Plant extracts are widely used for therapeutic purposes. The vegetal origin of these products satisfies people’s desire to cure themselves with natural drugs; this aspect, together with effectiveness and regulatory opportunities, is the base of the broad modern use of medicinal plants. Traditional uses and novel biological effects allow the availability of an extraordinarily high number of different compounds with formidable therapeutic potential. Nevertheless, pitfalls are hidden behind poor pharmacological and toxicological knowledge of plant extracts, nonstandardized methods of extraction, and undefined and nonrepeatable qualitative and quantitative composition. In this context, novel experimental studies on plant products and appreciated and are necessary to reinforce the scientific soundness of phytotherapy. This book aims to respond to this medical need comprehensively highlighting the newest discoveries in vegetal resources with an emphasis on pharmacological activity.