The urine collected from three dogs for 24 hr. after oral administration of but~olol-'~C contained 61.2% of the administered radioactivity. An acidic metabolite, representing 16% of the urinary IrC, was purified by ether extraction and preparative TLC. The methyl ester of the metabolite was prepared and submitted for analysis by mass spectrometry. The spectrum indicated the compound to be the methyl ester of 3-[(5,6,7,8-tetrahydro-5-oxo-l-naphthyl)oxyllactic 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-5-0xo-l-naphthyl)oxylacetic 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 RJ values confirmed the identity of the metabolite.
Keyphrases 0 Bunolol, metabolites-isolation, identification, dog urine 0 p-(5-Oxytetralonyl)lactic acid-isolation, identification, bunolol metabolite, dogs (5-0xytetralonyl)acetic acid-isolation, identification, bunolol metabolite, dogs 0 TLC-isolation, identification 0 Mass spectroscopy-identification A new, highly potent, P-adrenergic blocking agent, bunolol { dl-5-[3-(~ert-butylamino)-2-hydroxypropoxy]-3,4-dihydro-l(2H)-naphthalenone hydrochloride 1, was metabolized extensively following oral administration to dogs (1). Urine collected for 24 hr. following bun-0101-14C administration contained only 0.7 % of the urinary radioactivity as the unaltered drug. An experimental survey of the different classes of bunolol metabolites indicated the presence of as many as 18 urinary metabolites. Among these metabolites were three unconjugated and five conjugated bases and four unconjugated and six conjugated acids. The present report describes the isolation and identification of two acidic metabolites of bunolol from dog urine ; P-(5-oxytetra-1onyl)lactic acid and (5-oxytetralony1)acetic acid.
Methods
14C-Labeled Bunolol-Bunolol was synthesized with I4C in position 1 (carbonyl-C) of the saturated ring (2). The preparation was 99.0 pure, both chemically and radiochemically, as judged by TLC; it had a specific activity of 4.90 mc./g. Radioactivity Counting-Quantitative assays for 14C were performed using a liquid scintillation spectrometer'. The external standardization method was used for quench corrections.
TLC-Chromatograms for analytical purposes were run on 5 X 20-cm. glass plates coated with 250 IJ of silica gel G bound with calcium sulfate. For preparative efforts, 20 X 20-cm. plates were used. One-dimensional chromatograms were developed using the following solvents: 1, n-butanol-29.6% ammonia-water (4: 1 :3, upper phase); 2, Iz-butanol-glacial acetic acid-ether-water (9 :6: 3: I); 3, n-butanol-glacial acetic acid-ether-water (6 : 3 :9 : 1); 4, methanol-29.6% ammonia--water (12:l :7); 5, methanol-ethyl acetate (1 :4); 1 Packard Tri-Carb model 3320. 1516 0 Journal of Pharmaceutical Sciences * Packard model 7201. 3 Keuffel and Esser. 4 AEI model 902.