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

3.2. Lapacho

Lapacho tree or pau d’arco is the common name of Tabebuia impetiginosa Martius ex DC species, the family of Bignoniaceae. It is a tree indigenous to the Amazonian rainforest and other regions of South America and Latin America. Pau d’arco has been used in traditional medicine for many centuries due to its different physiological effects such as fungicide, antibacterial, antiviral, anti-inflammation, and anticancer [43]. Above all, special attention has been given to the antitumour activity of β-lapachone (i.e., a constituent of lapacho) against manyin vitro cancer cell lines, including breast cancer [44, 45] due to its action on reinforcing the immune system.

The clinical evidence of the health benefits of lapacho is restricted to studies related to its potential anticancer effects in phase I and II clinical trials [46]. However, this effect was not borne out by clinical trials [43]. The Food and Drug Administration (FDA) registered it as a dietary supplement with the following recommendation “to alleviate conditions and symptoms of cancer.”

Despite the underlying mechanism being under investigation [47], the cytotoxic effects to some cancer cells, including breast cancer cell lines, are confirmed [45, 48, 49]. β-Lapachone also sensitizes the response of different cancer cell lines to ionizing radiation [50, 51], interacting synergistically with this conventional cancer therapy. Bey and collaborators showed that the combination of β-lapachone and radiation exert synergistic effects against human mammary epithelial cells (HMEC 1585), in which β-lapachone sensitizes cells to radiation by inhibiting DNA repair, and radiation sensitizes cells to β-lapachone by increasing oxidoreductase enzyme, which reduces β-lapachone to an unstable semiquinone level, in tumour cells [51].

Concerning the toxicity issues of lapacho, limited data are available and more clinical trials are required to evaluate the toxicity of β-lapachone toward normal human tissue and to establish the best dosage range [52].Tabebuia impetiginosa tea emerges as generally safe and has a FDA regulatory classification of “generally recognized as safe” (GRAS) status. Recently, Lemos et al. [53] demonstrated genotoxic effects in rats at a comparatively high dose range. The most important interaction of this botanical product refers to the interference in the biological cycle of vitamin K [46]. It is also important to attend the variable quality and composition of the herbal products commercially available.