Phytotherapy and Nutritional Supplements on Breast Cancer 用于乳腺癌治疗的植物疗法和营养补充剂

3.4. Uncaria

Two species of Uncaria, commonly known as cat’s claw, Uncaria guianensis and Uncaria tomentosa, found in northern regions of South America and belonging to Rubiaceae family, have also promising medicinal outcomes, including in breast cancer patients, due to their immune-stimulant and antioxidant properties [102]. This botanical product contains a complex combination of phytochemicals, including glycosides, tannins, flavonoids, and sterol fractions that could be complementary and/or synergic in their pharmacological actions [3]. Some of these constituents can present selectively cytostatic/cytotoxic to some cancer cells such as pentacyclic oxindole alkaloids [103].

Although some studies revealed the in vitro efficacy of cat’s claw in breast cell lines [102, 249] no clinical trials investigating Uncaria species as an anticancer agent are available. It is fundamental that more research is performed in animal models and mainly in humans before any conclusions can be drawn in this topic.

Utilising Uncaria tomentosa appears to be a beneficial approach to minimize the adverse effects associated with traditional cancer therapies, namely, in the case of chemotherapy. The use of this Uncaria species can stimulate DNA restoration [250], preventing mutations and cell damage caused by chemotherapy agents [251], and myelopoiesis [252, 253]. Aqueous extracts of U. tomentosa also proved to improve leukocyte counts during a period of eight weeks in healthy animals [254] and after ten days of doxorubicin-induced neutropenia [251]. In addition, extracts or fractions of cat’s claw modulate the activity of the immune system [254, 255]. These preclinical data were proved in a randomized clinical trial. Santos Araujo Mdo et al. used 300 mg per day of U. tomentosa dried ethanolic extract, in patients diagnosed with Invasive Ductal Carcinoma Stage II, who underwent a treatment regimen known as FAC (Fluorouracil, Doxorubicin, and Cyclophosphamide) [56]. This adjuvant treatment for breast cancer patients was safe and effective in the recovery from neutropenia induced by cancer chemotherapy. The dose used in this trial was empiric and was based on the dose administrated in other (not cancer-related) clinical trials where the authors used different solvent extracts and, consequently, different phytochemicals. So, more clinical trials should identify the best dosage range for using cat’s claw as an adjuvant chemotherapy agent.

Budán et al. indicated that the combination of different phytotherapeutic (e.g., Clae of Dragon tea containing the bark of Uncaria guianensis, Uncaria tomentosa, and Tabebuia avellanedae) in a long-term experimental animal model acted as chemopreventive agent [256].

Concerning their safety, clinical trials with human volunteers reported no toxicity associated with the use of a commercially available aqueous extract of U. tomentosa named C-Med-100. The dose of Uncaria was different in the trials, using 250 mg or 350 mg/day over 8 weeks and 2  350 mg daily for 2 months [250, 257].

Cat’s claw could provoke adverse effects including diarrhoea or loose stools and lower blood pressure, which tend to diminish with continued usage. However, some literature reported that cat’s claw can interact with medications intended to suppress the immune system (e.g., cyclosporine) or other medications prescribed following an organ transplant; this information still needs to be proven scientifically. In vivo rat studies demonstrated that cat’s claw may protect against gastrointestinal injury attributed to nonsteroidal anti-inflammatory drugs (NSAIDs) and can diminish the platelet aggregation and may increase the effect of anticoagulants [103].