The Antiviral and Antimalarial Drug Repurposing in Quest of Chemotherapeutics to Combat COVID-19 Utilizing Structure-Based Molecular Docking.

BACKGROUND: The novel coronavirus disease (COVID-19) is caused by a new strain (SARS-CoV-2) that erupted in 2019. Nowadays, it is a great threat that claims uncountable lives worldwide. There is no specific chemotherapeutics developed yet to combat COVID-19. Therefore, scientists have been devoted to the quest of the medicine that can cure COVID-19. OBJECTIVE: Existing antivirals, such as ASC09/ritonavir, lopinavir/ritonavir with or without umifenovir in combination with antimalarial chloroquine or hydroxychloroquine, have been repurposed to fight the current coronavirus epidemic. Exact biochemical mechanisms of these drugs towards COVID-19 have not been discovered to date. METHODS: In-silico molecular docking can predict the mode of binding to sort out the existing chemotherapeutics having a potential affinity towards inhibition of the COVID-19 target. An attempt has been made in the present work to carry out docking analyses of 34 drugs, including antivirals and antimalarials, to explain explicitly the mode of interactions of these ligands towards the COVID-19protease target. RESULTS: 13 compounds having good binding affinity have been predicted towards protease binding inhibition of COVID-19. CONCLUSION: Our in silico docking results have been confirmed by current reports from clinical settings through the citation of suitable experimental in vitro data available in the published literature.

Potential Inhibitors of Protein Tyrosine Phosphatase (PTP1B) Enzyme: Promising Target for Type-II Diabetes Mellitus.

BACKGROUND: There has been growing interest in the development of highly potent and selective protein tyrosine phosphatase (PTP1B) inhibitors for the past 2-3 decades. Though most PTPs share a common active site motif, the interest in selective inhibitors, particularly against PTP1B is increasing to discover new chemical entities as antidiabetic agents. In the current paradigm to find potent and selective PTP1B inhibitors, which is currently considered as one of the best validated biological targets for non-insulin-dependent diabetic and obese individuals, resistance to insulin due to decreased sensitivity of the insulin receptor is a pathological factor and is also genetically linked, causing type II diabetes. OBJECTIVE: Insulin receptor sensitization is performed by a signal transduction mechanism via a selective protein tyrosine phosphatase (PTP1B). After the interaction of insulin with its receptor, autophosphorylation of the intracellular part of the receptor takes place, turning it into an active kinase (sensitization). PTP1B is involved in the desensitization of the receptor by dephosphorylation. PTP1b inhibitors delay the receptor desensitization, prolonging insulin effect and making PTP1B as a drug target for the treatment of diabetes II. Therefore, it has become a major target for the discovery of potent drugs for the treatment of type II diabetes and obesity. An attempt has been made in the present study to discuss the latest design and discovery of protein tyrosine phosphatase (PTP1B) inhibitors. METHODS: Many PTP1B inhibitors such as diaminopyrroloquinazoline, triazines, pyrimido triazine derivatives, 2-(benzylamino)-1-phenylethanol, urea, acetamides and piperazinylpropanols, phenylsulphonamides and phenylcarboxamide, benzamido, arylcarboxylic acid derivatives, arylsupfonyl derivatives, thiazoles, isothiozolidiones and thiazolodinones have been discussed, citing the disease mechanisms. RESULTS: The reader will gain an overview of the structure and biological activity of recently developed PTPs inhibitors. CONCLUSION: The co-crystallized ligands and the screened inhibitors could be used as a template for the further design of potent congeners.

Recent Breakthroughs in Various Antimicrobial Resistance Induced Quorum Sensing Biosynthetic Pathway Mediated Targets and Design of their Inhibitors.

OBJECTIVE: The world is under the grasp of dangerous post-antibiotics and antimicrobials attack where common infections may become untreatable, leading to premature deaths due to antimicrobial resistance (AMR). While an estimated 7,00,000 people die annually due to AMR, which is a public health threat to all communities in different parts of the world regardless of their economic status; however, this threat is serious in low- and middle-income countries having lack of sanitation and health infrastructure. The 68th World Health Assembly endorsed the Global Action Plan on antimicrobial resistance. Consequently, many countries started drafting and committing to National Action Plans against AMR. As strong as National Action Plans are in terms of prescribing rational use of antimicrobials, infection control practices, and related public health measures, without strong healthcare systems, these measures will have a limited impact on AMR in developing countries. METHODS: The major reason for AMR is microbial quorum sensing (QS) that may strengthen the microbial community to generate inter-communication and virulence effects via quorum sensing mechanisms. Global stewardship to combat antimicrobial resistance aims to develop anti-quorum sensing compounds that can inhibit the biosynthetic pathway mediated different quorum sensing targets. RESULTS: It may pave an effective attempt to minimize microbial quorum sensing mediated antimicrobial resistance. The present review describes QS mediated various potential target enzymes, their connection to AMR, and finds out the corresponding QS biosynthetic target inhibitors. CONCLUSION: These potential inhibitors can be derivatized to design and develop next-generation antimicrobial agents.

Synthesis, SAR and docking studies of substituted aryl phenylthiazolyl phenylcarboxamide as potential protein tyrosine phosphatase 1B (PTP1B) inhibitors.

In our continued effort to discover novel PTP1B inhibitor with improved in vivo activity, we attempted to optimize our previously discovered lead compound by replacing the sulfonyl group with benzoyl group to yield compound II. Additional structural modifications were performed on compound II to yield a series of 24 aryl phenylthiazolyl phenylcarboxamides as potential PTP1B inhibitors. Of the 24 tested, 6 compounds showed good PTP1B inhibitory activity while compound 38 as the most promising one. The plausible PTP1B-binding site interaction of compound 38 showed favourable binding similar to known PTP1B binders and suggests its selectivity towards PTP1B. Compound 38 also showed promising antihyperglycaemic, antidyslipidaemic and insulin resistant reversal activities in vivo in STZ model and db/db mice model. Altogether, the compound 38 presents an excellent candidate for future PTP1B targeted drug discovery.

Target Enzyme in Alzheimer's Disease: Acetylcholinesterase Inhibitors.

Alzheimer's Disease (AD), affecting a large population worldwide is characterized by the loss of memory and learning ability in the old population. The enzyme Acetylcholinesterase Enzyme (AChE) is the key enzyme in the hydrolysis of the neurotransmitter acetylcholine and is also the target of most of the clinically used drugs for the treatment of AD but these drugs provide only symptomatic treatment and have the limitation of loss of therapeutic efficacy with time. The development of different strategies targeting the AChE enzyme along with other targets like Butyl Cholinesterase (BChE), amyloid-ß (Aß), ß-secretase-1 (BACE), metals antioxidant properties and free radical scavenging capacity has been focused in recent years. Literature search was conducted for the molecules and their rational design which have shown inhibition for AChE and the other abovementioned targets. Several hybrid molecules incorporating the main sub-structures derived from diverse chemotypes like acridine, quinoline, carbamates, and other heterocyclic analogs have shown desired pharmacological activity with a good profile in a single molecule. It is followed by optimization of the activity through structural modifications guided by structure-activity relationship studies. It has led to the discovery of novel molecules 17b, 20, and 23 with desired AChE inhibition along with desirable activity against other abovementioned targets for further pre-clinical studies.

Identification of Therapeutically Active Molecules against Anthrax through Structure and Ligand based Drug Design.

BACKGROUND: People suffer from fatal diseases which are responsible for mortality. Potent devices and medicines are being developed to fight diseases caused by the microorganism for saving the lives of individuals. Highly pathogenic viruses and bacteria are being incorporated into biological warfare, which has become a major threat to mankind and causes the destruction of lives in a short span of time. OBJECTIVE: The pathogen Bacillus anthracis, which is the causative of anthrax, is used in bioterrorism. Efforts are therefore being made to study the progress of biodefense drug discovery research in combating anthrax-based bioterrorism. METHODS: This review describes the present status of the studies ontherapeutic measurement of anthrax toxin inhibitors towards inhibition of protective antigen, lethal and edema factors using chemometric and drug design tools to explore essential structural features for further design of active congeneric compounds. RESULTS: The inhibitors estimated to show high activity through different models may be proposed for further synthesis and testing of biological activity in terms of anthrax toxin inhibition and cytotoxicity testing by in vitro and in vivo assays. CONCLUSION: Such an attempt is an insight of biodefense drug design against the dreadful threat to the nation due to anthrax-based terrorism and biological warfare.

Lipid Lowering Oxopropanylindole Hydrazone Derivatives with Antioxidant and Anti-hyperglycemic Activity.

A series of substituted oxopropanylindole hydrazone derivatives was synthesized and evaluated for anti-oxidant and anti-dyslipidemic activity. Of the 12 tested, 3 compounds (6c, 7b and 7d) showed good anti-oxidant activity, compound 6c attenuated LDL oxidation by 32%. The compounds 6c and 7d also showed good anti-dyslipidemic activity by reducing serum levels of total cholesterol (TC), phospholipids (PL) and triglycerides (TG). These two compounds were further evaluated for antiadipogenic and anti-hyperglycemic activity, where 6c showed 44% reduction in lipid accumulation and 20.5% and 24.3% reduction in blood glucose at 5h and 24h respectively, as compared to standard drug metformin. Thus, compounds 6c and 7d with balanced anti-oxidant and anti-dyslipidimic activities may be excellent candidates for lead optimization and drug development for the treatment of metabolic disorders.

Synthesis of primaquine glyco-conjugates as potential tissue schizontocidal antimalarial agents.

Primaquine (PQ) is the only drug used to prevent relapse of malaria due to P. vivax and P. ovale, by eradicating the dormant liver form of the parasite (hypnozoites). The side-effects associated with PQ limits is uses in treatment of malaria. To overcome the premature oxidative deamination and to increase the life span of drug in the biological system, the novel glyco-conjugates of PQ were synthesized by coupling of primaquine with hexoses in phosphate buffer. The saccharide part of the hybrid molecules thought to direct the drug to the liver, where hypnozoites resides. All the synthesized compounds were fully characterized and evaluated for their radical curative activities. The three compounds viz glucoside (15a), galactoside (15b) and mannoside (15c) with high activity were tested for their activity in rhesus monkeys where the most active compound 15b showed twofold activity (100% radical curative activity at 1.92 mmol/kg) than the standard drug PQ diphosphate (3.861 mmol/kg). It is proposed that results from these studies may be advantageous to develop a new potent tissue schizonticide antimalarial compound.

Identification of novel amino acid derived CCK-2R antagonists as potential antiulcer agent: homology modeling, design, synthesis, and pharmacology.

The present study revisited the three-dimensional (3D) homology model of CCK-2R using human A(2a) adenosine receptor and the resolved NMR based structure of the third extracellular loop of the CCK-2R as templates. Further in order to identify novel antiulcer agents, rational designing have been performed utilizing the substructure of a well-known CCK-2R antagonist benzotript as a lead molecule and submitted to the combined docking and simulation studies. This led to the understanding of the essential structure requirement as well as variation of binding mode among conformational isomers of small molecule CCK-2R antagonists. In the next step, preparation of each configurational isomer of these molecules was carried out and submitted for their in vitro activity followed by in vivo screening into antiulcer rat model. The biological screening of these compounds has not only validated the developed homology model of CCK-2R but also led to the identification of highly potent CCK-2R antagonist 6a as an orally active and safe candidate molecule having better antiulcer properties than the well-known drug benzotript.

Integrated ligand and structure based studies of flavonoids as fatty acid biosynthesis inhibitors of Plasmodium falciparum.

A common feature pharmacophore with two hydrogen-bond acceptor and one aromatic hydrophobic feature has been generated using seven active flavonoids. Docking studies of these compounds well corroborates with the pharmacophore model. Therefore models could be useful for identification of potential novel FAS-II inhibitors.

Synthesis and QSAR studies on hypotensive 1-[3-(4-substituted phenylthio) propyl]-4-(substituted phenyl) piperazines.

A series of 1-[3-(4-substituted phenylthio) propyl]-4-(substituted phenyl) piperazines has been synthesized and evaluated for hypotensive activity. The QSAR studies indicate that resonance and hydrophobic parameters of the aryl substituents are important for hypotensive activity. The similar role of resonance parameter in describing the variance of 5-HT(2A) receptor binding affinities of these compounds suggests a possible role of 5-HT(2A) receptors in mediating the hypotensive action of title compounds.

Synthesis of some substituted pyrazinopyridoindoles and 3D QSAR studies along with related compounds: piperazines, piperidines, pyrazinoisoquinolines, and diphenhydramine, and its semi-rigid analogs as antihistamines (H1).

3D QSAR studies on the title compounds led to the development of a model with three biophoric sites and six secondary sites viz. H-acceptor (ACC), H-donor (DON), heteroatom (presence), hydrophobic (hydrophobicity), steric (refractivity), and a ring (presence) along with total hydrophobicity and total refractivity as global properties. The model predicted the test set of compounds reasonably well. Three of the five newly synthesized 2-substituted octahydropyrazinopyridoindoles have shown potent antihistaminic H(1) activity with less toxicity and sedation potential.

QSAR studies in substituted 1,2,3,4,6,7,12,12a-octa-hydropyrazino[2',1':6,1]pyrido[3,4-b]indoles--a potent class of neuroleptics.

A series of nineteen substituted 1,2,3,4,6,7,12,12a-octahydropyrazino[2',1':6,1]pyrido[3, 4-b]indoles analogues of neuroleptic drug, Centbutindole have been studied using quantitative structure-activity relationship analysis. The derived models display good fits to the experimental data (r>or=0.75) having good predictive power (r(cv)>or=0.688). The best model describes a high correlation between predicted and experimental activity data (r=0.967). Statistical analysis of the equation populations indicates that hydrophobicity (as measured by pi(R), logP(o/w) and SlogP_VSA8), dipole y and structural parameters in terms of indicator variable, (In(1)) and globularity are important variables in describing the variation in the neuroleptic activity in the series.