8-O-methyltransferase active on various hydroxylated flavonoid substrates, including 7,8,3'4'-tetrahydroxy-flavone, 7,8,4'-trihydroxy-flavone and 8-hydroxy-flavone 7-methyl ether. 3,3',4',5,7,8-hexahydroxyflavone + S-adenosyl-L-methionine = 3,3',4',5,7-pentahydroxy-8-methoxyflavone + H(+) + S-adenosyl-L-homocysteine Belongs to the class I-like SAM-binding methyltransferase superfamily. Cation-independent O-methyltransferase family. COMT subfamily.