In Silico and In Vitro Methods in the Characterization of Beta-Carotene as Pharmaceutical Material via Acetylcholine Esterase Inhibitory Actions.

Molecular docking is widely used in the assessment of the therapeutic potential of pharmaceutical agents. The binding properties of beta-carotene (BC) to acetylcholine esterase (AChE) proteins were characterized using the molecular docking method. The mechanism of AChE inhibition was assessed by an experimental in vitro kinetic study. In addition, the role of BC action was tested by the zebrafish embryo toxicity test (ZFET). The results of the docking ability of BC to AChE showed significant ligand binding mode. The kinetic parameter, i.e., the low AICc value shown as the compound was the competitive type of inhibition of AChE. Further, BC also showed mild toxicity at a higher dose (2200 mg/L) in ZFET assessment with changes in biomarkers. The LC50 value of BC is 1811.94 mg/L. Acetylcholine esterase (AChE) plays a pivotal role in the hydrolysis of acetylcholine, which leads to the development of cognitive dysfunction. BC possesses the regulation of acetylcholine esterase (AChE) and acid phosphatase (AP) activity to prevent neurovascular dysfunction. Therefore, the characterization of BC could be used as a pharmaceutical agent for the treatment of cholinergic neurotoxicity-associated neurovascular disorders such as developmental toxicity, vascular dementia, and Alzheimer's disease due to its AChE and AP inhibitory actions.

Therapeutic Investigation of Palm Oil Mill Effluent-Derived Beta-Carotene in Streptozotocin-Induced Diabetic Retinopathy via the Regulation of Blood-Retina Barrier Functions.

Diabetic retinopathy (DR) primarily progresses into retinal degeneration caused by microvascular dysfunction. The pathophysiology of DR progression is still uncertain. This study investigates the function of beta-carotene (PBC) originating from palm oil mill effluent in the treatment of diabetes in mice. An intraperitoneal injection of streptozotocin (35 mg/kg) was used to induce diabetes, which was then accelerated by an intravitreal (i.vit.) injection of STZ (20 µL on day 7). PBC (50 and 100 mg/kg) and dexamethasone (DEX: 10 mg/kg) were also administered orally (p.o.) for 21 days. At various time intervals, the optomotor response (OMR) and visual-cue function test (VCFT) responses were evaluated. Biomarkers, such as reduced glutathione (GSH), thiobarbituric acid reactive substances (TBARSs), and catalase activity were determined in retinal tissue samples. DR significantly lowers the spatial frequency threshold (SFT) and time spent in the target quadrant (TSTQ), increases the reaching time in the visual-cue platform (RVCP), lowers retinal GSH and catalase activity levels, and elevates TBARS levels. The treatments of PBC and DEX also ameliorate STZ-induced DR alterations. The potential ameliorative activity of PBC in DR is attributed to its anti-diabetic, anti-oxidative, and control of blood-retinal barrier layer properties.

Peptides-based therapeutics: Emerging potential therapeutic agents for COVID-19.

SARS-CoV-2 is a positive-sense RNA virus and it is the causative agent of the global COVID-19 outbreak. COVID-19 is similar to the previous outbreaks for instance SARS in 2002-2003 and MERS in 2012. As the peptides have many advantages, peptide-based therapeutics might be one of the possible ways in the development of COVID-19 specific drugs. SARS-CoV-2 enters into a human via its S protein by attaching with human hACE2 present on the cell membrane in the lungs and intestines of humans. hACE2 cleaves S protein into the S1 subunit for viral attachment and the S2 subunit for fusion with the host cell membrane. The fusion mechanism forms a six-helical bundle (6-HB) structure which finally fuses the viral envelope with the host cell membrane. hACE2 based peptides such as SBP1 and Spikeplug have shown their potential as antiviral agents. S protein-hACE2 interaction and the SARS-CoV-2 fusion machinery play a crucial part in human viral infection. It is evident that if these interactions could be blocked successfully and efficiently, it could be the way to find the drug for COVID-19. Several peptide-based inhibitors are potent inhibitors of S protein-hACE2 interaction. Similarly, the antiviral activity of the antimicrobial peptide, lactoferrin makes it an important candidate for the COVID-19 drug development process. A candidate drug, RhACE2-APN01 based on recombinant hACE2 peptide has already entered phase II clinical trials. This review sheds light on different aspects of the feasibility of using peptide-based therapeutics as the promising therapeutic route for COVID-19.

Physiological and Pathophysiological Role of Cysteine Metabolism in Human Metabolic Syndrome.

Cysteine is one of the major intermediate products of cellular amino-acid metabolism. It is a semi-essential amino acid for protein synthesis. Besides, it is also employed in the regulation of major endogenous anti-oxidant molecule i.e., reduced glutathione (GSH). Further, it is a precursor of multiple sulfur-containing molecules like hydrogen sulfide, lanthionine, taurine, coenzyme A and biotin. It is also one of the key molecules for post-translational modifications of various cellular proteins. In physiological conditions, it is employed in the sulfhydration process and plays a key role in the physiology modification of the inflammatory process in various organs, including the neurological system. The catabolism of cysteine is regulated by cysteine dioxygenase enzyme activity. The dysregulated conditions of cysteine and cysteine-associated hydrogen sulfide metabolism are widely employed in the acceleration of the neurodegenerative process. Moreover, the upregulation of cysteine and hydrogen sulfide synthesis occurs via the reverse trans-sulfuration process. This process helps to manage the worsening of a pathological condition of a cellular system. Moreover, it is also employed in the accumulation of homocysteine contents. Further, both cysteine and homocysteine molecules are widely accepted as biomarkers for various types of diseases. Therefore, the targets involved in the regulation of cysteine have been considered as valid targets to treat various disorders like cardiac disease, ischemic stroke, diabetes, cancer, and renal dysfunction.

Computer-Aided Drug Discovery (CADD) Approaches for the Management of Neuropathic Pain.

Neuropathic pain occurs due to physical damage, injury, or dysfunction of neuronal fibers. The pathophysiology of neuropathic pain is too complex. Therefore, an accurate and reliable prediction of the appropriate hits/ligands for the treatment of neuropathic pain is a challenging process. However, computer-aided drug discovery approaches contributed significantly to discovering newer hits/ligands for the treatment of neuropathic pain. The computational approaches like homology modeling, induced-fit molecular docking, structure-activity relationships, metadynamics, and virtual screening were cited in the literature for the identification of potential hit molecules against neuropathic pain. These hit molecules act as inducible nitric oxide synthase inhibitors, FLAT antagonists, TRPA1 modulators, voltage-gated sodium channel binder, cannabinoid receptor-2 agonists, sigma-1 receptor antagonists, etc. Sigma-1 receptor is a distinct type of opioid receptor and several patents were obtained for sigma-1 receptor antagonists for the treatment of neuropathic pain. These molecules were found to have a profound role in the management of neuropathic pain. The present review describes the validated therapeutic targets, potential chemical scaffolds, and crucial protein-ligand interactions for the management of neuropathic pain based on the recently reported computational methodologies of the present and past decades. The study can help the researcher to discover newer drugs/drug-like molecules against neuropathic pain.

Current Perspectives of Healthy Mitochondrial Function for Healthy Neurons.

The neuron is high-energy utilizing tissue. The rate of neuronal cell respiration is higher than in other cells. Cellular respiration occurs with mitochondria. The healthy production and functions of mitochondria play a key role in the maintenance of healthy neurons. In pathological conditions such as neurodegenerative diseases, healthy mitochondria help to alleviate pathological events in neuronal cells. Conversely, mitochondrial dysfunction promotes the acceleration of the neurodegenerative process. Furthermore, glial-derived mitochondria contribute to multiple roles in the regulation of healthy neuron functions. It also supports releasing of the neurotransmitters; generation of the impulses, regulation of the membrane potential and molecular dynamics; controlling of the axonal transport; controlling of the mitochondrial fission and fusion functions in the peripheral as well as the central nervous system. Moreover, it plays a key role in the regeneration process of neuronal cells. Therefore, healthy mitochondria can provide a healthy environment for neuronal cell function and can treat neurodegenerative disorders. In this review, we explore the current view of healthy mitochondria and their role in healthy neuronal functions.

Induction of Caspase-Mediated Apoptosis in HepG2 Liver Carcinoma Cells Using Mutagen-Antioxidant Conjugated Self-Assembled Novel Carbazole Nanoparticles and In Silico Modeling Studies.

In this study, novel self-assembled carbazole-thiooctanoic acid nanoparticles (CTNs) were synthesized from amino carbazole (a mutagen) and thiooctanoic acid (an antioxidant). The nanoparticles were characterized using hyperspectral techniques. Then, the antiproliferative potential of CTNs was determined in HepG2 liver carcinoma cells. This study employed a solvent-antisolvent interaction method to synthesize a spherical CTN of size less than 50 nm. Moreover, CT was subsequently capped to gold nanoparticles (AuNPs) in the additional comparative studies. The CT derivative was synthesized from carbazole and lipoic acid by the amide bond formation reaction using a coupling agent. Furthermore, it was characterized using infrared (IR), 1H nuclear magnetic resonance, dynamic light scattering (DLS), and transmission electron microscopy techniques. The CT-capped gold nanoparticles (CTAuNPs) were prepared from CT, chloroauric acid, and NaBH4. The CTAuNPs were characterized using ultraviolet-visible, high-resolution TEM, DLS, and Fourier transform IR techniques. The cytotoxicity and apoptosis-inducing ability of both nanoparticles were determined in HepG2 cells. The results demonstrate that CTNs exhibit antiproliferative activity in the cancerous HepG2 cells. Moreover, molecular docking and molecular dynamics studies were conducted to explore the therapeutic potential of CT against human EGFR suppressor protein to gain more insights into the binding mode of the CT, which may show a significant role in anticancer therapy.

Quantitative Structure-Activity Relationship (QSAR) Studies for the Inhibition of MAOs.

Monoamine oxidases are the crucial drug targets for the treatment of neurodegenerative disorders like depression, Parkinson's disease, and Alzheimer's disease. The enzymes catalyze the oxidative deamination of several monoamine containing neurotransmitters, i.e. serotonin (5-HT), melatonin, epinephrine, norepinephrine, phenylethylamine, benzylamine, dopamine, tyramine, etc. The oxidative reaction of monoamine oxidases results in the production of hydrogen peroxide that leads to the neurodegeneration process. Therefore, the inhibition of monoamine oxidases has shown a profound effect against neurodegenerative diseases. At present, the design and development of newer lead molecules for the inhibition of monoamine oxidases are under intensive research in the field of medicinal chemistry. Recently, the advancement in QSAR methodologies has shown considerable interest in the development of monoamine oxidase inhibitors. The present review describes the development of QSAR methodologies, and their role in the design of newer monoamine oxidase inhibitors. It will assist the medicinal chemist in the identification of selective and potent monoamine oxidase inhibitors from various chemical scaffolds.

Formation of a Toxic Quinoneimine Metabolite from Diclofenac: A Quantum Chemical Study.

BACKGROUND: Diclofenac is a non-steroidal antiinflammatory drug. It is predominantly metabolized by CYP2C9. 4'-hydroxydiclofenac and its quinoneimine are the metabolites of diclofenac. However, few numbers of serious cases of idiosyncratic hepatotoxicity due to diclofenac metabolism were reported. The formation of the quinoneimine metabolite was found to be responsible for this idiosyncratic toxicity. Quinoneimine is an over-oxidized metabolite of diclofenac. METHOD: In this work, computational studies were conducted to detail the formation of a quinoneimine metabolite from diclofenac. Further, the idiosyncratic toxicity of quinoneimine due to its reactivity was also investigated by quantum chemical analysis. RESULTS & CONCLUSION: The results demonstrate the possibility of formation of quinoneimine metabolite due to various factors that are involved in the metabolism of diclofenac. The present study may provide the structural in-sights during the drug development processes to avoid the metabolism directed idiosyncratic toxicity.

Ligand- and structure-based in silico studies to identify kinesin spindle protein (KSP) inhibitors as potential anticancer agents.

Kinesin spindle protein (KSP) belongs to the kinesin superfamily of microtubule-based motor proteins. KSP is responsible for the establishment of the bipolar mitotic spindle which mediates cell division. Inhibition of KSP expedites the blockade of the normal cell cycle during mitosis through the generation of monoastral MT arrays that finally cause apoptotic cell death. As KSP is highly expressed in proliferating/cancer cells, it has gained considerable attention as a potential drug target for cancer chemotherapy. Therefore, this study envisaged to design novel KSP inhibitors by employing computational techniques/tools such as pharmacophore modelling, virtual database screening, molecular docking and molecular dynamics. Initially, the pharmacophore models were generated from the data-set of highly potent KSP inhibitors and the pharmacophore models were validated against in house test set ligands. The validated pharmacophore model was then taken for database screening (Maybridge and ChemBridge) to yield hits, which were further filtered for their drug-likeliness. The potential hits retrieved from virtual database screening were docked using CDOCKER to identify the ligand binding landscape. The top-ranked hits obtained from molecular docking were progressed to molecular dynamics (AMBER) simulations to deduce the ligand binding affinity. This study identified MB-41570 and CB-10358 as potential hits and evaluated these experimentally using in vitro KSP ATPase inhibition assays.

Sequence, Structural Analysis and Metrics to Define the Unique Dynamic Features of the Flap Regions Among Aspartic Proteases.

Aspartic proteases are a class of hydrolytic enzymes that have been implicated in a number of diseases such as HIV, malaria, cancer and Alzheimer's. The flap region of aspartic proteases is a characteristic unique structural feature of these enzymes; and found to have a profound impact on protein overall structure, function and dynamics. Flap dynamics also plays a crucial role in drug binding and drug resistance. Therefore, understanding the structure and dynamic behavior of this flap regions is crucial in the design of potent and selective inhibitors against aspartic proteases. Defining metrics that can describe the flap motion/dynamics has been a challenging topic in literature. This review is the first attempt to compile comprehensive information on sequence, structure, motion and metrics used to assess the dynamics of the flap region of different aspartic proteases in "one pot". We believe that this review would be of critical importance to the researchers from different scientific domains.

Therapeutic, Molecular and Computational Aspects of Novel Monoamine Oxidase (MAO) Inhibitors.

Background Due to the limited number of MAO inhibitors in the clinics, several research efforts are aimed at the discovery of novel MAO inhibitors. At present, a high specificity and a reversible mode of inhibition of MAO-A/B are cited as desirable traits in drug discovery process. This will help to reduce the probability of causing target disruption and may increase the duration of action of drug. AIM: Most of the existing MAO inhibitors lead to side effects due to the lack of affinity and selectivity. Therefore, there is an urgent need to design novel, potent, reversible and selective inhibitors for MAO-A/B. Selective inhibition of MAO-A results in the elevated level of serotonin and noradrenaline. Hence, MAO-A inhibitors can be used for improving the symptoms of depression. The selective MAO-B inhibitors are used with L-DOPA and/or dopamine agonists in the symptomatic treatment of Parkinson's disease. The present study was aimed to describe the recently developed hits of MAO inhibitors. METHOD: At present, CADD techniques are gaining an attention in rationale drug discovery of MAO inhibitors, and several research groups employed CADD approaches on various chemical scaffolds to identify novel MAO inhibitors. These computational techniques assisted in the development of lead molecules with improved pharmacodynamics / pharmacokinetic properties toward MAOs. Further, CADD techniques provided a better understanding of structural aspects of molecular targets and lead molecules. CONCLUSIONS: The present review describes the importance of structural features of potential chemical scaffolds as well as the role of computational approaches like ligand docking, molecular dynamics, QSAR and pharmacophore modeling in the development of novel MAO inhibitors.

Identification of Binding Mode and Prospective Structural Features of Novel Nef Protein Inhibitors as Potential Anti-HIV Drugs.

Human immunodeficiency virus (HIV)-negative factor (Nef) protein is an accessory pathogenic factor, which plays a significant role in acquired immune deficiency syndrome (AIDS). Nef deficient HIV virus took a longer time to progress into AIDS. Therefore, targeting Nef protein is considered as a key strategy towards HIV/AIDS treatment. Up-to-date, only few compounds were reported as Nef inhibitors. This has prompted us to provide a first account of an integrated computational framework in order to identify more potential Nef inhibitors. Herein, using a hybrid ligand (shape similarity and pharmacophore) and structure-(molecular docking) based virtual screening approaches combined with molecular dynamics as well as post dynamics analysis, potential new hits were identified as HIV-Nef inhibitors. The top ranked compounds of molecular docking from the shape similarity-based library (ZINC04177596, ∆ G bind= -28.7482 kcal/mol) and pharmacophore-based library (ZINC36617540, ∆ G bind= -20.2271 kcal/mol) possess comparatively better binding affinities than the reference molecule, B9 (∆ G bind = -18.0694 kcal/mol). Both these hits (ZINC04177596 and ZINC36617540) showed similar binding mode at the binding site as like the prototype, B9. Hydrophobic and electrostatic interactions seemed to be the prominent binding forces that hold these ligands at the dimer interface of Nef protein. Finally, a set of chemical structural features that can be used as a guide in the design of novel potential Nef inhibitors is also highlighted herein. We believe that the information gained from this study would be of great importance in the discovery and design of potential small molecules targeting HIV-Nef.

Recent advancements in the development of anti-tuberculosis drugs.

Modern chemotherapy has significantly improved patient outcomes against drug-sensitive tuberculosis. However, the rapid emergence of drug-resistant tuberculosis, together with the bacterium's ability to persist and remain latent present a major public health challenge. To overcome this problem, research into novel anti-tuberculosis targets and drug candidates is thus of paramount importance. This review article provides an overview of tuberculosis highlighting the recent advances and tools that are employed in the field of anti-tuberculosis drug discovery. The predominant focus is on anti-tuberculosis agents that are currently in the pipeline, i.e. clinical trials.

Ischemic-reperfusion of unilateral external iliac artery in rat: A new model for vasculitic femoral neuropathy.

Clinically, ischemic environment during gynecological surgery at lithotomy position is most common causative factor for the development of vasculitic femoral neuropathy (VFN). The present study was designed to induce the clinically relevant rat model of VFN by ischemic-reperfusion (I/R) injury of unilateral external iliac artery (uEIA). The VFN was induced by 3, 4 and 5h occlusion of uEIA followed by reperfusion. The I/R of uEIA induced VFN was evaluated by (i) behavioral parameters i.e., hind limb temperature; weight bearing capacity; (ii) kinematic analysis i.e., paw posture, splay angle, static sciatic index (SSI), and ankle-angle tests; (iii) evaluation of pain perception i.e., plantar and pin prick; (iv) serum biochemical estimation i.e., nitrate, lipid peroxidation, TNF-α and calcium level; (v) evaluation of motor and sensory nerve conduction velocity; and (vi) measurement of nerve fiber density. The 4 and 5h occlusion of uEIA has produced the potential changes in behavioral, functional, electrophysiological, biochemical and histopathological assessment. The 5h occlusion of uEIA has shown to produce the mortality. Whereas, 3h occlusion does not produce the significant changes in the development of VFN. The 4h ischemic occlusion of uEIA has shown potential rat model of VFN due to its close mimicking capacity of VFN in human. Therefore, it can be useful to explore the newer anti-neuralgic medicine and with their pharmacodynamic action in the field of various neurovascular disorders.

Per-residue energy decomposition pharmacophore model to enhance virtual screening in drug discovery: a study for identification of reverse transcriptase inhibitors as potential anti-HIV agents.

A novel virtual screening approach is implemented herein, which is a further improvement of our previously published "target-bound pharmacophore modeling approach". The generated pharmacophore library is based only on highly contributing amino acid residues, instead of arbitrary pharmacophores, which are most commonly used in the conventional approaches in literature. Highly contributing amino acid residues were distinguished based on free binding energy contributions obtained from calculation from molecular dynamic (MD) simulations. To the best of our knowledge; this is the first attempt in the literature using such an approach; previous approaches have relied on the docking score to generate energy-based pharmacophore models. However, docking scores are reportedly unreliable. Thus, we present a model for a per-residue energy decomposition, constructed from MD simulation ensembles generating a more trustworthy pharmacophore model, which can be applied in drug discovery workflow. This work is aimed at introducing a more rational approach to the field of drug design, rather than comparing the validity of this approach against those previously reported. We recommend additional computational and experimental work to further validate this approach. This approach was used to screen for potential reverse transcriptase inhibitors using the pharmacophoric features of compound GSK952. The complex was subjected to docking, thereafter, MD simulation confirmed the stability of the system. Experimentally determined inhibitors with known HIV-reverse transcriptase inhibitory activity were used to validate the protocol. Two potential hits (ZINC46849657 and ZINC54359621) showed a significant potential with regard to free binding energy. Reported results obtained from this work confirm that this new approach is favorable in the future of the drug design industry.

γ-Cyclodextrin capped silver nanoparticles for molecular recognition and enhancement of antibacterial activity of chloramphenicol.

Computational studies were conducted to identify the favourable formation of the inclusion complex of chloramphenicol with cyclodextrins. The results of molecular docking and molecular dynamics predicted the strongest interaction of chloramphenicol with γ-cyclodextrin. Further, the inclusion complex of chloramphenicol with γ-cyclodextrin was experimentally prepared and a phenomenon of inclusion was verified by using different characterization techniques such as thermogravimetric analysis, differential scanning calorimetry, (1)H nuclear magnetic resonance (NMR) and two dimensional nuclear overhauser effect spectroscopy (NOESY) experiments. From these results it was concluded that γ-cyclodextrins could be an appropriate cyclodextrin polymer which can be used to functionalize chloramphenicol on the surface of silver nanoparticles. In addition, γ-cyclodextrin capped silver nanoparticles were synthesized and characterized using UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR) and zeta potential analysis. Molecular recognition of chloramphenicol by these cyclodextrin capped silver nanoparticles was confirmed by surface enhanced raman spectroscopy (SERS) experiments. Synergistic antibacterial effect of chloramphenicol with γ-cyclodextrin capped silver nanoparticles was evaluated against Pseudomonas aeruginosa (ATCC 27853), Enterococcus faecalis (ATCC 5129), Klebsiella pneumoniae (ATCC 700603) and Staphylococcus aureus (ATCC 43300). The results from the antibacterial experiment were favourable thus allowing us to conclude that the approach of modifying organic drug molecules with cyclodextrin capped inorganic silver nanoparticles could help to enhance the antibacterial activity of them.

In Silico Characterization of the Binding Affinity of Dendrimers to Penicillin-Binding Proteins (PBPs): Can PBPs be Potential Targets for Antibacterial Dendrimers?

We have shown that novel silver salts of poly (propyl ether) imine (PETIM) dendron and dendrimers developed in our group exhibit preferential antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus. This led us to examine whether molecular modeling methods could be used to identify the key structural design principles for a bioactive lead molecule, explore the mechanism of binding with biological targets, and explain their preferential antibacterial activity. The current article reports the conformational landscape as well as mechanism of binding of generation 1 PETIM dendron and dendrimers to penicillin-binding proteins (PBPs) in order to understand the antibacterial activity profiles of their silver salts. Molecular dynamics at different simulation protocols and conformational analysis were performed to elaborate on the conformational features of the studied dendrimers, as well as to create the initial structure for further binding studies. The results showed that for all compounds, there were no significant conformational changes due to variation in simulation conditions. Molecular docking calculations were performed to investigate the binding theme between the studied dendrimers and PBPs. Interestingly, in significant accordance with the experimental data, dendron and dendrimer with aliphatic cores were found to show higher activity against S. aureus than the dendrimer with an aromatic core. The latter showed higher activity against MRSA. The findings from this computational and molecular modeling report together with the experimental results serve as a road map toward designing more potent antibacterial dendrimers against resistant bacterial strains.

Self-association behavior of a novel nonproteinogenic ß-strand-mimic in an organic solvent.

The self-association behavior of a newly characterized ß-strand-mimic, presented by an achiral nonproteinogenic model system Boc-γ-Abz-NHMe (1: Boc = tert-butyloxycarbonyl; γ-Abz = γ-aminobenzoic acid; NHMe = N-methylamide), have been investigated using (1)H NMR and FT-IR absorption spectroscopy, in combination with computational ab initio calculations. The concentration dependence of (1)H NMR chemical shifts of the amide-NHs in CDCl3 exhibited noncooperative behavior of self-association, whereas the variable temperature (1)H NMR chemical shifts data of the amide-NHs, i.e., temperature-coefficient (Δδ/ΔT) values, could be accounted for by significant enhancement of self-association, i.e., aggregates higher than dimers. In the absence of N-H···O intramolecular H-bond in 1, the intense FT-IR absorption bands in informative amide-A region, i.e., N-H stretches at ∼3465 and 3438 cm(-1) in chloroform solution, could be interpreted in terms of intermolecular H-bonding. The ab initio quantum mechanical calculations performed on two discrete isolated antiparallel H-bonded duplexes with a face-to-face and an edge-to-edge aromatic-aromatic interaction provided strong support for their relative importance to stabilize favorable dimeric structures. The thermodynamic parameters deduced from van't Hoff plots, constructed from variable temperature (1)H NMR data of the amide-NHs in CDCl3, also substantiated the effectiveness of aromatic-aromatic interactions for dimer formation and higher-order self-association. In view of the enormous structural importance of ß-strand-like building blocks in peptide design, we highlight intrinsic self-associating potentials of the readily available γ-Abz moiety, besides the fact that such planar secondary structural mimics are presumed to offer greater prospective for constructing peptidomimetics and therapeutically relevant small molecules.

Drug therapy of neuropathic pain: current developments and future perspectives.

Understanding mechanism of neuropathic pain is too complex and involves both peripheral and central pathophysiological phenomenon. Accordingly the treatment of neuropathic pain is also very complex and is unsatisfactory. The present review attempts to discuss the currently employed pharmacological agents for the management of neuropathic pain including anti-depressants, anti-convulsants, NMDA receptor antagonists, topical & local anesthetics, and upload analgesics. However, the existing pharmacotherapy has marginal efficacy and significant side effects. The review also gives an insight into various pharmacological agents with potential neuropathic pain attenuating properties in experimental models that include NSAIDs, corticosteroids, ion channel blockers (Ca(2+), Na(+), K(+), and TRP channel); ion exchange modulators (NCE and NHE); ion/molecule transport modulators (NKCC-1 and glycine); receptor modulators (kinin, histamine, 5-HT1A, dopamine, alpha & beta adrenergic, purinergic, excitatory amino acid, sigma, ORL1, endothelin, melanocortin, ephrin and PAR); enzyme inhibitors (cytosolic kinase, metalloproteinase, protease, vasopeptidase, D-amino acid oxidase, fatty acid amide hydrolase, aldose reductase and sorbitol dehydrogenase); other ligands (AGE, RAGEs, neuropeptides, neurotrophic factor, complement cascade, cytokine, glial cell & gap junction, nitrous oxide, growth factor, cell adhesion molecule and neuronal sprouting molecule). Moreover, some advanced therapeutic approaches such as neuronal cell transplantation, stem cell therapy, anti-sense oligonucleotide and recombinant therapy have also been dicussed.