Scopolamine N-Oxide - CAS 97-75-6

1. Donepezil (DPZ) is an acetylcholinesterase (AchE) inhibitor used in the mild to moderately severe Alzheimer's disease. Among its major metabolites, 6-O-desmethyl DPZ (6-DDPZ), 5-O-desmethyl DPZ (5-DDPZ) and DPZN-oxide, the anti-AchE activities of 5-DDPZ and DPZN-oxide have never been clearly identified before. Besides, there is no report on simultaneous determination of DPZ and its three metabolites in the brain, thus their uptake in hippocampus and cortex are unknown. Therefore, the current studies are proposed aiming to: (1) investigate the anti-AchE activities and brain uptake of DPZ and its three metabolites and (2) compare their pharmacokinetics and brain uptake between normal and scopolamine-induced rats.2. DPZ and its three metabolites demonstrated anti-AchE activities with the IC50in the order of DPZ (7.20 × 10-2μM), 6-DDPZ (1.14 × 10-1μM), 5-DDPZ (4.03 × 10-1μM) and DPZN-oxide (1.61 μM). They were also evenly distributed in the brain and retained much longer in the brain than that in plasma in normal rats.3. Compared to normal rats, Cmax, AUC0→24hand AUC0→∞of DPZ were reduced by 52.0%, 31.2% and 30.1%, respectively; Tmaxof DPZ and its three metabolites were prolonged and their brain uptake were decreased in scopolamine-induced rats, suggesting the potential reduced absorption of DPZ.

Objectives:The current study was undertaken to characterize the binding of propiverine to muscarinic receptors in mouse tissues by measuring plasma concentrations of the drug and its metabolite.Methods:At 0.5-24 h after the oral administration of propiverine at pharmacologically relevant doses, muscarinic receptors in tissue homogenates were measured by a radioligand binding assay using [N-methyl- (3) H]scopolamine (NMS), along with the drug's concentration in plasma by the liquid chromatography-tandem mass spectrometric method.Results:In the in vitro experiments, propiverine and its metabolite 1-methy-4-piperidyl benzilate N-oxide competed with [(3) H]NMS for binding sites in the bladder, submaxillary gland and heart of mice in a concentration-dependent manner. After the oral administration of propiverine, dose- and time-dependent increases in the dissociation constant for specific [(3) H]NMS binding were observed in the bladder and other tissues of mice, indicating that orally administered propiverine and/or its metabolite undergo significant binding to muscarinic receptors in mouse tissues. A longer-lasting binding of muscarinic receptor was seen in the bladder than in the submaxillary gland at relatively low doses of propiverine. Furthermore, the decrease in maximal number of binding sites values for [(3) H]NMS binding was more remarkable in the bladder than submaxillary gland of propiverine treated mice. There was a dose-dependent rise in the plasma concentrations of propiverine and 1-methy-4-piperidyl benzilate N-oxide in mice after the oral administration of propiverine.Conclusion:The oral administration of propiverine exerts a more prominent and longer-lasting effect in the bladder than in the submaxillary gland of mice. The N-oxide metabolite may contribute significantly to the blockade of muscarinic receptors caused by oral propiverine.

A rapid and sensitive method is described for the determination of scopolamine and its metabolites in rat urine by combining liquid chromatography and tandem mass spectrometry (LC-MS/MS). Various extraction techniques (free fraction, acid hydrolyses and enzyme hydrolyses) and their comparison were carried out for investigation of the metabolism of scopolamine. After extraction procedure, the pretreated samples were injected into a reversed-phase C18 column with mobile phase of methanol/ ammonium acetate (2mM, adjusted to pH 3.5 with formic acid) (70:30, v/v) and detected by an on-line MS/MS system. Identification and structural elucidation of the metabolites were performed by comparing their changes in molecular masses (DeltaM), retention-times and full scan MS(n) spectra with those of the parent drug. The results revealed that at least 18 metabolites (norscopine, scopine, tropic acid, aponorscopolamine, aposcopolamine, norscopolamine, hydroxyscopolamine, hydroxyscopolamine N-oxide, p-hydroxy-m-methoxyscopolamine, trihydroxyscopolamine, dihydroxy-methoxyscopolamine, hydroxyl-dimethoxyscopolamine, glucuronide conjugates and sulfate conjugates of norscopolamine, hydroxyscopolamine and the parent drug) and the parent drug existed in urine after ingesting 55mg/kg scopolamine to healthy rats. Hydroxyscopolamine, p-hydroxy-m-methoxyscopolamine and the parent drug were detected in rat urine for up 106h after ingestion of scopolamine.