Basic Studies on Quantitative Determination of Two Glucuronides of Befunolol Metabolite by Selected Ion Monitoring(SIM)Using Mono-deuterium Labelled Compound

Selected ion monitoring has heen developed for the determination of two glucuronides detected in human urine after oral administration of befunolol(BF). It was confirmed that not only multi-deuterium labelled compound(I-d6)but also mono-deuterium labelled one(I-d1)were useful internal standard at determination of the common aglycone, 2-(1-hydroxyethyl)-7-(2-hydroxy-3-isopropylaminopropoxy)benzofuran of these glucuronides. The glucuronides had been identified as O-glucuronide of side-chain of I(II)and O-glucuronide of 2-side-chain of I(III). Each glucuronide was determined by the combination of enzymatic hydrolysis, thin layer chromatography and selected ion monitoring using II-d1 as internal standard. The overall recoveries(%)of II and III were 101.3±1.9(SE)and 101.1±1.4(SE)respectively. Over 70% of dose determined as I, II and III in the urine of man received BF 15-20 mg orally. It can therefore be presumed that major metabolic pathway of BF in man is the reduction followed by the glucuronidation.