Medicinal Chemistry - Volume 14, Issue 6, 2018

Background: In previous reports, the antibacterial properties of certain tetrazole derivatives have been described. We have previously reported the antibacterial properties of aryl 1Htetrazole compounds. Objective: To study the antibacterial activity of 5-substituted heteroaryl, vinyl, benzyl, and alkyl 1H-tetrazole derivatives. Methods: The antibacterial properties of heteroaryl, vinyl, benzylic, and aliphatic tetrazole derivatives were investigated against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. The activity was assessed by determining the minimum inhibitory concentration of these tetrazole derivatives and comparing them to the known antibiotics amoxicillin, trimethoprim and sulfamethoxazole. Results: The tetrazole compounds were prepared utilizing cerium(III) chloride heptahydrate catalysis at 160 °C for 1-4 h in a microwave reactor using an aqueous solvent mixture. The most active derivatives exhibited minimum inhibitory concentration values between 125-250 μg/mL against Escherichia coli. More importantly, these compounds were considerably more active when used in combination with trimethoprim and a significant synergistic effect was observed (MIC = 0.98-7.81 μg/mL) against E. coli and S. aureus. Conclusion: The tetrazole derivatives were synthesized in high yield and short reaction times in water. Several of the tetrazole compounds showed a significant synergistic antibacterial effect when used with trimethoprim.

Background: Chagas disease is caused by the protozoan parasite Trypanosoma cruzi. This illness is found mainly in 21 Latin American countries and an estimated 8 million people are infected worldwide. The unsatisfactory chemotherapy provokes severe toxicity and resistant strains. Medicinal plants constitute a promising source of new drugs and remedies against all kinds of disorders, mainly infectious diseases arousing interest worldwide. Objective: The aim of this study is the isolation, structural identification and evaluation of the trypanocidal activity of samples present in the Excoecaria lucida Sw. leaves. Methods: Total extract (TE) of E. lucida Sw. leaves was obtained by ethanol extract therefore fractionated sequentially with hexane, ethyl acetate and n-butanol, to obtain three phases: Hex, EA and But, respectively. Ellagic acid (EL1) was purified from both EA and But phases, while EL2; a 1:1 stigmasterol-3-O-β-D-glucopyranoside plus sitosterol-3-O-β-D-glucopyranoside mixture was obtained from the Hex phase. Activity assays were performed using bloodstream and intracellular forms of T. cruzi and cytotoxicity assays using L929 fibroblasts. Results: The EL1 and EL2 samples were more active against bloodstream trypomastigote forms with EC50 of 53.0±3.6 and 58.2±29.0 μg/mL, respectively; at 100 μg/mL. These samples also showed 70% of inhibition of L929 cells infection. Toxicity assays demonstrated that after 96 h of treatment only the fractions Hex and EA presented detectable cytotoxicity. Conclusion: Ellagic acid, stigmasterol-3-O-β-D-glucopyranoside and sitosterol-3-O-β-Dglucopyranoside are reported for the first time in E. lucida Sw. leaves as well as their biological activity studies supporting further investigations for Chagas disease treatment.

Background: Leishmaniasis is endemic in 98 countries and is closely associated with poverty. On the basis of current evidence, it may be safely suggested that over time Leishmania spp. have evolved coexistence in different macrophage types and developed adaptations in order to ensure their intracellular survival. Considering new drugs, the need of the hour the present study deals with the synthesis of novel compounds of biological importance based on naturally occurring scaffolds. Objective: Synthesis, anti-leishmanial and anti-trypanosomal activities of a series of thirty three (eighteen newly synthesized and fifteen previously reported) 7-arylbenzo[c]acridine-5,6-diones. Method: A series of thirty-three 7-arylbenzo[c]acridine-5,6-diones was designed and synthesized. The anti-leishmanial and anti-trypanosomal activities of the newly synthesized compounds were done. Results: Seven compounds (14, 17, 19, 26, 27, 38 and 39) were found to exhibit excellent antiparasitic activities. Compound 14 was identified as the most potent compound against L. donovani promastigotes while compound 27 showed most significant inhibition activity against amastigotes. Compounds 14 and 27 showed remarkable inhibitory activity with IC50 values of 0.38 and 0.53 μM, respectively, when tested in human macrophage cell line (THP) infected with L. donovani amastigotes. Against trypanomastigotes, six compounds (15, 17, 19, 25, 26 and 43) demonstrated remarkable inhibition. Conclusion: Compound 19 was found to be the best anti-trypanosomal agent and showed 300-fold superior inhibitory activity to that of the standard drug DFMO. Significant anti-leishmanial and anti-trypanosomal activities combined with the non-cytotoxic profile presents 7-arylbenzo[c]acridine- 5,6-diones as new candidates with therapeutic potential in the treatment of parasitic diseases.

Background: Neglected diseases are becoming more prevalent due to globalization. This has inspired active research in the development of new drugs for the treatment of parasitic diseases such as Chagas disease. Objectives: With the aim of finding new trypanocidal agents, we report the in vitro evaluation of a new series of 3-amidocoumarins with or without hydroxyl substituents at position 4 of the coumarin ring. Methods: Electrochemical and biological assays were performed in order to assess the antioxidant and trypanocidal potential of these compounds and to better understand the mechanisms involved in their activity. Results: Most of the studied compounds showed high trypanocidal activity against both epimastigote and trypomastigote forms, with IC50 values in the low micromolar range. Some of them have greater activity and selectivity than the reference compound, nifurtimox. Conclusion: Compound 2 is the most active of this series, being also non-cytotoxic against murine RAW 264.7 macrophages. Electrochemical and radical scavenging experiments were carried out, providing new information about the profile of the best derivatives, and the potential therapeutic application of the new 3-amidocoumarins.

Background: Methicillin resistant Staphylococcus aureus (MRSA) usually invalidate powerful antibiotics in the clinic. Pleuromutilin derivatives have been reported to possess antibacterial activity against MRSA. Objective: The antibacterial activities against MRSA of a series of thirteen synthetic pleuromutilin derivatives were investigated through in vitro models. Methods: A series of novel thioehter pleuromutilin derivatives incorporating various aromatic substituents into the C14 side chain have been reported. The in vitro antibacterial activities of these derivatives against MRSA and Escherichia coli were tested by the broth dilution method. Results: Twelve pleuromutilin derivatives were designed, synthesized and evaluated for in vitro antibacterial activities against four Staphylococcus aureus strains. From structure-activity relationship studies, compound 11c was identified as promising compounds with the most potent in vitro antibacterial activity among the series (MIC = 0.0625-0.125 μg/ml) against Staphylococcus aureus strains. The binding of compound 11c to the 50s ribosome was investigated by molecular modeling. Conclusion: It was found that there is a reasonable correlation between the binding free energy and the antibacterial activity.

Background: T-705 (Favipiravir) is a broad spectrum antiviral agent approved for stockpiling in Japan and currently in Phase 3 testing in the United States. Against influenza, it acts as a prodrug, converted intracellularly to selectively inhibit viral RNA-dependent RNA polymerase or similar enzymes. This is regarded as a novel antiviral mechanism of action, reducing crossresistance to other existing anti-influenza drugs. Objective: To develop new analogs, a class of 1,3-oxathiolane nucleoside derivatives of T-705 was designed and synthesized in this work. Results: Anti-influenza activity and Anti-HIV activity of these compounds were evaluated. Compound 1a displayed activity against A H1N1 with an IC50 of 40.4 μmol/L. Compound 1b showed weak activity against HIV with a viral suppression rate of 70-80% at 30 μmol/L. Conclusion: A class of 1,3-oxathiolane nucleoside derivatives of T-705 was designed and synthesized, and one of them was identified as a novel scaffold against viral infection.

Background: RNase P-mediated cleavage of target RNAs has been proposed as a promising tool for gene silencing. Ets-2 proto-oncogene controls the expression of a wide variety of genes involved in cancer and immunity. Objective: Construction of a functional RNase P-based ribozyme (M1GS303) that targets Ets-2 mRNA. Methods: The accessible sites for targeting of Ets-2 mRNA were identified by footprinting analysis. M1GS303 ribozyme was constructed by cloning. The activity of the ribozyme in the presence or absence of spiramysin in E. coli cells and human cell lines was quantified by RT-PCR. The efficiency of the ribozyme in silencing the endogenous expression of Ets-2 in human cell lines was examined by RT-PCR, western blot and immunofluorescence analysis. Results: In E. coli cells co-transformed with plasmids bearing M1GS303 and the ets-2 target gene, Ets-2 mRNA was decreased by 93% 12h after IPTG induction in the absence, and after 4h in the presence of spiramycin. Ets-2 was rapidly downregulated in the human embryonic kidney cell line HEK293 and the T-cell line Jurkat transfected with an M1GS303 plasmid; the silencing effect of M1GS303 was considerably faster when the cells were cultured with spiramycin. In Jurkat cells, Ets-2-downregulation resulted in upregulation of the expression of IL-2, IL-4 and IFN-α cytokine genes that have Ets-2 binding sites on their promoters, whereas it had no effect on the expression of the IL-10 gene that lacks Ets-2 binding sites on its promoter. Conclusions: M1GS303 ribozyme cleaves effectively Ets-2 mRNA in bacteria and mammalian cells, and its activity is enhanced by spiramycin. Downregulation of ets-2 gene in the T-cell line Jurkat upregulates IL-2, IL-4 and IFN-α cytokine genes. M1GS technology may be a better alternative to conventional gene-interference therapies and the delineation of the effects of gene silencing in various pathologies.

Background: Oleanolic acid (OA) is a known natural compound with many important biological activities. Thirteen oleanolic acid derivatives linked at C-3 and C-28 were synthesized and their structures were confirmed by 1H- and 13C NMR and mass spectral analyses. Among them, compounds 4, 6, 8-10, 12, 13 were synthesized for the first time. They were evaluated for their cytotoxic activity. They showed proliferative effect at low concentrations while cytotoxic effect was observed at high concentrations in a dose dependent manner. Methods: We have first synthesized compounds 1 and 2 from the reaction of methyl iodide and OA. Compound 1 was reduced with LiAlH4 to give compound 3, and compound 2 gave compound 9 with MOMBr as a new compound. The compound 10 was then obtained from the reduction of compound 9 with LiAlH4 as a new oleanolic acid derivative. A diol derivative 11 was synthesized from OA and LiAlH4 at the room temperature. Compound 4 was obtained from the reaction of compound 3 with CBr4 as a new analogue of OA, and the reduction of compound 4 afforded compound 5 as a known product. In addition, we synthesized compounds 6-8 from compound 3 using MsCl, MeI and p-nitrobenzoyl chloride, respectively, in good yields. Compounds 6 and 8 are new analogues of OA. The new compounds 12 and 13 were also synthesized starting from OA using with MOMBr and TBDMSiCl as the reagents. The all synthesized compounds were purified by using column chromatography and/or crystallization. Results: In the present study, thirteen OA derivatives linked at C-28 and (or) C-3 were synthesized and evaluated for their cytotoxic activity on 3T3 cell lines which are the standard fibroblast cell lines, derived from Swiss albino mouse embryo tissue. 3T3 cell viability was observed at low concentrations of the tested triterpenoids while they displayed anti-proliferative effect at higher concentrations. Conclusion: Oleanolic acid 28-methyl ester (2) showed fairly different behavior from all the other compounds tested and found to be the least cytotoxic compound. However, at 200 μM concentration, it exhibited the same cytotoxicity with compounds 3, 9 and 10 around 58-59%. Among the tested 13 compounds, 7 exhibited the most drastic decline for the viability from 12,5 μM to 25 μM concentration. Compound 6 displayed the most cytotoxic effect, almost in all concentrations, particularly at 6.25 and 25 μM concentrations while the highest cytotoxic effect at 50 μM was observed for compound 11 among all the tested triterpenoids. As a result, all the tested OA derivatives showed proliferative effect at 1,56 μM although no proliferative effect was observed for OA. Moreover, OA exhibited higher cytotoxic effect than its derivatives, particularly at higher concentrations (50, 100, 200 μM) with an exception for compound 11. Because, the latter showed highest proliferative effect at lowest concentration, and highest anti-proliferative effect at highest concentration which surpassed all the OA derivatives.

Background: Designing a novel antagonist against VEGFR-2 is being applied currently to inhibit cancer growth and metastasis. Because of the unexpected side effects incurred by the contemporary anticancer medications, the focus has been laid towards identifying natural compounds that might carry the potential to inhibit tumor progression. VEGR-2 remains an important target for anticancer drug development as it is the master regulator of vascular growth. Objective: The study focuses on virtual screening of compounds from plants of Asteraceae family that bears antiangiogenic potential and thus, inhibiting VEGFR-2 using a computational approach. Materials and Methods: Structures of phytochemicals were prepared using ChemDraw Ultra 10 software and converted into its 3D PDB structure and minimized using Discovery Studio client 2.5. The target protein, VEGFR-2 was retrieved from RCSB PDB. Lipinski's rule and ADMET toxicity profiling were carried out on the phytochemicals of the Asteraceae family and the filtered compounds were further promoted for molecular docking and MD simulation analysis. The study extends towards the SOM analysis of Pinocembrin to predict the possible toxic and non-toxic in vivo metabolites via in silico tools (Xenosite Web and PASS online server). Results: The docking results revealed promising inhibitory potential of Pinocembrin against VEGFR-2 with binding energy of -8.50 kcal/mole as compared to its known inhibitors Sorafenib and YLT192 having binding energy of -6.49 kcal/mole and -8.02 kcal/mol respectively. Further, molecular dynamics (MD) simulations for 10ns were conducted for optimization, flexibility prediction, and determination of folded VEGFR-2 stability. The Hsp90-Pinocembrin complex was found to be quite stable with RMSD value of 0.2nm. Pinocembrin was found to be metabolically stable undergoing phase I metabolism with non-toxic metabolites compared to the standard drug Sorafenib and YLT192. Conclusion: Obtained results propose Pinocembrin as a multi-targeted novel lead compound that bears outstanding antiangiogenic potential against VEGFR-2.

Background: Black carrot is known to be effective against Type 2 diabetes. The phenolic compounds present in black carrot are responsible for this property, but limited information was available about the mechanism of action and target enzymes. Objective: The present study aims at understanding molecular interactions of phenolic compounds of black carrot with enzymes involved in glucose metabolism in human to identify the potential inhibitor that can be used as candidate drug molecule to control diabetes. Method: In vitro assay for inhibition of α-amylase, α-glucosidase and DPP-IV was carried out using black carrot purified extract and the standard inhibitor acarbose and vildagliptin, recpectively. The inhibition activity of selected phenolic compounds was also studied by in silico docking with all these three enzymes for the proper understanding of interactions. Encapsulation of purified black carrot extract was also carried out. Results: In vitro IC50 value of purified extract was found to be better than the standard inhibitor acarbose for α-amylase and α-glucosidase, and vildagliptin for DPP-IV. Similarly, docking scores of few anthocyanin molecules were found to be higher than their respective inhibitors, suggesting more effective inhibition. Among anthocyanin molecules of black carrot, cyanidin 3-xylosyl galactoside was found to be the potential drug to inhibit these enzymes, whereas dipeptidyl peptidase IV was identified as the best target to control diabetes with anthocyanins of black carrot. Conclusion: Anthocyanins from black carrot were found to be effective to control diabetes and very first time we propose that cyanidin 3-xylosyl galactoside is the best potential molecule for inhibiting enzymes involved in glucose metabolism. The study also shows the encapsulation of anthocyanin compounds using β-cyclodextrin.