The metabolism and excretion of 3-O-methyl-(+)-catechin in the rat, mouse, and marmoset.

Following oral or intravenous administration to the rat, 3-O-methyl-(+)-catechin was metabolized by methylation of a B-ring phenolic hydroxyl group to 3,3'(or 4')-dimethyl-(+)-catechin, which was further conjugated with glucuronic acid and excreted both in urine and bile. Small amounts of unchanged 3-O-methyl-(+)-catechin was excreted in rat urine following parenteral but not oral administration. Excretion of radioactivity following parenteral administration of 3-O-[14C]methyl-(+)-catechin to the rat and marmoset was similar (approximately 50% in urine and 35% in feces). The mouse excreted 79% of radioactivity in urine and 22% in feces. Radioactivity in mouse and marmoset urine was associated with free dimethyl-(+)-catechin rather than the glucuronide conjugate prevalent in rat urine. Following oral administration to the marmoset, urinary excretion of 14C was lower than in the rat and again the major metabolite was the free dimethyl-(+)-catechin. In bile duct-cannulated rats approximately half of administered radioactivity was excreted in bile. In each experiment more than 85% of the 14C in bile was in the form of dimethylcatechin glucuronide. It is concluded that biological methylation is the major route of 3-O-methyl(+)-catechin metabolism in all species investigated, and that the compound does not undergo ring fission as has been reported in respect of the parent compound, (+)-catechin.