Publications by authors named "Ibrahim M Abdou"

11 Publications

  • Page 1 of 1

Solubilization of Pyridone-Based Fluorescent Tag by Complexation in Cucurbit[7]uril.

ACS Omega 2019 Jan 10;4(1):953-960. Epub 2019 Jan 10.

Chemistry Department, College of Science, United Arab Emirates University, P.O. Box 15551, Al Ain, United Arab Emirates.

Aimed at further exploring the hosting properties of cucurbit[7]uril (CB7), we have exploited the spectroscopic and photophysical properties of a known fluorescent label as the guest molecule, namely, 3-cyano-6-(2-thienyl)-4-trifluoromethyl pyridine (TFP), in neat solvents. The formation of an inclusion host-guest complex with CB7 was checked by UV-vis absorption spectroscopy, and the value of binding constant (9.7 × 10 M) was extracted from the spectrophotometric data. The modulation of keto-enol equilibrium in TFP by the local environment is governed by the interplay between dimerization through intermolecular hydrogen bonding between individual solute molecules, favoring the enol form, and intermolecular hydrogen bonding between TFP and the surrounding solvents, favoring the keto form. Time-resolved fluorescence results established that the macromolecular CB7 host stabilizes preferentially the neutral enol form over the keto form of TFP. Unprecedentedly, our results reveal a linear dependence of the amplitudes of the extracted decay-associated spectra from the time-resolved fluorescence spectra of TFP on the sum of polarity/polarizability and hydrogen bonding parameters of the local environment, confirming that TFP at micromolar concentration in the CB7 complexes is experiencing a methanol-like environment. The results rationalized the 42-fold enhancement in the solubility of TFP in water media by complexation in CB7.
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http://dx.doi.org/10.1021/acsomega.8b02761DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6648827PMC
January 2019

Synthesis and in vitro biological evaluation of new pyrimidines as glucagon-like peptide-1 receptor agonists.

Bioorg Med Chem Lett 2017 11 14;27(22):5071-5075. Epub 2017 Sep 14.

Department of Chemistry, College of Science, UAE University, Al-Ain 15551, United Arab Emirates. Electronic address:

The therapeutic success of peptide glucagon-like peptide-1 (GLP-1) receptor agonists for the treatment of type 2 diabetes mellitus has inspired discovery efforts aimed at developing orally available small-molecule GLP-1 receptor agonists. In this study, two series of new pyrimidine derivatives were designed and synthesized using an efficient route, and were evaluated in terms of GLP-1 receptor agonist activity. In the first series, novel pyrimidines substituted at positions 2 and 4 with groups varying in size and electronic properties were synthesized in a good yield (78-90%). In the second series, the designed pyrimidine templates included both urea and Schiff base linkers, and these compounds were successfully produced with yields of 77-84%. In vitro experiments with cultured cells showed that compounds 3a and 10a (10-10M) significantly increased insulin secretion compared to that of the control cells in both the absence and presence of 2.8mM glucose; compound 8b only demonstrated significance in the absence of glucose. These findings represent a valuable starting point for the design and discovery of small-molecule GLP-1 receptor agonists that can be administered orally.
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http://dx.doi.org/10.1016/j.bmcl.2017.09.032DOI Listing
November 2017

Antibacterial activity and mechanism of action of the benzazole acrylonitrile-based compounds: In vitro, spectroscopic, and docking studies.

Eur J Med Chem 2017 Aug 4;136:270-282. Epub 2017 May 4.

Department of Chemistry, College of Science, UAE University Al-Ain, 15551, United Arab Emirates. Electronic address:

A new series of pyrimidine derivatives 5, 9a-d and 12a-d was synthesized by an efficient procedure. The antibacterial activity of the new compounds was studied against four bacterial strains. Compound 5 was found to exhibit the highest potency, with = 1.0 μg/ml, against both Escherichia coli and Pseudomonas aeruginosa when compared with amoxicillin (MIC = 1.0-1.5 μg/mL). Transmission electron microscope results confirmed that activities against bacteria occurred via rupturing of the cell wall. Molecular modeling results suggested that compounds 5, 9a-d and 12a-d have the potential to irreversibly bind to the penicillin-binding protein (PBP) Ser62 residue in the active site and were able to overcome amoxicillin resistance in bacteria by inhibiting the β-lactamase enzyme. Docking studies showed that compounds 5, 9a-d and 12a-d inhibit the β-lactamase enzyme through covalent bonding with Ser70. The synergistic effect with amoxicillin was studied. The newly synthesized compounds reported in this study warrant further consideration as prospective antimicrobial agents.
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http://dx.doi.org/10.1016/j.ejmech.2017.05.010DOI Listing
August 2017

Cytotoxic activity of the novel heterocyclic compound G-11 is primarily mediated through intrinsic apoptotic pathway.

Apoptosis 2016 07;21(7):873-86

Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University (NSU), Fort Lauderdale, FL, 33328, USA.

Natural and chemically synthesized heterocyclic compounds have been explored for their potential use as anticancer agents. We had synthesized non-natural heterocyclic analogs and evaluated their anti-tumor activity by measuring effect on cell proliferation and induction of apoptosis in different cell lines. Previously, we identified a pyrazole-containing compound (G-11) showing cytotoxic effect towards leukemia and lymphoma cell lines. In this study, we further investigated the mechanistic aspects of anticancer properties of G-11 in HL-60 cell line. We demonstrated that cytotoxic effect of G-11 is mediated by caspase-dependent apoptosis. However, the involvement of mitochondrial dysfunction induced by G-11 was independent of caspases. G-11 triggered generation of ROS, caused disruption of mitochondrial transmembrane potential, increased release of cytochrome c to the cytosol, and altered the expression of Bcl-2 and Bax proteins. These results suggest significant involvement of intrinsic apoptotic pathway. This study comprehensively details the possible mechanisms of action of a novel heterocyclic compound which could find its potential use as an anticancer agent.
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http://dx.doi.org/10.1007/s10495-016-1248-zDOI Listing
July 2016

Interaction of human telomeric G-quadruplex DNA with thymoquinone: a possible mechanism for thymoquinone anticancer effect.

Biochim Biophys Acta 2015 Feb 24;1850(2):329-42. Epub 2014 Oct 24.

School of Biological Sciences, College of Science, Nanyang Technological University, Singapore 637551, Singapore.

Background: Thymoquinone (TQ) has been documented to possess chemo-preventive and chemotherapeutic antitumor effects. Studies reported that TQ inhibits the growth of cancer cells in animal models, culture and xenografted tumors. Molecular mechanisms underlying these anticancer effects were attributed to inductions of cell cycle arrest, apoptosis, oxidative damage of cellular macromolecules, blockade of tumor angiogenesis and inhibitions in migration, invasion and metastasis of cancer cells. On the other hand, human telomere DNA plays a role in regulating genes' transcriptions. It folds up into G-quadruplex structures that inhibit telomerase enzyme over-expressed in cancerous cells. Molecules that selectively stabilize G-quadruplex are potential anticancer agents. Therefore, this work aimed to explore the interaction of TQ with G-quadruplex DNA as a possible underlying mechanism for the anticancer effect of TQ.

Methods: Interactions of TQ with telomeric G-quadruplex (5'-AGGG(TTAGGG)3-3') and duplex DNAs were studied using UV-vis, fluorescence, circular dichroism, liquid and solid NMR (1H and 13C), melting temperature and docking simulation.

Results: Changes in UV-vis, CD, fluorescence, 1H NMR and 13C NMR, spectra as well as melting temperatures and docking simulations provided evidences for TQ's interactions with G-quadruplex. TQ was found to interact with G-quadruplex on two binding sites adjacent to the TTA loop with binding constants 1.80×10(5) and 1.12×10(7) M(-1). Melting temperatures indicated that TQ stabilized G-quadruplex by 5.6 °C and destabilized ct-DNA by 5.1 °C. Selectivity experiment indicated that TQ is preferentially binding to G-quadruplex over duplex with selectivity coefficients of 2.80-3.33×10(-3). Results suggested an intercalation binding mode based on π-π stacking.

Conclusion: Our results propose that TQ can possibly act as a G-quadruplex DNA stabilizer and subsequently contribute to the inhibition of telomerase enzyme and cancer's proliferation.

General Significance: Our results represent a change in the paradigms reported for structural features of G-quadruplex's stabilizers and anticancer mechanisms of TQ.
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http://dx.doi.org/10.1016/j.bbagen.2014.10.018DOI Listing
February 2015

Antimicrobial evaluation of new synthesized pyridine nucleosides under solvent-free conditions.

Nucleosides Nucleotides Nucleic Acids 2013 ;32(9):493-509

a Department of Chemistry, Faculty of Science , Cairo University , Cairo , Egypt.

Two series of novel 3-cyano-2-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyloxo) pyridines and 3-cyano-2-(2,3,5-tri-O-acetyl-β-D-ribofuranosyloxy)-4-trifluromethyl-6-phenyl pyridine were synthesized using efficient microwave methods. The targeted compounds were obtained in high yields by reacting 2-(1H)-pyridone or its salt with activated sugars using SiO₂ under solvent-free conditions. Ammonolysis of the resulted acetylated nucleosides produced 3-cyano-2-(β-D-glucopyranosyloxo)-pyridines and 3-cyano-2-(β-D-ribofuranosyloxy)-4-trifluoromethyl-6-phenyl pyridine. These new products were fully characterized using 1D and 2D NMR. These compounds were screened for their antibacterial activities against G(+) and G(-) bacteria and some found to exhibit better antibacterial activities than the control drug.
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http://dx.doi.org/10.1080/15257770.2013.827206DOI Listing
April 2014

Application of quantitative nuclear magnetic resonance spectroscopy for the determination ofamantadine and acyclovir in plasma and pharmaceutical samples.

J AOAC Int 2012 Nov-Dec;95(6):1644-51

UAE University, Department of Chemistry, Faculty of Science, Al-Ain, United Arab Emirates.

Rapid, simple, and selective methods for determining amantadine HCI and acyclovir antiviral drugs in pharmaceutical and plasma samples were developed using 1H-NMR spectroscopy with dimethyl sulfoxide (DMSO-d6) as the solvent. Integrations of the 1H-NMR signals at 2.07 and 7.82 ppm were used, respectively, for quantifying the two drugs, with the malonic acid signal at 3.24 ppm as the internal reference signal. Average recoveries of 98.24-101.00 +/- 4.82% and 97.7-100.38 +/- 3.36% were obtained for amantadine HCI and acyclovir in pharmaceutical samples, respectively. Average recoveries of 97.36-103.68 +/- 2.99 and 93.81-99.80 +/- 2.93 were obtained, respectively, for both drugs in plasma samples. The statistical Student's t-test gave t-values < or = 1.41 for analyzed pharmaceutical samples and t-values < or = 0.29 for analyzed plasma samples. These values indicated insignificant difference between the real and measured contents at the 95% confidence level. Application of the statistical F-test for the analytical results of amantadine HCI gave F-values < or = 6.44 and 2.80 in pharmaceutical and plasma samples, respectively. F-values < or = 6.82 and 3.86 were obtained for acyclovir in pharmaceutical and plasma, respectively. These values indicated insignificant differences in precisions between the developed NMR methods and arbitrarily chosen HPLC methods reported for determining both drugs in pharmaceutical and plasma samples.
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http://dx.doi.org/10.5740/jaoacint.11-165DOI Listing
April 2013

Microwave-assisted synthesis of 2(1H)-pyridones and their glucosides as cell proliferation inhibitors.

Nucleosides Nucleotides Nucleic Acids 2011 Feb;30(2):120-34

Department of Chemistry, Faculty of Science, United Arab Emirates University, Al-Ain, United Arab Emirates.

A new series of substituted 2(1H)-pyridones (4a-i) and their glucosides (5, 6a-e) were prepared as potential agents against leukemia (HL-60) cells. Glucosides (5,6a-e) were synthesized using three independent methods. Microwave protocol as an ecologically new method was used to synthesize the target compounds. Structures of the new products were confirmed using one- and two-dimensional NMR spectroscopy. In vitro exposure of pyridones substituted at position 4 with a 2-thienyl or 2-(trifluoromethyl)phenyl were found to exhibit high antiproliferation activities; in particular, 3-cyano-4-(thien-2'-yl)-6-(4''-chlorophenyl)-2(1H)-pyridone (4c) and its glucoside analogue (6c) had the highest activity.
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http://dx.doi.org/10.1080/15257770.2010.551646DOI Listing
February 2011

Synthesis and antitumor activity of 5-trifluoromethyl-2,4- dihydropyrazol-3-one nucleosides.

Molecules 2004 Feb 28;9(3):109-16. Epub 2004 Feb 28.

Department of Chemistry, Faculty of Science, UAE University, Al-Ain P.O. Box 17551, UAE.

2,4-Dihydropyrazole glucosides 3a-3c were prepared and tested for their antitumor activity. The structures of these compounds were established by (1)H and (13)C-NMR spectroscopy. Glucoside 3b shows an in vitro IC(50) value of 16.4 muM against proliferation of the human promyelotic leukemia (HL60) cell line.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6147422PMC
http://dx.doi.org/10.3390/90300109DOI Listing
February 2004

Solvent and linker influences on AQ(*-)/dA(*+) charge-transfer state energetics and dynamics in anthraquinonyl-linker-deoxyadenosine conjugates.

J Phys Chem A 2006 Apr;110(13):4320-8

Department of Chemistry, Georgia State University, P.O. Box 4098, Atlanta, Georgia 30302-4098, USA.

The goal of this work is to produce high yields of long-lived AQ(*-)/dA(*+) charge transfer (CT) excited states (or photoproducts). This goal fits within a larger context of trying generally to produce high yields of long-lived CT excited states within DNA nucleoside conjugates that can be incorporated into DNA duplexes. Depending upon the energetics of the anthraquinonyl (AQ) (3)(pi,pi) state as well as the reduction potentials of the subunits in particular anthraquinonyl-adenine conjugates, CT quenching of the AQ (3)(pi,pi*) state may or may not occur in polar organic solvents. In MeOH, bis(3',5'-O-acetyl)-N(6)-(anthraquinone-2-carbonyl)-2'-deoxyadenosine (AQCOdA) behaves as intended and forms a (3)(AQ(*-)/dA(*+)) CT state with a lifetime of 3 ns. However, in nonpolar THF the AQ(*-)/dA(*+) CT states of AQCOdA are too high in energy to be formed, and in DMSO a (1)(AQ(*-)/dA(*+)) CT state is formed but lives only 6 ps. Although the lowest energy excited state for AQCOdA in MeOH is a (3)(AQ(*-)/dA(*+)) CT state, for N(6)-(anthraquinone-2-methylenyl)-2'-deoxyadenosine (AQMedA) in the same solvent it is a (3)(pi,pi*) state. Changing the linking carbonyl in AQCOdA to methylene in AQMedA makes the anthraquinonyl subunit harder to reduce by 166 mV. This raises the energy of the (3)(AQ(*-)/dA(*+)) CT state above that of the (3)(pi,pi*) in AQMedA. The conclusion is that anthraquinonyl-dA conjugates will not have lowest energy AQ(*-)/dA(*+) CT states in polar organic solvents unless the anthraquinonyl subunit is also substituted with an electron-withdrawing group that raises the AQ-subunit's reduction potential above that of AQ. A key finding in this work is that the lifetime of the (3)(AQ(*-)/dA(*+)) CT excited state (ca. 3 ns) is ca. 500-times longer than that of the corresponding (1)(AQ(*-)/dA(*+)) CT excited state (ca. 6 ps).'
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http://dx.doi.org/10.1021/jp054395qDOI Listing
April 2006

Glucopyranosides derived from 6-aryl-5-cyano-2-(methylthio)pyrimidin-4(3H)ones.

Nucleosides Nucleotides Nucleic Acids 2002 ;21(1):15-21

Department of Chemistry, Georgia State University, Atlanta 30303, USA.

The reaction of 2,3.4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide with a 6-aryl-5-cyano-2-(methylthio)pyrimidin-4(3H)one in aqueous acetone in the presence of KOH furnishes a 4-(beta-D-glucopyranosyloxy)pyrimidine and a 3-(beta-D-glucopyranosyl)pyrimidine as the major and minor product. respectively.
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http://dx.doi.org/10.1081/NCN-120006527DOI Listing
February 2003
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