The most abundant flavones in plants are luteolin (5,7,3’,4’-tetrahydr-oxyflavone) and apigeo= n (5,7,4’-trihydroxyflavone). B-ring of isoflavo-noids is connected to 3-C. Most frequently occurring isoflavonoids are isoflavones with a double bond at the 2-3-C-position. Major isoflavones are genistein (5,7,4’-trihydroxyisoflavone), daidzein (7,4’-dihydroxyiso-flavone), formononetin (7-hydroxy-4’-methoxyiso-flavone) and biochanin A (5,7-dihydroxy-4’-methoxyisoflavone).