Synthesis of some novel heterocylic compounds derived from 2-[3-(4-chlorophenyl)-5-(4-methoxybenzyl)-4H-1,2,4-triazol-4-yl]acetohydrazide and investigation of their lipase and α-glucosidase inhibition

In-vitro high-throughput library screening-Kinetics and molecular docking studies of potent inhibitors of α-glucosidase

High throughput screening of synthetic compounds against vital enzymes is the way forward for the determination of potent enzyme inhibitors. In-vitro high throughput library screening of 258 synthetic compounds (comp. 1-258), was performed against α-glucosidase. The active compounds out of this library were investigated for their mode of inhibition and binding affinities towards α-glucosidase through kinetics as well as molecular docking studies. Out of all the compounds selected for this study, 63 compounds were found active within the IC50 range of 3.2 μM to 50.0 μM. The most potent inhibitor of α-glucosidase out of this library was the derivative of an oxadiazole (comp. 25). It showed the IC50 value of 3.23 ± 0.8 μM. Other highly active compounds were the derivatives of ethyl-thio benzimidazolyl acetohydrazide with IC50 values of 6.1 ± 0.5 μM (comp. 228), 6.84 ± 1.3 μM (comp. 212), 7.34 ± 0.3 μM (comp. 230) and 8.93 ± 1.0 μM (comp. 210). For comparison, the standard (acarbose) showed IC50 = 378.2 ± 0.12 μM. Kinetic studies of oxadiazole (comp. 25) and ethylthio benzimidazolyl acetohydrazide (comp. 228) derivatives indicated that Vmax and Km, both change with changing concentrations of inhibitors which suggests an un-competitive mode of inhibition. Molecular docking studies of these derivatives with the active site of α-glucosidase (PDB ID:1XSK), revealed that these compounds mostly interact with acidic or basic amino acid residues through conventional hydrogen bonds along with other hydrophobic interactions. The binding energy values of compounds 25, 228, and 212 were -5.6, -8.7 and -5.4 kcal.mol-1 whereas RMSD values were 0.6, 2.0, and 1.7 Å, respectively. For comparison, the co-crystallized ligand showed a binding energy value of -6.6 kcal.mol-1 along with an RMSD value of 1.1 Å. Our study predicted several series of compounds as active inhibitors of α-glucosidase including some highly potent inhibitors.

Design and synthesis of new heterocyclic compounds containing 5-[(1H-1,2,4-triazol-1-yl)methyl]-3H-1,2,4-triazole-3-thione structure as potent hEGFR inhibitors

EGFR is one of the important mediators of the signaling cascade that determines key roles in various biological processes such as growth, differentiation, metabolism and apoptosis in the cell in response to external and internal stimuli. In recent years, it has been proven that although this enzyme activity is tightly regulated in normal cells, if the enzyme activity cannot be controlled, it can lead to malignancy. EGFR is also considered a prominent macromolecule in targeted cancer chemotherapy. For this purpose, a comprehensive modeling studies were conducted against EGFR protein and novel molecules containing 5-[(1H-1,2,4-triazol-1-yl)methyl]-3H-1,2,4-triazole-3-thione structure were suggested to be synthesized. Among the synthesized molecules, compounds 7c, 8c, 8f and 8g were determined to have significant IC50 values. Compound 8g was found to have the IC50 value closest to the very well-known EGFR inhibitor Gefitinib with its noncompetitive inhibition form. Ki value of compound 8g was calculated as 0.00232 µM.Communicated by Ramaswamy H. Sarma.

Semisynthesis, biological activities, and mechanism studies of Mannich base analogues of magnolol/honokiol as potential α-glucosidase inhibitors

Magnolol and honokiol, derived from a Magnolia officinalis Rehd. et Wils, are a class of natural biphenolic lignans. Currently, the discovery of new α-glucosidase inhibitors from natural analogues is of interest. Here, four series of thirty new Mannich base analogues of magnolol/honokiol were prepared and evaluated for their α-glucosidase inhibitory activities. Among these Mannich base analogues of magnolol/honokiol, 3k and 3l exhibited more potent inhibitory effects on α-glucosidase than the reference drug acarbose, and their IC50 values were 14.94 ± 0.17 µM and 13.78 ± 1.42 µM, respectively. Some interesting structure-activity relationships (SARs) were also analyzed. The enzyme inhibition kinetics indicated that 3k and 3l were noncompetitive inhibitors. This result was in agreement with molecular docking studies, where the binding sites of 3k and 3l to α-glucosidase were different from that of the competitive inhibitor acarbose to α-glucosidase. Moverover, compounds 3k and 3l exhibited low toxicity to normal cells (LO2). Thus, analogues 3k and 3l could be deeply developed for the discovery of natural products based antidiabetic candidates.

Dihydropyrimidinones Against Multiresistant Bacteria

The increase in bacterial resistance to antimicrobials has led to high morbidity and mortality rates, posing a major public health problem, requiring the discovery of novel antimicrobial substances. The biological samples were identified as the Gram-negative bacilli Acinetobacter baumannii, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Morganella morgannii, Pseudomonas aeruginosa and Serratia marcescens and the Gram-positive cocci Enterococcus faecium, and Staphylococcus aureus, all of them resistant to at least three classes of antimicrobials. The antibacterial activity of the compounds was checked in vitro by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) by the broth microdilution method and plating in brain heart infusion (BHI) agar, respectively. The chemical characterization of the compounds was performed by measuring the melting point and gas chromatography coupled with mass spectrometry (GC–MS) on a Shimadzu GC–MS-QP system 2010SE. Synthetic compounds showed antimicrobial activity against Gram-positive cocci at MIC concentrations 0.16–80 μg/ml and Gram-negative bacilli at MIC concentrations 23.2–80 μg/ml. Enterococcus faecium and S. aureus had the best MIC values. The results of the cytotoxicity test indicated that the synthetic compounds showed no significant difference in three concentrations tested (5, 20, and 80 μg/ml), allowing cell viability not different from that assigned to the control, without the tested compounds. In this context, the development of DHPM derivatives brings an alternative and perspective on effectiveness of drugs as potential future antimicrobial agents.

Design, synthesis, molecular docking, and in vitro α-glucosidase inhibitory activities of novel 3-amino-2,4-diarylbenzo[4,5]imidazo[1,2-a]pyrimidines against yeast and rat α-glucosidase

In an attempt to find novel, potent α-glucosidase inhibitors, a library of poly-substituted 3-amino-2,4-diarylbenzo[4,5]imidazo[1,2-a]pyrimidines 3a–ag have been synthesized through heating a mixture of 2-aminobenzimidazoles 1 and α-azidochalcone 2 under the mild conditions. This efficient, facile protocol has been resulted into the desirable compounds with a wide substrate scope in good to excellent yields. Afterwards, their inhibitory activities against yeast α-glucosidase enzyme were investigated. Showing IC₅₀ values ranging from 16.4 ± 0.36 µM to 297.0 ± 1.2 µM confirmed their excellent potency to inhibit α-glucosidase which encouraged us to perform further studies on α-glucosidase enzymes obtained from rat as a mammal source. Among various synthesized 3-amino-2,4-diarylbenzo[4,5]imidazo[1,2-a]pyrimidines, compound 3k exhibited the highest potency against both Saccharomyces cerevisiae α-glucosidase (IC₅₀ = 16.4 ± 0.36 μM) and rat small intestine α-glucosidase (IC₅₀ = 45.0 ± 8.2 μM). Moreover, the role of amine moiety on the observed activity was studied through substituting with chlorine and hydrogen resulted into a considerable deterioration on the inhibitory activity. Kinetic study and molecular docking study have confirmed the in-vitro results.

Synthesis of new 1,2,4-triazole-(thio)semicarbazide hybrid molecules: Their tyrosinase inhibitor activities and molecular docking analysis

Tyrosinase inhibition is very important in controlling melanin synthesis. If melanin synthesis is not controlled in metabolism, an unwanted increase in melanin synthesis occurs. As melanin plays a role in the formation of skin color, its unusual levels cause some skin disorders such as pregnancy scars, age spots, and especially skin cancer (melanoma). However, the tyrosinase activity is also related to Parkinson's disease and some neurodegenerative diseases. For all these reasons, the medicinal as well as the cosmetic industries focus on research on tyrosinase inhibitors for the treatment of skin disorders and some neurodegenerative diseases. In this study, 32 new 1,2,4-triazole-(thio)semicarbazide hybrid molecules (6a-p and 7a-p) were synthesized, starting from 4-amino-1-pentyl-3-phenyl-1H-1,2,4-triazole-5(4H)-one. These compounds were evaluated for their inhibitory activity against mushroom tyrosinase. The results indicated that 6h, 6m, 6n, and 6p exhibited the most effective inhibitory activity, with IC₅₀ values of 0.00162 ± 0.0109, 0.00166 ± 0.0217, 0.00165 ± 0.019, and 0.00197 ± 0.0063 μM, respectively, compared with kojic acid as the reference drug (IC₅₀  = 14.09 ± 0.02 μM). Also, molecular docking analyses were performed to suggest possible binding poses for the ligands. As a result, derivatives 6h, 6m, 6n, and 6p can be used as promising tyrosinase inhibitor candidates in the medicinal, cosmetics, or food industries.

Pancreatic lipase inhibitors: The road voyaged and successes

Human pancreatic lipase (triacylglycerol acyl hydrolase EC3.1.1.3) is the most widely studied member of the human lipase superfamily related to carboxyl esterase. It is secreted from the acinar cell of pancreas and has strong preference for triacylglycerides over cholesterol esters, phospholipids, and galactolipids. Apart from the hydrolysis of triacylglycerides, pancreatic lipase may cause the hydrolysis of retinyl esters in vivo. So, it is very much evidenced that pancreatic lipase with its cofactor colipase has prominent role in efficient digestion of dietary fat. Hence, the modulation of human pancreatic lipase may represent a new insight in the discovery of a number of therapeutics that can inhibit the absorption of fat in body and can be used in obesity and other related metabolic disorders. Even, the only Food and drug administration (FDA) approved antiobesity drug, orlistat, is also an inhibitor of pancreatic lipase. This review summarizes studies about structure, mechanistic approach of pancreatic lipase enzyme while emphasizing on the various synthetic pancreatic lipase inhibitors with their structure activity relationship (SAR).

Synthesis of some novel quinazolin-4(3H)-one hybrid molecules as potent urease inhibitors

A new series of quinazolinone hybrid molecules containing coumarin, furan, 1,2,4-triazole and 1,2,4-thiadiazole rings was designed, synthesized, and screened for their urease inhibition activities. All newly synthesized compounds showed outstanding urease inhibitory potentials with IC₅₀ values ranging between 1.26 ± 0.07 and 7.35 ± 0.31 μg/mL. Among the series, coumarin derivatives (10a-d) exhibited the best inhibitory effect against urease in the range of IC₅₀  = 1.26 ± 0.07 to 1.82 ± 0.10 μg/mL, when compared to standard urease inhibitors such as acetohydroxamic acid and thiourea (IC₅₀  = 21.05 ± 0.96 and 15.08 ± 0.71 μg/mL, respectively). Molecular docking studies were also performed to analyze the binding mode of compound 10b, and supported the experimental results.

Use of Simplified Molecular Input Line Entry System and molecular graph based descriptors in prediction and design of pancreatic lipase inhibitors

Aim: The inhibition of pancreatic lipase (PL) enzyme is the most explored strategy for the treatment of obesity. The present study describes the development of quantitative structure–activity relationship (QSAR) models for a diverse set of 293 PL inhibitors by means of the Monte Carlo optimization technique. Methodology & results: The hybrid optimal descriptors were used to build QSAR models with three subsets of three splits. The developed QSAR models were further validated with corresponding external sets. The best QSAR model has the following statistical particulars: R2 = 0.752, Q LOO 2 = 0 . 736 for the test set and R2 = 0.768, Q F 1 2 = 0 . 628 , Q F 2 2 = 0 . 621 for the validation set. Conclusion: The developed QSAR models were robust, stable and predictive and led to the design of novel PL inhibitors.

Recent developments concerning the application of the Mannich reaction for drug design

INTRODUCTION

The versatile multicomponent Mannich reaction occupies a salient position in organic chemistry and drug design. Sound knowledge of its scope and variations and of the biological activities of Mannich bases is crucial for the development and improvement of drugs for various diseases. Areas covered: The following article provides an overview of the latest developments in the field of drugs based on the Mannich reaction. Web-based literature searching tools such as PubMed and SciFinder were applied to obtain useful articles. In addition, pertinent literature that was recently published by the authors is discussed in this manuscript. The chemical structures of bioactive Mannich bases are also given. Expert opinion: The Mannich reaction represents a feasible and cost-effective procedure with great potential for drug development. Several newly discovered Mannich bases exhibit sound activities against various human diseases as well as favorable pharmacokinetics. Thus, scientific research about Mannich bases is prospering and appears very attractive both for chemists and for clinicians.