Studies on Drug Metabolism by Use of Isotopes. XVIII.1) Ion Cluster Technique for Detection of Urinary Metabolites of 1-Butyryl-4-cinnamylpiperazine

The structural elucidation of several unidentified metabolites of 1-butyryl-4-cin-namylpiperazine (I) in mice and guinea pigs was made by the ion cluster technique. A single dose of 100mg/kg of an equimolar mixture (I : I-d5) of 1-butyryl-4-(cinnamyl-arom.-d5)piperazine (I-d5) hydrochloride and I hydrochloride was injected subcutaneously into animals. After the administration of I : I-d5 the urine was collected for 24 hr. An aliquot of the urine sample was extracted with AcOEt at pH 11, the extract was subjected to thin-layer chromatography twice, and the isolated sample was introduced directly into the ion source, and its mass spectrum was recorded. The chemical structures of the metabolites in question were readily determined by the presence of doublet peaks separated by 3-5 mass units, and by the shift of the fragment ions. The possible structures of the unidentified metabolites were elucidated as 1-butyryl-4-(3-methoxy-4-hydroxycinnamyl)piperazine (V), 1-(3-hydroxybutyryl)-4-cinnamylpiperazine or 1-(4-hydroxybutyryl)-4-cinnamylpiperazine, and 1-(3-hydroxybutyryl)-4-(4-hydroxycinnamyl)piperazine or 1-(4-hydroxybutyryl)-4-(4-hydroxycinnamyl) piperazine. Unchanged I, 1-butyryl-4-(4-hydroxycinnamyl)piperazine (II), 1-cinnamylpiperazine (III), and 1-(4-hydroxycinnamyl) piperazine (IV), which had been identified by the inverse isotope dilution analysis, were also detected by this technique.