The potential of secondary metabolites from plants as drugs or leads against protozoan neglected diseases - part I

Infections with protozoan parasites are a major cause of disease and mortality in many tropical countries of the world. Diseases caused by species of the genera Trypanosoma (Human African Trypanosomiasis and Chagas Disease) and Leishmania (various forms of Leishmaniasis) are among the seventeen "Neglected Tropical Diseases" (NTDs) defined as such by WHO due to the neglect of financial investment into research and development of new drugs by a large part of pharmaceutical industry and neglect of public awareness in high income countries. Another major tropical protozoan disease is malaria (caused by various Plasmodium species), which -although not mentioned currently by the WHO as a neglected disease- still represents a major problem, especially to people living under poor circumstances in tropical countries. Malaria causes by far the highest number of deaths of all protozoan infections and is often (as in this review) included in the NTDs. The mentioned diseases threaten many millions of lives world-wide and they are mostly associated with poor socioeconomic and hygienic environment. Existing therapies suffer from various shortcomings, namely, a high degree of toxicity and unwanted effects, lack of availability and/or problematic application under the life conditions of affected populations. Development of new, safe and affordable drugs is therefore an urgent need. Nature has provided an innumerable number of drugs for the treatment of many serious diseases. Among the natural sources for new bioactive chemicals, plants are still predominant. Their secondary metabolism yields an immeasurable wealth of chemical structures which has been and will continue to be a source of new drugs, directly in their native form and after optimization by synthetic medicinal chemistry. The current review, published in two parts, attempts to give an overview on the potential of such plant-derived natural products as antiprotozoal leads and/or drugs in the fight against NTDs.

Propolis: Biological and pharmacological activies. Therapeutic uses of this bee-product

This review aims to present an update of propolis properties, with emphasis on Brazilian samples. It also brings attention to points, such as standardization protocols and scientific evidence, that needed to be further investigated in order to broaden the potential therapeutic use of this bee product. Propolis became a traditional remedy in folk medicine. In recent decades a great interest has arisen in more knowledge a out its composition and therapeutic activities. Its composition is very complex, varying with the geographic region, with more than 300 constituents having been identified to date. The biological activity of propolis is associated mainly with phenolic compounds such as flavonoids and derivatives of hydroxycinnamic acids. In recent years, Brazilian propolis became the subject of increasing interest, due to its unusual chemical composition when compared with samples from other contries. Several compounds isolated presented a variety of biological activities, such as microbicidal, antioxidant and antitumoral. Although there is a huge amount of information about the chemistry and biological activity of propolis, its application in human and veterinary therapies has hardly changed. Propolis is used both in human and veterinary clinics in Eastern Europe countries, Cuba and in Uruguay. Most of the therapeutic effect of this resin is associated with microbicidal properties and the ability to scavenge free radicals. A multidisciplinary study correlating chemical composition, basic plant sources in different geographic regions, as well as and biological and pharmacological activities, open the possibility of a classification of a limited number of "chemical types" of propolis which will be possible only with the combined effort of the national and international scientific communities.