Treatment of Rheumatic Diseases with Uncaria tomentosa

1. Possible mechanism of action, active substances, available preparations

Application

Uncaria tomentosa (U.t., cat’s claw, Spanish: Una de Gato) belongs to the Rubiaceae family, which also includes the coffee plant. Species of the genus Uncaria are used in folk medicine in Asia and South America (overview at [18]). U.t. is an evergreen climbing plant found, among other places, in the rainforests of the entire Amazon region. Among the indigenous peoples there, the plant is used to treat a wide range of conditions, including abscesses, arthritis, asthma, allergies, menstrual disorders, and skin diseases (overview at[18]). Water-based extracts from the bark of the stem and roots are primarily used (overview at [18]).

In Germany, 7 Uncaria preparations can be found via MMI Pharmindex Plus (see table).

The products listed are freely available online. The sales listings we reviewed did not contain specific information regarding indications, effects, or adverse effects.

The Yellow List (www.gelbe-liste.de) lists 8 additional products under “Una de Gato” in the form of capsules, bark powder, tea, and liquid. All are classified as dietary supplements not requiring a pharmacy prescription; package inserts or professional information are not available in the Yellow List.

Chemical and pharmacological composition:

The root of cat’s claw contains a very high concentration of oxindole alkaloids. Plant compounds with an oxindole backbone possess numerous pharmacologically significant effects, including antiproliferative, anti-inflammatory, antiviral, antitubercular, and antioxidant effects [22]. Terpenoids, such as quinovic acid glycosides, urol acid derivatives, and sterols (primarily β-sitosterol), as well as flavonoids such as procyanidins and quinconaine, have been detected in the stem and root [18]. In addition, hydroxycarboxylic acids such as quinic acid are present [39]. Within the species, there appear to be significant differences in active ingredient content due to the existence of so-called chemotypes, which contain either predominantly tetracyclic or predominantly pentacyclic oxindoles [21].

Effects in vitro and in animal models

A PubMed search for the keyword “uncaria tomentosa” yielded 292 studies (as of June 3, 2025). Of these, 132 related to research in humans, and 129 were written in English or German. All statements in this opinion are based on these 129 articles. Within this pool, a search using the keywords “uncaria tomentosa and arthritis” yielded 16 publications.

The biological effects of U.t. constituents are diverse and, in some cases, variable. In addition to the aforementioned genetic variability of the plants, the method of harvesting and storage, but above all the method of extraction (aqueous or alcoholic), has an impact on the active ingredient content and the composition of the extracts, as well as on potential toxicity in clinical applications [35]

A large portion of the scientific research focuses on the potential growth-inhibiting effect of individual U.t. constituents on tumor cells in vitro [7, 31, 34], which is based, among other things, on the inhibition of the Wnt signaling pathway [17]and the induction of apoptosis [7, 16, 34]. The inhibition of caspase-3 is considered a mediator of apoptosis [15]. Further studies on human cell cultures investigate the effects of U.t. components on oxidative stress [8, 14]. Inhibition of platelet aggregation and thrombin function by U.t. extracts in vitro has also been described [23]. Cell culture and ex vivo studies focus on the antimicrobial properties of U.t. extracts [12, 19, 36]or their potential use against SARS-CoV-2 [38]or dengue fever [24, 30].

Numerous anti-inflammatory and immunomodulatory effects have been described for U.t. For example, aqueous extracts of U.t. appear to inhibit lymphocyte apoptosis in animal models [3], an effect attributed primarily to quinic acid [2]. Aqueous extracts also impair the activation of peripheral blood mononuclear cells (PBMCs) by interferon gamma [37]. Ethanol extracts of the bark promote the apoptosis of these mononuclear cells in vitro [9]. Such extracts also cause a significant inhibition of TNF-alpha in cell cultures by inhibiting NF-KB [6, 32]. Quinic acid obtained from aqueous extracts of U.t. is also capable of inhibiting NF-KB [39]. In an animal model, feeding U.t. inhibits the development of experimentally induced gastritis [32]. Experimentally induced inflammatory paw edema in mice heals more quickly with alcoholic extracts of U.t. than with aqueous extracts [1].

Studies on the effects of U.t. components on joints, joint structures, cartilage, or bone tissue are significantly scarcer. A mixture of extracts containing U.t., as well as Boswellia and Peruvian ginseng, demonstrated anti-inflammatory and chondroprotective effects on cartilage explants and chondrocytes [4]. Another study described the suppression of the pro-inflammatory effect of interleukin-1 on chondrocyte cultures and cartilage explants by extracts of Uncaria guianensis [25]. Oral treatment of adjuvant-induced arthritis in rats with aqueous U.t. extracts resulted in significant anti-inflammatory effects via modulation of ATP metabolism [11].

2. Overview of the scientific evidence regarding clinical efficacy in the literature

Clinical studies on U.t. for rheumatological indications are scarce. In one study, 45 patients with knee

osteoarthritis were treated in a 2:1 ratio with freeze-dried aqueous extract of U.t. or with a placebo for 4 weeks. The researchers observed an improvement in the overall assessment by both physician and patient and a reduction in pain during movement starting in the first week; however, there was no effect on pain at rest or knee swelling [28]. Another four-arm study, in which scientists from the previous study were involved, compared a mineral mixture in two dosages as well as a combination of the mineral supplement with U.t. for osteoarthritis in 107 patients. No significant changes in the WOMAC score or analgesic use were achieved; the effect of U.t. in this study is difficult to assess [26].

For rheumatoid arthritis, there is a small study involving a U.t. extract of a pentacyclic chemotype [27]. Here, 40 patients were treated who had previously been stably maintained on sulfasalazine or hydroxychloroquine for 6 months and exhibited significant disease activity. The majority of patients were seronegative. Treatment was placebo-controlled for the first 24 weeks, followed by 24 weeks of treatment with the active drug for all patients. Compared to placebo, administration of U.t. in capsule form significantly reduced the number of painful joints, but not the number of swollen joints. The analog scales for global disease activity and global pain, as well as inflammatory parameters and the Health Assessment Questionnaire (HAQ), remained unaffected [27].

3. Potential applications in rheumatology, including expected positive effects

Preparations with a clearly characterized formulation and a defined and standardized active ingredient content are not available in Germany. A meaningful application in rheumatology is therefore not apparent.

4. Possible side effects and limitations

In animal models, defined extracts of U.t. are well tolerated even at high doses [33]. The aforementioned clinical studies reported good tolerability of U.t. [27, 28]. Nevertheless, use in humans does not appear to be risk-free. U.t. preparations have been linked to serotonin syndrome [29]. The administration of U.t. has led to cases of interstitial nephritis [5]. A case of acute renal failure following U.t. treatment of a patient with SLE has been published [20]. In addition, worsening of motor Parkinson’s symptoms following U.t. administration has been described [13]. In vitro studies show that U.t. can inhibit the cytochrome P450 (CYP3A4) system, so drug interactions cannot be ruled out [10].

5. Final Recommendation of the Commission

The available evidence is insufficient to recommend the use of preparations containing U.t. for rheumatological indications. Preparations with a clearly characterized formulation and a defined and standardized active ingredient content are not available in Germany. Self-medication should therefore be discouraged at this time. , even if pain-relieving effects of U.t. ingredients cannot be ruled out, there is no evidence of genuine anti-inflammatory or disease-modifying effects. Therefore, better-characterized alternatives should be used.

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Last updated: March 11, 2026