Suresh Paudel

Design and synthesis of 4-benzylpiperidine carboxamides as dual serotonin and norepinephrine reuptake inhibitors.

A series of 4-benzylpiperidine carboxamides were designed and synthesized, and tested for their dual (serotonin and norepinephrine) reuptake inhibition. The synthesis of 4-benzylpiperidine carboxamides involved two main steps: amidation and substitution. Derivatives with 3 carbon linker displayed better activity than with 2 carbon linker. 4-Biphenyl- and 2-naphthyl-substituted derivatives 7e and 7j showed greater dual reuptake inhibition than standard drug venlafaxine HCl.

Exploration of substituted arylpiperazine–tetrazoles as promising dual norepinephrine and dopamine reuptake inhibitors

In the search for potent dual norepinephrine and dopamine reuptake inhibitors, several substituted arylpiperazine-tetrazoles were designed, synthesized and evaluated for their neurotransmitter reuptake inhibitory activities. Various derivatives exhibited selective and strong neurotransmitter reuptake inhibitory activity. In particular, compounds with a three-carbon linker displayed selective and stronger potency than those with two-carbon and four-carbon linkers. Interestingly, six compounds, 9b, 9c, 9d, 9o, 9q and 9u displayed more effective activity than the standard drug, bupropion. The provided SAR data and potent biological activity can offer useful guidelines for designing dual norepinephrine and dopamine reuptake inhibitors as effective therapeutic agents for treatment of several central nervous system diseases.

Design, synthesis, and biological evaluation of arylpiperazine–benzylpiperidines with dual serotonin and norepinephrine reuptake inhibitory activities

The limitations of established serotonin (5-hydroxytryptamine, 5-HT) and norepinephrine (NE) reuptake inhibitors necessitate the development of safer and more effective therapeutic agents. Based on the structures of 4-benzylpiperidine carboxamides and trazodone, arylpiperazine-benzylpiperidines with chemical scaffolds different from those of marketed drugs were designed, synthesized, and evaluated for their neurotransmitter reuptake inhibitory activities. The majority of the synthesized compounds showed greater NE than 5-HT reuptake inhibition. The activities were even greater than those of the standard drug, venlafaxine hydrochloride were. The derivatives with a three-carbon linker showed better activities than the derivatives with a two-carbon linker. Among the newly synthesized compounds, 2d exhibited the strongest reuptake inhibition of the neurotransmitters (IC50=0.38 μM for NE and 1.18 μM for 5-HT). The biological activity data demonstrate that arylpiperazine-benzylpiperidines have the potential to be developed as a new class of therapeutic agents to treat neuropsychiatric and neurodegenerative disorders.

Design, synthesis and in vitro activity of 1,4-disubstituted piperazines and piperidines as triple reuptake inhibitors

Monoamine transporters regulate the concentration of monoamine neurotransmitters, which are essential for vital physiological processes, and their dysfunction can cause several central nervous system diseases. Monoamine transporters currently appear to be the potential target in the management of these disorders. In this study, homologation and bioisosterism techniques have been used in the designing of new 1,4-disubstituted piperazines and piperidines. These derivatives were synthesized and evaluated as potential triple reuptake inhibitors for studying the structure-activity relationships. The most advanced compound, 1-(4-(5-benzhydryl-1H-tetrazol-1-yl)butyl)-4-(3-phenylpropyl)piperazine (2i), was able to inhibit monoamine neurotransmitter reuptake in an in vitro test (IC50=158.7nM for 5-HT, 99nM for NE and 97.5nM for DA). These novel potent triple reuptake inhibitor-based 1,4-disubstituted piperazine and piperidine scaffolds deserve further systematic optimization and pharmacological evaluation.

Synthesis and evaluation of arylpiperazine-reverse amides as biased dopamine D3 receptor ligands.

The dopamine D3 receptor (D3R) preferential ligands have been universally adopted as a strategy for the treatment of drug addiction and other neuropsychiatric disorders due to fewer side effects. However, the high sequence homology between D3R and the D2 receptor (D2R) challenges the development of D3R-biased compounds. Herein, we design and synthesize a novel series of reverse amide-piperazine hybrid ligands and evaluate their biological affinities in vitro. Compound 4d was found to be the most potent D3R-selective ligand among these hybrid derivatives. Molecular modeling revealed that extracellular loop 1 (EL1) and loop 2 (EL2) of D3R together likely contribute to D3R selectivity over D2R. In particular, Gly94 in EL1 of D3R may act as a molecular determinant for D3R specificity.

Antidiabetic effect of SN158 through PPARα/γ dual activation in ob/ob mice

In this study, we aimed to demonstrate the antidiabetic potential of (E)-N-(4-(3-(5-bromo-4-hydroxy-2-methoxyphenyl)acryloyl) phenyl)-4-tert-butylbenzamide (SN158) through peroxisome proliferator-activated receptor (PPAR)-α/γ dual activation. SN158 interacted with both PPARα and PPARγ, and increased their transcriptional activities. Simultaneously, SN158 treatment led to an increase in adipogenic differentiation of 3T3-L1 preadipocytes and fatty acid oxidation in hepatocytes. In addition, glucose uptake in myotubes was significantly increased by SN158 treatment. Finally, SN158 significantly lowered the plasma levels of glucose, triglycerides, and free fatty acids in ob/ob mice without severe weight gain and hepatomegaly. These results suggest that SN158 can be useful as a potential therapeutic agent against type 2 diabetes and related metabolic disorders by alleviating glucose and lipid abnormalities.

Triple reuptake inhibitors: Design, synthesis and structure–activity relationship of benzylpiperidine–tetrazoles

Monoamine transporters are important targets in the treatment of various central nervous disorders. Several limitations of traditional reuptake inhibitors, like delayed onset of action, insomnia, and sexual dysfunction, have compelled the search for safer, more effective compounds. In this study, we have sought to identify novel monoamine reuptake inhibitors. Based upon the docking study of compounds that we had reported previously, aromatic rings (A1) were modified to generate a novel series of benzylpiperidine-tetrazoles. Thirty-one compounds were synthesized and evaluated for their triple reuptake inhibition of serotonin, norepinephrine and dopamine. Triple reuptake inhibitor, compound 2q, in particular, showed potent serotonin reuptake inhibition, validating our design approach.

Design, synthesis and docking study of 4-arylpiperazine carboxamides as monoamine neurotransmitters reuptake inhibitors

Rational drug design method has been used to generate 4-arylpiperazine carboxamides in an effort to develop safer, more potent and effective monoamine neurotransmitters reuptake inhibitors. Out of twenty-seven synthesized compounds, compound 9 displayed potent monoamine neurotransmitter reuptake inhibitory activity against HEK cells transfected with hSERT or hNET. A Surflex-Dock docking model of 9 was also studied.

Design, synthesis, and systematic evaluation of 4-arylpiperazine- and 4-benzylpiperidine napthyl ethers as inhibitors of monoamine neurotransmitters reuptake

Two series of 4-arylpiperazine- and 4-benzylpiperidine naphthyl ethers were designed based on structure-activity relationship (SAR) and docking model of reported monoamine neurotransmitters reuptake inhibitors. The compounds were synthesized in 3-simple steps and their biological activities were evaluated. Several compounds were proven to be potent inhibitors of serotonin and norepinephrine reuptake. Computer docking was performed to study the interaction of the most potent compound 35 with human serotonin transporter. The results of the analyses suggest that 4-arylpiperazine- and 4-benzylpiperidine naphthyl ethers might be promising antidepressants worthy of further studies.