Classification Methods and Diversity of Medicinal Plants

This chapter discusses the diversity and classification of medicinal plants. Medicinal plants occupy a place of prime importance due to their complementary applications in modern medicines, and their use as food supplements, nutraceuticals, pharmaceutical intermediates, folk medicines, and secondary metabolites they provide for novel drugs. Therefore, an understanding of the diversity and classification of medicinal plants is useful for practitioners of ethnomedicine, botanists, and the common man for home remedies. Medicinal plants are mostly either angiosperms or gymnosperms with about 4171 and 706 plant species, respectively. Among angiospermic medicinal plants, dicotyledons have the most common representation of medicinal plants. Medicinal plants may be classified based on the following; parts used, habitat, habit, therapeutic, and ayurvedic formulations. The majority of medicinal plants are herbaceous, and about 51.3% grow mainly in the wild. Tropical rain forest provides the highest percentage of species (54.6%), followed by home gardens (25.4%) and unused land (19.5%). The medicinal use of about 72 (38.5%) plants has not before been reported. Many medicinal plants and their related indigenous values have not been adequately documented despite numerous investigations on medicinal plant products. The bulk of plant parts utilized in phytomedicine are the leaves (145 species), followed by the roots (119 species), and the stem (53 species). Herbs make up the highest percentage of species in terms of habit (44%), followed by trees (26%), shrubs (16%), lianas (5%), and others. Also, the sustainable use of medicinal plants should be ensured, and thorough documentation of the traditional knowledge linked with their usage should also be made and passed down across generations.