3',4',7-trihydroxyisoflavone + S-adenosyl-L-methionine = 7,4'-dihydroxy-3'-methoxyisoflavone-7-olate + S-adenosyl-L-homocysteine + H(+)
3',4',7-trihydroxyisoflavone + s-adenosyl-l-methionine = 7,4'-dihydroxy-3'-methoxyisoflavone-7-olate + s-adenosyl-l-homocysteine + h(+)