Evaluation of anxiolytic, sedative-hypnotic and amnesic effects of novel 2-phenoxy phenyl-1,3,4-oxadizole derivatives using experimental models

Benzodiazepines [BZDs] are widely used in clinical practice as anxiolytics, hypnotics, anticonvulsants and muscle relaxants. However, they have some undesired effects including memory problems. In continuing our research on novel benzodiazepine ligands, we are looking for ligands with less adverse effects. Previously, 4 novel derivatives of 2-phenoxy phenyl-1,3,4-oxadiazole were synthesized as agonists of BZD receptors. In this study, the pharmacological effects of novel compounds were evaluated. Pentobarbital induced loss of righting reflex, elevated plus maze, open-field locomotor activity and passive avoidance test were used to evaluate the sedative-hypnotic, anxiolytic and amnesic effects of compounds respectively. The results revealed that the novel compounds with NH[2], SH and SCH[3] substituents at the 2-position of the oxadiazole ring increase righting reflex time significantly. In the elevated plus maze test none of the derivatives increased open arm duration and open arm entry indicating no anxiolytic properties. Moreover, the novel compounds didn't influence step-down latencies in the mice. The fact that the hypnotic activity of these compounds were significantly reduced by flumazenil, confirmed that this effect is mediated by BZD receptors

Design, synthesis and biological evaluation of 4-benzamidobenzoic acid hydrazide derivatives as novel soluble epoxide hydrolase inhibitors

Inhibitors of soluble epoxide hydrolase [sEH] represent one of the novel pharmaceutical approaches for treating hypertension, vascular inflammation, pain and other cardiovascular related diseases. Most of the potent sEH inhibitors reported in literature often suffer from poor solubility and bioavailability. Toward improving pharmacokinetic profile beside favorable potency, two series of 4-benzamidobenzoic acid hydrazide derivatives with hydrazide group as a novel secondary pharmacophore against sEH enzyme were developed. The designed compounds were synthesized in acceptable yield and their in vitro assay was determined. Most of the synthesized compounds have appropriate physical properties and exhibited considerable in-vitro sEH inhibitory activity in comparison with 12-[3-Adamantan-1-yl-ureido]-dodecanoicacid [AUDA], a potent urea-based sEH inhibitor. 4-[2-[4-[4-chlorobenzamido] benzoyl]hydrazinyl]-4-oxobutanoic acid 6c was found to be the most potent inhibitor with inhibitory activity of 72% targeting sEH enzyme

Optimum conditions of radioligand receptor binding assay of ligands of benzodiazepine Receptors

To obtain drugs which are more selective at benzodiazepine [BZD] receptors, design and synthesis of functionally selective ligands for BZD receptors is the current strategy of our pharmaceutical chemistry department. The affinity of newly synthesized ligands is assessed by radioligand receptor binding assays. Based on our previous studies, 2-phenyl-5-oxo-7-methyl-1,3, 4-oxadiazolo[a,2,3]-pyrimidine [compound A] was chosen for design and synthesis of new triazole derivatives as GABA[A] BZD receptor agonist. The cortical membrane of male Sprague-Dawley rats was prepared as the source of the BZD receptors. Different concentrations of membrane protein and [[3]H]-flumazenil were incubated at room temperature at different time periods to reach the steady-state. To saturate the receptors, increased amounts of radioligand were incubated with membrane protein. The bound and un-bound ligands were separated by centrifugation. The affinity of compound A was measured in competition studies at optimum conditions by displacement of [[3]H]-Flumazenil from rat cortical membrane. Based on results, the optimum conditions of radioligand receptor binding assay of benzodiazepines were 35 min incubation of ligands with 100 micro g cortical membrane protein and 8.6 x 10[-5] nmole [3]H-flumazenil in a final volume of 0.5 mL Tris-HCl buffer [50 mM, pH 7.4] at 30 [degree sign]C. The binding parameters of [[3]H]-flumazenil, B[max] and K[d] were determined through saturation studies as 0.638 +/- 0.099 pmol/mg and 1.35 +/- 0.316 nM respectively. The affinity of compound A was 1.9 nM comparable with diazepam [1.53nM]. This finding makes the compound an interesting lead for further optimization. Starting from this compound, new ligands were synthesized and screened in-vitro by competitive binding assays

Design, synthesis and pharmacological evaluation of novel 2-[2-[2-chlorophenoxy] phenyl]-1,3,4-oxadiazole derivatives as benzodiazepine receptor agonists

New derivatives of 2-[2-[2-Chlorophenoxy]phenyl]-1,3,4-oxadiazole as candidates for agonistic effect on benzodiazepine receptors were synthesized. Conformational analysis and superimposition of energy minima conformers of the novel compounds on estazolam, a known benzodiazepine agonist, revealed that the main proposed benzodiazepine pharmacophores were well matched. In pharmacological evaluation, anticonvulsant activity of the compounds determined by pentylenetetrazole-induced lethal convulsion and maximal electroshock tests. The results showed that the introduction of an amino substituent in position 5 of 1,3,4- oxadiazole ring generates compound 6 that has a considerable effect. Compound 8 with a hydroxyl substituent on position 5 of 1,3,4- oxadiazole ring showed a relatively mild anticonvulsant activity, which was significantly weaker than that of diazepam and compound 6. Anticonvulsant effects of active compounds were antagonized by flumazenil, an antagonist of benzodiazepine receptors, indicating the involvement of benzodiazepine receptors in these effects.

Application of narrow-bore HPLC columns in rapid determination of sildenafil citrate in its pharmaceutical dosage forms

A special type of silica-based columns has been recently introduced into the market which is called narrow-bore columns. They have lower internal volume than the standard high-performance liquid chromatography [HPLC] columns and thus reduce the solvent consumption by almost 80%. A simple, accurate and environmentally friendly reversed phase- HPLC [RP-HPLC method] which could be used in fast and high throughput analyses has been developed for the purpose of determining the sildenafil in bulk and pharmaceutical dosage forms, using narrow-bore C[18] column [50 _ 3.2 mm, 5 micro m particle size] in isocratic mode, with mobile phase comprising of buffer [pH = 3] and acetonitrile in the ratio of 75:25 v/v. The flow rate was 0.7 mL/min and the detection was monitored through Ultraviolet detector [UV detector] at 292 nm. Clonazepam was used as the internal standard and the run time was 4 min. The proposed method has permitted the quantification of sildenafil over the linearity in the range of 30-4000 ng/mL and its percentage recovery was found to be 99-105%. Limit of quantitation [LOQ] is determined as 30 ng/mL. The intra-day and inter-day precisions were found 1.2-2.2% and 1.56-3.4% respectively. The solvent consumption was 2.8 mL per sample of which ca 0.7 mL was acetonitrile. This study shows that the application of narrow-bore column instead of the conventional reversed phase column in HPLC analyses has the advantages of shorter run time and less organic solvent consumption. This method is highly sensitive with excellent recoveries and precision and there is no need for special column and pre-column or post-column treatment of the sample. Moreover, the method is free from interference by common additives and excipients, suggesting applications in routine quality control analyses