obsolete gossypetin 8-methyl ester 3'-O-methyltransferase activity (obsolete GO:0102630)
OBSOLETE. Catalysis of the reaction: 3',4',5,7-pentahydroxy-8-methoxyflavon-3-olate + S-adenosyl-L-methionine = gossypetin 3',8-dimethyl ether + S-adenosyl-L-homocysteine + H+.