Antibacterial thyme oil-loaded organo-hydrogels utilizing cellulose acetoacetate as reactive polymer emulsifier.

Organo-hydrogels are widely used in various fields, due to functional organic ingredients immobilized by the gel network or stored and protected by the gels. Herein, cellulose acetoacetate (CAA) served as reactive natural polymer emulsifier to stabilize thyme oil-in-water (O/W) emulsions. Hydroxypropyl chitosan (HPCS) was added to the continuous phase in emulsions to achieve the organo-hydrogel via the enamine bonds under mild conditions. The thyme@CAA emulsion with different loadings of the inner phase (up to 50%) displayed uniform droplets distribution (3-5 µm) and favorable stability. The organo-hydrogel was systematically analyzed by Fourier transform infrared spectroscopy, optical microscope, rheology analyses. The emulsion droplets evenly dispersed in the three-dimensional network. The modulus of organo-hydrogels depended on the viscosity of precursor emulsions and the crosslinking density. The resulting organo-hydrogel displayed favorable antibacterial activity against E. coli and S. aureus. CAA, as the reactive emulsifier and crosslinking agent, was a promising alternative candidate to fabricate a series of organo-hydrogel.

Exquisite stability and catalytic performance of immobilized lipase on novel fabricated nanocellulose fused polypyrrole/graphene oxide nanocomposite: Characterization and application.

This work was performed to describe the facile procedure of a novel nanobiocatalyst, nano cellulose fused polypyrrole/graphene oxide nanocomposite for the efficacious immobilization of lipase, a versatile hydrolytic enzyme having potential applications in industries. The fabricated nanocomposite was characterized using Fourier transform infrared spectroscopy, differential thermal analysis, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and Candida rugosa lipase was immobilized onto nanocomposite through physical adsorption. The catalytic efficiency and operational stabilities of immobilized lipase were improved significantly compared to the free lipase. The reusability profile outcomes showed that the immobilized lipase formulation was an outstanding nanobiocatalyst as it retained 85% of its original catalytic activity after 10 cycles of application. The nanobiocatalyst was employed for the synthesis of the fruit flavour compound, ethyl acetoacetate. The immobilized lipase successfully synthesised flavour compound in solvent free media and n-hexane having 27.5% and 75.5% ester yields respectively. Moreover, these outcomes demonstrating graphene oxide modified carrier induced stabilization, amended solvent tolerance and operational stability of immobilized enzyme, will have quintessential influence on practical scale up of biotechnological industries.

Novel hyperbranched polysiloxanes containing acetoacetyl groups synthesized through transesterification reaction.

Development of an innovative strategy to prepare hyperbranched polysiloxanes (HBPS) is highly desirable due to the significant shortcomings of conventional fabrication approaches: the precursors need pre-synthesis, the hydrosilylation reaction is conducted using costly catalysts, and hydrolysis of organosiloxanes easily results in gelation. Here, novel HBPS containing acetoacetyl groups (HBPS-Ac) are synthesized through a cost-efficient and easily controllable transesterification reaction. It is shown by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), (1) H NMR, and gas chromatography (GC) measurements that the polymerization process is a straightforward technique to prepare new HBPS. The polymers are capable to remove formaldehyde due to the highly efficient reaction of the active methylene in the acetoacetyl group with formaldehyde at room temperature. Notably, coatings incorporating 4 wt% of the polymers allow for formaldehyde absorption, while integrated performances are kept almost unaffected. Therefore, HBPS-Ac are promising as scavengers for formaldehyde.

Synthesis, characterization, and antimicrobial evaluation of a small library of ferrocene-containing acetoacetates and phenyl analogs: the discovery of a potent anticandidal agent.

A library of 16 2-substituted methyl acetoacetates containing ferrocenyl or phenyl units was designed to disclose differences in the antimicrobial activity of ferrocene-containing compounds and their phenyl analogs. Two methyl acetoacetates, whose structures do not contain an aromatic nucleus, were also included in order to probe the inherent activity of the scaffold itself. The acetoacetates were synthesized (low-to-good yields) and fully characterized by spectral (MS, IR, UV-Vis, 1D and 2D NMR) and electrochemical (cyclic voltammetry) techniques. Single-crystal X-ray analysis has been performed for methyl 2-acetyl-2-(ferrocenylmethyl)-5-methylhex-4-enoate. All compounds have demonstrated in vitro antimicrobial activity against six bacterial (three Gram-positive and three Gram-negative) and two fungal strains with minimal inhibitory concentration values of 0.0050-20.6 µmol mL(-1). The most active compound was 2-acetyl-2-(ferrocenylmethyl)-4-methylpent-4-enoate whose activity was comparable to that of nystatin against the yeast Candida albicans. Agglomerative hierarchical clustering statistical analysis of the antimicrobial assay data demonstrated that ferrocene-containing compounds have statistically different and greater antimicrobial activity when compared to their phenyl analogs.

Regulation of the Escherichia coli AtoSC two component system by synthetic biologically active 5;7;8-trimethyl-1;4-benzoxazine analogues.

The Escherichia coli AtoSC two component system;upon acetoacetate induction;regulates the expression of the atoDAEB operon;through His→Asp phopshotransfer;thus modulating important cellular processes. In this report the effect of seven 5,7,8-trimethyl-1,4-benzoxazine derivatives on the regulation of the E. coli AtoSC system was studied. The new compounds were tested for their effectiveness on the expression of the atoC and the regulated atoDAEB operon. The non-substituted 5,7,8-trimethyl-1,4-benzoxazine (4a), was the most potent inducer on atoC transcription;resulting in accumulation of AtoC protein. The induction of atoC by 4a was specific;since no effect was observed on the other genes of the system (atoS and atoDAEB). Moreover;compound 4a was shown to significantly up-regulate the in vitro kinase activity of the histidine kinase AtoS without altering the protein levels in the cell. Interestingly;this compound appeared to modulate the acetoacetate-mediated induction of the atoDAEB promoter by the AtoSC system. These data provide the first evidence for a differential modulator role of 5,7,8-trimethyl-1,4-benzoxazine;on the AtoSC two component system mediated signaling.

Mecanismo de oxidação aeróbica de acetoacetato e 2-metilacetoacetato catalisada por mioglobina: implicações em desordens cetogênicas / Mechanism of the aerobic oxidation of acetoacetate and 2- methylacetoacetate catalyzed by Mb: implications for ketogenic disorders

Acetoacetato (AA) e 2-metilacetoacetato (MAA) são compostos β-cetoácidos acumulados em diversas desordens metabólicas como no diabetes e na isoleucinemia, respectivamente. Examinamos o mecanismo de oxidação aeróbica de AA e MAA iniciada por intermediários reativos de mioglobina de coração de cavalo (Mb) gerados pela adição de H2O2. Uma rota quimioluminescente que envolve um intermediário dioxetânico cuja termólise gera espécies α-dicarbonílicas (metilglioxal e biacetilo) foi proposta e estudada. Emissão de luz ultra fraca acompanha a reação, e sua intensidade aumenta linearmente pelo aumento da concentração tanto de Mb (10-500 µM) quando AA (10-100 mM). Estudos de consumo de oxigênio mostraram que MAA é, como esperado, quase uma ordem de grandeza mais reativo que AA. Estudos de EPR com captação de spin, utilizando MNP, possibilitaram detectar adutos de MAA atribuíveis a um radical centrado no Cα (aN = 1.55 mT) e ao radical acetila (aN = 0.83 mT). O sinal do radical acetila é totalmente suprimido por sorbato, um conhecido e eficiente supressor de espécies tripletes, o que é consistente com uma rota reacional envolvendo um intermediário dioxetânico. Clivagem-α da ligação carbonila-carbonila do produto biacetilo triplete produziria, de fato, radicais acetila. Além disso, utilizando AA como substrato para Mb/H2O2, um sinal de EPR atribuível ao aduto MNP-AA• (aN = 1.46 mT e aH = 0.34 mT) foi observado e confirmado por efeito isotópico. O consumo de oxigênio e o rendimento de compostos α-dicarbonílicos foram dose-dependentes à concentração de AA ou MAA (1-50 mM) bem como à concentração de H2O2 adicionado às misturas de reação contendo Mb (até 1:10 quando medido o consumo de oxigênio, e até 1:25 quando medido o rendimento de compostos α-dicarbonílicos) e tert-butilhidroperóxido (até 1:200). Os perfis de pH (5,8-7,8) para consumo de oxigênio e rendimento de compostos α-dicarbonílicos mostraram maiores rendimentos para baixos valores de pH, indicativo de ferrilMb...

Acetoacetate (AA) and 2-methylacetoacetate (MAA) are β-ketoacids accumulated in several metabolic disorders such as diabetes and isoleucinemia, respectively. Here we examine the mechanism of AA and MAA aerobic oxidation initiated by the reactive enzyme intermediates formed by the reaction of muscle horse myoglobin (Mb) with H2O2. A chemiluminescent route involving a dioxetane intermediate whose thermolysis yields triplet α-dicarbonyl species (methylglyoxal and diacetyl) is envisaged. Accordingly, the ultraweak light emission that accompanies the reaction increases linearly by raising the concentration of both Mb (10-500 µM) and AA (10- 100 mM). Oxygen uptake studies revealed that MAA is, expectedly, almost one order of magnitude more reactive than AA. EPR spin-trapping studies with MNP detected spin adducts from MAA attributable to an α-carbon-centered radical (aN = 1.55 mT) and to an acetyl radical (aN = 0.83 mT). As the acetyl radical signal is totally suppressed by sorbate, a well-known efficient triplet species quencher, the dioxetane hypothesis seems to be reliable. The α-cleavage of the carbonyl-carbonyl bond of a putative excited triplet diacetyl product would, in fact, leads to an acetyl radical. Furthermore, using AA as substrate for Mb/H2O2, an EPR signal assignable to a MNP-AA• adduct (aN = 1.46 mT and aH = 0.34 mT) was observed and confirmed by isotope effect. Oxygen consumption and α-dicarbonyl yield were also dependent on AA or MAA concentrations (1-50 mM) as well as on the concentration of peroxide added to the Mb-containing reaction mixtures: H2O2 (up to 1:10 when measuring oxygen uptake and up to 1:25 when measuring the α-dicarbonyl yield) and t-butOOH (up to 1:200). The pH profiles (5.8-7.8) of oxygen consumption and α-dicarbonyl yield show higher reaction rates at lower pHs, indicative of a ferrylMb intermediate. Evaluating Mb lesion, both β-ketoacids reduced disorganization of the secondary and tertiary protein structure elicited by H2O2...

Cyclization of arylacetoacetates to indene and dihydronaphthalene derivatives in strong acids. Evidence for involvement of further protonation of O,O-diprotonated beta-ketoester, leading to enhancement of cyclization.

The chemical features, such as substrate stability, product distribution, and substrate generality, and the reaction mechanism of Brønsted superacid-catalyzed cyclization reactions of aromatic ring-containing acetoacetates (beta-ketoesters) were examined in detail. While two types of carbonyl cyclization are possible, i.e., keto cyclization and ester cyclization, the former was found to take place exclusively. The reaction constitutes an efficient method to synthesize indene and 3,4-dihydronapthalene derivatives. Acid-base titration monitored with (13)C NMR spectroscopy showed that the acetoacetates are fully O(1),O(3)-diprotonated at H(0) = -11. While the five-membered ring cyclization of the arylacetoacetates proceeded slowly at H(0) = -11, a linear increase in the rate of the cyclization was found with increasing acidity in the high acidity region of H(0) = -11.8 to -13.3. Therefore, the O(1),O(3)-diprotonated acetoacetates exhibited some cyclizing reactivity, but they are not the reactive intermediates responsible for the acceleration of the cyclization in the high acidity region. The reactive cationic species might be formed by further protonation (or protosolvation) of the O(1),O(3)-diprotonated acetoacetates; i.e., they may be tricationic species. Thermochemical data on the acid-catalyzed cyclization of the arylacetoacetates showed that the activation energy is decreased significantly as compared with that of the related acid-catalyzed cyclization reaction of a compound bearing a single functional group, such as a ketone. These findings indicate that intervention of the trication contributes to the activation of the cyclization of arylacetoacetates in strong acid, and the electron-withdrawing nature of the O-protonated ester functionality significantly increases the electrophilicity of the ketone moiety.

Automated synthesis of 11C-acetoacetic acid, a key alternate brain fuel to glucose.

An automated, one-pot radio-synthesis module for the routine preparation of 1-[(11)C]acetoacetic acid has been developed. The enolate anion of acetone was reacted with [(11)C]CO(2) in tetrahydrofuran (THF), followed by hydrolysis and purification by ion-exchange chromatography. The total synthesis time was 18 min and radiochemical yield was 34% after decay correction. HPLC analysis showed < or =3% impurities while residual THF (< or =200 ppm) and ethanol (< or =500 ppm) were well under the tolerable limits for human studies.

Biotinylated biphenyl ketone-containing 2,4-dioxobutanoic acids designed as HIV-1 integrase photoaffinity ligands.

The diketo acid (DKA) class of HIV-1 integrase inhibitors are thought to function by chelating divalent metal ions within the enzyme catalytic center. However, differences in mutations conferring resistance among sub-families of DKA inhibitors suggest that multiple binding orientations may exist. In order to facilitate identification of DKA-binding sites, biotin-tagged biphenyl ketone-containing 2,4-dioxobutanoic acids were prepared as DKA photoaffinity probes. Introduction of biotin was obtained by means of Huisgen [3+2] cycloaddition 'click chemistry.' Two photoprobes, 5a and 5b, were prepared bearing short and long linker segments, respectively, between the biotin and DKA nucleus. The greatest inhibitory potency was shown by 5b, which inhibited 3'-processing and strand transfer reactions with IC50 values of > 333 microM and 12.4 microM, respectively. In cross-linking assays designed to measure disruption of substrate DNA binding, the photoprobes behaved similarly to a reference DKA inhibitor. Analogues 5a and 5b represent novel photoaffinity ligands, which may be useful in clarifying the HIV-1 binding interactions of DKA inhibitors.

Phenoxydifluoromethyl substituted nitrogen heterocycles. Synthesis and heterocyclization reactions of ethyl 4,4-difluoro- 4-phenoxyacetoacetate.

Ethyl 4,4-difluoro-4-phenoxyacetoacetate was obtained and studied as a precursor to new heterocyclic compounds. 6-Hydroxypyrimidine, 1,3-dihydro-1,5- benzodiazepin-2-one, quinolin-2-one and 6-hydroxypyrazolo[3,4-b]pyridine derivatives containing phenoxydifluoromethyl groups were synthesized. These results make it possible to introduce aryloxydifluoromethyl substituents for the design of biologically active heterocycles.

Synthesis, characterization and evaluation of antituberculosis activity of some hydrazones.

Several new hydrazone derivatives were prepared by the reaction of some active hydrogen compounds with the diazonium salts of 4-amino-3,5-di/1,3,5-trimethylpyrazoles at 0-5 degrees C. Structures of the new substances were confirmed using UV, IR, 1H NMR, 13C NMR and EI-mass spectral data. In vitro antituberculosis activity of these compounds were tested on Mycobacterium tuberculosis H37Rv at 6.25 microg/ml. Both hydrazone products, ethyl 2-[(3,5-dimethylpyrazole-4-yl)hydrazono]-3-oxobutyrate (3d) and methyl 2-[(3,5-dimethylpyrazole-4-yl)hydrazono]4-methoxy-3-oxobutyrate (3e) showed 29 and 28% inhibition against M. tuberculosis, respectively.

Structure activity of 3-aryl-1,3-diketo-containing compounds as HIV-1 integrase inhibitors.

The 4-aryl-2-hydroxy-4-oxo-2-butenoic acids and their isosteric tetrazoles are among an emerging class of aryl beta-diketo (ADK)-based agents which exhibit potent inhibition of HIV-1 integrase (IN)-catalyzed strand transfer (ST) processes, while having much reduced potencies against 3'-processing (3'-P) reactions. In the current study, L-708,906 (10e) and 5CITEP (13b), which are two examples of ADK inhibitors that have been reported by Merck and Shionogi pharmaceutical companies, served as model ADK leads. Structural variations to both the "left" and "right" sides of these molecules were made in order to examine effects on HIV-1 integrase inhibitory potencies. It was found that a variety of groups could be introduced onto the left side aryl ring with maintenance of good ST inhibitory potency. However, introduction of carboxylic acid-containing substituents onto the left side aryl ring enhanced 3'-P inhibitory potency and reduced selectivity toward ST reactions. Although both L-708,906 and 5CITEP show potent inhibition of IN in biochemical assays, there is a disparity of antiviral activity in cellular assays using HIV-1-infected cells. Neither 5CITEP nor any other of the indolyl-containing inhibitors exhibit significant antiviral effects in cellular systems. Alternatively, consistent with literature reports, L-708,906 does provide antiviral protection at low micromolar concentrations. Interestingly, several analogues of L-708,906 with varied substituents on the left side aryl ring, while having good inhibitory potencies against IN in extracellular assays, are not antiviral in whole-cell systems.

Synthesis and intravenous infusion into the rat of glyceryl bisacetoacetate, 1-acetoacetamido-2, 3-propane diol, and partially reduced glucosyl pentaacetoacetate.

The efficacy of parenteral nutrition could be improved by finding a more effective energy source. Esters of short-chain fatty acids have exhibited some promise as alternatives to glucose. The present study reports on two new esters and one amide, each containing acetoacetate as the organic acid. The three compounds: glyceryl bisacetoacetate, N-2',3'-dihydroxypropyl-3-oxo-butanamide (1-acetoacetamido-2,3-propane diol), and partially reduced glucosyl pentaacetoacetate, were synthesized and then continuously infused into rats for 7 d. The infusion rate provided 50% of the rats' estimated metabolic energy requirements, and rats were fed with a reduced-energy oral diet that provided the remaining 50% of energy plus adequate protein. Rat groups for each compound were: (1) experimental-compound-infused and ad libitum-fed, (2) isoenergetic glucose-infused and pairfed, and (3) saline infused and pair-fed. Body-weight changes, N losses and N retention were measured daily. All rats died from partially reduced glucosyl pentaacetoacetate infusion at 100% and 50% of the intended rate. Rats infused with 1-acetoacetamido-2,3-propane diol failed to gain weight and to increase the plasma ketone-body concentration. Glyceryl bisacetoacetate produced hyperketonaemia, and weight gain and N variables that were similar to those for glucose-infused rats. It was concluded that only glyceryl bisacetoacetate would make a satisfactory parenteral nutrient.

An improved synthesis of carbon-11 labeled acetoacetic acid and an evaluation of its potential for the investigation of cerebral pathology by positron emission tomography.

1-11C-acetoacetic acid was synthesized by carboxylation of the acetone carbanion. Purification was carried out using HPLC. The product was obtained with a radiochemical yield of up to 58%, corrected for decay, in a total preparation time of 30 min. The distribution of 1-11C-acetoacetic acid after injection into adult Wistar rats and cats was investigated by PET. When the tracer was injected into cats, 3 weeks after inflicting a unilateral freezing lesion upon the brain, accumulation of 1-11C-acetoacetic acid in the ipsilateral brain hemisphere was observed.