Aqueous phase synthesis, crystal structure and antimicrobial activity of 4-(substituted phenylazo)-3-methyl-4H-isoxazol-5-one azo dyes

3-Methyl-4H-isoxazol-5-one was synthesized at room temperature by simple stirring method from ethyl acetoacetate and hydroxylamine hydrochloride in aqueous medium and coupled with diazotized substituted amine to form series of 4-(substituted phenylazo)-3-methyl-4H-isoxazol-5-ones through green chemistry. All the compounds formed were characterized by IR, 1H and 13C NMR spectroscopy, MS and elemental analysis. Crystal structure of novel 4-(4-fluorophenylazo)-3-methyl-4H-isoxazol-5-one was determined by the X-ray diffraction. Antibacterial and antifungal activity was studied against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus pyogenus and Candida albicans, Aspergillus niger, Aspergillus clavatus, respectively. All synthesized compounds were found to be active against a gram-positive bacterium Staphylococcus aureus. Two compounds showed antifungal activity against Candida albicans close to standard greseofulvin.               KEY WORDS: Azo dyes, Substituted amines, Antibacterial and antifungal activity, X-ray diffraction, Spectroscopy, Green chemistry Bull. Chem. Soc. Ethiop. 2018, 32(2), 249-257.DOI: https://dx.doi.org/10.4314/bcse.v32i2.

In silico study of CYP450 inhibitor activity of (E)-1-(3-((4-chlorophenyl) diazenyl)-4-hydroxyphenyl)ethanone

Molecular docking and single crystal study of azo dye (E)-1-(3-((4-chlorophenyl)diazenyl)-4-hydroxyphenyl)ethanone (3) is reported here. It has been synthesized by diazotization of 4-chloroaniline followed by coupling with 4-hydroxyacetophenone. Molecule is almost planar with acetyl as well as azo groups only slightly deviating from the plane of C3–C8 phenyl ring as evident by C1–C2–C3–C8 and N2–N1–C7–C6 torsion angles of –3.6(3)° and –3.9(3)°, respectively. Torsion angle N1–N2–C9–C14 between azo group and chlorophenyl ring is somewhat larger being –13.1(3)° leading to torsion angle between phenyl C3–C8 and chlorophenyl C9–C14 ring of 17.26(11)°. Intramolecular O2–H2···N2 hydrogen-bonding is observed here. Pillars along b-axis are formed due to π∙∙∙π stacking interactions of parallel molecules in head-to-head fashion with centroid-to-centroid distance of 3.8829(14) Å and ring slippage of 1.416 Å. Title compound shows good binding affinity towards six enzymes of CYP450 family. Both nitrogens of the azo bond show significant involvement in bonding interactions with proteins in case of all the six enzymes

From carbohydrates to drug-like fragments: Rational development of novel [alfa]-amylase inhibitors

K

Structural Analysis of a Peptide Fragment of Transmembrane Transporter Protein Bilitranslocase

Using a combination of genomic and post-genomic approaches is rapidly altering the number of identified human influx carriers. A transmembrane protein bilitranslocase (TCDB 2.A.65) has long attracted attention because of its function as an organic anion carrier. It has also been identified as a potential membrane transporter for cellular uptake of several drugs and due to its implication in drug uptake, it is extremely important to advance the knowledge about its structure. However, at present, only the primary structure of bilitranslocase is known. In our work, transmembrane subunits of bilitranslocase were predicted by a previously developed chemometrics model and the stability of these polypeptide chains were studied by molecular dynamics (MD) simulation. Furthermore, sodium dodecyl sulfate (SDS) micelles were used as a model of cell membrane and herein we present a high-resolution 3D structure of an 18 amino acid residues long peptide corresponding to the third transmembrane part of bilitranslocase obtained by use of multidimensional NMR spectroscopy. It has been experimentally confirmed that one of the transmembrane segments of bilitranslocase has alpha helical structure with hydrophilic amino acid residues oriented towards one side, thus capable of forming a channel in the membrane

Functional Rotation of the Transporter AcrB: Insights into Drug Extrusion from Simulations

The tripartite complex AcrAB-TolC is the major efflux system in Escherichia coli. It extrudes a wide spectrum of noxious compounds out of the bacterium, including many antibiotics. Its active part, the homotrimeric transporter AcrB, is responsible for the selective binding of substrates and energy transduction. Based on available crystal structures and biochemical data, the transport of substrates by AcrB has been proposed to take place via a functional rotation, in which each monomer assumes a particular conformation. However, there is no molecular-level description of the conformational changes associated with the rotation and their connection to drug extrusion. To obtain insights thereon, we have performed extensive targeted molecular dynamics simulations mimicking the functional rotation of AcrB containing doxorubicin, one of the two substrates that were co-crystallized so far. The simulations, including almost half a million atoms, have been used to test several hypotheses concerning the structure-dynamics-function relationship of this transporter. Our results indicate that, upon induction of conformational changes, the substrate detaches from the binding pocket and approaches the gate to the central funnel. Furthermore, we provide strong evidence for the proposed peristaltic transport involving a zipper-like closure of the binding pocket, responsible for the displacement of the drug. A concerted opening of the channel between the binding pocket and the gate further favors the displacement of the drug. This microscopically well-funded information allows one to identify the role of specific amino acids during the transitions and to shed light on the functioning of AcrB

Copper(II) ions mediated crystal formation of 3-(3-hydroxy phenyl)-1-phenyl-1h-pyrazole- 4-carbaldehyde

Schiff base obtained from 3-hydroxyacetophenone and phenylhydrazine was subjected to Vilsmeier-Haack reaction to obtain 3-(3-hydroxyphenyl)-1-phenyl-1H-pyrazole-4-carbaldehyde (2). Successful formation of crystals of 2 was achieved using copper ions (Cu2+) as template. Present paper reports study of spectroscopic characterization and single-crystal X-ray study of 2. Hydrogen bonding network between 2 and water molecules enable the formation of 2D layer along ab-plane supported also by π···π stacking interactions of parallel molecules in head-to-head fashion.                     KEY WORDS: Cu2+ assisted crystal growth, Pyrazole-4-carbaldehyde, X-ray crystal study, Hydrogen bonding study   Bull. Chem. Soc. Ethiop. 2020, 34(3), 589-596. DOI: https://dx.doi.org/10.4314/bcse.v34i3.1

In silico study of CYP450 inhibitor activity of (E)-1-(3-((4-chlorophenyl) diazenyl)-4-hydroxyphenyl)ethanone

147-152Molecular docking and single crystal study of azo dye (E)-1-(3-((4-chlorophenyl)diazenyl)-4-hydroxyphenyl)ethanone (3) is reported here. It has been synthesized by diazotization of 4-chloroaniline followed by coupling with 4-hydroxyacetophenone. Molecule is almost planar with acetyl as well as azo groups only slightly deviating from the plane of C3–C8 phenyl ring as evident by C1–C2–C3–C8 and N2–N1–C7–C6 torsion angles of –3.6(3)° and –3.9(3)°, respectively. Torsion angle N1–N2–C9–C14 between azo group and chlorophenyl ring is somewhat larger being –13.1(3)° leading to torsion angle between phenyl C3–C8 and chlorophenyl C9–C14 ring of 17.26(11)°. Intramolecular O2–H2ꞏꞏꞏN2 hydrogen-bonding is observed here. Pillars along b-axis are formed due to π∙∙∙π stacking interactions of parallel molecules in head-to-head fashion with centroid-to-centroid distance of 3.8829(14) Å and ring slippage of 1.416 Å. Title compound shows good binding affinity towards six enzymes of CYP450 family. Both nitrogens of the azo bond show significant involvement in bonding interactions with proteins in case of all the six enzymes

Synthesis, structural determination, in vitro and in silico biological evaluation of divalent or trivalent cobalt complexes with indomethacin

The interaction of cobalt chloride with the non-steroidal anti-inflammatory drug indomethacin (Hindo) led to the formation of the polymeric complex [Co(indo-O)2(H2O)2(μ-Cl)]n·n(MeOH·H2O) bearing one chlorido bridge between the cobalt atoms. The presence of the nitrogen-donor co-ligands 2,2′-bipyridine (bipy), 2,2′-bipyridylamine (bipyam), 1,10-phenanthroline (phen) or 1H-imidazole (Himi) resulted in the isolation of complexes [Co2(μ-indo-O,O′)2(indo-O)2(bipy)2(μ-H2O)]·3.3MeOH, [Co(indo-O,O′)2(bipyam)]·0.9MeOH·0.2H2O, [Co(indo-O,O′)2(phen)] (4) and [Co(indo-O)2(Himi)2] (5), respectively, where the indomethacin ligands were coordinated in diverse manners. The study of the affinity of the complexes for calf-thymus DNA revealed their intercalation between the DNA-bases. The binding of the complexes to albumins was also examined and the corresponding binding constants and binding subdomain were determined. The free radical scavenging activity of the compounds was evaluated towards 1,1-diphenyl-picrylhydrazyl and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid). Molecular modeling calculations may usually provide a molecular basis for the understanding of both the impairment of DNA by its binding with the studied complexes and the ability of these compounds to transportation through serum albumin proteins. This study can provide information for the elucidation of the mechanism of action of the compounds in a molecular level. © 2020 Elsevier Inc

In Silico Discovery of a Substituted 6-Methoxy-quinalidine with Leishmanicidal Activity in Leishmania infantum

There is an urgent need for the discovery of new antileishmanial drugs with a new mechanism of action. Type 2 NADH dehydrogenase from Leishmania infantum (LiNDH2) is an enzyme of the parasite’s respiratory system, which catalyzes the electron transfer from NADH to ubiquinone without coupled proton pumping. In previous studies of the related NADH: ubiquinone oxidoreductase crystal structure from Saccharomyces cerevisiae, two ubiquinone-binding sites (UQI and UQII) were identified and shown to play an important role in the NDH-2-catalyzed oxidoreduction reaction. Based on the available structural data, we developed a three-dimensional structural model of LiNDH2 using homology detection methods and performed an in silico virtual screening campaign to search for potential inhibitors targeting the LiNDH2 ubiquinone-binding site 1–UQI. Selected compounds displaying favorable properties in the computational screening experiments were assayed for inhibitory activity in the structurally similar recombinant NDH-2 from S. aureus and leishmanicidal activity was determined in the wild-type axenic amastigotes and promastigotes of L. infantum. The identified compound, a substituted 6-methoxy-quinalidine, showed promising nanomolar leishmanicidal activity on wild-type axenic promastigotes and amastigotes of L. infantum and the potential for further development.Acknowledgments: The authors would like to gratefully acknowledge COST Action CM1307 “Targeted chemotherapy towards diseases caused by endoparasites” and COST Action CM1306–Understanding Movement and Mechanism in Molecular Machines. This work was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Grant no. 173001) and Ministry of Higher Education, Science and Technology of the Republic of Slovenia through Grant P1-0012. FVS and FMS are recipients of fellowships from Fundação para a Ciência e a Tecnologia (PD/BD/113985/2015, PD/BD/128213/2016, respectively, within the scope of the PhD program Molecular Biosciences PD/00133/2012). The work was also funded by Fundação para a Ciência e a Tecnologia FCT (IF/01507/2015 to MMP) and the Norte-01-0145-FEDER-000012-Structured program on bioengineered therapies for infectious diseases and tissue regeneration, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (FEDER). We thank Kaja Bergant for her kind assistance with Figure preparations