Flavonoids of leguminous plants: Structure, biological activity, and biosynthesis

Flavonoids are common to most vascular plants and are postulated to be invo lved in a number of plant functions. Leguminous plants are intriguing mater ials for studies on flavonoids for several reasons. First, legumes produce flavonoids with specific chemical structures i.e. isoflavonoids and 5-deoxy (iso)flavonoids. Second, leguminous flavonoids are postulated to play impor tant roles both as defensive compounds against pathogenic microorganisms an d as chemical signals in symbiotic nitrogen fixation. Third, as constituent s of food and forage, leguminous flavonoids have striking biological activi ty in humans and animals. This article reviews the chemical structure, biol ogical activity, and biosynthesis of leguminous flavonoids. Recent achievem ents in the identification and characterization of cytochrome P450 monooxyg enases, which play important roles in (iso) flavonoid biosynthesis, are als o introduced. Perspectives of molecular genetic studies on flavonoids with the model legume are discussed.