HPLC同时测定苦豆子总碱中8种生物碱含量

目的:建立苦豆子总碱中生物碱的含量测定方法.方法:采用HPLC,乙腈-0.05 mol· L-1磷酸二氢钾(三乙胺调pH ＞6.45),梯度洗脱,柱温35℃,检测波长205 nm,流速1.0 mL·min-1.结果:8种生物碱分离良好,8种生物碱含量＞50％.结论:该方法简便,可以作为苦豆子总碱的含量测定方法,比原标准中的滴定法测定总碱含量更方便、精确.     

Pharmacokinetics of cytisine,an α4β2 nicotinic receptor partial agonist,in healthy smokers following a single dose

Cytisine, an α₄β₂ nicotinic receptor partial agonist, is a plant alkaloid that is commercially extracted for use as a smoking cessation medication. Despite its long history of use, there is very little understanding of the pharmacokinetics of cytisine. To date, no previous studies have reported cytisine concentrations in humans following its use as a smoking cessation agent. A high performance liquid chromatography‐ultraviolet (HPLC‐UV) method was developed and validated for analysis of Tabex® and nicotine‐free oral strips, two commercial products containing cytisine. A sensitive liquid chromatography‐mass spectrometry (LC‐MS) method was developed and validated for the quantification of cytisine in human plasma and for the detection of cytisine in urine. Single‐dose pharmacokinetics of cytisine was studied in healthy smokers. Subjects received a single 3 mg oral dose administration of cytisine. Cytisine was detected in all plasma samples collected after administration, including 15 min post‐dose and at 24 h. Cytisine was renally excreted and detected as an unchanged drug. No metabolites were detected in plasma or urine collected in the study. No adverse reactions were reported. Copyright © 2014 John Wiley & Sons, Ltd.     

Age-related alterations of GABAergic input to CA1 pyramidal neurons and its control by nicotinic acetylcholine receptors in rat hippocampus

The aim of this study was to determine whether age-associated alterations in the GABAergic input to pyramidal neurons in the hippocampus are due to a dysfunction of GABAergic interneurons, and/or a decrease in their cholinergic control via nicotinic receptors (nAChRs). Electrophysiological recordings were obtained from pyramidal cells in the CA1 area of hippocampal slices from young (3-4 months old) and aged (25-30 months old) Sprague-Dawley rats. Synaptic GABA(A) receptor-mediated inhibitory postsynaptic currents and inhibitory postsynaptic potentials induced by stimulation of the stratum oriens were significantly smaller in aged rats. The frequency (but not amplitude) of spontaneous and miniature GABA inhibitory postsynaptic currents (IPSCs) was reduced in aged rats, suggesting a presynaptic alteration. Tetanic stimulation of cholinergic afferents to release endogenous acetylcholine, or an exogenous application of the nAChR agonist cytisine, increased the frequency of spontaneous IPSCs in young rats; however these effects were not evident in aged rats, indicating that the nicotinic control of GABA release is lowered during aging. None of these age-related alterations were reversed by a chronic treatment with donepezil, a cholinesterase inhibitor. Immunofluorescent labeling of GABA interneurons with somatostatin (SOM), parvalbumin (PV) or calbindin (CB), together with the vesicular acetylcholine transporter VAChT, revealed a selective loss of subpopulations of SOM and CB positive interneurons. This loss was associated with a general decrease in density of the cholinergic network in aged rats. Thus, the lower GABAergic inhibition observed in the aged rat hippocampus is due to a selective loss/dysfunction of subpopulations of GABAergic interneurons, associated with a widespread cholinergic deficit.     

Pre-clinical properties of the α4β2 nicotinic acetylcholine receptor partial agonists varenicline,cytisine and dianicline translate to clinical efficacy for nicotine dependence

Background and purpose:

Smoking cessation trials with three high-affinity partial agonists of α4β2 neuronal nicotinic acetylcholine receptors (nAChRs) have demonstrated differences in their clinical efficacy. This work examines the origin of the differences by taking into account brain exposure and pharmacological effects at human α4β2 nAChRs.

Experimental approach:

Rat plasma and brain pharmacokinetics were characterized and used to predict human steady-state plasma and brain concentrations following recommended doses of each of the three compounds. The pharmacological characterization included in vitro affinities at different nAChR subtypes, functional efficacies and potencies at the human α4β2 nAChR, as well as in vivo effects on rat mesolimbic dopamine turn-over.

Key results:

A comparison of predicted human brain concentrations following therapeutic doses demonstrated that varenicline and nicotine, but not dianicline and cytisine, can extensively desensitize and, to a lesser extent, activate α4β2 nAChRs. The limited clinical efficacy of dianicline may be accounted for by a combination of weak functional potency at α4β2 nAChRs and moderate brain penetration, while recommended doses of cytisine, despite its high in vitro potency, are predicted to result in brain concentrations that are insufficient to affect α4β2 nAChRs.

Conclusions and implications:

The data provide a plausible explanation for the higher abstinence rate in smoking cessation trials following treatment with varenicline than with the two other α4β2 nAChR partial agonists. In addition, this retrospective analysis demonstrates the usefulness of combining in vitro and in vivo parameters with estimated therapeutic human brain concentrations for translation to clinical efficacy.     

In vitro characterization of 6-[18F]fluoro-A-85380, a high-affinity ligand for alpha4beta2* nicotinic acetylcholine receptors

Nicotinic acetylcholine receptors are involved in tobacco dependence and several other neuropathologies (e.g., Alzheimer's disease, Parkinson's disease), as well as in attention, learning, and memory. Performing in vivo imaging of these receptors in humans holds great promise for understanding their role in these conditions. Recently, three radiohalogenated analogs of 3-(2(S)-azetidinylmethoxy)pyridine (A- 85380) were used successfully for the in vivo visualization of alpha4beta2* nicotinic receptors in the human brain with PET/SPECT. Herein, we present the results of the in vitro characterization of one of these radioligands, 6-[18F]fluoro-3-(2(S)-azetidinylmethoxy)-pyridine (6-[18F]fluoro-A-85380), which is a fluoro-analog of the potent nonopioid analgesic ABT-594. In human postmortem cortical tissue, 6-[18F]fluoro-A-85380 reversibly binds with high affinity to a single population of sites (Kd = 59 pM at 37 degrees C, Bmax = 0.7 pmol/g tissue). The binding is fully reversible and is characterized at 37 degrees C by T(1/2assoc) = 2.2 min (at a ligand concentration of 39 pM) and by T(1/2dissoc) = 3.6 min. 6-Fluoro-A-85380 exhibits clear selectivity for alpha4beta2* over the other major mammalian nicotinic receptor subtypes: alpha7, alpha3beta4, and muscle-type. These results suggest that 6-[18F]fluoro-A-85380 is a promising radioligand for in vivo imaging of brain alpha4beta2* nicotinic receptors.     

From ligand design to therapeutic efficacy: the challenge for nicotinic receptor research

S-Nicotine, the principal psychoactive constituent of Nicotiana tabacum, underpins addiction to tobacco smoking. Although tobacco consumption is a leading cause of death worldwide, nicotine itself is also proposed to have potential therapeutic benefits for a diverse range of conditions. Nicotine interacts with its cognate receptors in the central nervous system to exert a predominantly modulatory influence, making neuronal nicotinic receptors attractive therapeutic targets. Here, we focus on three natural products as lead compounds for drug discovery programs, nicotine, epibatidine and cytisine, and consider the aims and limitations that shape these drug discovery endeavors.     

披针叶黄华地上部分金雀花碱的分离纯化工艺研究

目的研究采用树脂从披针叶黄华地上部分中分离纯化金雀花碱的工艺条件。方法以金雀花碱为目标成分,以N-甲酰基金雀花碱为杂质的指标成分,对多种树脂材料的纯化效果进行筛选,并对影响分离纯化效果的主要因素,如上样液pH值、浓度及洗脱剂组成等进行优化。结果以氢型001×7型阳离子交换树脂为纯化载体,调节披针叶黄华地上部分提取液pH至12左右上样后,再以1.0 mol·L-1氨水-体积分数为90%的乙醇洗脱,可有效去除部分生物碱杂质成分,提取物中金雀花碱质量分数最高达到44.61%,纯化倍数达到6倍以上,N-甲酰基金雀花碱的去除率最低为89.75%。结论提供了一种从披针叶黄华地上部分高效分离纯化金雀花碱的方法。     

Cytisine inhibits the anticonvulsant activity of phenytoin and lamotrigine in mice

BackgroundCytisine (CYT), the most commonly used drug for smoking cessation in Poland, was experimentally found to induce convulsions. There is a lack of studies on the influence of CYT on the anticonvulsant activity of antiepileptic drugs (AEDs).MethodsThe effects of CYT on the anticonvulsant activity of six AEDs were examined in maximal electroshock (MES)-induced seizures in mice.ResultsSingle intraperitoneal (ip) administration of CYTin a subthreshold dose of 2 mg/kg antagonized the protective activity of ip phenytoin and lamotrigine against MES-induced seizures in mice. Adose of 1 mg/kg did not reverse the protective activity of phenytoin and lamotrigine. CYT in a dose of 2 mg/kg had no effect on the anticonvulsive activity of carbamazepine, oxcarbazepine, phenobarbital, and valproate magnesium.ConclusionCYT ability to antagonize the anticonvulsive activity of phenytoin and lamotrigine can be of serious concern for epileptic smokers, who might demonstrate therapeutic failure to these drugs resulting in possible breakthrough seizure attacks.