Theoretical study on the antioxidant properties of 2′-hydroxychalcones: H-atom vs. electron transfer mechanism

The free radical scavenging activity of six 2′-hydroxychalcones has been studied in gas phase and solvents using the density functional theory (DFT) method. The three main working mechanisms, hydrogen atom transfer (HAT), stepwise electron-transfer-proton-transfer (ET-PT) and sequential-proton-loss-electron-transfer (SPLET) have been considered. The O-H bond dissociation enthalpy (BDE), ionization potential (IP), proton affinity (PA) and electron transfer energy (ETE) parameters have been computed in gas phase and solvents. The theoretical results confirmed the important role of the B ring in the antioxidant properties of hydroxychalcones. In addition, the calculated results matched well with experimental values. The results suggested that HAT would be the most favorable mechanism for explaining the radical-scavenging activity of hydroxychalcone in gas phase, whereas SPLET mechanism is thermodynamically preferred pathway in aqueous solution.     

Synthesis,Biological Evaluation and in Silico Studies of 3-Hydroxy-N-(2-(substituted phenyl)-4-oxothiazolidin-3-yl)-2-napthamide Derivatives

In the present study, a series of 3-hydroxy-N-(2-(substituted phenyl)-4-oxothiazolidin-3-yl)-2-napthamide derivatives were synthesized, characterized and evaluated for theirin vitroactivity, i. e., antimicrobial, antioxidant and anti-inflammatory. The target compounds were synthesized by condensation reaction of 3-hydroxy-2-naphthoic acid hydrazide with substituted benzaldehydes which were subjected to cyclization reaction with thioglycolic acid and ZnCl₂ to get target compounds. The synthesized 3-hydroxy-N-(2-(substituted phenyl)-4-oxothiazolidin-3-yl)-2-napthamide derivatives were examined for their antimicrobial activity and 3-hydroxy-N-(4-oxo-2-(3,4,5-trimethoxyphenyl)thiazolidin-3-yl)-2-naphthamide ( S20 ) exhibited the highest antimicrobial potential. The N′-(2,3-dichlorobenzylidene)-3-hydroxy-2-naphthohydrazide ( S5 ) displayed good antifungal potential against Rhizopus oryzae, whereas N′-(2,3-dichlorobenzylidene)-3-hydroxy-2-naphthohydrazide ( S20 ) showed the highest antioxidant potential and N-(2-(2,6-dichlorophenyl)-4-oxothiazolidin-3-yl)-3-hydroxy-2-naphthamide ( S16 ) displayed the highest anti-inflammatory activity. The results of molecular docking studies revealed that existence of hydrogen bonding and hydrophobic interactions with their respective proteins. In silico ADMET studies were carried out by Molinspiration, Pre-ADMET and OSIRIS property explorer to predict the pharmacokinetic behaviour of synthesized 3-hydroxy-N-(2-(substituted phenyl)-4-oxothiazolidin-3-yl)-2-napthamide derivatives.     

Density functional computational studies on (E)-2-[(2-Hydroxy-5-nitrophenyl)-iminiomethyl]-4-nitrophenolate

Density functional calculations of the structure, atomic charges, molecular electrostatic potential and thermodynamic functions have been performed at B3LYP/6-31G(d,p) level of theory for the title compound (E)-2-[(2-hydroxy-5-nitrophenyl)-iminiomethyl]-4-nitrophenolate. The results show that the phenolate oxygen atom and all of the nitro group oxygen atoms have bigger negative charges, and the coordination ability of these atoms differs in different solvents. The energetic behavior of the title compound in solvent media has been examined using B3LYP method with the 6-31G(d,p) basis set by applying the Onsager method and the isodensity polarized continuum model (IPCM). The results obtained with these methods reveal that the IPCM method yielded a more stable structure than Onsager’s method. In addition, natural bond orbital and frontier molecular orbital analysis of the title compound were performed using the B3LYP/6-31G(d,p) method.     

Novel 2-(2-(4-aryloxybenzylidene) hydrazinyl)benzothiazole derivatives as anti-tubercular agents

A series of structurally novel, substituted 2-(2-(4-aryloxybenzylidene) hydrazinyl)benzothiazole derivatives incorporating 2-hydrazinyl benzothiazole and 4-(aryloxy)benzaldehyde were designed and synthesized using molecular hybridization approach. All the synthesized compounds exhibited promising activity (MIC 1.5-29.00μg/ml) against Mycobacteriumtuberculosis H37Rv strains of using REMA. Five of the evaluated compounds exhibit MIC <3.0μg/ml. Compound (E)-6-chloro-2-(2-(4-(2,4-dichlorophenoxy)benzylidene)hydrazinyl) benzothiazole showed MIC of 1.5μg/ml. Thus, this compound could act as a potential lead for further development of new anti-tubercular drugs.     

Quantum chemical investigation of the intra- and intermolecular proton transfer reactions and hydrogen bonding interactions in 4-amino-5-(2-hydroxyphenyl)-2H-1,2,4-triazole-3(4H)-thione

The intramolecular thione-thiol tautomerism and intermolecular double proton transfer reaction of the hydrogen-bonded thione and thiol dimers in the title triazole compound were studied at the B3LYP level of theory using 6?311++G(d,p) basis function. The influence of the solvent on the single and double proton transfer reactions was examined in three solvents (chloroform, methanol and water) using the polarizable continuum model (PCM) approximation. The computational results show that the thione tautomer is the most stable isomer with a very high tautomeric energy barrier both in the gas phase and in solution phase, indicating a quite disfavored process. The solvent effect is found to be sizable with increasing polarity. In the double proton transfer reaction, the thione dimer is found to be more stable than thiol dimer both in the gas phase and in solution phase. The energetic and thermodynamic parameters of the double proton transfer process show that the double proton exchange from thione dimer to thiol dimer is thermodynamically unfavored. However, the exchange from thiol dimer to thione dimer for the gas phase and water phase seems to be feasible with a low barrier height and with a negative value in enthalpy and free energy changes. In addition, the hydrogen bonding interactions were analyzed in the gas phase regarding their geometries and energies. It is found that all complex formations are enthalpically favored, and the stability of the H-bonds comes in the order of S1—H2···N2 > N2—H2···S1 > N3—H3B···O1. Finally, non-linear optical properties were carried out at the same calculation level in the gas phase.

Design and synthesis of quinazoline-3,4-(4H)-diamine endowed with thiazoline moiety as new class for DPP-4 and DPPH inhibitor

New N3-benzylidene (substituted)-2-phenyl-N4-(thiazol-2-yl)-quinazoline-3,4-(4H)-diamine derivatives were design and synthesized by a sequence of reactions starting from appropriate 6-methyl anthranilic acid. The title compounds were screened for in vitro dipeptidyl peptidase IV (DPP-4) inhibitory activity and diphenyl-2-picryl-hydrazyl (DPPH) assay and results showed significant to good activity in compared to Linagliptin for antidiabetic activity and Ascorbic acid for antioxidant activity. Compound 7g (IC₅₀ = 0.76 nM) exhibited most promising DPP-4 inhibitory activity and also showed good antioxid and result. Docking study was also performed to provide an insight about the binding mode into binding sites of DPP-4 enzyme. Hopefully in future, compound 7g could be used as a lead compound for developing new antidiabetic agent with good antioxidant property.     

Discovery of 3-(3-cyano-4-pyridyl)-5-(4-pyridyl)-1,2,4-triazole,FYX-051-a xanthine oxidoreductase inhibitor for the treatment of hyperuricemia

Our previous study identified 2-[2-(2-methoxy-ethoxy)-ethoxy]-5-[5-(2-methyl-4-pyridyl)-1H-[1,2,4]triazol-3-yl]-benzonitrile (2) as a safe and potent xanthine oxidoreductase (XOR) inhibitor for the treatment of hyperuricemia. Here, we synthesized a series of 3,5-dipyridyl-1,2,4-triazole derivatives and, in particular, examined their in vivo activity in lowering the serum uric acid levels in rats. As a result, we identified 3-(3-cyano-4-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (FYX-051, compound 39) to be one of the most potent XOR inhibitors; it exhibited an extremely potent in vivo activity, weak CYP3A4-inhibitory activity and a better pharmacokinetic profile than compound 2. Compound 39 is currently being evaluated in a phase 2 clinical trial.     

Antitrypanosomal and antioxidant properties of 4-hydroxycoumarins derivatives

In the present communication we prepared a series of six 4-hydroxycoumarin derivatives, isosters of quercetin, recognized as an antioxidant natural compound, with the aim of evaluating the antitrypanosomal activity against Trypanosoma cruzi, the parasite responsible for Chagas disease, and the antioxidant properties. We have used the 4-hydroxycoumarin moiety (compound 1) as the molecular template for the synthesis of compounds 2-7. These derivates have shown moderate trypanocidal activity. However they have been proved to be good antioxidants. In particular compound 7 is the most active antioxidant and it is, therefore, a potential candidate for a successful employment in conditions characterized by free radicals overproduction.     

Computational study of conformational and chiroptical properties of (2R,3S,4R)-(+)-3,3',4,4',7-flavanpentol

Conformational analysis of (2R,3S,4R)-(+)-3,3',4,4',7-flavanpentol, a flavonoid compound displaying both antioxidant and pro-oxidant properties, is performed by molecular mechanics and density functional theory calculations both in the gas phase and in methanol solution by using the Polarizable Continuum Model. Nine different conformations are identified. Absorption (UV) and circular dichroism (CD) spectra and optical rotations are calculated by means of time dependent density functional theory (TDDFT) and compared with experiments. The effects of a complex environment formed by water and proline-rich peptide molecules on the conformational characteristics of (2R,3S,4R)-(+)-3,3',4,4',7-flavanpentol and therefore on its UV and CD spectra are investigated by atomistic molecular dynamics simulations.     

In vitro antioxidant activity of 2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman (alpha-CEHC), a vitamin E metabolite

2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman (alpha-CEHC) has been identified as a major water-soluble metabolite of vitamin E, which circulates in the blood and is excreted with the urine. The aim of this study was to assess the antioxidant activity of alpha-CEHC using several methods with different prooxidant challenges. In the Oxygen Radical Absorbance Capacity assay, a fluorescent protein acts as a marker for oxidative damage induced by peroxyl radicals. In the Trolox Equivalent Antioxidant Capacity (TEAC) assay, a stable free radical, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS.+) is reduced directly by antioxidants. Scavenging properties vs. reactive nitrogen species were studied measuring the effects on tyrosine nitration after reaction with peroxynitrite. Trolox, alpha-tocopherol, ascorbic acid, and (-)-epicatechin were simultaneously tested in order to compare their antioxidant activities. In all mentioned systems, alpha-CEHC exhibited antioxidant properties similar to those of Trolox. We conclude that alpha-CEHC is a molecule with good antioxidant activity, having the advantage over Trolox of being a naturally occurring compound. These properties might be useful for research or industrial purposes.     

Synthesis of (2E)-3-{2-[(substituted benzyl)oxy]phenyl}acrylaldehydes as novel anti-inflammatory agents

As part of our continuing effort for development of novel anti-inflammatory agents, the highly potential agent CCY1a, which we reported recently, was selected as lead compound to synthesize a series of its derivatives for evaluation. Most of the newly synthesized compounds exhibited superior inhibitory activity than both the lead compound and the positive control (trifluoperazine) toward fMLP-stimulated neutrophil superoxide formation. (2E)-3-[2-(Benzyloxy)-5-methoxyphenyl]-acrylaldehyde (31) was among the most potent with action mechanism different from CCY1a in that it does not act as cAMP-elevating agent but inhibits the increase in cellular Ca(2+) with greater potency.     

Antioxidant activity and low toxicity of (E)-1-(1-(methylthio)-1-(selenopheny) hept-1-en-2-yl) pyrrolidin-2-one

The aim of the present study was to evaluate the potential pharmacological and toxicological properties of (E)-1-(1-(methylthio)-1-(selenopheny) hept-1-en-2-yl) pyrrolidin-2-one (compound 1), an organoselenium compound. In vitro experiments showed that compound 1 presented a reduction in the lipid peroxidation induced by Fe2? in thiobarbituric acid-reactive species (TBARS) production, and in the generation of reactive species caused by Fe2?/malonate in DCFH-DA oxidation. The high dose (500 mg/kg) induced an increase on ALT but not on AST activity. Hepatic, but not cerebral, δ-ALA-D activity from mice treated with 500 mg/kg presented a significant inhibition. Brain catalase activity was significantly inhibited by 100 mg/kg whereas hepatic catalase activity showed a significant increase at all doses. Hepatic lipid peroxidation was diminished only at lowest dose (100 mg/kg) whereas for brain tissue, all doses induced a significant reduction in TBARS levels. Brain and liver ascorbic acid contents were increased only at highest dose of compound 1. Urea and creatinine levels were not significantly altered by treatments. This is a promising compound with antioxidant activity and low toxicity, suggesting the potential beneficial activity of compound 1 against oxidative damage in many parameters studied in rats and mice.     

Selective inhibition of trypsin by (2R,4R)-4-phenyl-1-[Nalpha-(7- methoxy-2-naphthalenesulfonyl)-L-arginyl]-2-piperidinecarboxylic acid

Evidence is accumulating indicating that trypsin stimulates divergent cellular reactions through the proteinase-activated receptor, in addition to its role as the digestive enzyme. In this report, we introduce (2R,4R)- 4-phenyl-1-[N(alpha)-(7-methoxy-2-naphthalenesulfonyl)-l-arginyl]- 2-p iperidinecarboxylic acid as a potent and selective trypsin inhibitor. The agent inhibited trypsin competitively with the K(i) value of 0. 1 micrometer. It inhibited thrombin weakly (K(i) = 2 micrometer) and did not inhibit plasmin, plasma kallikrein, urokinase, and mast cell tryptase (K(i) values for these enzymes are >60 micrometer). Comparative studies with several established proteinase inhibitors revealed that the compound was the first small molecular weight trypsin inhibitor without tryptase inhibitory activity. A docking study has provided a plausible explanation for the molecular mechanism of the selective inhibition showing that the agent fits into the active site of trypsin without any severe collision but that it comes into clash at the 4-phenyl group of piperidine ring against the "60-insertion loop" of thrombin and at the 7-methoxy-2-naphthalenesulfonyl group against Gln(98) of tryptase.     

Potential antitumour and pro-oxidative effects of (E)-methyl 2-(7-chloroquinolin-4-ylthio)-3-(4-hydroxyphenyl) acrylate (QNACR)

Context: Characterization of the pro-oxidant activity of QNACR.

Objectives: Reactive oxygen species (ROS) induce cellular damage and represent unique opportunities to kill malignant cells. In this study, we synthesized and evaluated the new compound, (E)-methyl 2-(7-chloroquinolin-4-ylthio)-3-(4-hydroxyphenyl) acrylate (QNACR) as potential pro-oxidative agent against breast cancer.

Methods: Oxidative stress biomarkers such as ROS, thiobarbuturic acid reactive species (TBARs) and different antioxidant enzyme activities were determined in cell lysates.

Results: QNACR showed cytotoxic and more selective effects to tumour MCF7 cells (IC₅₀ < 25 µM) compared to antitumour controls, inducing ROS and TBARs parallel to inhibitions of catalase (CAT), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH). Longer exposures to QNACR triggered adaptive effects increasing the overall activities of CAT, glutathione reductase, G6PDH and 6PGDH, but eventually the adaptation changes faded and cells died.

Conclusion: QNACR led to remarkable modifications in the oxidative status of tumour cells, proposing this compound as potential alternative for antitumour therapy.     

Synthesis of dermorphin-(1-4) derivatives catalyzed by proteases in organic solvents.

In order to extend the use of proteases to organic synthesis and seek the rules of enzymatic reactions in organic media, we focused on unnatural substrates for proteases to form amide bonds. In this paper, the study of unnatural substrates containing D-amino acid residue, which act as acyl acceptors as well as acyl donors for proteases in organic media, is reported. Dermorphin is a heptapeptide (H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH(2)) with potent analgesic activity. The N-terminal tetrapeptide is the minimum sequence that retains dermorphin activity, and is selected as the model compound in our study. Two dermorphin-(1-4) derivatives, Boc-Tyr-D-Ala-Phe-Gly-N(2)H(2)Ph and Boc-Tyr-D-Ala-Phe-Gly-NH(2), which contained a d-amino acid residue, were synthesized by proteases in organic media for the first time. The synthesis of these two dermorphin-(1-4) derivatives could be catalyzed by subtilisin with Boc-Tyr-D-Ala-OCH(2)CF(3) as an acyl donor substrate in AcOEt. The synthesis of dermorphin-(1-2) derivative Boc-Tyr-D-Ala-N(2)H(2)Ph was catalyzed by alpha-chymotrypsin in different organic solvents and D-Ala-N(2)H(2)Ph was used as an acyl acceptor substrate. Factors influencing the above enzymatic reactions were systematically studied.     

Design,synthesis, and mechanism of action of 2-(3-hydroxy-5-methoxyphenyl)-6-pyrrolidinylquinolin-4-one as a potent anticancer lead

New 6- (or 6,7-) substituted 2-(hydroxyl substituted phenyl)quinolin-4-one derivatives were synthesized and screened for antiproliferative effects against cancer cell lines. Structure–activity relationship correlations were established and the most promising compound 2-(3-hydroxy-5-methoxyphenyl)-6-pyrrolidin-1-ylquinolin-4-one (6h) exhibited strong inhibitory activity against various human cancer cell lines, particularly non-small cell lung cancer NCI-H522. Additional studies suggested a mechanism of action resembling that of the antimitotic drug vincristine. The presence of a C-ring OH group in 6h will allow this compound to be converted readily to a water soluble and physicochemically stable hydrophilic prodrug. Compound 6h is proposed as a new anticancer lead compound.     

Mechanistic study of the structure–activity relationship for the free radical scavenging activity of baicalein

Density functional theory calculations were performed to evaluate the antioxidant activity of baicalein. The conformational behaviors of both the isolated and the aqueous-solvated species (simulated with the conductor-like polarizable continuum solvation model) were analyzed at the M052X/6-311 + G(d,p) level. The most stable tautomers of various forms of baicalein displayed three IHBs between O4 and OH5, O5 and OH6, and O6 and OH7. The most stable tautomer of the baicalein radical was obtained by dehydrogenating the hydroxyl at C6, while the most stable anion tautomer was obtained by deprotonating the C7 hydroxyl in gaseous and aqueous phases. The expected antioxidant activity of baicalein was explained by its ionization potentials (IPs) and homolytic O–H bond dissociation enthalpies (BDEs), which were obtained via the UM052X optimization level of the corresponding radical species. Heterolytic O–H bond cleavages (proton dissociation enthalpies, PDEs) were also computed. The calculated IP, BDE, and PDE values suggested that one-step H-atom transfer, rather than sequential proton loss–electron transfer or electron transfer–proton transfer, would be the most favorable mechanism for explaining the antioxidant activity of baicalein in the gas phase and in nonpolar solvents. In aqueous solution, the SPLET mechanism was more important.     

Purification, characterization and comparison with mammalian SCP2 of a chicken SCP2-like protein.

1. Three proteins have been isolated from chicken (Gallus domesticus) liver that bind antibodies directed against authentic rat sterol carrier protein2 (SCP2) and have similar molecular mass to the three major immunoreactive rat liver proteins (12 kDa, 30-36 kDa, 55-60 kDa). 2. Bile from both chicken and rat contains the high molecular mass immunoreactive species. 3. The chicken 12 kDa SCP2-like protein purifies similarly to rat SCP2 but the homogeneous chicken SCP2-like protein is dissimilar in amino acid composition and N-terminal amino acid sequence. 4. The activity of chicken SCP2-like protein differs from rat SCP2 in that it was consistent with fusion (transfer of both polar surface and non-polar core lipids) rather than transfer of polar lipids only.     

Discovery of 6-[5-(4-fluorophenyl)-3-methyl-pyrazol-4-yl]-benzoxazin-3-one derivatives as novel selective nonsteroidal mineralocorticoid receptor antagonists

In the course of our study on selective nonsteroidal mineralocorticoid receptor (MR) antagonists, a series of novel benzoxazine derivatives possessing an azole ring as the core scaffold was designed for the purpose of attenuating the partial agonistic activity of the previously reported dihydropyrrol-2-one derivatives. Screening of alternative azole rings identified 1,3-dimethyl pyrazole 6a as a lead compound with reduced partial agonistic activity. Subsequent replacement of the 1-methyl group of the pyrazole ring with larger lipophilic side chains or polar side chains targeting Arg817 and Gln776 increased MR binding activity while maintaining the agonistic response at the lower level. Among these compounds, 6-[1-(2,2-difluoro-3-hydroxypropyl)-5-(4-fluorophenyl)-3-methyl-1H-pyrazol-4-yl]-2H-1,4-benzoxazin-3(4H)-one (37a) showed highly potent in vitro activity, high selectivity versus other steroid hormone receptors, and good pharmacokinetic profiles. Oral administration of 37a in deoxycorticosterone acetate-salt hypertensive rats showed a significant blood pressure-lowering effect with no signs of antiandrogenic effects.