Herbal pharmacognosy: An introduction

Herbal medicines are complex compounds with multiple synergistic mechanisms of action that modulate (patho)physiological functions. Pharmacognosy is the study of medicine derived from natural sources that include plants, animals, and microorganisms, and the scope of the field depends on knowledge about the safety, purity, and efficacy of complex multicompound products. Herbal pharmacognosy is the application of this science specifically to traditional herbal medicine sources. Traditional medicines, particularly herbal medicine, remain the primary source of medicine in many countries and cultures globally. Although the root of this field is within traditional medicine, there is increased scientific focus on herbal pharmacognosy in recent years for novel therapeutic molecules. Modern pharmacognosy includes the application of molecular, genomic, and metabolomic techniques, providing a significant increase in knowledge on the biological and clinical applications of herbal medicines. Secondary plant metabolites serve numerous roles in plant biology, including innate immunity, defense against herbivores and pathogens, antioxidant activity, and attraction of pollinators for cellular communication. These compounds have been used by humans throughout recorded and prerecorded history as various commodities, including pigments, condiments, nutrition sources, and medicines. This chapter considers some of the major and well-defined groups of secondary plant metabolites, specifically terpenoids, glycosides, saponins, phenols (including flavonoids, phenolic acids, stilbenes, lignans), tannins, alkaloids, and essential oils. Currently, an interdisciplinary approach is needed in basic and clinical research for the identification and standardized extraction of secondary metabolites from suitable herbs, and for the development of medicines for clinical practice.