Bunolol metabolism by dogs: isolation and identification of two acidic metabolites.

The urine collected from three dogs for 24 hr. after oral administration of bunolol-14C contained 61.2% of the administered radioactivity. An acidic metabolite, representing 16% of the urinary 14C, was purified by ether extraction and preparative TLC. The methyl ester of the metabolite was prepared and submitted for analysis by massspectrometry. The spectrum indicated the compound to be the methyl ester of 3-[(5,6,7,8-tetrahydro-5-oxo-1-naphthyl)-oxy]lactic acid, and this compound was synthesized from 5-hydroxytetralone. The identity of the esterified urinary metabolite and the synthetic compound was established by mass spectrometry. A second unconjugated acid constituted 7% of the urinary 14C. Its identity was established as [(5,6,7,8-tetrahydro-5-oxo-1-naphthyl)-oxy]acetic acid by synthesis and comparative TLC. The 2,4-dinitrophenylhydrazones and the methyl esters of the metabolite and the synthetic material were prepared; comparison of their Rf values confirmed the identity of the metabolite.