Benzylpiperazine derivatives. IV. Syntheses and cerebral vasodilating activities of 1-benzyl-4-diphenylmethylpiperazine derivatives

Design, synthesis and anti-Chikungunya virus activity of lomerizine derivatives

Chikungunya fever is an acute infectious disease caused by Chikungunya virus (CHIKV) and transmitted by Aedes mosquito. It is characterized by fever, rash and arthralgia with no effective drugs. Lomerizine (Lom) is a new generation calcium antagonist, which is mainly used in the treatment of migraine. Certain antiviral function of Lom was shown by some research. In our study, a series of new derivatives of Lom were designed and synthesized, and their in-vitro anti-CHIKV activity was tested. The results showed that Lom and its derivatives had potent anti-CHIKV activity and low cytotoxicity. Among them, compounds B1 and B7 showed most potent antiviral activity. Besides, structure-activity relationships, in-silico ADMET properties were also analyzed. Molecular docking study was performed to rationalize the SAR and analyze the possible binding modes between B1 and amino acid residues in the active site of nsP3 protein to enhance the understanding of their action as antiviral agents. These finding provides research basis for the design and synthesis of effective anti-CHIKV drugs with Lom as the lead compound.

Synthesis of Novel 3-Aryl-N-Methyl-1,2,5,6-Tetrahydropyridine Derivatives by Suzuki coupling: As Acetyl Cholinesterase Inhibitors

Alzheimer’s disease (AD) is a neurodegenerative disorder affecting the central nervous system, which is also associated with progressive loss of memory and cognition. The development of numerous structural classes of compounds with different pharmacological profile could be an evolving, promising therapeutic approach for the treatment of AD. Thus, providing a symptomatic treatment for this disease are cholinomimetics with the pharmacological profile of Acetylcholinesterase (AChE) inhibitors. In view of this, we have synthesized novel 3-aryl-N-methyl-1,2,5,6-tetrahydropyridine derivatives 5a-k by Suzuki coupling and screened the efficacy of these derivatives for their AChE inhibitor activity.

Synthesis and efficacy of 1-[bis(4-fluorophenyl)-methyl]piperazine derivatives for acetylcholinesterase inhibition, as a stimulant of central cholinergic neurotransmission in Alzheimer’s disease

The cholinergic hypothesis of Alzheimer's disease (AD) has spurred the development of numerous structural classes of compounds with different pharmacological profile aimed at increasing central cholinergic neurotransmission. Thus proving a symptomatic treatment for this disease are cholinomimetics with the pharmacological profile of acetyl cholinesterase (AchE) inhibitors. The novel bioactive 1-[bis(4-fluorophenyl)-methyl]piperazine derivatives were synthesized under mild conditions using different aryl/alkyl halides and heterocyclic alkyl halides with 1-[bis(4-fluorophenyl)-methyl]piperazine in the presence of powdered potassium carbonate in N,N-dimethylformamide. All the synthesized compounds were characterized by spectroscopic techniques, elemental analysis and were screened for their efficacy as AchE inhibitor. Some derivatives in this class showed good inhibition against AchE as compared to neostigmine as standard.

Synthesis and in vitro antimicrobial studies of medicinally important novel N-alkyl and N-sulfonyl derivatives of 1-[bis(4-fluorophenyl)-methyl]piperazine

A series of novel substituted 1-[bis(4-fluorophenyl)-methyl]piperazine derivatives (4a-g) and (5h-m) have been synthesized. The synthesized compounds were characterized by IR and 1H NMR. All the synthesized compounds were evaluated in vitro for their efficacy as antimicrobial agents against representative strains of Gram-positive (Staphylococcus aureus ATCC 25953, Streptococcus pneumoniae ATCC 49619, Bacillus cereus 11778, and Bacillus subtilis 6051) and Gram-negative bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 2853, Proteus vulgaris ATCC 2853, and Salmonella typhi ATCC 9484) by paper disc diffusion and microdilution methods. Among the newly synthesized compounds 4e, 5l, and 5m showed potent antimicrobial activities, when compared to the standard drug.

Structure-activity studies on the protection of Trimetazidine derivatives modified with nitroxides and their precursors from myocardial ischemia-reperfusion injury

Trimetazidine, the known anti-anginal and anti-ischemic drug, was modified by pyrroline and tetrahydropyridine nitroxides and their hydroxylamine and sterically hindered secondary amine precursors. The synthesized new compounds proved to be better superoxide scavenger molecules compared to the parent Trimetazidine in an in vitro experiment. This reactive oxygen species (ROS) scavenging activity was further supported by ischemia/reperfusion (I/R) studies on Langendorff-perfused rat hearts pretreated with Trimetazidine and with the modified Trimetazidine derivatives before ischemia. Two of the investigated compounds, containing 2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole and 4-phenyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole substituents on the piperazine ring, provided significant protection from the cardiac dysfunction caused by I/R. The protective effect could be attributed to the combined anti-ischemic and antioxidant effects.

Selective effects of lomerizine, a novel diphenylmethylpiperazine Ca2+ channel blocker, on cerebral blood flow in rats and dogs

1. In the present study we examined the effects of a new Ca2+ channel blocker (lomerizine), an antimigraine drug, on cerebral cortical blood flow (CBF) in anaesthetized rats (laser Doppler flowmetry) and on vertebral blood flow in anaesthetized beagle dogs (electromagnetic flowmeter). 2. Lomerizine (1.25-10 mg/kg, p.o.) dose-dependently increased CBF in rats without affecting blood pressure (BP) or heart rate (HR). 3. The plasma concentration of lomerizine (free base) in anaesthetized rats at 30 and 60 min after the initial administration of 5 mg/kg, p.o., time at which there was a significant increase in CBF, was similar to that reported in healthy subjects receiving lomerizine at 10 mg (2 x 5 mg)/day, p.o., a dose that significantly reduces the frequency and mean duration of headache attacks. 4. Flunarizine (10 mg/kg, p.o.) did not increase CBF significantly. Flunarizine (20 mg/kg, p.o.) did not increase CBF, but did decrease BP 30-120 min after its administration. 5. Lomerizine (2.5 and 5 mg/kg, intraduodenally) dose-dependently increased vertebral blood flow in dogs without significantly changing BP or HR. With 10 mg/kg intraduodenal lomerazine, vertebral blood flow remained elevated from 20 to 240 min after administration and BP was decreased from 20 to 120 min. 6. Thus, lomerizine had a greater effect on CBF than on BP and HR and, therefore, it may be clinically effective in conditions associated with circulatory disturbances in the brain, such as migraine, without producing systemic effects (e.g. hypotension) generally seen with other Ca2+ channel blockers.

Effects of KB-2796, a new diphenylpiperazine calcium antagonist, on renal hemodynamics and urine formation in anesthetized dogs

The effects of KB-2796, a new calcium antagonist with a diphenylpiperazine moiety, on renal hemodynamics and urine formation were investigated in anesthetized dogs. Intravenous infusion of KB-2796 (10, 30, and 100 micrograms/kg/min) decreased mean blood pressure (MBP) and renal vascular resistance (RVR) in a dose-dependent manner, but did not change renal blood flow (RBF). At the highest dose, glomerular filtration rate (GFR) and urine flow (UF) tended to decrease. Nicardipine (0.1, 0.3, and 1 microgram/kg/min) also dose-dependently decreased MBP, RVR, GFR, and UF. When KB-2796 was infused into the renal artery at lower doses of 3 and 10 micrograms/kg/min, UF and urinary excretion of electrolytes increased without a significant change in RBF and GFR. Intrarenal infusion of KB-2796 at 30 micrograms/kg/min and nicardipine at 0.3 microgram/kg/min produced a significant increase in GFR, RBF, UF, urinary excretion of electrolytes, and renin secretion rate. These results suggest that KB-2796 administered intrarenally exerts a diuretic action via tubular effects and the alteration of renal hemodynamics. However, its diuretic action might be masked by diminished urine formation via a reflex activation of the sympathetic nerves and/or via a reduction of renal perfusion pressure when it is administered systemically.

Calcium antagonism by KB-2796, a new diphenylpiperazine analogue, in dog vascular smooth muscle

The effects of KB-2796, a new diphenylpiperazine analogue, on [3H]nitrendipine ([3H]NTD) binding, KCl-induced contraction and 45Ca influx has been examined in dog vascular smooth muscle, and compared with those of other diphenylpiperazines. In the binding study, [3H]NTD was found to bind with a high affinity to a single class of sites on aortic membranes (Kd = 0.41 nM and Bmax = 31 fmol (mg protein)-1). KB-2796 inhibited specific [3H]NTD binding in a concentration-dependent manner, with a Ki value of 0.34 microM. The other diphenylpiperazine derivatives such as flunarizine and cinnarizine also inhibited binding in the same manner. Also, in the contraction study, all the diphenylpiperazines antagonized the 50 mM KCl-induced contraction of isolated mesenteric arteries concentration-dependently. The IC50 values of the compounds for KCl-induced contraction correlated strongly with the respective Ki values obtained in the [3H]NTD binding study. In the 45Ca influx study, KB-2796 also effectively inhibited KCl-induced 45Ca influx in mesenteric arteries, with an IC50 value of 0.14 microM. This was close to the IC50 value found in the KCl-induced contraction study. These findings suggest that calcium antagonism by KB-2796 is responsible for its vasorelaxing action in vascular smooth muscle.

Age-related changes in the uptake of calcium channel blockers by brain capillary endothelial cells and synaptosomal fractions

The effects of aging on the uptake of calcium channel blockers through brain capillaries to brain parenchyma were investigated. Two different piperazine derivatives, flunarizine and 1-[bis(fluorophenyl)-methyl]-4-(2,3,4-trimethoxybenzyl)piperazine (abbreviated as KB-2796), were orally administered to young and aged rats. The concentrations of the blockers in plasma, endothelial cells of the brain capillaries and synaptosomal fractions of the three brain regions were determined by high-performance liquid chromatography. Flunarizine was more incorporated into brain tissues than KB-2796 in both young and aged rats. The uptake efficiency of KB-2796 from the circulation to the brain decreased more remarkably than that of flunarizine in aged rats. The partition coefficients between n-octanol and water indicated that KB-2796 was less hydrophobic than flunarizine. These results suggest that the uptake of the chemicals seems to be influenced by their hydrophobicity and the age of animals given.

Effects of KB-2796, a new calcium antagonist, and other diphenylpiperazines on [3H]nitrendipine binding

The effect of KB-2796, a new diphenylpiperazine calcium antagonist, on [3H]nitrendipine ([3H]NTD) binding was investigated in synaptosomal membranes prepared from the guinea pig cerebral cortex. KB-2796 inhibited [3H]NTD binding in a dose-dependent manner with an IC50 value of 86 nM. In this respect, KB-2796 was the most potent among the diphenylpiperazine derivatives tested. Saturation binding data indicated that this inhibition resulted from a decrease in the binding affinity without changes in the maximal number of binding sites. KB-2796, however, significantly increased the dissociation rate constant of [3H]NTD from radiolabeled membranes. This finding suggests that KB-2796 inhibits [3H]NTD binding by a negative heterotropic allosteric mechanism. Other diphenylpiperazines tested also showed similar inhibitory properties. Diphenylpiperazines may act at a site, which is different from the 1,4-dihydropyridine binding site, on the voltage-dependent calcium channel.