A Note on Isolation and Identification of a Drug Conjugate
ICI 55, 897 ( ‘Clozic’ ) was developed by ICI for potential use as a treatment for rheumatoid arthritis. Metabolism studies in animals and man using14C-labelled Clozic showed marked species variation in the route and rates of excretion after oral administration (Table 1). However, in all species the compound is excreted as a single conjugate of unchanged Clozic. Early attempts to characterize this conjugate using14C-labelled Clozic were hampered by the fact that the conjugate hydrolyzed spontaneously and rapidly at pH values more alkaline than 3. This made conventional enzymic tests for conjugates difficult to interpret, as control samples also showed rapid hydrolysis. In fact, urine samples have to be acidified immediately after collection to keep the total conjugate intact. The Clozic conjugate was eventually isolated from hamster urine by solvent extraction at acid pH and purified by RP-HPLC. Chemical identification as a glucuronide has been made on the basis of both proton and13C NMR analysis.
KeywordsGlucuronic Acid Proton Spectrum Methylene Carbon LiChroprep RP18 Metabolite Isolation
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