Novel Thiazolidinedione and Rhodanine Derivatives Regulate Glucose Metabolism, Improve Insulin Sensitivity, and Activate the Peroxisome Proliferator-Activated γ Receptor.

Sixteen novel thiazolidinedione (TZD) and rhodanine (RD) derivatives were designed and synthesized by introducing a pyrimidine moiety at different sites of pioglitazone's structure. The effects of synthesized compounds on regulating glucose metabolism, improving insulin sensitivity, and activating the peroxisome proliferator-activated γ receptor (PPAR-γ) were evaluated in ßTC6 cells. Compounds TZDs # 7a, 7b, 7c, and 29 reduced the basal insulin secretion by ∼20.0-67.0% and increased insulin secretion stimulated by glucose by ∼25.0-50.0% compared to control. Compounds TZDs # 14 and 21 and RDs # 33a-b and 33d-f increased basal insulin secretion by ∼20.0-100.0%, while its glucose-stimulated secretion remained unchanged. These findings suggested that the former compounds can act as antihypoglycemic during fasting and antihyperglycemic during postprandial conditions. The latter compounds should be administered before meals to avoid their hypoglycemic effect. Additionally, both TZDs and RDs improved insulin sensitivity by increasing glucose uptake by 17.0-155.0% relative to control. In silico molecular docking of synthesized drugs onto the PPAR-γ structure revealed exothermic binding modes through hydrogen bonding, van der Waals forces, and π-π stacking with binding affinities of -6.02 to -9.70 kcal/mol. Insights into the structure-activity relationship revealed that the introduction of pyrimidine linked to sulfonyl or peptide groups accounted for increased antidiabetic activity. These results demonstrated novel TZDs and RDs with high potency in stimulating insulin secretion, enhancing insulin sensitivity, and activating PPAR-γ relative to pioglitazone. They are recommended for further development as potential antidiabetic agents.

GW-2974 and SCH-442416 modulators of tyrosine kinase and adenosine receptors can also stabilize human telomeric G-quadruplex DNA.

GW-2974 is a potent tyrosine kinase receptor inhibitor while SCH-442416 is a potent adenosine receptors' antagonist with high selectivity towards human adenosine A2A receptor over other adenosine receptors. The two compounds were reported to possess anti-cancer properties. This study aimed to investigate whether stabilization of human telomeric G-quadruplex DNA by GW-2974- and SCH-442416 is a plausible fundamental mechanism underlying their anti-cancer effects. Human telomeric G-quadruplex DNA with sequence AG3(TTAGGG)3 was used. The study used ultraviolet-visible (UV-Vis), fluorescence, fluorescence quenching, circular dichroism (CD), melting temperatures (Tm) and molecular docking techniques to evaluate interactions. The results showed that GW-2974 and SCH-442416 interacted with G-quadruplex DNA through intercalation binding into two types of dependent binding sites. Binding affinities of 1.3 × 108-1.72 × 106 M-1 and 1.55 × 107-3.74 × 105 M-1 were obtained for GW-2974 and SCH-442416, respectively. An average number of binding sites between 1 and 2 was obtained. Additionally, the melting temperature curves indicated that complexation of both compounds to G-quadruplex DNA provided more stability (ΔTm = 9.9°C and 9.6°C, respectively) compared to non-complexed G-quadruplex DNA. Increasing the molar ratios over 1:1 (drug:G-quadruplex) showed less stabilization effect on DNA. Furthermore, GW-2974 and SCH-442516 have proven ≥ 4.0 folds better selective towards G-quadruplex over double-stranded ct-DNA. In silico molecular docking and dynamics revealed favorable exothermic binding for the two compounds into two sites of parallel and hybrid G-quadruplex DNA structures. The results supported the hypothesis that GW-2974 and SCH-442416 firmly stabilize human telomeric G-quadruplex DNA in additions to modulating tyrosine kinase and adenosine receptors. Consequently, stabilizing G-quadruplex DNA could be a mechanism underlying their anti-cancer activity.

Characterization of human serum albumin's interactions with safranal and crocin using multi-spectroscopic and molecular docking techniques.

Interaction mechanisms of human serum albumin (HSA) with safranal and crocin were studied using UV-Vis absorption, fluorescence quenching and circular dichroism (CD) spectroscopies as well as molecular docking techniques. Changes in absorbance and fluorescence of HSA upon interactions with both compounds were attributed to their binding to amino acid chromophores located in subdomains IIA and IIIA. Fluorescence secondary inner filter effect was excluded using 278 nm and 340 nm as the wavelengths of HSA's excitation and fluorescence while safranal and crocin absorbed at 320 nm and 445 nm, respectively. Stern-Volmer model revealed a static quenching mechanism involve the formation of non-fluorescent ground state complexes. Stern-Volmer, Hill, Benesi-Hilbrand and Scatchard models gave apparent binding constants ranged in 4.25 × 103 - 2.15 × 105 for safranal and 7.67 × 103 - 4.23 × 105 L mol-1 for crocin. CD measurements indicated that 13 folds of safranal and crocin unfolded the α-helix structure of HSA by 7.47-21.20%. In-silico molecular docking revealed selective exothermic binding of safranal on eight binding sites with binding energies ranged in -3.969 to -6.6.913 kcal/mol. Crocin exothermally bound to a new large pocket located on subdomain IIA (sudlow 1) with binding energy of -12.922 kcal/mol. These results confirmed the formation of HSA stable complexes with safranal and crocin and contributed to our understanding for their binding characteristics (affinities, sites, modes, forces … etc.) and structural changes upon interactions. They also proved that HSA can solubilize and transport both compounds in blood to target tissues. The results are of high importance in determining the pharmacological properties of the two phytochemical compounds and for their future developments as anticancer, antispasmodic, antidepressant or aphrodisiac therapeutic agents.

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

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 × 105 M-1) 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.

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

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 (10-15-10-9M) 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.

Determination of Some ß-Blockers and ß2-Agonists in Plasma and Urine Using Liquid Chromatography-tandem Mass Spectrometry and Solid Phase Extraction.

A highly sensitive method for the determinations of acebutolol, clenbuterol, nadolol, oxprenolol, propranolol, terbutaline and timolol ß-blockers and ß2-agonists in plasma and urine was developed. The method was optimized using electrospray ionization liquid chromatography-tandem mass spectrometry (LC-ESI-MS-MS) and clean screen solid phase extraction cartridges. Matrix effect was reduced by removing co-extractives from the SPE cartridges using methanol prior to drugs' elution. Using blood and serum matrices for calibration and applying the internal standard method has also contributed to the reduction of matrix effect. Method's validation yielded linear dynamic ranges of 5.0-50.0 and 50.0-1000.0 ng/ml for drugs spiked in plasma and urine respectively. It also gave correlation coefficients of 0.94-0.99, detection limits ranged in 0.06-5.04 pg/ml and quantification limits ranged in 0.14-22.88 pg/ml for the target drugs. Developed method was successfully applied to the analysis of ß-blockers and ß2-agonists in plasma and urine samples. Plasma samples fortified with drugs at 7.5, 40.0 and 75.0 ng/ml gave percentage recoveries ranged in 78.66-118.10, 67.02-83.97 and 74.77-93.80, respectively. Urine samples fortified with drugs at 80.0, 400.0 and 800.0 ng/ml gave percentage recoveries ranged in 104.68-130.18, 110.23-125.16 and 109.46-116.89, respectively. Variance coefficients ranged in 0.05-0.35 and 0.04-0.12 were, respectively, obtained for the analyses of drugs in plasma and urine samples. Results suggest that developed method is well suited for the analysis of investigated drugs in biological fluids.

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

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 ß-lactamase enzyme. Docking studies showed that compounds 5, 9a-d and 12a-d inhibit the ß-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.

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

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.

Novel flow injection analysis methods for the determination of total iron in blood serum and water.

This work describes rapid, sensitive and highly precise methods for the determination of total iron in blood serum and water samples, using batch, nFIA and rFIA techniques. The proposed methods are based on the selective oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) by iron(III). The absorbance of the resultant green solution of radical cation (ABTS(·+)) was monitored spectrophotometrically at λ max=415 nm. The reaction is stoichiometric with a ratio of 1:1 (Fe(III):ABTS) as determined by Job's and molar ratio methods. The proposed methods allow for the determination of Fe(III) in the ranges 0-4.5 mg L(-1) (LOD 25.5 µg L(-1), %RSD 0.97%, n=7); 0 to 4.5 mg L(-1) (LOD 370 µg L(-1), %RSD 1.28%, n=7) and 0 to 2.7 mg L(-1) (81.6 µg L(-1), %RSD 0.76%, n=6) for batch, nFIA and rFIA techniques, respectively. The proposed methods show high selectivity to Fe(III), as indicated by the high tolerance limits for common interfering ions. The nFIA method was applied in total iron assay in camel blood serum, whereas batch and rFIA methods were successful in the determination of total iron in municipal pipeline water and spiked groundwater. Statistical analysis indicated insignificant differences in accuracy and precision between the results obtained by the developed methods and ICP-AES or phenanthroline methods.

Trace determination of ß-blockers and ß2-agonists in distilled and waste-waters using liquid chromatography-tandem mass spectrometry and solid-phase extraction.

A highly sensitive method for simultaneous determinations of eleven ß-blockers and ß-agonists in distilled and waste-waters using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS-MS) was developed, optimized and validated. The method was used for trace determinations of acebutolol, atenolol, metoprolol, propranolol, timolol, nadolol, labetalol, oxprenolol, pindolol, alprenolol and terbutaline. Oasis MCX and Clean Screen cartridges were used for solid phase extractions and an alkaline mixture of dichloromethane-propanol was used as mobile phase. Matrix effect was reduced by using methanol as a pre-eluant for removing co-extractives on the SPE cartridges and by applying the internal standard method for quantification. Using Oasis MCX-SPE cartridges, developed method gave average recoveries of 77.20-97.30% for drugs spiked at 150.00-500.00pg/ml. Intra-day precisions gave RSD of 3.367-12.489% while as inter-day precisions gave RSD of 6.425-19.768%. Detection limits of 0.11-6.74pg/ml and quantification limits of 0.14-22.88pg/ml were obtained. Signal's suppression in the range of 4.50-24.50% was recorded due to the matrix effect. Drugs spiked in wastewater at 500.00pg/ml concentrations level and stored at 4°C for 6 days, showed insignificant degradation. Developed method was successfully applied to the analysis of pharmaceutical residues in effluents wastewaters. Five ß-blockers and one ß-agonists were detected in Al-Ain and Abu Dhabi wastewaters at average concentrations of 3.44-19.05pg/ml. Atenolol was detected at higher average concentration ranged in 125.60-234.28pg/ml. Results obtained suggest that adopted wastewater treatment processes are not enough to degrade these compounds.

Method validation and determinations of levofloxacin, metronidazole and sulfamethoxazole in an aqueous pharmaceutical, urine and blood plasma samples using quantitative nuclear magnetic resonance spectrometry.

Selective, rapid and accurate quantitative proton nuclear magnetic resonance (qHNMR) method for the determination of levofloxacin, metronidazole benzoate and sulfamethoxazole in aqueous solutions was developed and validated. The method was successfully applied to the determinations of the drugs and their admixtures in pharmaceutical, urine and plasma samples. Maleic acid and sodium malate were used as internal standards. Effect of temperature on spectral measurements was evaluated. Linear dynamic ranges of 0.50-68.00, 0.13-11.30 and 0.24-21.00 mg per 0.60 mL solution were obtained for levofloxacin, metronidazole benzoate and sulfamethoxazole, respectively. Average recovery % in the range of 96.00-104.20 ± (0.17-2.91) was obtained for drugs in pure, pharmaceutical, plasma and urine samples. Inter and intra-day analyses gave average recoveries % in the ranges 96.10-98.40 ± (1.68-2.81) and 96.00-104.20 ± (0.17-2.91), respectively. Instrumental detection limits ≤0.03 mg per 0.6 mL were obtained for the three drugs. Developed method has demonstrated high performance characteristics for analyzing investigated drugs and their admixtures. Student t-test at 95% confidence level revealed insignificant bias between the real and measured contents of investigated drugs in pure, pharmaceutical, urine and plasma samples and its admixtures. Application of the statistical F-test revealed insignificant differences in precisions between the developed method and arbitrary selected reference methods.

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

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.

New spectrophotometric method for determining nitrogen dioxide in air using 2,2-azino-bis(3-ethyl benzothiazoline)-6-sulfonic acid-diammonium salt and passive sampling.

A new simple and highly sensitive spectrophotometric method for determining nitrogen dioxide in air was developed. The method is based on converting atmospheric nitrogen dioxide to nitrite ions within the IVL passive samplers used for samples collection. Acidifying nitrite ions with concentrated HCl produced the peroxynitrous acid oxidizing agent which was measured using 2, 2-azino-bis(3-ethyl benzothiazoline)-6-sulfonic acid-diammonium salt (ABTS) as reducing coloring agent. A parallel series of collected samples were measured for its nitrite content using a validated ion chromatographic method.The results obtained using both methods were compared in terms of their sensitivity and accuracy. Developed spectrophotometric method was shown to be one order of magnitude higher in sensitivity compared to the ion chromatographic method. Quantitation limits of 0.05 ppm and 0.55 µg/m(3) were obtained for nitrite ion and nitrogen dioxid, respectively. Standard deviations in the ranges of 0.05-0.59 and 0.63-7.92 with averages of 0.27 and 3.11 were obtained for determining nitrite and nitrogen dioxide, respectively.Student-t test revealed t-values less than 6.93 and 4.40 for nitrite ions and nitrogen dioxide, respectively. These values indicated insignificant difference between the averages of the newly developed method and the values obtained by ion chromatography at 95% confidence level.Compared to continuous monitoring techniques, the newly developed method has shown simple, accurate, sensitive, inexpensive and reliable for long term monitoring of nitrogen dioxide in ambient air.

Determination of nitrogen dioxide, sulfur dioxide, ozone, and ammonia in ambient air using the passive sampling method associated with ion chromatographic and potentiometric analyses.

Concentrations of nitrogen dioxide (NO(2)), sulfur dioxide (SO(2)), ozone (O(3)), and ammonia (NH(3)) were determined in the ambient air of Al-Ain city over a year using the passive sampling method associated with ion chromatographic and potentiometric detections. IVL samplers were used for collecting nitrogen and sulfur dioxides whereas Ogawa samplers were used for collecting ozone and ammonia. Five sites representing the industrial, traffic, commercial, residential, and background regions of the city were monitored in the course of this investigation. Year average concentrations of