Plant Toxins as Sources of Drugs

Abstract

Plant toxins are representative of a large group of structurally diverse small molecules that result from the plant secondary metabolism. These toxins can be synthesized by plants themselves or by nonpathogenic endophytic microorganisms living within plants. Among the plant secondary metabolites that exhibit evident toxicity to humans and animals, alkaloids, terpenes, steroids, and phenolic compounds have led to drugs or templates for drug design. Many of these molecules affect neural transmission or cell division processes, which have given rise to drugs for treating central nervous disorders and cancer. In addition to secondary metabolites, toxic plant proteins such as lectins have emerged as tools for disease diagnosis and as candidates to develop new anticancer drugs. This text describes the most important plant toxins (from a therapeutic point of view), such as curare, ergot alkaloids, indole alkaloids, cardiac glycosides, and taxanes, according to their main pharmacological properties and clinical uses. The most representative examples of plants are Papaver somniferum, Digitalis purpurea, Catharanthus roseus, and Taxus spp. Traditional uses laid the foundation for the development of the majority of these drugs. At present, analytical tools based on genomics, proteomics, metabolomics, bioinformatics, and other twenty-first-century technologies are accelerating the identification and characterization of natural products. On the other hand, many new bioactive compounds are failing due to a lack of efficacy in the clinic, which demands new strategies for pharmacological research. The fusion of ‘omics technologies’ with ethnomedicine, systems biology, and studies of plant endophytes are exciting approaches to search for new drugs from natural sources.