Flavonoids in cell function.

Flavonoids (and isoflavonoids) are a large subgroup of secondary metabolites categorized as phenolics or polyphenols. Their wide distribution in the plant kingdom and prokaryotes, and the exceptional variety of these compounds, over 4000 have been identified so far, contributed to the attractiveness for study by chemists, geneticists, taxonomists and investigators in numerous other areas. The early investigators concentrated primarily on the purification and identification of these compounds. The studies of chemical structures of phenolics and their biochemical interrelations eventually expanded to cover the area of classification, leading to a distinct field of chemical or biochemical taxonomy. This approach greatly aided and often clarified classification schemes based on traditional methods relying on morphology, and later, genetic studies. The literature dealing with the chemistry, biochemistry and related aspects of flavonoids is extensive. This volume is not intended to be an exhaustive reference on flavonoids. Excellent information on these compounds can be found in numerous compilations of the chemistry, isolation and other techniques (Geissman,1962; Harborne, 1967; Mabry et al., 1970; Harborne et al., 1975; Harborne and Baxter, 1999).