotype, and target condition. The following reflect doses as reported in specific referenced studies and are not recommendations.

In the Piscoya et al. (2001) osteoarthritis trial, cat's claw (U. guianensis) was administered at 100 mg once daily for 4 weeks.
In the Mur et al. (2002) rheumatoid arthritis trial, cat's claw extract was administered at 30 mg daily vs. placebo in 40 patients over 24 weeks.
In the colorectal cancer chemotherapy trial, patients received 300 mg of Uncaria tomentosa daily during 6 cycles of FOLFOX4 chemotherapy.
One gram of root bark given 2 to 3 times daily is a typical dose referenced in the literature, while 20 to 30 mg of a root bark extract has been recommended.
A standardized extract containing 8% to 10% carboxy alkyl esters and less than 0.5% oxindole alkaloids has been used in clinical studies in doses of 250 to 300 mg.
Despite multiple purported effects, controlled clinical trials are lacking to support appropriate dosages.
The HPLC analysis of one dry U. tomentosa extract used in a clinical trial presented a content of 2.57% pentacyclic oxindole alkaloids (POAs), calculated with reference to external calibration curves of mitraphylline.

8. Safety Considerations and Drug Interactions

8.1 General Tolerability

Uncaria tomentosa has been found to be safe and to have minimal side effects in a variety of animal and human studies. Human studies ranging from four to 52 weeks showed side effects that were similar to those of the placebo. Cat's claw has not been implicated in causing liver injury. Cat's claw appears to have no serious toxicity when used orally; ALT elevations and hepatotoxicity are not mentioned in extensive toxicological reviews.

8.2 Reported Adverse Events

In the Mur et al. (2002) randomized trial of cat's claw vs. placebo in 40 patients with rheumatoid arthritis, adverse events were uncommon and minor, the most common being dyspepsia and pruritus.

U. tomentosa has been associated with the development of acute interstitial nephritis leading to acute renal failure in at least one case report. This represents an isolated case and should be noted, though causality has not been definitively established.

8.3 Drug Transporter and Enzyme Interactions

One of the major risks associated with the concomitant use of herbal products and therapeutic drugs is herb–drug interactions (HDIs). The most common mechanism leading to HDIs is the inhibition and/or induction of transport proteins and drug-metabolizing enzymes by herbal ingredients, causing changes in the pharmacokinetic disposition of the victim drug.

UT extract significantly inhibited all ABC transporters and the majority of the SLC transporters tested. Of the investigated oxindole alkaloids, isopteropodine significantly inhibited OATP, OCT1 and OCT2, OAT3, ENT4, MDR1, and BCRP transporters. Based on calculated intestinal concentration of UT extract, interactions with intestinal transporters, especially OATP2B1, ENTs, MRP1, MRP2, MDR1, and BCRP could be relevant in vivo. These data can help predict the clinical consequences of UT co-administration with drugs, such as increased toxicity or altered efficacy.

CYP3A4 was inhibited about 40% at a Samento (UT extract) concentration of 1%. Samento significantly induced mRNA expression of CYP2J2, UGT1A3, UGT1A9, ABCB1, and SLCO1B1 and strongly activated PXR. Clinical studies are strongly recommended to clarify whether the effects observed in vitro are of clinical relevance. These findings indicate a theoretical potential for interactions with drugs metabolized by CYP3A4 or transported by the above systems, but in vivo clinical significance has not been established.

8.4 Chemotype-Specific Considerations

Tetracyclic oxindole alkaloids present in Uncaria mainly act on the central nervous system, whereas pentacyclic oxindole alkaloids affect the cellular immune system. Some commercial preparations are specifically standardized to contain only one chemotype or the other (TOA-free or POA-standardized), and the biological activity profile may differ meaningfully depending on chemotype composition.

8.5 Cytotoxicity to Normal Cells

In vitro, a crude ethanolic stem bark extract, PAC-rich fractions or purified extracts, and a POA-trans-rich decoction were non-toxic to Vero, NHDF, and LEC cells. The purified TOA-rich extract was potentially non-toxic, while crude POA-trans-rich bark extract was potentially toxic to HL cells. The most worrisome case was the crude aqueous extract of bark, which was toxic to HaCaT keratinocyte cells at low IC50. Additional in vivo studies would be necessary to establish clinical safety.

8.6 In Vitro vs. In Vivo Safety

The acute median lethal dose in mice was found to be greater than 16 g/kg body weight. This very high value in rodent models suggests low acute toxicity at conventional supplemental doses, but long-term and high-dose human safety data remain limited.

9. Summary of Evidence Quality

The overall evidence base for Uncaria genus preparations is heterogeneous in quality. The strongest human clinical evidence is for U. tomentosa and U. guianensis in arthritic conditions (osteoarthritis, rheumatoid arthritis), where small randomized controlled trials have returned positive signals, but the studies are limited by small sample sizes, short durations, and concurrent use of conventional treatments. Cat's claw has some evidence for analgesic but little for anti-inflammatory activity in humans.

For neuroprotective, anticancer, antiviral, and antimicrobial applications, evidence is predominantly in vitro or from animal models. Uncaria tomentosa is a medicinal plant with documented immunomodulatory and anti-inflammatory properties; recent studies suggest potential anticancer effects, but evidence remains fragmented. The same assessment applies broadly to most other claimed benefits. Rigorous, adequately powered, Phase II and Phase III human clinical trials are largely absent from the literature as of 2025.

References

Condiciones de Salud

Condiciones de salud que Uncaria puede ayudar a apoyar.

Contaminación ElectromagnéticaCientífico
Uncaria tomentosa (cat's claw) has a randomized double-blind clinical trial in RA showing reduction in painful joints, morning stiffness, pain intensity, and joint edema versus placebo. It contains immunomodulatory alkaloids and polyphenols that modulate T-cell balance and reduce NF-κB and IL-6. Traditional Amazonian use for inflammatory and rheumatic conditions is well-established.

Sistemas Corporales

Sistemas corporales que Uncaria puede ayudar a apoyar.

No hay sistemas corporales disponibles.