A. Isoflavone ring system showing the ring nomenclature and numbering
 
  R1 R2 R3
Genistein -H -OH -OH
Daidzein -H -H -OH
Glycitein -OCH3 -H -OH
Formononetin -H -H -OCH3
Biochanin A -H -OH -OCH3
B. Structures of Isoflavones discussed in this article
Table 1: Position of Ring A in the isoflavone ring.