Medicinal plants in Brazil: Pharmacological studies, drug discovery, challenges and perspectives

This review article focuses on pre-clinical and clinical studies with some selected Brazilian medicinal plants in different areas of interest, conducted by research groups in Brazil and abroad. It also highlights the Brazilian market of herbal products and the efforts of Brazilian scientists to develop new phytomedicines. This review is divided into three sections. The section I describes the Brazilian large biodiversity and some attempts of Brazilian scientists to assess the pharmacological profile of most plant extracts or isolated active principles. Of note, Brazilian scientists have made a great effort to study the Brazilian biodiversity, especially among the higher plants. In fact, more than 10,000 papers were published on plants in international scientific journals between 2011 and 2013. This first part also discussed the main efforts to develop new medicines from plants, highlighting the Brazilian phytomedicines market. Despite the large Brazilian biodiversity, notably with the higher plants, which comprise over 45,000 species (20-22% of the total worldwide), and the substantial number of scientific publications on medicinal plants, only one phytomedicine is found in the top 20 market products. Indeed, this market is still only worth about 261 million American dollars. This represents less than 5% of the global Brazilian medicine market. The section II of this review focus on the use of Brazilian plant extract and/or active principles for some selected diseases, namely: central nervous systems disorders, pain, immune response and inflammation, respiratory diseases, gastrointestinal tract and metabolic diseases. Finally, section III discusses in more details some selected Brazilian medicinal plants including: Cordia verbenacea, Euphorbia tirucalli, Mandevilla velutina, Phyllanthus spp., Euterpe oleracea, Vitis labrusca, Hypericum caprifoliatum and Hypericum polyanthemum, Maytenus ilicifolia, Protium kleinii and Protium heptaphylium and Trichilia catigua. Most of these publications are preliminary and only report the effects of crude extracts, both in vitro and in vivo studies. Only very few studies have been dedicated to investigate the mechanisms of action of isolated compounds. Likewise, studies on safety (toxicology), pharmacokinetic, and especially on well-conducted clinical trials are rare. In conclusion, in spite of the abundant Brazilian biodiversity and the thousands of academic publications on plants in international peer-reviewed scientific journals, few patents and medicines have been derived from such studies. Undoubtedly, great efforts must be made to improve the development of plant-derived medicine market in Brazil, especially by involving the partnership between academia and pharmaceutical companies.