Reaction catalyzed by 8-hydroxyquercetin 8-O-methyltransferase (2.1.1.88), emodin O-methyltransferase (2.1.1.283)

		+			=			+
	S-adenosyl-L-methionine	+		beta-sitosterol	=		S-adenosyl-L-homocysteine	+		3-methoxy-beta-sitosterol