Carboxy-alkyl-esters

Synopsis

Carboxy-Alkyl-Esters (CAEs): A Comprehensive Reference

1. Identity: Botanical and Chemical Background

1.1 Nomenclature and Chemical Classification

Carboxy-Alkyl-Esters (CAEs), also referred to as carboxyl alkyl esters, are a class of compounds produced by Uncaria species and are considered chlorogenic acid derivatives, well known for their anti-inflammatory properties. The terms carboxy alkyl esters and carboxyl alkyl esters are used interchangeably in the scientific literature and refer to the same class of phytochemicals. Quinic alkyl esters and their analogs are a subset of active ingredients contained within the broader carboxyl alkyl ester fraction.

Chlorogenic acid, one of the parent structures in the CAE family, arises from the esterification of caffeic acid and quinic acid, featuring a molecular architecture characterized by three labile groups: ester bonds, unsaturated double bonds, and dibasic phenols. The chlorogenic acid family includes quinic acid, caffeic acid, ferulic acid, and the p-coumaric acid group, including caffeoylquinic acids and feruloylquinic acids.

The precise chemical identification of all active ingredients in the primary CAE-rich extract has not been fully achieved; however, the chemical and biological characteristics of those ingredients have been sufficiently documented to standardize commercial manufacture. Using thin layer chromatography (TLC) as a purification tool, the active CAE ingredients were shown to have a UV absorption maximum at approximately 200 nm and to react with hydroxylamine and ferric chloride, thereby characterizing them as esters.

1.2 Botanical Source

The primary botanical source is Uncaria tomentosa (Willd. ex Schult.) DC., of the family Rubiaceae, commonly known as cat's claw — a tropical medicinal vine originating in the Amazon rainforest and other areas of South and Central America. This liana derives its common name from hook-like thorns that resemble the claws of a cat, and it can grow to a length of up to 30 meters, climbing by means of these thorns.

Two species of cat's claw are commonly used in North America and Europe — Uncaria tomentosa and Uncaria guianensis — which have different properties and uses; U. tomentosa is the more commonly used in traditional medicine. Most commercial preparations of cat's claw in the United States contain U. tomentosa.

The bioactive components of U. tomentosa can be divided into hydrophobic and hydrophilic chemotypes. The hydrophobic chemotypes include uncarine F, speciophylline, mitraphylline, isomitraphylline, pteropodine, and isopteropodine, which have received considerable attention for their role in immunomodulation and antimicrobial activity. By contrast, carboxy alkyl esters are the bioactive components of the hydrophilic chemotypes.

1.3 Plant Part and Preparation Forms

Commercial CAE-rich extracts are formulated based on the historical medicinal uses of cat's claw, in which an important step is exhaustive hot water extraction for approximately 18 hours at around 95°C. The extract is then ultrafiltered to remove high molecular weight (>10,000 MW) toxic conjugates, and spray-dried to contain 8–10% carboxy alkyl esters as active ingredients.

The CAE-rich extract, sold as AC-11®, is a refined extract that comes from the inner bark only of the cat's claw vine, and is relatively alkaloid-free (<0.05%). This proprietary ultra-filtration process produces a low molecular weight (less than 10,000 Daltons) bioavailable, scientifically indole alkaloid-free extract. The patented process standardizes carboxy alkyl esters (CAEs), the biologically active ingredient, to a minimum of 8%.

Several formulations of cat's claw more broadly — including tinctures, decoctions, capsules, extracts, and teas — are available in the market. For medicinal purposes, the root and bark of the cat's claw vine are made into tea, tinctures, capsules, or tablets. The CAE-standardized extract specifically, however, is produced only through the aqueous/hot-water ultra-filtration process described above, not through tincture or alcohol-based preparations.

2. Traditional and Historical Use

2.1 Indigenous Amazonian Peoples

Uncaria tomentosa, also known as uña de gato or cat's claw, is a multifunctional medicinal vine that has been used for over 2,000 years by ancient civilizations, including that of the Tahuantinsuyo (Inca) Empire. Cat's claw has been used medicinally by the Aguaruna, Ashaninka, Cashibo, Conibo, and Shipibo tribes of Peru for at least 2,000 years. The Ashaninka community in central Peru has the longest recorded history of use of the plant and is one of the largest commercial sources of Peruvian cat's claw.

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; to control inflammation and gastric ulcers; and for cancer. Indigenous tribes in Piura use cat's claw to treat tumors, inflammations, rheumatism, and gastric ulcers. Other Peruvian indigenous tribes use cat's claw to treat diabetes, urinary tract conditions in women, hemorrhages, menstrual irregularity, cirrhosis, fevers, and abscesses.

2.2 Traditional Preparation Methods

The Asháninka Indians of the Amazon basin typically boiled U. tomentosa in water and consumed the resulting hydrophilic chemotypes. This hot-water decoction method is of particular relevance to the CAE fraction: the hydrophilic (water-soluble) extract obtained by boiling the bark specifically yields the CAE-rich chemotype rather than the alkaloid-rich chemotype produced by alcohol extraction. A decoction of cat's claw 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.

2.3 Entry into Western Research

Western scientific study of cat's claw began in the early 1970s, when Klaus Keplinger, a journalist and self-taught ethnologist from Innsbruck, Austria, organized the first definitive work on the plant. Keplinger's work in the 1970s and 1980s led to several extracts of cat's claw being sold in Austria and Germany as herbal drugs. Keplinger's discovery, in the early 1960s, of the presence of oxindole alkaloids was an important early milestone.

The specific CAE chemotype was subsequently characterized through the work of researcher Ronald W. Pero at the University of Lund, Sweden. His observation of the CampaMed Indians for their unusually long and disease-free lifespan led him to study their behaviors, and he witnessed the tribal Shamans, who were natural experts in plant-based rainforest medicines for over 2,000 years, using a crude hot-water extract of Uncaria tomentosa. Upon studying this extract at his laboratory at the University of Lund, Pero isolated the active components — Carboxy Alkyl Esters — and launched further studies that proved powerful effects at the cellular level on DNA repair, inflammation, and apoptosis.

3. Key Constituents and Active Compounds

3.1 The Phytochemical Profile of Cat's Claw

Uncaria tomentosa is rich in many phytoconstituents, including oxindole and indole alkaloids, glycosides, organic acids, proanthocyanidins, sterols, and triterpenes. The full list of documented compounds in cat's claw includes ajmalicine, akuammigine, campesterol, catechin, carboxyl alkyl esters, chlorogenic acid, cinchonain, corynantheine, corynoxeine, daucosterol, epicatechin, hirsuteine, hirsutine, iso-pteropodine, loganic acid, lyaloside, mitraphylline, oleanolic acid, procyanidins, pteropodine, quinovic acid glycosides, rhynchophylline, rutin, sitosterols, speciophylline, stigmasterol, uncaric acid, and vaccenic acid.

3.2 Carboxy-Alkyl-Esters as the Hydrophilic Active Fraction

The Pero extract is a novel cat's claw extract quite unlike any other commercial versions in that it contains only traces of alkaloids (<0.05%). Instead, the extract contains a new class of active ingredients — carboxyl alkyl esters (CAEs) — having demonstrated efficacy in multiple patented and peer-reviewed applications. CAEs were characterized as the only active ingredients of C-MED-100® based on their absorption (85%) onto charcoal; no biological activity was observed in the unabsorbed fraction.

Research efforts have aimed to produce adventitious roots capable of generating CAEs including chlorogenic acid and 3,4-di-O-caffeoylquinic acid, and to evaluate their cytotoxic potential. Quinic alkyl esters and their analogs are a subset of active ingredients contained in carboxyl alkyl esters, and studies isolating these patented ingredients have determined that CAEs, quinic alkyl esters, and their analogs contribute to all the health benefits associated with the CAE extract.

3.3 Quinic Acid as a Core Component

Preclinical studies have been used to demonstrate the broad range of clinical indications attributed to C-MED-100® and other cat's claw water extracts, and quinic acid (QA) has been further identified as a biologically active component in vivo, demonstrating that QA increases splenic leukocyte numbers in vivo and inhibits NF-κB activity in cells grown in tissue culture in vitro.

4. Established and Proposed Mechanisms of Action

4.1 NF-κB Inhibition and Anti-Inflammatory Action

Quinic acid esters found in hot-water extracts of Uncaria tomentosa exert anti-inflammatory activity through mechanisms involving inhibition of the pro-inflammatory transcription factor nuclear factor kappa B (NF-κB). NF-κB is well known to control the nuclear events that salvage cells from apoptotic cell death and the production of pro-inflammatory cytokines. Inhibiting NF-κB has anti-inflammatory properties because it prevents over-reaction of the inflammatory process that can be harmful to normal body tissues.

Chlorogenic acid, a key member of the CAE family, executes its anti-inflammatory function by moderating the synthesis and secretion of inflammatory mediators, namely TNF-α, IL-1β, IL-6, IL-8, NO, and PGE2, and modulates key signaling pathways including NF-κB, MAPK, and Nrf2.

4.2 DNA Repair Enhancement

The documented health benefits of CAEs include antioxidant protection, augmentation of DNA repair, anti-inflammation, and immunomodulation. These and other health benefits are based on the potency of CAEs to potentiate several biochemical cascades in order to increase the overall capacity of cells to survive and maintain functional integrity.

In response to stress, spiral ganglion neurons may remodel intracellular pools of DNA repair proteins. This was addressed by determining the intracellular location of three classic DNA excision repair proteins (XPA, CSA, and XPC) under normal conditions and following DNA repair adjuvant therapy with carboxy alkyl esters (CAEs at 160 mg/kg/28 days). After noise stress, each repair protein aggregated in the cytoplasm; after CAE therapy, each intracellular compartment was enriched with the three DNA repair proteins.

4.3 Apoptosis Induction

Apoptosis is an essential biochemical process in the body that regulates cells from division into differentiation and toward increased functional capacity; cells entering apoptosis will not only be stimulated to differentiate and increase functionality, but will eventually die from this "programmed cell death." Induced apoptosis resulting from NF-κB inhibition by C-MED-100® would effectively kill tumor cells by forcing them out of replication, while simultaneously increasing immune cell responsiveness because more immune-competent cells would be forced to differentiate and live longer due to parallel enhancement of DNA repair.

4.4 Antioxidant Activity

Chlorogenic acid (3-caffeoyl-D-quinic acid) is an ester formed between caffeic acid and quinic acid, and acts as a potent antioxidant. Both chlorogenic acid and caffeic acid are capable of scavenging nitric oxide (NO•), a pro-inflammatory oxygen radical produced via the L-arginine pathway by infiltrating leukocytes. The chlorogenic acid family has shown multiple protective effects on mitigating chronic inflammatory and age-related disorders through the central actions of anti-inflammation, antioxidation, and metabolic homeostasis modulation.

4.5 Immunomodulation and Lymphocyte Support

Proposed immunological mechanisms include regulating inflammation in the body by stabilizing levels of the inflammatory compound NF-κB, and increasing the lifespan of lymphocytes (white blood cells), thereby enhancing immunity. C-Med-100, rich in quinic acid and quinic acid glycoconjugates, appears to promote lymphocyte survival in mice and enhance DNA repair activity independent of alkaloids.

5. Scientific Evidence by Area of Use

5.1 DNA Repair and Leukocyte Enhancement

Human/Clinical Evidence: The Uncaria tomentosa water extract (C-Med-100) has been shown to enhance DNA repair, mitogenic response, and leukocyte recovery after chemotherapy-induced DNA damage in vivo. In a human volunteer study, twelve apparently healthy adults working in the same environment were randomly assigned into three groups, matched for age and gender; one group was daily supplemented with a 250 mg tablet containing an aqueous extract of C-Med-100, and another with a 350 mg tablet, for 8 consecutive weeks. There was a statistically significant decrease of DNA damage and a concomitant increase of DNA repair in the supplement groups (250 and 350 mg/day) compared with non-supplemented controls (p < 0.05), and there was also an increased tendency of PHA-induced lymphocyte proliferation in the treatment groups. There were no drug-related toxic responses to C-Med-100 supplement when judged in terms of clinical symptoms, serum clinical chemistry, whole blood analysis, or leukocyte differential counts.

Evidence Strength: This is a small (n=12), short-duration human trial. While statistically significant and consistent with pre-clinical data, the sample size is too small to allow definitive conclusions.

5.2 Immune Function

Human/Clinical Evidence: In a clinical trial with human volunteers, cat's claw aqueous extract (C-Med-100) at doses of 250 and 350 mg/day increased the number of lymphocytes and leukocytes, which could be ascribed to the carboxyl alkyl esters of quinic acids. An in vivo study showed significant health benefit for 14 subjects treated for 4 weeks with a C-Med-100/mushroom extract formulation, in that they had reduced pain, reduced fatigue, weight loss, and a reduced presence of DNA damage in peripheral blood assessed by (8-OH) guanine DNA adducts and elevation in serum protein thiols.

Evidence Strength: Preliminary. Sample sizes are very small (n=12 to n=14). The combination formulation study makes it impossible to attribute effects specifically to CAEs alone. Larger, independent, placebo-controlled studies are needed.

5.3 Inflammation and Arthritis

Osteoarthritis: Limited clinical studies suggest an anti-inflammatory action of cat's claw in osteoarthritis. A small trial (N=45) found improved subjective measures of pain with cat's claw; however, other objective measures were not significantly altered, and adverse effects were comparable with placebo.

Among 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 nighttime 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.

Rheumatoid Arthritis: One study of 40 participants using 60 mg of cat's claw as adjunctive therapy for rheumatoid arthritis was conducted over 52 weeks; all participants had active rheumatoid arthritis and were taking either sulfasalazine or hydroxychloroquine. Results indicated a modest improvement in joint tenderness with few side effects; however, there are limited scientific data in this area, and as a consequence it is not possible to make a definitive recommendation for its use at this time.

A study in 40 people with rheumatoid arthritis determined that 60 mg of cat's claw extract per day alongside regular medication resulted in a 29% reduction in the number of painful joints compared to a control group. Although these results are promising, the evidence is weak. Larger, better-quality studies are needed to confirm these benefits.

A 2010 systematic review identified 4 randomized controlled trials that studied cat's claw for osteo- or rheumatoid arthritis; 2 of the trials used the herb in combination with other herbs.

Evidence Strength: There have been very few high-quality clinical trials of cat's claw, and there is no conclusive scientific evidence based on studies in people that supports using cat's claw for any health purpose. Some research has been done in people on the effect of cat's claw on various conditions, but many of the studies did not use rigorous methods and did not include enough study participants to allow definite conclusions.

5.4 Cognitive Function and Attention

Human/Clinical Evidence: A published randomized double-blind cross-over placebo-controlled trial tested the null hypothesis that oral intake of the dietary supplement carboxy alkyl ester (CAE) would have no effect on attention as revealed by mean rapid visual information processing (RVIP) scores. Healthy participants aged 19–66 years of both sexes were randomly assigned to consume 700 mg of CAE or 700 mg of placebo. A priori statistical computation revealed that 30-day oral intake of CAE improved mean RVIP test scores (t = 2.4, p < 0.05) relative to baseline, resulting in a rejection of the null hypothesis.

Evidence Strength: This is a single published randomized controlled trial using a cross-over design. While it provides preliminary positive evidence for cognitive attention, replication in larger, independently-conducted trials is required. The study was conducted specifically with the CAE fraction and is one of the few human trials to isolate CAEs as the tested ingredient.

5.5 Sensorineural Recovery (Noise-Induced Hearing Loss)

Animal (Preclinical) Evidence Only: A study tested the hypothesis that hydrophilic chemotypes of U. tomentosa (specifically CAEs) would facilitate recovery of sensorineural functions following exposure to damaging noise. Long–Evans rats were divided into four treatment groups: vehicle-control, noise-only, CAE-only, and CAE + noise. The noise exposure was an 8 kHz octave band at 105 dB SPL for 4 hours. The study found that carboxy alkyl esters augmented recovery of neural functions following noise injury, cytocochleograms revealed preservation of sensory cells, and carboxy alkyl esters were described as a new class of otoprotectants.

Treatment with the DNA repair-enhancing chemotype reduced the noise-induced increase of γ-H2Ax, which was associated with an accelerated rate of functional recovery from noise exposure, implicating molecular mechanisms of DNA damage and repair in the pathophysiology of noise-induced hearing loss.

Evidence Strength: Preclinical animal data only. No human clinical trials have yet examined CAEs specifically for sensorineural recovery.

5.6 Anti-Inflammatory and Immunomodulatory Activities (Systematic Review)

Uncaria tomentosa is traditionally used by Amazonian indigenous groups to treat inflammatory diseases. To date, there are no systematic reviews and meta-analyses on the use of U. tomentosa for inflammation control in animals that have comprehensively supported the traditional knowledge. A systematic review and meta-analysis of preclinical studies published before July 2023 was conducted to evaluate the effect of U. tomentosa extracts in modulating inflammatory mediators, identified from PubMed, Embase, and Scopus. The models examined in preclinical studies included asthma, diabetes, arthritis, obesity, gastric ulcers, and intestinal diseases.

An important aspect noted is that U. tomentosa extracts preserve CD4+ and CD8+ T cells and possibly stimulate cytokines that favor the polarization of CD4+ Th2 cells, which play an important role in autoimmune diseases such as rheumatoid arthritis, by modulating the excessive activity of Th1 cells. Interestingly, U. tomentosa extracts can either stimulate or inhibit the release of different cytokines, depending on the animal's health status or the modeled disease.

6. Body Systems and Health Areas

Based on the available peer-reviewed and patent literature, CAEs from Uncaria tomentosa are associated with the following body systems and areas of research:

Immune system: A class of compounds referred to as carboxyl alkyl esters found in cat's claw has been documented with immunostimulant, anti-inflammatory, anticancerous, and cell-repairing properties.
Musculoskeletal system: Cat's claw is used as an analgesic and anti-inflammatory agent to treat gastrointestinal, rheumatologic, and other chronic inflammatory conditions.
Cellular and genomic health: Primary research has demonstrated the natural ability of the CAE-rich extract to help the body repair its own DNA; additional studies have demonstrated its ability to reduce proinflammatory cytokines, encourage cell apoptosis of damaged cells, enhance the immune system, and decrease the rate of telomere truncation.
Neurological/cognitive function: The randomized cross-over trial (described in Section 5.4) documented preliminary improvements in sustained attention scores in healthy adults using CAE supplementation.
Auditory/sensorineural system: Preclinical findings described in Section 5.5 suggest a potential role in hearing recovery after acoustic trauma, via DNA repair mechanisms.
Skin and connective tissue: The CAE-rich extract has been associated with increases in production of natural collagen III, a form of collagen associated with soft, supple, youthful-looking skin.
Gastrointestinal system: Traditional use includes treatment of conditions such as osteoarthritis, cancer, infections, menstrual disorders, and gastric ulcers.

7. Dosage Forms and Reported Dosages

7.1 Standardized CAE-Rich Extracts

A standardized extract attributed to a specific chemotype of U. tomentosa, consisting of less than 0.5% oxindole alkaloids and 8% to 10% carboxy alkyl esters, has been used in doses of 250 to 300 mg in several clinical studies. 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.

Daily oral doses of C-MED-100® between 250 and 700 mg have proven efficacious in humans according to the Pero patent literature. In the attention/cognitive cross-over trial, participants consumed 700 mg of CAE or 700 mg of placebo. In the human DNA repair volunteer study, one group received a 250 mg daily tablet and another group received a 350 mg daily tablet for 8 consecutive weeks.

7.2 General Cat's Claw (Non-Standardized) Dosages

One gram of root bark given 2 to 3 times daily is a typical dose for non-standardized preparations, while 20 to 30 mg of a root bark extract has been recommended in some contexts. The typical and recommended dose of U. tomentosa more broadly is one gram given two to three times daily.

7.3 Dosages in Specific Clinical Studies

Osteoarthritis of the knee trial: 100 mg cat's claw once daily for 4 weeks (N=45).
Rheumatoid arthritis trial: 60 mg Uncaria tomentosa tablets once daily for 24 weeks (Phase A), alongside conventional treatment (N=40).
DNA repair human volunteer study: 250 mg or 350 mg C-Med-100 daily for 8 weeks (N=12).
Attention/RVIP study: 700 mg CAE daily for 30 days, crossover design.

The suggested dosage for C-Med-100, a patented extract of cat's claw bark, is cited as 300 milligrams daily in some sources. Despite multiple purported effects, controlled clinical trials are lacking and clinical trials are generally insufficient to support definitive appropriate dosages.

8. Safety Considerations and Known Interactions

8.1 General Tolerability

In the C-Med-100 human volunteer trial, there were no drug-related toxic responses when judged in terms of clinical symptoms, serum clinical chemistry, whole blood analysis, and leukocyte differential counts. In the osteoarthritis knee trial, cat's claw was well tolerated and there were no serious adverse events or changes in serum ALT and AST values during treatment. 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.

8.2 Liver Safety

Cat's claw is an herbal medicine used for its anti-inflammatory and immune-modulating effects. Cat's claw has not been implicated in causing liver injury in the LiverTox database maintained by the NCBI. However, an isolated case report exists: A 59-year-old woman with mantle-cell lymphoma and no hepatic involvement took a range of unconventional medicines; during a routine check-up she had raised liver enzymes, and self-medication with cat's claw was deemed the most likely cause. Cat's claw was withdrawn and her liver tests normalized within 60 days.

8.3 Contraindications

It is known that cat's claw should not be used by patients with organ transplants or skin grafts who are using immunosuppressant drugs, due to its immunostimulant properties. Cat's claw safety has not been documented in breastfeeding and pregnant women, or children under three years of age, because of insufficient safety research.

8.4 Drug Interactions — Pharmacokinetic

A study investigated the effect of U. tomentosa extract and its major oxindole alkaloids on multispecific solute carrier (SLC) and ATP-binding cassette (ABC) drug transporters. Results showed that U. tomentosa 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.

Herb–drug interactions (HDIs) are clearly not negligible. HDIs can alter the pharmacokinetics or pharmacodynamics of a drug by changing the absorption, distribution, metabolism, excretion, and toxicity properties as a result of metabolizing enzyme and drug transporter modulation. Laboratory studies suggest potential inhibition of the cytochrome P450 3A4 (CYP3A4) enzyme system.

8.5 Drug Interactions — Pharmacodynamic

There are theoretical reasons to suspect that cat's claw might interact with anticoagulant, antiplatelet, and blood pressure drugs, and other supplements as well. More specifically: certain individuals should exercise caution; immunosuppressants (e.g., cyclosporine, corticosteroids) may have their effects counteracted due to cat's claw's immune-stimulating potential; anticoagulants/antiplatelets (e.g., warfarin, clopidogrel, aspirin, NSAIDs) may carry an increased risk of bleeding when taken concurrently; and antihypertensives may have enhanced effects, potentially leading to hypotension.

8.6 Alkaloid Content Distinction

Most cat's claw products are simply ground-up whole-plant preparations; these products are usually high in alkaloid content, which can be harmful. The CAE-standardized AC-11® extract is a refined extract that comes from the inner bark only of the cat's claw vine and is relatively alkaloid-free (<0.05%). This distinction is pharmacologically significant because the alkaloid and CAE chemotypes are associated with different biological activities and different safety profiles.

8.7 Regulatory Status

AC-11® is registered as a dietary supplement under the Dietary Supplement Health and Education Act (DSHEA) and listed under its INCI (International Nomenclature of Cosmetics Ingredients) names Maltodextrin and C1-8 Alkyl Tetrahydroxy-cyclohexanoate with the Personal Care Products Council. Despite the beneficial effects reported by users, the indiscriminate use of U. tomentosa extracts without any medical criteria can be dangerous in some cases; moreover, there are few studies about drug interactions and side effects of medicinal plants like U. tomentosa.