Natural products for human health: an historical overview of the drug discovery approaches.

Natural products (NPs) are secondary metabolites produced and used by organisms for defending or adapting purposes. These molecules were naturally selected during thousands of years to improve the specificity and cover a very wide range of functions, depending on the origin, the habitat and the specific activity carried out in the organism of origin. Due to these intrinsic features, NPs have been used as healing agents since thousands of years and still today continue to be the most important source of new potential therapeutic preparations.The purpose of this review is to provide information about the historical evolution of the NPs investigation methods, focusing attention on the relative benefit/problems emerged after the improvement of the scientific investigations about them, especially over the last two centuries. Taken together, the reported information lead to the central role of NPs in the future of drug development for human needs.