**3.13 Distinctive flavonoid profiles in legume**

Legumes have sparked a lot of attention because of their health benefits and their polyphenolic compounds. The xanthine oxidase XO inhibitory activity appears to be reduced when a glycoside or a methyl group is substituted for the hydroxyl groups at C7 and C3 of the basic flavonoid structure [120].

Recently, isolation of genes encoding the critical enzymes of various phenylpropanoid branch pathways has opened the door for engineering crucial agricultural plants like alfalfa for:


The recognition of flavonoids in legume root exudates by the bacterium, originates in the rhizosphere and activates a particular set of genes involved in bacterial nodulation (*Nod*). These nodulations produce and secretes a very specific signal known as lipochito-oligosaccharides or Nod factors. The formation of rhizobia-infected root nodules is the result of a variety of host responses brought on by the perception of Nod factors by the plant LysM receptors, including bacterial invasion of the root hairs, root hair curling, cortical cell divisions and induced expression of the host symbiotic genes [122].
