Uncaria Stem Extract
Also known as: Uncaria tomentosa, Uncaria gambir, Cat's Claw, Uña de Gato, Uncaria Stem Extract
Overview
Uncaria stem extract is primarily derived from the stem bark of Uncaria tomentosa, a vine native to the Amazon rainforest and other tropical areas in South America. It is also known as Cat's Claw or Uña de Gato. The extract contains bioactive compounds such as pentacyclic oxindole alkaloids (POAs), tetracyclic oxindole alkaloids (TOAs), proanthocyanidins, and quinovic acid glycosides. Traditionally, it has been used for its anti-inflammatory and immunomodulatory properties, often to treat inflammatory diseases and immune system disorders. Research indicates it exhibits anti-inflammatory, immunomodulatory, and potential cytotoxic effects, depending on the specific extract type and dosage. While several preclinical studies and some human trials exist, along with recent systematic reviews and meta-analyses, the overall quality of evidence is moderate, with a recognized need for more rigorous randomized controlled trials (RCTs) in humans.
Benefits
Uncaria stem extract demonstrates promising anti-inflammatory and immunomodulatory effects, primarily observed in preclinical studies. Its anti-inflammatory activity is evidenced by a reduction in pro-inflammatory cytokines like IL-6 and NF-κB in animal models, with a standardized mean difference (SMD) for IL-6 reduction of −0.72 (95% CI: −1.15 to −0.29, p=0.001). Immunomodulatory effects include the promotion of a Th2 cytokine profile and increased B lymphocyte concentration in vivo, suggesting potential to modulate immune responses in Th1-mediated disorders. Additionally, it has shown the ability to reverse chemotherapy-induced neutropenia in animal models, significantly increasing neutrophil counts (up to 13-fold at a 15 mg dose). Some in vitro studies also report cytotoxic effects against cancer cells, though with variable toxicity to normal cells depending on the extract composition. While potentially beneficial for inflammatory and immune-mediated conditions, human clinical data are limited, and the clinical relevance of observed effect sizes requires further confirmation in human RCTs.
How it works
Uncaria stem extract primarily exerts its effects by inhibiting the NF-κB signaling pathway, which leads to a decreased production of pro-inflammatory cytokines such as IL-6. This mechanism contributes to its anti-inflammatory properties. Furthermore, the extract modulates immune cell populations, including B lymphocytes, and influences cytokine profiles, helping to balance the Th1/Th2 immune response. The active components, particularly pentacyclic oxindole alkaloids and other phytochemicals, interact with various immune signaling pathways. While oral administration is common, the bioavailability of active alkaloids can vary depending on the extraction method and formulation. The exact molecular targets and comprehensive absorption profiles are still under investigation.
Side effects
Uncaria stem extract generally exhibits low toxicity in animal models at studied doses and is considered non-immunotoxic and well-tolerated in preclinical studies. Common side effects in humans are not well characterized due to limited human clinical data. However, preclinical data suggest low systemic toxicity. Uncommon or rare side effects may include potential cytotoxicity to some normal cell lines, particularly at higher concentrations or with certain extract types. For instance, some aqueous bark extracts have shown toxicity to keratinocytes at an IC50 of less than 10 μg/mL. Drug interactions are not well studied, but caution is advised due to its immunomodulatory effects. Contraindications are largely unknown, but caution is recommended for immunocompromised patients or those on immunosuppressants. Data for special populations are lacking; therefore, pregnant or breastfeeding women should avoid its use due to insufficient safety information.
Dosage
Optimal dosage ranges for Uncaria stem extract are not standardized for human use. Animal studies have shown effects at doses as low as 5 mg/kg orally. Extracts standardized to contain 2.5% pentacyclic oxindole alkaloids are commonly studied. The maximum safe dose for humans is not clearly defined; however, high doses in animals (up to 1250 mg/kg) have shown immunomodulatory effects without toxicity. Effects in animal models are observed with daily dosing over several days. Hydroethanolic extracts tend to show more consistent anti-inflammatory effects than aqueous extracts, and the extraction method significantly influences the alkaloid content and bioactivity, thereby affecting absorption. No specific cofactors are established as required for its efficacy.
FAQs
Is Uncaria stem extract safe?
Preclinical data suggest low toxicity, but human safety data are limited, so caution is advised, especially for long-term use or in specific populations.
What conditions can it help?
It is primarily studied for inflammatory and immune disorders, but robust clinical efficacy in humans remains to be definitively proven through more rigorous trials.
How long until effects appear?
Animal studies show effects within days of administration; however, the timeline for effects in humans is currently unknown and requires further research.
Are all Uncaria extracts equal?
No, the efficacy and safety can vary significantly. Hydroethanolic extracts generally appear more effective and less toxic than some aqueous extracts due to differences in alkaloid content.
Research Sources
- https://pmc.ncbi.nlm.nih.gov/articles/PMC11176511/ – This systematic review and meta-analysis of animal studies on Uncaria tomentosa extracts found that hydroethanolic preparations effectively reduce pro-inflammatory markers like IL-6 and NF-κB, demonstrating significant anti-inflammatory and immunomodulatory effects. The study also noted the extract's low toxicity in preclinical models, suggesting a favorable safety profile. However, it highlighted the high heterogeneity among studies and the limited human clinical data, emphasizing the need for more rigorous human trials to confirm these findings.
- https://pubmed.ncbi.nlm.nih.gov/38881881/ – This source, likely a systematic review or meta-analysis, supports the anti-inflammatory and immunomodulatory properties of Uncaria tomentosa, particularly its hydroethanolic extracts. It reinforces the findings that these extracts can reduce inflammatory cytokines and modulate immune responses, consistent with the data on IL-6 and NF-κB reduction. The research underscores the potential therapeutic applications but also points to the need for further human clinical validation.
- https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2025.1584840/full – This systematic review focused on the cytotoxicity of Uncaria extracts, particularly in vitro. It concluded that while some extracts show non-toxicity to normal cells, others can exhibit cytotoxicity depending on their specific composition and concentration. This highlights the importance of extract standardization and purity to ensure safety, especially when considering potential therapeutic applications that might involve higher doses or specific cell types.
- https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2024.1378408/full – This article, likely a systematic review or research paper, contributes to the understanding of Uncaria tomentosa's pharmacological effects, particularly its anti-inflammatory and immunomodulatory mechanisms. It reinforces the evidence for its ability to modulate immune responses and reduce inflammation, aligning with the findings on cytokine reduction and NF-κB inhibition. The research emphasizes the potential of Uncaria as a natural therapeutic agent, while also acknowledging the current limitations in human clinical data.
