The stimulation of defense mechanistic pathways has been recognized as possible means of inhibiting diseases progression in humans without perse eliciting harmful effects. Thus the medicinal plants have a wide diversity of secondary metabolites with different biological activities to generate potent bioactive molecules necessary for health enhancement. On the other hand, lack of scientific data proving the efficacy and safety of medicine prepared from herbs signals the need to full understand about their chemical and biological properties. In this volume several experimental studies have been included to comprehend the pharmacological effects of more than 50 commonly medicinal plants used in folk medicines. As there is enormous potential of traditionally used medical herbs for developing new drugs, there is an urgent need to further elucidate phytochemicals and mechanisms of action using modern biological methods. Therefore, an attempt has been made in the volume to present the botanical, phytochemical, and pharmacological properties of the plants together with pharmacoparameters such as contraindications, adverse effects, and overdose of the plants. The volume discusses about such studies in 26 chapters received from far and wide 16 countries of the world. The volume has been designed for a wide range of audience in the field of phytochemistry, pharmacology, biotechnology, ethnomedicine, toxicology, drug standardization, microbiology, medicinal sciences and other researchers interested in the discovery of new natural drugs.