Chemical and biological characterization of novel derivatives of 4-aryl-2,4-dioxobutanoic acids, and molecular modeling for the rationalization of biological activity and physico-chemical properties.

Rastuća otpornost bakterija prema dejstvu gotovo svih poznatih antibiotika zahteva pronalaženje novih hemijskih struktura koje efikasno deluju na multirezistentne (Multi-drug resistant, MDR) bakterije. Kao nastavak istraživanja antibakterijske aktivnosti 4-aril-2,4-dioksobutanskih kiselina (arildiketokiselina, ADK) započetih ranije u okviru naše istraživačke grupe, u okviru ove doktorske disertacije sintetisana je nova serija od dvadeset i jedne ADK (jedinjenja 1-21) i ispitana im je antibakterijska aktivnost prema MDR sojevima bakterija. Jedinjenja sa voluminoznim alkil supstituentima u orto-položaju fenilnog jezgra pokazala su se najaktivnijim prema norfloksacin-rezistentnom soju bakterije Staphylococcus aureus, a jedinjenje 12 (4-(2,5-di-cikloheksilfenil)-2,4-dioksobutanska kiselina) je pokazalo 10-11 puta veću aktivnost prema istom soju bakterija od najaktivnijeg jedinjenja iz prethodno objavljene serije ADK, kao i 10 puta veću aktivnost od norfloksacina. Narušavanjem strukture diketo dela molekula značajno se smanjuje antibakterijska aktivnost ADK...Growing bacterial resistance toward almost all known antibiotics demands rapid discovery of the novel chemical entities active toward multidrug resistant (MDR) bacterial strains. As a continuation of research on antibacterial activity of 4-aryl-2,4- dioxobutanoic acids (ADK), synthesis and antibacterial activity of twenty one novel ADKs (compounds 1-21) are reported in this thesis. Compounds bearing bulky alkyl substituents in ortho-position on phenyl ring were the most active against norfloxacinresistant strain of Staphylococcus aureus. Compound 12 was 10-11 times more potent than the most potent ADK from previously published set of compounds, and also 10 times more potent than norfloxacin tested against the same bacterial strain. Diketo moiety was proven to be essential for antibacterial activity of ADK..

Dynamics of the Water Molecules at the Intrinsic Liquid Surface As Seen from Molecular Dynamics Simulation and Identification of Truly Interfacial Molecules Analysis

Dynamic properties at the liquid-vapor interface of water are investigated at 298 K on the basis of molecular dynamics simulations and intrinsic surface analysis. The mean surface residence time and diffusion coefficient of the molecules as well as H-bond lifetimes are calculated at the liquid surface and compared to the bulk values. It is found that surface molecules have a non-negligible diffusion component along the surface normal, although this component is limited in time to 7-15 ps, a value comparable with the mean surface residence time. It is also seen that interfacial molecules move considerably faster, and their H-bonds live shorter, than in the bulk liquid phase. This finding is explained by the relation between the number of H-bonded neighbors and mobility, namely that molecules being tethered by more H-bonds move slower, and their H-bonds live longer than in the case of molecules of less extensive H-bonding. Finally, it is found that molecules residing long at the surface are clustering around each other, forming more and longer living H-bonds within the surface layer, but much less outside this layer than other interfacial molecules, indicating that longer surface residence is related to weaker interaction with the subsurface region. © 2016 American Chemical Society

Human Serum Albumin Binding of 2-[(Carboxymethyl)sulfanyl]-4-oxo-4-(4-tert-butylphenyl)butanoic Acid and its Mono-Me Ester

Interactions of 2-[(carboxymethyl)sulfanyl]-4-oxo-4-(4-tert-butylphenyl)butanoic acid (compound 1) and its mono-Me ester (compound 2) with the human serum albumin (HSA) have been studied by fluorescence spectroscopy. Comp. 1 exerts antiproliferative activity toward human tumor cells and significant selectivity (tumor vs. healthy cells) in vitro. Competitive binding study with warfarin and ibuprofen as binding site probes, revealed that one molecule of comp. 1 selectively binds to HSA Sudlow site I (warfarin site) with moderate binding constant (Kb = (2.8 ± 0.5) x 104 M-1 at 37 ± 1 oC), while comp. 2 binds to Sudlow site II (Kb = (3.2 ± 0.9) x 104 M-1 at 37 ± 1 oC). Fluorescence quenching at different temperatures was analyzed using classical Stern-Volmer equation, and a static quenching mechanism was proposed. Energy resonance transfer between HSA and comp. 1 was examined according to Förster’s non-radiative energy transfer theory. Distance of about 10 Å between ligand and Trp214 (HSA) was obtained. Docking studies confirmed HSA Sudlow site I as a preferable comp. 1 binding site, and Sudlow site II as comp. 2 binding site. Molecular dynamics simulations proved the stability of comp. 1/HSA complex

The effect of the filter type on the quality of “shake flask” solubility determinations

Određivanje rastvorljivosti je važno u svim fazama razvoja leka. Dobijeni podaci se koriste za nalaženje potencijalnih lekova-kandidata, biofarmaceutsku klasifikciju i optimizaciju formulacije leka. Na merenje rastvorljivosti utiču različiti faktori: vreme mešanja, vreme sedimentacije, sastav pufera, temperatura, višak čvrste faze i tehnika odvajanja faza.[1] Cilj ovog rada je ispitivanje uticaja vrste membrane filtera u procesu odvajanja faza pri određivanju rastvorljivosti „shake-flask“ metodom. Izabrani su polietar-sulfon (hidrofobni) i poliviniliden-fluorid (hidrofilni) filteri. Koncentracija je merena pomoću UV/Vis spektrofotometrije. Kao model supstance korišćeni su karvedilol (baza) i ibuprofen (kiselina). Minijaturizovanom „shake-flask“ metodom i optimizovanom metodom potenciometrijske titracije određene su i logP vrednosti. Pokazano je da rezultat određivanja rastvorljivosti može zavisiti od vrste membrane filtera koji se koristi za odvajanje filtrata nakon uspostavljanja ravnoteže u rastvoru tokom rastvaranja. Jačina uticaja zavisi od lipofilnosti i pKa vrednosti ispitavanog molekula kao i od pH vrednosti rastvora u kom se izvodi određivanje.Solubility determination is important in both early and development phase of drug research. This data is used to screen out drug-like candidates, biopharmaceutical classification and formulation optimization. Solubility measurements are influenced by several experimental factors: stirring and sedimentation time, composition of the aqueous buffer, temperature, amount of solid excess and the technique of phase-separation.1 The aim of the present study was to examine the influence of the filter type during phase separation on solubility determination. Polyether sulfone (hydrophobic) and polyvinylidene fluoride (hydrophilic) filters were chosen. The concentration was measured by UV/Vis spectrophotometry. Carvedilol (base) and ibuprofen (acid) are used as a model compounds. LogP values were determined by miniaturized shake-flask method and by optimized potentiometric titration. It is shown that solubility data can be influenced by membrane filter type which is used for filtration, after the equilibrium is established during dissolution. Magnitude of this influence depends of lipophilicity and pKa value of molecule and a solution pH valu

Human serum albumin binding of certain antimalarials

Tested compounds, previously synthesized, are derivatives of chloroquine, drug commonly used in the treatment and prevention of malaria. Human serum albumin (HSA) has the role in transport of endogenous (fatty acids, hormones, bile acids, amino acids) and exogenous compounds (drug molecules and nutrients). Interaction between tested compounds and HSA has been studied by fluorescence spectroscopy in phosphate buffered saline (1× PBS, pH 7.4) [1]. Results show that among tested compounds, all positively charged at pH 7.4, derivatives with thiophene substructure bind to HSA. Molecular docking studies were used to determine HSA–compound binding mode. Fluorescence quenching data were processed using Stern-Volmer (S-V) equation [2]. Almost linear S-V plot for binding of 1 to HSA (Fig. 1a) indicates single type of quenching mechanism. Results show that Ksv decreases (20C: (2.60±0.07)×105 M -1 ; 25C: (2.33±0.07)×105 M -1 and 37C: (2.18±0.08)×105 M -1 ) as temperature increases indicating static quenching mechanism. Downward curvature in S-V plots of 2 and 3 (Fig. 1b and 1c) indicates that tryptophan residues are not fully accessible to the drug and that dynamic quenching dominates over static. Fraction of tryptophan residues that are buried and inaccessible to the quencher and effective quenching constants can be determined by modified S-V equation. The effective quenching constant for 2 and 3 increases as temperature increases, this is another indication that dynamic quenching process is dominant in binding of 2 and 3 to HSA. Effective quenching constants of all three compounds are in the order of 10 5 M-1, meaning that these compounds can be effectively carried and stored by HSA in the human body

Везивање неких антималарика за хумани серум албумин

Human serum albumin (HSA) is the most abundant protein in blood plasma and it transports endogenous (fatty acids and bilirubin) and exogenous compounds (drugs) through the blood. In the present study binding of several derivatives of our new antimalarials, and chloroquine, to HSA was investigated by fluorescence spectroscopy (in 0.15 М HEPES, pH 7.35). Results show that among ten studied compounds only those with additional thiophene substructure bind to HSA, with moderate binding constants (comp. 1 logKb = 4.33(±0.46) and comp. 2 logKb = 3.81(±0.29)), representative spectra shown on Fig. 1. Competitive binding method with site specific probes (warfarin for Sudlow site I and ibuprofen for Sudlow site II) indicate that compounds 1 and 2 compete with both site probes, with slight preference toward Sudlow site I. Molecular docking studies were used to determine the binding mode of compounds 1 and 2 to HSA.Хумани серум албумин (ХСА) је најзаступљенији протеин у крвној плазми који преноси ендогенe (масне киселине и билирубин) и егзогенe супстанце (лекове) кроз крв. Флуоресцентном спектроскопијом je проучавано везивање ХСА са хлорокином и неколико наших нових аминохинолинских антималарика (у 0,15 М HEPES пуферу, pH 7,35). Показано је да се од испитиваних једињења за ХСА везују само једињења која садрже тиофенско језгро (logKb = 4,33(±0,46) за једињење 1 и logKb = 3,81(±0,29) за једињење 2). Методом компетитивног везивања са специфичним пробама (варфарин и ибупрофен) показано је да се 1 и 2 везују за оба места, уз нешто већи афинитет према варфаринском месту. Докинг студије су коришћене у циљу утврђивања начина везивања једињења 1 и 2 за ХСА

Chemical and biological characterization of novel derivatives of 4-aryl-2,4-dioxobutanoic acids, and molecular modeling for the rationalization of biological activity and physico-chemical properties.

Rastuća otpornost bakterija prema dejstvu gotovo svih poznatih antibiotika zahteva pronalaženje novih hemijskih struktura koje efikasno deluju na multirezistentne (Multi-drug resistant, MDR) bakterije. Kao nastavak istraživanja antibakterijske aktivnosti 4-aril-2,4-dioksobutanskih kiselina (arildiketokiselina, ADK) započetih ranije u okviru naše istraživačke grupe, u okviru ove doktorske disertacije sintetisana je nova serija od dvadeset i jedne ADK (jedinjenja 1-21) i ispitana im je antibakterijska aktivnost prema MDR sojevima bakterija. Jedinjenja sa voluminoznim alkil supstituentima u orto-položaju fenilnog jezgra pokazala su se najaktivnijim prema norfloksacin-rezistentnom soju bakterije Staphylococcus aureus, a jedinjenje 12 (4-(2,5-di-cikloheksilfenil)-2,4-dioksobutanska kiselina) je pokazalo 10-11 puta veću aktivnost prema istom soju bakterija od najaktivnijeg jedinjenja iz prethodno objavljene serije ADK, kao i 10 puta veću aktivnost od norfloksacina. Narušavanjem strukture diketo dela molekula značajno se smanjuje antibakterijska aktivnost ADK...Growing bacterial resistance toward almost all known antibiotics demands rapid discovery of the novel chemical entities active toward multidrug resistant (MDR) bacterial strains. As a continuation of research on antibacterial activity of 4-aryl-2,4- dioxobutanoic acids (ADK), synthesis and antibacterial activity of twenty one novel ADKs (compounds 1-21) are reported in this thesis. Compounds bearing bulky alkyl substituents in ortho-position on phenyl ring were the most active against norfloxacinresistant strain of Staphylococcus aureus. Compound 12 was 10-11 times more potent than the most potent ADK from previously published set of compounds, and also 10 times more potent than norfloxacin tested against the same bacterial strain. Diketo moiety was proven to be essential for antibacterial activity of ADK..

Chemical and biological characterization of novel derivatives of 4-aryl-2,4-dioxobutanoic acids, and molecular modeling for the rationalization of biological activity and physico-chemical properties.

Rastuća otpornost bakterija prema dejstvu gotovo svih poznatih antibiotika zahteva pronalaženje novih hemijskih struktura koje efikasno deluju na multirezistentne (Multi-drug resistant, MDR) bakterije. Kao nastavak istraživanja antibakterijske aktivnosti 4-aril-2,4-dioksobutanskih kiselina (arildiketokiselina, ADK) započetih ranije u okviru naše istraživačke grupe, u okviru ove doktorske disertacije sintetisana je nova serija od dvadeset i jedne ADK (jedinjenja 1-21) i ispitana im je antibakterijska aktivnost prema MDR sojevima bakterija. Jedinjenja sa voluminoznim alkil supstituentima u orto-položaju fenilnog jezgra pokazala su se najaktivnijim prema norfloksacin-rezistentnom soju bakterije Staphylococcus aureus, a jedinjenje 12 (4-(2,5-di-cikloheksilfenil)-2,4-dioksobutanska kiselina) je pokazalo 10-11 puta veću aktivnost prema istom soju bakterija od najaktivnijeg jedinjenja iz prethodno objavljene serije ADK, kao i 10 puta veću aktivnost od norfloksacina. Narušavanjem strukture diketo dela molekula značajno se smanjuje antibakterijska aktivnost ADK...Growing bacterial resistance toward almost all known antibiotics demands rapid discovery of the novel chemical entities active toward multidrug resistant (MDR) bacterial strains. As a continuation of research on antibacterial activity of 4-aryl-2,4- dioxobutanoic acids (ADK), synthesis and antibacterial activity of twenty one novel ADKs (compounds 1-21) are reported in this thesis. Compounds bearing bulky alkyl substituents in ortho-position on phenyl ring were the most active against norfloxacinresistant strain of Staphylococcus aureus. Compound 12 was 10-11 times more potent than the most potent ADK from previously published set of compounds, and also 10 times more potent than norfloxacin tested against the same bacterial strain. Diketo moiety was proven to be essential for antibacterial activity of ADK..

Assessing the potential of para-donor and para-acceptor substituted 5-benzylidenebarbituric acid derivatives as push-pull electronic systems: Experimental and quantum chemical study

Electronic interactions in donor-pi-linker-acceptor systems with barbituric acid as an electron acceptor and possible electron donor were investigated to screen promising candidates with a push-pull character based on experimental and quantum chemical studies. The tautomeric properties of 5-benzylidenebarbituric acid derivatives were studied with NMR spectra, spectrophotometric determination of the pKa values, and quantum chemical calculations. Linear solvation energy relationships (LSER) and linear free energy relationships (LFER) were applied to the spectral data - UV frequencies and C-13 NMR chemical shifts. The experimental studies of the nature of the ground and excited state of investigated compounds were successfully interpreted using a computational chemistry approach including ab initio MP2 geometry optimization and time-dependent DFT calculations of excited states. Quantification of the push-pull character of barbituric acid derivatives was performed by the (CNMR)-C-13 chemical shift differences, Mayer pi bond order analysis, hole-electron distribution analysis, and calculations of intramolecular charge transfer (ICT) indices. The results obtained show, that when coupled with a strong electron-donor, barbituric acid can act as the electron-acceptor in push-pull systems, and when coupled with a strong electron-acceptor, barbituric acid can act as the weak electron-donor