Medicinal Chemistry - Volume 15, Issue 8, 2019

Background: Due to emerging resistances against antibiotics there is a strong need to find novel antibacterial agents with a novel structure to prevent early resistance developments. Objective: Bisindole compounds with antibacterial activities which formally result from the reaction of an aldehyde with indole motivated to investigate the reaction of a dialdehyde and indole to give novel structures with potential antibacterial activities. Methods: Compounds were yielded by chemical synthesis and purified using column chromatography. The antibacterial activity was determined as minimal inhibitory growth activity in cultures of Gram-positive strains of Staphylococcus aureus and Enterococcus species. Results: Cyclohepta[2,3-b]indoles have been yielded in a one-step reaction procedure with indole substitutions at the cycloheptane central core matching a solution for achieving fused novel cycloalkane indoles with functionalized residues of promising biological activity. So far fused cycloalkane indoles have not been available in a one-step procedure and moreover, core functionalizations have been additional challenges. Various indole substitutions have been done to provide a first set of compounds. Conclusion: Substituent-dependent effects have been suggested to influence the antibacterial activity and first compounds were identified with specific Staphylococcus activities and Enterococcus species effects towards Enterococcus faecalis as critical pathogens in the hospital with upcoming resistances against standard antibiotics.

Background: Rhodanine is known for its potential and important role in the medicinal chemistry since its derivatives exhibit a wide range of pharmacological activities such as antibacterial, antifungal, antidiabetic, antitubercular, anti-HIV, antiparasitic, antioxidant, anticancer, antiproliferative and anthelmintic agents. Objectives: Since N-substituted rhodanine synthons are rarely commercially available, it is desirable to develop a straightforward synthetic approach for the synthesis of these key building blocks. The objective was to synthesize a series of rhodanine derivatives and to investigate their antimicrobial and antioxidant activity. Also, in order to obtain an insight into their structure-activity relationship, QSAR studies on the antioxidant activity were performed. Methods: 1H and 13C FTNMR spectra were recorded on Bruker Avance 600 MHz NMR Spectrometer, mass analysis was carried out on ESI+ mode by LC-MS/MS API 2000. 2,2-Diphenyl-1- picrylhydrazyl radical scavenging activity (% DPPH) was determined in dimethylsulfoxide (DMSO) as a solvent. The antibacterial activity was assessed against Bacillus subtilis, Staphylococcus aureus (Gram positive) and Escherichia coli, Pseudomonas aeruginosa (Gram negative) bacteria in terms of the minimum inhibitory concentrations (MICs) by a modified broth microdilution method. Results: A series of N-substituted-2-sulfanylidene-1,3-thiazolidin-4-ones were synthesized and characterized by 1H NMR, 13C NMR, FTIR, GC MS, LCMS/MS and C,H,N,S elemental analysis. Most of the synthesized compounds showed moderate to excellent antibacterial activity (MIC values from 125 μg/ml to 15.62 μg/mL) and DPPH scavenging activity (from 3.60% to 94.40%). Compound 2-thioxo-3- (4-(trifluoromethyl)-phenyl)thiazolidin-4-one showed the most potent activity against Escherichia coli (3.125 μg/mL), equivalent to antibiotic Amikacin sulphate and against Staphylococcus aureus (0.097 μg/ml), 100 times superior then antibiotic Amikacin sulphate. It has also shown a potent antioxidant activity (95% DPPH scavenging). Two best QSAR models, obtained by GETAWAY descriptor R7p+, Balabans molecular connectivity topological index and Narumi harmonic topological index (HNar), suggest that the enhanced antioxidant activity is related to the presence of pairs of atoms higher polarizability at the topological distance 7, substituted benzene ring and longer saturated aliphatic chain in N-substituents. Conclusion: A series of novel N-substituted-2-thioxothiazolidin-4-one derivatives were designed, synthesized, characterized and evaluated for their antibacterial and antioxidant activity in vitro. Majority of the compounds showed excellent antibacterial activity compared to ampicillin and few of them have an excellent activity as compared to Chloramphenicol standard antibacterial drug. The QSAR study has clarified the importance of presenting a pairs of atoms higher polarizability, such as Cl and S at the specific distance, as well as the substituted benzene ring and a long saturated aliphatic chain in N-substituents for the enhanced antioxidant activity of 2-sulfanylidene-1,3- thiazolidin-4-one derivatives.

Background: Ischemic heart disease, cerebrovascular accident, and venous thromboembolism have the presence of a thrombotic event in common and represent the most common causes of death within the population. Objective: Since Schiff base copper(II) complexes are able to interact with polyphosphates (PolyP), a procoagulant and potentially prothrombotic platelet agent, we investigated the antiplatelet aggregating properties of two novel tridentate Schiff base ligands and their corresponding copper( II) complexes. Methods: The Schiff base ligands (L1) and (L2), as well as their corresponding copper(II) complexes (C1) and (C2), were synthesized and characterized by chemical analysis, X-ray diffraction, mass spectrometry, and UV-Visible, IR and far IR spectroscopy. In addition, EPR studies were carried out for (C1) and (C2), while (L1) and (L2) were further analyzed by 1H and 13C NMR. Tests for antiplatelet aggregation activities of all of the four compounds were conducted. Results: X-ray diffraction studies show that (L1) and (L2) exist in the enol-imine tautomeric form with a strong intramolecular hydrogen bond. NMR studies show that both ligands are found as enol-imine tautomers in CDCl3 solution. In the solid state, the geometry around the copper(II) ion in both (C1) and (C2) is square planar. EPR spectra suggest that the geometry of the complexes is similar to that observed in the solid state by X-ray crystallography. Compound (C2) exhibited the strongest antiplatelet aggregation activity. Conclusion: Schiff base copper(II) complexes, which are attracting increasing interest, could represent a new approach to treat thrombosis by blocking the activity of PolyP with a potential anticoagulant activity and, most importantly, demonstrating no adverse bleeding events.

Background: Platelet aggregation plays a pathogenic role in the development of arterial thrombi, which are responsible for common diseases caused by thrombotic arterial occlusion, such as myocardial infarction and stroke. Much efforts are directed toward developing platelet aggregation inhibitors that act through several mechanisms: The main antiplatelet family of COXinhibitors, phosphodiesterase inhibitors, and thrombin inhibitors. Recently, the important role in the platelet aggregation of adenosine diphosphate (ADP)-activated P2Y12 and P2Y1 receptors, Gprotein coupled receptors of the P2 purinergic family, has emerged, and their inhibitors are explored as potential therapeutic antithrombotics. P2Y12 inhibitors, i.e. clopidogrel, prasugrel, ticagrelor, and cangrelor, are already used clinically to reduce coronary artery thrombosis risk and prevent acute coronary syndromes. The search for new P2Y12 inhibitors, with better risk-to-benefit profiles is still ongoing. Methods: Several years ago, our group prepared a series of 6-amino-2-thio-3H-pyrimidin-4-one derivatives that displayed an interesting platelet aggregation inhibiting activity. In order to probe the structure-activity relationships and improve their inhibitory effects of these compounds, we synthesized variously substituted 6-amino-2-thio-3H-pyrimidin-4-one derivatives and substituted 4-amino-2-thiopyrimidine-5-carboxylic acid analogues. All the synthesized compounds were tested by light trasmission aggregometry (LTA) as inducers or inhibitors of platelet aggregation in citrated platelet-rich plasma (PRP). Results: Among the 6-amino-2-thio-3H-pyrimidin-4-one derivatives, compounds 2c and 2h displayed marked inhibitory activity, with a capability to inhibit the ADP(10-6M)-induced platelet aggregation by 91% and 87% at 10-4M concentration, respectively. Selected 4-amino-2- thiopyrimidine-5-carboxylic acid derivatives were tested as P2Y12 and P2Y1 antagonists and found to display negligible activity. Conclusion: These negative findings demonstrated that this heterocyclic nucleus is not a useful common pharmacophore for developing P2Y-dependent inhibitors of platelet aggregation. Nevertheless, compounds 2c and 2h could represent a new chemotype to further develop inhibitors of platelet aggregation.

Background: Marine sponges and tunicates have been a wealthy source of cytotoxic compounds such as indole alkaloids. Most of the indole alkaloids show in vitro cytotoxic and antineoplastic activities against a wide range of cancer cell lines. Objective: Three series of bioisosteres of marine indole alkaloids (meridianins) were synthesized and the compounds were tested for their in vitro anti-proliferative activity against HCT-116 cellline. In the design of the targeted analogues, the 2-aminopyrimidine ring of merdianins was replaced with 5-aminopyrazole, pyrazolo[1,5-a]pyrimidine and pyrazolo[3,4-b]pyridine rings. Results: The cytotoxic screening of the synthesized compounds revealed that pyrazolo[1,5- a]pyrimidines (compounds 9c and 11a) had the most potent cytotoxic activity with IC50 = 0.31 μM and 0.34 μM respectively. Compounds 9c and 11a were further investigated for their kinase inhibitory potencies toward six kinases (CDK5/p25, CK1ð/, GSK-3α/β, Dyrk1A, Erk2, and CLK1). They exhibited effective inhibition of GSK-3α/β (IC50 = 0.196 μM and 0.246 μM, respectively) and Erk2 (IC50 = 0.295 μM and 0.376 μM, respectively). Conclusion: Meridianins emerged as promising lead structures that need further development to obtain more selective and potent cytotoxic agents. One of these modifications involved the replacement of 2-aminopyrimidinyl ring of meridianins with other heterocyclic rings. Both pyrazolo[ 1,5-a]pyrimidine and pyrazolo[3,4-b]pyridine rings showed promising cytotoxic activity compared to the five membered 5-aminopyrazole.

Background: Previously, we have identified 3,3′–carbonyl–bis(chromones) (1a-h, 5e) and 3–(5–(benzylideneamino)thiozol–3–yl)–2H–chromen–2–ones (7a-j) as potent inhibitors of tissue non-specific alkaline phosphatase (TNAP). The present study was designed to investigate the cytotoxic and pro-apoptotic effect of the said derivatives. Methods: The anti-proliferative effect of the derivatives was investigated in three cancer cell lines i.e., MCF-7, K-562, HeLa and normal BHK21 cells using MTT assay. The pro-apoptotic effect of the most potent derivatives was investigated by using flow cytometry, DAPI and PI staining and DNA binding studies. Results: Among all the screened compounds, 1f, 1d, 1c (from 3,3′–carbonyl–bis(chromones), 7c, 7h and 7i (from 3–(5–(benzylideneamino)thiozol–3–yl)–2H–chromen–2–ones) exhibited remarkable growth inhibitory effects. Compounds 1f and 7c were found to be the most potent cytotoxic derivatives against MCF-7; 1d and 7h inhibited most of the proliferation of K-562 cells, whereas 1c and 7i showed maximum growth inhibition in HeLa cells. The identified compounds exerted lower micromolar potency against the respective cell line with significant selectivity over the normal cells (BHK–21). The identified compounds also induced either G2 or S-phase arrest within the respective cancer cells, chromatin condensation and nuclear fragmentation, as well as maximum interaction with DNA. Conclusions: These results provide evidence that the characteristic chemical features of attached groups are the key factors for their anticancer effects and play a useful role in revealing the mechanisms of action in relation to the known compounds in future research programs.

Background: Cancer is a far-reaching and lethal but curable disease. Researchers have investigated numerous anticancer agents with only a few commercially available effective drugs which are very costly. Objective: Herein, we report the synthesis , characterization and anti cancer assays of a series of novel dithiocarbamates derivatives. Methods: All compounds were synthesized from different secondary amines and substituted benzyl chlorides in a single step. The structures of newly synthesized dithiocarbamate derivatives were confirmed by spectroscopic techniques (IR, NMR and HR-MS). Results: The synthesized compounds showed a significant anti-proliferative effect in cancer cells (HeLa) with the maximum inhibitory activity of compound SHD-2 with an IC50 = 0.31 ± 0.09 μM. However, the same compound exhibited 19.2% inhibition towards Baby Hamster Kidney fibroblasts (BHK-21), normal cell lines. Moreover, quantification of cellular DNA by flow cytometry for the evaluation of pro-apoptotic activity in HeLa cells demonstrates that arrest in cell cycle along with apoptosis advance towards drug cytotoxicity. However, molecular docking studies of the potent compound suggested that it binds to the major groove of the DNA. Conclusion: The cytotoxic and pro-apoptotic potential of the potent inhibitor may be further investigated in the animal models to advance their anti-cancer prospective.

Background: Hydrazine-hydrazones represent a group of bioactive compounds that display antibacterial, anti-inflammatory, antiviral or anticancer activities. Objective: In this study, we designed new derivative compounds from groups of hydrazones. Methods: The group of new derivatives was evaluated by the viability assay in human cancer and normal cells. Results: The dimethylpyridine hydrazones showed potent inhibition of cell proliferation of breast, colon cancer cells, human melanoma and glioblastoma. Compound 12 inhibited proliferation of cancer cells exhibiting a drug-resistant phenotype (MCF-7/DX and LoVoDX) at low millimolar concentrations. Whereas, antimelanoma activity was revealed by Compounds 2, 4, 7 and 12. Conclusion: The present results highlighted newly synthetized hydrazine derivatives an excellent base for the design of new anticancer agents and resistance inhibitors.

Background: Pyrroles and fused pyrroles are of great interest as biologically active compounds, among these activities; antidepressant activity is of special concern. Objective: Synthesis of a series of pyrrolopyrazoles and their pyrimidine derivatives and their characterization using spectral data to be monitored for antidepressant activity using behavioral techniques. Methods: A control group was administered the vehicle i.p., positive control group received fluoxetine as standard and all other groups were administered the tested compounds. The groups were subjected to tail suspension test (TST) to determine the antidepressant activity compared with fluoxetine as a standard drug. The compounds exhibiting antidepressant activity were then used to analyze changes in serotonin (5HT) level in the brain of albino mice. Results: TST results showed that both pyrazoles and pyrazolopyrimidines derivatives exhibit promising anti-depressant activity. Conclusion: Compounds [pyrazoles & pyrazlopyrimidines] showed promising antidepressant activity possibly mediated by the increased levels of 5HT.

Background: Antioxidant, anti-inflammatory, antiviral and antitumoral activities among others are essential characteristics in the development of novel therapeutic compounds. Acid hydrazides can form complexation with certain metal ions that positively enhance these biological characteristics. Objective: Five new complexes of uranium with hydrazide ligands were synthesized at room temperature. Methods: The characterization was done by spectroscopic methods (ESI-Mass, IR, 1H-NMR, 13CNMR), CHN analysis and conductivity measurements. Metal complexes along with their respective ligands were further screened for their antioxidant (DPPH, superoxide and nitric oxide free radicals) properties and enzyme inhibition (α-glucosidase) activities. Results: Elemental and spectral data indicate octahedral geometry around uranyl (UO2 2+) species. Magnetic moments indicate the diamagnetic nature of uranyl(VI) ion in the complex in solid state. IC50 values showed potential antioxidant behavior of uranyl complexes demonstrating interesting structure-activity relationships. In general, hydrazide ligands were not active against superoxide and nitric oxide radicals while varying degree of results were observed against DPPH radical whereas all uranyl-complexes showed promising radical scavenging activities against all of them. Promising inhibitory potential was displayed by UO2 +2 hydrazide complexes against α- glucosidases whereas free hydrazide ligands were inactive. Conclusion: Structure function relationship demonstrates that the nature of ligand, position of substituent, electronic and steric effects are significant factors affecting the radical scavenging and enzyme inhibition activities of the compounds.