Cat’s Claw (Uncaria tomentosa)

The Amazon rainforest is a unique ecosystem in many aspects, with relevance in many spheres of life, since it provides food, chemical compounds for pharmaceutical research, raw materials, and more. Therefore, direct or indirect interactions with Amazon ecosystems and their vast diversity of plant species provide many benefits to human life [6]. These attracted the attentions of pharmaceutical companies, who have been studying the Amazon rainforest for over a century as a potential source of new medicinal components and a treasure trove of botanicals for the herbal supplement industry. “Cat’s claw” (Uncaria tomentosa) is one of the most promising of the many Amazon botanicals that have come to light in recent years.

Cat’s claw is a tropical vine that mainly blooms in the Amazon River basin and it has been used in traditional South American medicine for ages. Its name was inspired from the curving thorns that grow along with its woody branches, which look similar to cats’ claws. Uncaria tomentosa and Uncaria guinaensis are the two species of cat’s claw, but the extract of cat’s claw is usually prepared from the root bark of Uncaria tomentosa. Cat’s claw extracts mainly contain oxindole alkaloids (including pteropodine, isopteropodine, rhynchophylline, mytraphylline, speciophylline, uncarine E and uncarine F), and polyphenols (for example, tannis). Another
important components found in cat’s caw extracts, are the indole alkaloidal glucosides (3-dihydrocadambine, cadambine, and 3-isodihydrocadambine), quinovic acid glycosides, catechins, and sterols. However, the exact active constituents in cat’s claw extracts remain unknown [1].

The substances found in cat’s claws have piqued curiosity due to their variety of chemical groups that have pharmacological and even nutritional impacts. Generally, cat’s claw is known for its immune-modulating and anti-inflammatory effects, treating gastrointestinal, rheumatologic, and other chronic inflammatory conditions. According to in vitro studies, cat’s claw extracts can be very beneficial for human health since it also provide antiviral and antimutagenic activities in addition to the anti-inflammatory effects that it has. The oxindole alkaloids contained in cat’s
claw root bark, for example, are known to have anti-inflammatory actions [7].

A noteworthy finding from a study revealed that cat’s claw’s anti-inflammatory action is due to its capacity to decrease iNOS gene expression, nitrate synthesis, cell death, PGE2 production, and NF-κB and TNF-α activation [2]. Hence, patients can effectively treat a variety of medical conditions by using this plant. In particular, several scientific experiments on the use of medicinal plants and herbal treatments, have found that the usage of cat’s claw and its main phytochemicals can be effective for Alzheimer’s disease treatment. The findings of a study that used a transgenic mouse model of Alzheimer’s disease were one of the most crucial forms of evidence for this statement. The study detected that after treating 8-month-old mice with cat’s
claw extract for 14 days there was a significant reduction in Aβ load (by 59%) and plaque number (by 78%) in the hippocampus and cortex. A significant decline in astrocytosis and microgliosis was also observed, as well as an improvement in hippocampus-dependent memory [2].

Aside from its role in the treatment of Alzheimer’s disease, other in vitro studies showed that cat’s claw also has anti-tumor activities. In particular, results of a number of studies that used animal models suggested that a dried hydroalcoholic extract of cat’s claw could be considered an efficient adjuvant treatment for breast cancer and have a DNA-protective effect, as well as the oxindole alkaloids (primarily the mitraphylline) in cat’s claw extract found to have anti-tumor activity and especially having higher tumor selectivity due to the fact that it is less toxic to
nonmalignant cells [4].

Finally, recent research has found that cat’s claw can be beneficial in the treatment of Covid-19 [8], which contains four structural proteins, namely the spike (S), envelope (E), membrane (M), and nucleocapsid (N) proteins. The S glycoprotein of COVID-19 interacts with the angiotensinconverting enzyme 2 (ACE-2) receptor, facilitating the viral entry into host target cells [5]. Cat’s claw components, according to studies, can prevent SARS-CoV-2 protein maturation and infection transmission by blocking the virus from adhering to human cell receptors (such as ACE-2) and disrupting the virus cycle [8].

However, in order for the cat’s claw to be effective in treating diseases, it must be properly prepared and administered in the suggested dosages. The local people of Peru traditionally boil 20 to 30 grams of the root or inner bark in a litter of water for 30 to 60 minutes for the appropriate preparation. Dosage recommendations have not been determined, however, according to the WHO, an average daily dose for extracts is 20–350 mg of dried stem bark or 300–500 mg for capsules, taken every 8 hours (2–3 doses throughout the day,) between meals.

Rheumatoid arthritis and osteoarthritis of the knee have been treated with daily doses of 60 and 100 mg of cat’s claw extract, respectively. The correct dosage is critical since, although cat’s claw side effects are rare, overdose might result in negative consequences. This is because high levels of tannins contained in cat’s
claw can cause nausea, stomach distress, and diarrhea. Other probable side effects, such as low blood pressure, nerve damage, increased risk of bleeding, anti-estrogen effects, and negative effects on kidney function, are also supported by case reports and test-tube research.

Hence, it is recommended that some groups of people should avoid or limit their use of the cat’s claw, as the negative effects may intensify or have an impact on their health. Pregnant or breastfeeding women, people with specific medical disorders, and those taking certain drugs are among these groups of people. One of the reasons that pregnant or breastfeeding women should avoid taking cat’s claw is that it is unsafe due to a lack of safety information.

Therefore, while there is a base of information about cat’s claw medicinal use, it is limited in scope. In order to improve the findings of studies on cat’s claw, researchers should consider the existence of a few undiscovered chemicals of this plant that could have a substantial part in the overall effects of cat’s claw extracts [3].