ABSTRACT
Plants, in addition to primary metabolites, produce some novel compounds by a series of chemical reactions under enzymatic control, and these secondary metabolites are activated more during particular stages of growth as well as in response to biotic and abiotic stress. Flavonoids comprise the largest group of naturally occurring secondary metabolites as phenolic compounds responsible for much of the flavor and color of flowers. Large numbers of flavonoids are generally yellow in color. They play an important role in signaling molecules, UV protection, growth, and development, defense against herbivores and pathogens, pollinators, and seed dispersers. This group of natural products is divided into three classes: flavonoids, isoflavonoids, and neoflavonoids, based on the position of the linkage of the aromatic ring to the benzopyrano moiety. These are derived from subunits supplied by the acetate and Shikimate pathways. The present chapter deals with flavonoids, their function and classification, along with their biosynthesis.
