Isolation, identification, and synthesis of 4-amino-6,7-dimethoxy-3-quinolinol, the major metabolite of amiquinsin hydrochloride in rats and humans

The metabolism of amiquinsin hydrochloride (4-amino-6,7-dimethoxyquinoline hydrochloride monohydrate, I) was studied in rats and humans. The major metabolite isolated from human urine was identified through synthesis as 4-amino-6,7-dimethoxy-3-quinolinol hydrochloride hydrate (II). Acid hydrolysis of the major metabolite from rat urine also gave II. The structure of the rat metabolite subsequently was tentatively identified as the potassium salt of the 3-O-sulfate of II. The pharmacological and toxicological properties of I and II are discussed.