Medicinal Chemistry - Volume 18, Issue 2, 2022

Background: Leishmaniasis is a worldwide health problem, highly endemic in developing countries. Among the four main clinical forms of the disease, visceral leishmaniasis is the most severe, fatal in 95% of cases. The undesired side-effects from first-line chemotherapy and the reported drug resistance search for effective drugs that can replace or supplement those currently used in an urgent need. Aminoguanidine hydrazones (AGH's) have been explored for exhibiting a diverse spectrum of biological activities, in particular the antileishmanial activity of MGBG. The bioisosteres thiosemicarbazones (TSC's) offer a similar biological activity diversity, including antiprotozoal effects against Leishmania species and Trypanosoma cruzi. Objectives: Considering the impact of leishmaniasis worldwide, this work aimed to design, synthesize, and perform a screening upon L. chagasi amastigotes and for the cytotoxicity of the small "inhouse" library of both AGH and TSC derivatives and their structurally-related compounds. Methods: A set of AGH's (3-7), TSC's (9, 10), and semicarbazones (11) were initially synthesized. Subsequently, different semi-constrained analogs were designed and also prepared, including thiazolidines (12), dihydrothiazines (13), imidazolines (15), pyrimidines (16, 18) azines (19, 20), and benzotriazepinones (23-25). All intermediates and target compounds were obtained with satisfactory yields and exhibited spectral data consistent with their structures. All final compounds were evaluated against L. chagasi amastigotes and J774.A1 cell line. Molecular docking was performed towards trypanothione reductase using GOLD^® software. Results: The AGH's 3i, 4a, and 5d, and the TSC's 9i, 9k, and 9o were selected as valuable hits. These compounds presented antileishmanial activity compared with pentamidine, showing IC50 values ranged from 0.6 to 7.27 μM, maximal effects up to 55.3%, and satisfactory SI values (ranged from 11 to 87). On the other hand, most of the resulting semi-constrained analogs were found cytotoxic or presented reduced antileishmanial activity. In general, TSC class is more promising than its isosteric AGH analogs, and the beneficial aromatic substituent effects are not similar in both series. In silico studies have suggested that these hits are capable of inhibiting the trypanothione reductase from the amastigote forms. Conclusion: The promising antileishmanial activity of three AGH’s and three TSC’s was characterized. These compounds presented antileishmanial activity compared with PTD, showing IC50 values ranged from 0.6 to 7.27 μM, and satisfactory SI values. Further pharmacological assays involving other Leishmania strains are in progress, which will help choose the best hits for in vivo experiments.

Background: Aedes aegypti is the primary vector of dengue, a significant public health problem in many countries. Controlling of Ae. aegypti is the biggest challenge in the mosquito control programe, and there is a need for finding bioactive molecules to control Ae. aegypti in order to prevent dengue virus transmission. Objective: To assess the mosquitocidal property of lawsone and its 3-methyl-4H-chromen-3-yl-1- phenylbenzo[6,7]chromeno[2,3,c]pyrazole-dione derivatives (6a-6h) against various life stages of Ae. aegypti. Besides, to study the mode of action of the active compound by molecular docking and histopathological analysis. Methods: All derivatives were synthesized from the reaction between 2-hydroxy-1,4-naphthoquinone, chromene-3-carbaldehyde, and 1-phenyl-3-methyl-pyrazol-5-one by using one pot sequential multicomponent reaction. The mosquito life stages were subjected to diverse concentrations ranging from 1.25, 2.5, 5.0, and 10 ppm for lawsone and its derivatives. The structure of all synthesized compounds was characterized by spectroscopic analysis. Docking analysis was performed using autodock tools. Midgut sections of Ae. aegypti larvae were analyzed for histopathological effects. Results: Among the nine compounds screened, derivative 6e showed the highest mortality on Ae. aegypti life stages. The analyzed LC<50 and LC90 results of derivative 6e were 3.01, 5.87 ppm, and 3.41, 6.28 ppm on larvae and pupae of Ae. aegypti, respectively. In the ovicidal assay, the derivative 6e recorded 47.2% egg mortality after 96-hour post-exposure to 10 ppm concentration. In molecular docking analysis, the derivative 6e confirmed strong binding interaction (-9.09 kcal/mol and -10.17 kcal/mol) with VAL 60 and HIS 62 of acetylcholinesterase 1 (AChE1) model and LYS 255, LYS 263 of kynurenine aminotransferase of Ae. aegypti, respectively. The histopathological results showed that the derivative 6e affected the columnar epithelial cells (CC) and peritrophic membrane (pM). Conclusion: The derivative 6e is highly effective in the life stages of Ae. aegypti mosquito and it could be used in the integrated mosquito management programe.

Background: Synthesis of new heterocyclic drugs in short reaction time with sufficient quantity is considered as a target for several pharmaceutical scientists. Thus, organic reactions proceeded on the surface of nano-sized catalysts to speed up the stimulation process. Objective: We aimed in this research to synthesize a new series of heterocyclic compounds carrying pyrazole moiety in the presence of ZnO nano-catalyst to investigate their anti-tubercular activity. Methods: ZnO(NPs) were used in the synthesis of novel series of thienylpyrazolopyrimidines bearing arylazo group by the reaction of thiophene-enaminone and the amino-arylazopyrazoles in excellent yield. On the other hand, another series of theinyl-pyrazoles was synthesized through the reaction of the same enaminone with hydrazonoyl chlorides, but the usage of ZnO(NPs) failed in such reactions. Results: The proposed structures of the products and the mechanistic pathways of the reactions were assured based on the spectral data and chemical evidences. Thienylpyrazole derivatives were assessed for their activity as Mycobacterium tuberculosis inhibitor and their results revealed that two thienylpyrazole derivatives 24d & 24f showed the most significant anti-mycobacterial activity with MIC values 0.70 & 1.29 μM/mL, respectively comparing with the MIC value = 0.60 μM/mL of the standard drug Rifampicin. Furthermore, the most active thienylpyrazole derivatives were investigated for their cytotoxic impact versus normal cells WI-38 (Normal human Lung fibroblast cells) using MTT assay. These thienylpyrazole derivatives exhibited good selective index profile. Moreover, 1,3,4-trisubstituted pyrazole analogs showed good interaction with the active site of enoyl-acyl carrier protein reductase (Mt InhA) through molecular docking studies. Conclusion: We synthesized a new series of heterocyclic compounds carrying pyrazole moiety in the presence of ZnO nano-catalyst as anti-tubercular agents.

Background: Heterocyclic compounds display versatile biological applications, so the aim of this paper was to prepare biologically important heterocycles with enhanced bacterial resistance and to evaluate for their various structural features that are responsible for their biological properties. Objective: The objective was to synthesize bacterial resistance compounds with enhanced antibacterial properties. Methods: Ester moiety containing thiazole ring was converted into its hydrazide derivatives. These heterocyclic derivatives were cyclized into another ring oxadiazole; hence a hybrid ring system of two biologically active rings was prepared. Results: All the synthesized compounds were characterized by spectroscopic techniques and were screened for their antibacterial potential; they possess significant antibacterial activities. Conclusion: New hybrid heterocyclic ring systems were synthesized by cyclization of hydrazide derivatives by adopting two step strategy in good yields. All the synthesized compounds were evaluated for their antioxidant activities; they showed moderate to significant activities. QSAR and Molecular docking studies were performed to determine the mode of interaction. Experimental and computational data is in accordance with the determined antibacterial activities.

Objective: In this study, we describe the synthesis, docking study and biological evaluation of 1,2-benzothiazines 1,1-dioxide derivatives. Methods: Taking the well-known drug, Piroxicam as a lead compound, we designed and synthesized two series of 1,2-benzothiazines 1,1-dioxide derivatives to assay their ability in inhibition of HIV-1 replication in cell culture. Results: Most of the new compounds were active in the cell-based anti-HIV-1 assay with EC50 < 50 μM. Among them, compound 7g was found to be the most active molecule.Docking study using 3OYA pdb code on the most active molecule 7g with EC50 values of 10 μM showed a similar binding mode to the HIV integrase inhibitors. Conclusion: Since all the compounds showed no remarkable cytotoxicity (CC50> 500 μM), the designed scaffold is promising structure for the development of new anti-HIV-1 agents.

Background: The Covid-19 virus emerged a few months ago in China, and infections rapidly escalated into a pandemic. Objective: To date, there is no selective antiviral agent for the management of pathologies associated with covid-19 and the need for an effective agent against it is essential. Methods: In this work, two home-made databases from synthetic quinolines and coumarins were virtually docked against viral proteases (3CL and PL), human cell surface proteases (TMPRSS2 and furin) and spike proteins (S1 and S2). Chloroquine, a reference drug without a clear mechanism against coronavirus was also docked on mentioned targets and the binding affinities compared with title compounds. Results: The best compounds of synthetic coumarins and quinolines for each target were determined. All compounds against all targets showed binding affinity between -5.80 to -8.99 kcal/mol in comparison with the FDA-approved drug, Chloroquine, with binding affinity of -5.7 to -7.98 kcal/mol. Two compounds, quinoline-1 and coumarin-24, were found to be effective on three targets – S2, TMPRSS2 and furin – simultaneously, with good predicted affinity between -7.54 to -8.85 kcal/mol. In silico ADME studies also confirmed good oral absorption for them. Furthermore, PASS prediction was calculated and coumarin-24 had higher probable activity (Pa) than probable inactivity (Pi) with acceptable protease inhibitory as well as good antiviral activity against Hepatitis C virus (HCV), Human immunodeficiency virus (HIV) and influenza. Conclusion: Quinoline-1 and Coumarin-24 have the potential to be used against Covid-19. Hence these agents could be useful in combating covid-19 infection after further in vitro and in vivo studies.

Background: Thiobezimidazoles reveal various pharmacological activities due to similarities with many natural and synthetic molecules; they can easily interact with biomolecules of living systems. Objective: A series of substituted 2-thiobezimidazoles have been synthesized. Twelve final compounds were screened for in vitro anti-cancer activities against sixty different cell lines. Methods: The spectral data of the synthesized compounds were characterized. A docking study for active anticancer compounds and CDK2/CyclinA2 Kinase assay against standard reference; Imatinib, were performed. Results: Two compounds (3c&3l) from the examined series revealed effective antitumor activity in vitro against two-cancer cell lines (Colon Cancer (HCT-116) and Renal Cancer (TK-10). The docking study of synthesized molecules discovered a requisite binding pose in the CDK-ATP binding pocket .3c &3l were promoted in the CDK2/CyclinA2 Kinase assay against standard reference Imatinib. Conclusion: Against all tested compounds; two compounds 3c &3l were found active against two types of cell-lines.

Background: The progression of ovarian cancer seems to be related to HDAC1, HDAC3, and HDAC6 activity. A possible strategy for improving therapies for treating ovarian carcinoma, minimizing the preclinical screenings, is the repurposing of already approved pharmaceutical products as inhibitors of these enzymes. Objective: This work was aimed to implement a computational strategy for identifying new HDAC inhibitors for ovarian carcinoma treatment among approved drugs. Method: The CHEMBL database was used to construct training, test, and decoys sets for performing and validating HDAC1, HDAC3 and HDAC6 3D-QSAR models obtained by using the FLAP program. Docking and MD simulations were used in combination with the generated models to identify novel potential HDAC inhibitors. Cell viability assays and Western blot analyses were performed on normal and cancer cells for a direct evaluation of the anti-proliferative activity and an in vitro estimation of HDAC inhibition of the compounds selected through in silico screening. Result: The best quantitative prediction was obtained for the HDAC6 3D-QSAR model. The screening of approved drugs highlighted a new potential use as HDAC inhibitors for some compounds, in particular nitrofuran derivatives, usually known for their antibacterial activity and frequently used as antimicrobial adjuvant therapy in cancer treatment. Experimental evaluation of these derivatives highlighted a significant antiproliferative activity against cancer cell lines overexpressing HDAC6, and an increase in acetylated alpha-tubulin levels. Conclusion: Experimental results support the hypothesis of potential direct interaction of nitrofuran derivatives with HDACs. In addition to the possible repurposing of already approved drugs, this work suggests the nitro group as a new zinc-binding group, able to interact with the catalytic zinc ion of HDACs.

Background: Iminostilbene and 1,2,3-triazole ring containing compounds are considered as beneficial substrates in drug design. Objectives: This study was aimed at the synthesis of novel series of iminostilbene linked 1,2,3- triazole pharmacophores (7c-n) by Cu(I) catalyzed 1,3 dipolar cycloaddition reaction between 5- (Prop-2-yn-1-yl)-5H-dibenzo[b,f]azepine (7b) and various substituted azidobenzene derivatives (3cn). Methods: The chemical structures of compounds were confirmed by ¹H NMR, ¹³C NMR, LC-MS and molecular docking studies were carried out through HEX docking software. Results: The in vivo anti anxiety capacity of the compounds was evaluated by using “elevated plus maze” (EPM), anxiety model. The results exhibited that compounds (7d, 7e, 7j and 7k) have a higher anti anxiety effect close to diazepam. The anti-inflammatory activities of the synthesized compounds were evaluated by “Carrageenan-induced rat paw edema” model, compounds (7b, 7c, 7d, 7f, and 7j) demonstrated statistically significant inflammatory activity. Molecular docking analysis revealed that compounds (7d, 7e and 7j) bound to GABA(A) proteins show more efficiency when compared to the other analogues in the series. Conclusion: These results suggest that compounds (7b, 7c, 7d, 7e, 7f, and 7j) can be considered as novel candidates for anti-anxiety and anti-inflammatory agents. Moreover, docking method was used to elucidate anti-anxiety effect of compounds. This study furnished insight into the molecular interactions of synthesized compounds with their physiological targets, and the potential to develop bioactive heterocyclic compounds.

Aim: To synthesize and evaluate the fused heterocyclic imidazo[1,2-a]pyridine based oxime as a reactivator against paraoxon inhibited acetylcholinesterase. Background: Organophosphorus compounds (OPs) include parathion, malathion, chlorpyrifos, monocrotophos, and diazinon, which are commonly used in agriculture for enhancing agricultural productivity via killing crop-damaging pests. However, people may get exposed to OPs pesticides unintentionally/intentionally via ingestion, inhalation, or dermal. The current treatment regimen includes reactivator such as mono or bis-pyridinium oximes along with anticholinergic and anticonvulsant drugs that are recommended for the treatment of OP poisoning. Unfortunately, the drawback of the existing reactivator is the permanent charge present on the pyridinium, making them inefficient to cross the blood-brain barrier (BBB) and reactivate OP-inhibited central nervous system (CNS) acetylcholinesterase. Therefore, there is a need of a reactivator that could cross the BBB and reactivate the OP inhibited acetylcholinesterase. Objective: The objectives of the study were synthesis, molecular docking, BSA binding, and in-vitro estimation of oximes of various substituted imidazo [1,2-a]pyridine against paraoxon inhibited acetylcholinesterase. Methods: The reactivators were synthesized in three steps and characterized using various spectroscopic techniques. The molecular docking study was performed on 2WHP and 3ZLV PDB using the Glide-XP software. The acid dissociation constant (pKa) of oximes was calculated experimentally, and the drug-likeness properties of the oximes were calculated in silico using Molinspiration and Swiss ADME software. The binding of oximes with bovine serum albumin (BSA) was also investigated using a Fluorescence spectrophotometer. The reactivation potential of the oximes was determined by in vitro enzymatic assay. Results: The In-silico study inferred that the synthesized molecules fulfilled the parameters required for a successful CNS drug candidate. Furthermore, in-vitro enzymatic assay indicated reasonable reactivation potential of the oximes against paraoxon-inhibited AChE. The binding of oximes with bovine serum albumin (BSA) revealed that there was a static quenching of intrinsic fluorescence of BSA by the oxime. The binding constant value and number of binding sites were found to be 0.24 x 10⁴ mol^-1 and 1, respectively. Conclusion: The results of the study concluded that this scaffold could be used for further designing of more efficient uncharged reactivators.

Background: New potential biological targets prediction through inverse molecular docking technique is another smart strategy to forecast the possibility of compounds being biologically active against various target receptors. Objective: In this case of designed study, we screened our recently obtained novel acetylenic steroidal biotransformed products [(1) 8- β-methyl-14-α-hydroxyΔ⁴tibolone (2) 9-α-HydroxyΔ⁴ tibolone (3) 8- β-methyl-11- β-hydroxyΔ⁴tibolone (4) 6- β-hydroxyΔ⁴tibolone, (5) 6- β-9-α-dihydroxyΔ⁴tibolone (6) 7- β-hydroxyΔ⁴tibolone)] from fungi Cunninghemella Blakesleana to predict their possible biological targets and profiling of ADME properties. Methods: The prediction of pharmacokinetic properties, membrane permeability, and bioavailability radar properties was carried out by using Swiss target prediction and Swiss ADME tools, respectively. These metabolites were also subjected to predict the possible mechanism of action along with associated biological network pathways by using Reactome database. Results: All the six screened compounds possessed excellent drug ability criteria and exhibited exceptionally excellent non-inhibitory potential against all five isozymes of the CYP450 enzyme complex, including CYP1A2, CYP2C19, CYP2C9, CYP2D6, and CYP3A4. All the screened compounds are lying within the acceptable pink zone of bioavailability radar and showing excellent descriptive properties. Compounds [1-4 & 6] are showing high BBB (Blood Brain Barrier) permeation, while compound 5 is exhibiting high HIA (Human Intestinal Absorption) property of (Egan Egg). Conclusion: In conclusion, the results of this study smartly reveal that in-silico based studies are considered to provide robustness towards a rational drug design and development approach; therefore, in this way, it helps to avoid the possibility of failure of drug candidates in the later experimental stages of drug development phases.