Design, synthesis and QSAR study of arylidene indoles as anti-platelet aggregation inhibitors

Synthesis and Biological Evaluation of Novel Thiadiazole Derivatives as Antiplatelet Agents

A novel series of thiadiazole compounds was synthesized through the reaction of thiosemicarbazone intermediates with 2, 3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The antiplatelet activity of the synthesized compounds was evaluated using an aggregation test with adenosine diphosphate (ADP) and arachidonic acid (AA) as platelet aggregation inducers. Among the synthesized analogs, compound 3b exhibited the most potent inhibition of platelet aggregation induced by ADP (half maximal inhibitory concentration [IC50] = 39 ± 11 µM). Molecular docking studies of 3b revealed hydrogen bonds between the nitrogen of the thiadiazole ring and Lys280. The tolyl ring exhibited hydrophobic interactions with Tyr105, similar to the antagonist co-crystallized with P2Y12 (PDB ID: 4NTJ). These compounds have the potential to serve as lead molecules for designing P2Y12 inhibitors.

Design, synthesis, spectroscopic characterization, in vitro tyrosinase inhibition, antioxidant evaluation, in silico and kinetic studies of substituted indole-carbohydrazides

In the current study, twenty-five indole-carbohydrazide derivatives linked to different aryl substitutions were rationally designed and synthesized. The structures of all derivatives were confirmed using different spectroscopic techniques including ¹H NMR, ¹³C NMR, Mass spectrometry, and elemental analysis. The tyrosinase inhibitory activities of all synthetic compounds exhibited IC₅₀ values in the range of 0.070 to > 100 μM. Structure-activity relationships showed that compounds 4f (R = 4-OH, IC₅₀ = 0.070 μM), 8f (R = 4-OH, IC₅₀ = 0.072 μM), and 19e (IC₅₀ = 0.19 μM) with para-OH substituent at the R position was found to be the most active members of all three tested series. Kinetic studies exhibited that compounds 4f, 8f, and 19e are mixed-type inhibitors. Furthermore, toxicity and cell-based anti-melanogenesis assessments were performed on the most potent derivatives and it was shown that 4f, 8f, and 19e had no toxicity at 8 µM and reduced the percent of melanin content to 68.43, 72.61, 73.47 at 8 μM, respectively. In silico analyses of absorption, distribution, metabolism, and excretion (ADME) profile of synthesized compounds showed that these molecules followed drug-likeness rules and acceptable predictive ADMET features. Results of the docking study were almost in line with biological results with ChemPLP values of 53.56 to 79.33. Also, the docking study showed the critical interactions of potent inhibitors with the active site of the enzyme which affects the potency of the synthesized hybrids. Based on molecular dynamic simulations, compound 4f exhibited pronounced interaction with the critical residues of the tyrosinase active site so that the indole ring participated in H-bond interaction with Gly281 and 4-hydroxy benzylidene recorded another H-bond interaction with Asp289 plus hydrophobic interactions with Phe292. Hydrazide linker also exhibited three H-bond interactions with His263 and Gly281.

Synthesis, structural characterization, and evaluation of new peptidomimetic Schiff bases as potential antithrombotic agents

New Schiff bases functionalized with amide and phenolic groups synthesized by the condensation of 2-hydroxybenzaldehyde and 2-hydroxyacetophenone with amino acid amides which in turn were prepared in two steps from N-Boc-amino acids and homoveraltrylamine through intermediate compounds N-Boc-amino acids amides. The compounds were characterized by elemental analysis, FT-IR, UV–Vis, and NMR spectroscopy. The crystal structures of three Schiff bases were determined by single crystal X-ray diffraction. There exists O–H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\cdots $$\end{document}⋯N, N–H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\cdots $$\end{document}⋯O, and C–H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\cdots $$\end{document}⋯O types of hydrogen bonds and C–H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\cdots\uppi $$\end{document}⋯π secondary bonding interactions in these crystalline solids. The Schiff bases have been screened for anticoagulant and antiplatelet aggregation activities. All the compounds showed procoagulant activity which shortens the clotting time of citrated human plasma in both platelet-rich plasma and platelet-poor plasma except the derivatives of L-methionine which showed anticoagulant activity by prolonging the clotting time. In addition, the compounds derived from benzyl cysteine and phenylalanine showed adenosine diphosphate induced antiplatelet aggregation activity, whereas others did not show any role. Moreover, all these compounds revealed non-hemolytic activity with red blood cells.

Synthesis of new urease enzyme inhibitors as antiulcer drug and computational study

In search of potent urease inhibitor indole analogues (1-22) were synthesized and evaluated for their urease inhibitory potential. All analogues (1-22) showed a variable degree of inhibitory interaction potential having IC₅₀ value ranging between 0.60 ± 0.05 to 30.90 ± 0.90 µM when compared with standard thiourea having IC₅₀ value 21.86 ± 0.90 µM. Among the synthesized analogues, the compounds 1, 2, 3, 5, 6, 8, 12, 14, 18, 20 and 22 having IC₅₀ value 3.10 ± 0.10, 1.20 ± 0.10, 4.60 ± 0.10, 0.60 ± 0.05, 5.30 ± 0.20, 2.50 ± 0.10, 7.50 ± 0.20, 3.90 ± 0.10, 3.90 ± 0.10, 2.30 ± 0.05 and 0.90 ± 0.05 µM respectively were found many fold better than the standard thiourea. All other analogues showed better urease interaction inhibition. Structure activity relationship (SAR) has been established for all analogues containing different substituents on the phenyl ring. To understand the binding interaction of most active analogues with enzyme active site docking study were performed.Communicated by Ramaswamy H. Sarma.

Discovery of Pimprinine Alkaloids as Novel Agents against a Plant Virus

Plant viral diseases cause tremendous decreases in crop yield and quality. Natural products have always been a valuable source for lead discovery in medicinal and agricultural chemistry. A series of pimprinine alkaloids and their derivatives were prepared and identified by nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HR-MS). The antiviral activities of these alkaloids against tobacco mosaic virus (TMV) were systematically investigated for the first time. Most of the compounds exhibited higher antiviral activities than ribavirin. Compounds 5l, 9h, and 10h, which had similar or higher antiviral activities than ningnanmycin (perhaps the most widely used antiviral agent at present), emerged as new antiviral pilot compounds. This systematic structure-activity-relationship research lays the foundation for simplifying the structure of these alkaloids. The ring-open products, acylhydrazones 9a-9u, were also found to possess good antiviral activities. Moreover, all the synthesized compounds displayed broad-spectrum fungicidal activities. This study provides important information for the research and development of pimprinine alkaloids as novel antiviral agents.

Indole derivatives as multifunctional drugs: Synthesis and evaluation of antioxidant, photoprotective and antiproliferative activity of indole hydrazones

Two series of indole derivatives 4-17, 20-22 were easily prepared and assayed for their radical-scavenging ability. Arylidene-1H-indole-2-carbohydrazones showed different extent antioxidant activity in DPPH, FRAP and ORAC assays. Good antioxidant activity is related to the number and position of hydroxyl groups on the arylidene moiety as well as to the presence of methoxy or 4-(diethylamino) group. On the contrary low antioxidant activity is showed by the isomeric 1H-indol-2-yl(methylene)-benzohydrazides. Furthermore, hydrazones 4-17 showed photoprotective capacities with satisfactory in vitro SPF as compared to the commercial PBSA sunscreen filter. The indole 16 and 17, showing the best antioxidant and photoprotective profile, were included in different formulation and their topical release was evaluated. Varying the formulation composition, it was possible to optimize skin adsorption and solubility of the active indole in the formulation. The antiproliferative effect of the hydrazones 4-17 was tested on human erythroleukemia K562 and melanoma Colo-38 cells. Hydrazones 11, 16 and 17 showed growth inhibition at sub micromolar concentrations on both cell lines. These results indicate indole hydrazones as potential multifunctional molecules especially in the treatment of neoplastic diseases being the good antioxidant properties of 16 and 17 correlated to their high antiproliferative activity.

Synthesis of Imine Congeners of Resveratrol and Evaluation of Their Anti-Platelet Activity

Resveratrol (3,5,4′-trihydroxy-trans-stilbene) is a cardioprotective phytochemical occurring in many plant products. In this study, a new series of imine congeners of resveratrol has been synthesized in which the imine moiety replaced the double bond in the structure of resveratrol. In addition, the in vitro antiplatelet activity of these resveratrol derivatives has been evaluated against adenosine diphosphate (ADP), arachidonic acid (AA), and collagen as platelet aggregation inducers. In general, the synthesized compounds were active as antiplatelet agents, and, therefore, the imine functional group may be considered as an effective replacement for a double bond in resveratrol for developing new and promising antiplatelet drugs.

An integrated QSAR modeling approach to explore the structure-property and selectivity relationships of N-benzoyl-L-biphenylalanines as integrin antagonists

Integrins [Formula: see text] and [Formula: see text] are important targets to treat different inflammatory diseases, such as multiple sclerosis, inflammatory bowel diseases, rheumatoid arthritis, atherosclerosis, and asthma. Despite being valuable targets, only a few work has been reported to date regarding molecular modeling studies on these integrins. Not only that, none of these reports addressed the selectivity issue between integrins [Formula: see text] and [Formula: see text]. Therefore, a major challenge regarding the design and discovery of selective integrin antagonists remains. In this study, a series of 142 N-benzoyl-L-biphenylalanines having both integrin [Formula: see text] and [Formula: see text] inhibitory activities were considered for a variety of QSAR approaches including regression and classification-based 2D-QSARs, Hologram QSARs, 3D-QSAR CoMFA and CoMSIA studies to identify the structural requirements of these integrin antagonists. All these QSAR models were statistically validated and subsequently correlated with each other to get a detailed understanding of the activity and selectivity profiles of these molecules.

Rational Design and Synthesis of 1-(Arylideneamino)-4-aryl-1H-imidazole-2-amine Derivatives as Antiplatelet Agents

Based on previous studies indicating the pharmacophoric role of a hydrazone group and azole rings for antiplatelet aggregation activity, a few series of compounds with both hydrazone and an azole (imidazole) ring in their structures were synthesized, and their platelet aggregation inhibitory effects were evaluated. Two of these 1-(arylideneamino)-4-aryl-1H-imidazole-2-amine derivatives, compounds 4 a [(E)-1-(benzylideneamino)-4-phenyl-1H-imidazol-2-amine] and 4 p [(E)-4-phenyl-1-((thiophen-2-ylmethylene)amino)-1H-imidazol-2-amine], exhibited IC₅₀ values similar to that of acetylsalicylic acid against collagen as a platelet aggregation inducer. Structural comparison of the synthesized compounds revealed that those with a para-substituted phenyl ring on the imidazole were among the most active compounds against platelet aggregation induced by arachidonic acid (AA), and the presence of a thiophene ring in these compounds maximized their antiplatelet activity.