Release Of Aldehyde Research Articles

Tuning Antioxidant Function through Dynamic Design of Chitosan-Based Hydrogels.

Dynamic chitosan-based hydrogels with enhanced antioxidant activity were synthesized through the formation of reversible imine linkages with 5-methoxy-salicylaldehyde. These hydrogels exhibited a porous structure and swelling capacity, influenced by the crosslinking degree, as confirmed by SEM and POM analysis. The dynamic nature of the imine bonds was characterized through NMR, swelling studies in various media, and aldehyde release measurements. The hydrogels demonstrated significantly improved antioxidant activity compared to unmodified chitosan, as evaluated by the DPPH method. This research highlights the potential of developing pH-responsive chitosan-based hydrogels for a wide range of biomedical applications.

Bacterial-Infection-Triggered Release of Antibacterial Aldehyde from Triblock Copolyether Hydrogels.

Bacterial infections pose a significant threat to public health worldwide. Hydrogel-based biomaterials have proven to be particularly useful in addressing persistent bacterial infections due to their stimuli-responsive degradability, high biocompatibility, ability to release antibacterial agents on demand, and long-lasting antibacterial activity. Herein, we fabricated ABA-type triblock copolyether hydrogels, wherein, hexanal, a bioactive aldehyde with antibacterial activity, was affixed to the hydrophobic micellar core via acetal linkage. The hydrogel exhibited degradation under acidic environment via the hydrolysis of acetal linkages, leading to the concomitant release of hexanal to exhibit highly potent bactericidal activity against both Escherichia coli and Staphylococcus aureus. Furthermore, a dual-mode release of the model therapeutic agent Nile Red from the hydrophobic micellar core of the hydrogel in conjunction with hexanal was demonstrated using this system. We anticipate that this study will provide a new platform for the development of hydrogels with tailorable release profiles for biologically active compounds that are activated by the acidification triggered by bacterial infection.

Cyclodextrin-based Schiff base pro-fragrances: Synthesis and release studies.

A simple method for the preparation of β-cyclodextrin derivatives containing covalently bonded aldehydes via an imine bond was developed and used to prepare a series of derivatives from 6I-amino-6I-deoxy-β-cyclodextrin and the following volatile aldehydes – cinnamaldehyde, cyclamen aldehyde, lilial, benzaldehyde, anisaldehyde, vanillin, hexanal, heptanal, citral, and 5-methylfurfural. Subsequently, the rate of release of the volatile compound from selected pro-fragrances, as a function of the environment (solvent, pH), was studied by 1H NMR spectroscopy (for benzaldehyde) and static headspace-gas chromatography (for benzaldehyde, heptanal, and 5-methylfurfural). The aldehyde release rate from the imine was shown to depend substantially on the pH from the solution and the air humidity from the solid state.

Infectious Inflammatory Processes and the Role of Bioactive Agent Released from Imino-Chitosan Derivatives Experimental and Theoretical Aspects.

The paper focuses on the development of a multifractal theoretical model for explaining drug release dynamics (drug release laws and drug release mechanisms of cellular and channel-type) through scale transitions in scale space correlated with experimental data. The mathematical model has been developed for a hydrogel system prepared from chitosan and an antimicrobial aldehyde via covalent imine bonds. The reversible nature of the imine linkage points for a progressive release of the antimicrobial aldehyde is controlled by the reaction equilibrium shifting to the reagents, which in turn is triggered by aldehyde consumption in the inhibition of the microbial growth. The development of the mathematical model considers the release dynamic of the aldehyde in the scale space. Because the release behavior is dictated by the intrinsic properties of the polymer–drug complex system, they were explained in scale space, showing that various drug release dynamics laws can be associated with scale transitions. Moreover, the functionality of a Schrödinger-type differential equation in the same scale space reveals drug release mechanisms of channels and cellular types. These mechanisms are conditioned by the intensity of the polymer–drug interactions. It was demonstrated that the proposed mathematical model confirmed a prolonged release of the aldehyde, respecting the trend established by in vitro release experiments. At the same time, the properties of the hydrogel recommend its application in patients with intrauterine adhesions (IUAs) complicated by chronic endometritis as an alternative to the traditional antibiotics or antifungals.

C=C Bond Oxidative Cleavage of BODIPY Photocages by Visible Light.

Photocages for protection and the controlled release of bioactive compounds have been widely investigated. However, the vast majority of these photocages employ the cleavage of single bonds and high-energy ultraviolet light. The construction of a photoactivation system that uses visible light to cleave unsaturated bonds still remains a challenge. Herein, we report a regioselective oxidative cleavage of C=C bonds from a boron-dipyrrolemethene (BODIPY)-based photocage by illumination at 630 nm, resulting in a free aldehyde and a thiol fluorescent probe. This strategy was demonstrated in live HeLa cells, and the generated α-formyl-BODIPY allowed real-time monitoring of aldehyde release in the cells. In particular, it is shown that a mannose-functionalized photocage can target HepG2 cells.

A Theoretical Model for Release Dynamics of an Antifungal Agent Covalently Bonded to the Chitosan

The aim of the study was to create a mathematical model useful for monitoring the release of bioactive aldehydes covalently bonded to the chitosan by reversible imine linkage, considered as a polymer–drug system. For this purpose, two hydrogels were prepared by the acid condensation reaction of chitosan with the antifungal 2-formyl-phenyl-boronic acid and their particularities; influencing the release of the antifungal aldehyde by shifting the imination equilibrium to the reagents was considered, i.e., the supramolecular nature of the hydrogels was highlighted by polarized light microscopy, while scanning electron microscopy showed their microporous morphology. Furthermore, the in vitro fungicidal activity was investigated on two fungal strains and the in vitro release curves of the antifungal aldehyde triggered by the pH stimulus were drawn. The theoretical model was developed starting from the hypothesis that the imine-chitosan system, both structurally and functionally, can be assimilated, from a mathematical point of view, with a multifractal object, and its dynamics were analyzed in the framework of the Scale Relativity Theory. Thus, through Riccati-type gauges, two synchronous dynamics, one in the scale space, associated with the fungicidal activity, and the other in the usual space, associated with the antifungal aldehyde release, become operational. Their synchronicity, reducible to the isomorphism of two SL(2R)-type groups, implies, by means of its joint invariant functions, bioactive aldehyde compound release dynamics in the form of “kink–antikink pairs” dynamics of a multifractal type. Finally, the theoretical model was validated through the experimental data.

Aldehyde-conjugated chitosan-graphene oxide glucodynamers: Ternary cooperative assembly and controlled chemical release

Simultaneous condensation of aromatic aldehydes (ArxCHO; x = 1–4) on chitosan biopolymer (CS) affords, after water-evaporation, structurally-conjugated aryl-functionalized CS-Arx-f films. Similarly, cooperative assembly of two-dimensional nanometric graphene oxide (GO), aromatic aldehyde and chitosan provides transparent, flexible and crack-free aldehyde-functionalized, ternary-reinforced CS-Arx-GO-f nanocomposite films. Homogenous films were obtained using ortho-hydroxybenzaldehyde Ar1 while the para-hydroxybenzaldehyde Ar4 was prone to packing inside. Textural and mechanical properties were investigated and expectedly, significant improvement was found for CS-Ar1-GO-f because of the great dispersion of the aromatic and the presence of the filler. The sensitivity of unsaturated CN imine bond to hydrolysis was explored for triggering controlled release of aromatics from the as-prepared films. All of them were found to induce a time-dependent aromatic release. It has been moreover observed that the release was significantly delayed in CS-Arx-GO-f compared to CS-Arx-f, a fact attributed to the interplay of the ring with the basal and edges of graphene oxide, through π-π stacking and additional hydrogen bonding interactions. This finding shows that beyond the conventional wisdom using fillers for improving thermal and mechanical properties, the tiny carbon sheets can act as a regulator for aldehyde release, thereby providing a way for more controlled chemical delivery from confined nanocomposites.

Exploring Aldehyde Release in Beer by 4-Vinylpyridine and the Effect of Cysteine Addition on the Beer’s Pool of Bound Aldehydes

As a continuation of our previous work, which concerned the binding of aldehydes to bisulfite and cysteine, this article presents more results on the applicability of 4-vinylpyridine addition to beer prior to analysis aiming at release of aldehydes from these preformed bound states, thus making them quantifiable with the headspace solid-phase microextraction method combined with gas chromatography-mass spectrometry. This article also presents the first results on spiking beer samples with cysteine prior to forced-aging, pointing to the important role of cysteine in beer flavor stability. Both the levels in free and bound aldehydes show a relatively large degree of variation among different beers, but also between marker aldehydes. For some aldehydes (e.g., hexanal), the bound amount was shown to increase rather strongly upon forced beer aging, whereas for others (e.g., 2-methylpropanal), large amounts appeared to already be present in a bound state in the fresh samples. Spiking beer samples with cysteine prior to aging significantly lowered the aldehyde levels compared with nonspiked samples. Flavor stability of the cysteine-spiked beers was thereby greatly improved through aldehyde-cysteine adduct formation. It was further hypothesized that, in addition to efficient binding of aldehydes, cysteine also inhibits the formation of furfural during beer aging from Maillard reaction intermediates.

Application of meta‐ and para‐Phenylenediamine as Enhanced Oxime Ligation Catalysts for Protein Labeling, PEGylation, Immobilization, and Release

Meta- and para-phenylenediamines have recently been shown to catalyze oxime and hydrazone ligation reactions at rates much faster than aniline, a commonly used catalyst. Here, we demonstrate how these new catalysts can be used in a generally applicable procedure for fluorescent labeling, PEGylation, immobilization, and release of aldehyde- and ketone- functionalized proteins. The chemical orthogonality of phenylenediamine-catalyzed oxime ligation versus copper-catalyzed click reaction has also been harnessed for simultaneous dual labeling of bifunctional proteins containing both aldehyde and alkyne groups in high yield.

Correction: Phytoplankton Cell Lysis Associated with Polyunsaturated Aldehyde Release in the Northern Adriatic Sea

Correction: Phytoplankton Cell Lysis Associated with Polyunsaturated Aldehyde Release in the Northern Adriatic Sea

Effect of human saliva and sip volume of coffee brews on the release of key volatile compounds by a retronasal aroma simulator

The influence of human saliva and sip volume on aroma release in coffee brew was studied under mouth-simulated conditions. 24 aroma compounds of coffee brew were monitored and quantified in dynamic headspace of four different coffee brews by SPME–GC–MS in selective ion monitoring (SIM) modality.In the first part of our study, American, Neapolitan, moka and espresso coffee brews showed a different partition of aroma compounds when coffee brew comes into contact with saliva, with respect to the initial amount of volatiles analyzed by the orthonasal way. In addition, every brewing technique seems to imply a different behavior in the aroma release.In the second part, a significant influence of coffee sip volume on aroma headspace was observed. By analyzing the headspace concentration of aroma compounds after retronasal aroma simulation assay, an increase was obtained for some aldehydes assuming 25mL coffee in one sip, while when smaller sips were considered, the aldehyde release decreased and the levels of β-damascenone and 4-vinylguaiacol increased. The different aroma release could not be attributed to direct action of salivary constituents, but rather to the modification of volatile partition into the different phases of coffee brew caused by the presence of saliva. This modification could be mainly related to the chemical properties of volatile compounds and to the non-volatile matrix composition of different coffee brews, which affects the partitioning of volatile compounds and their perception.

Phytoplankton Cell Lysis Associated with Polyunsaturated Aldehyde Release in the Northern Adriatic Sea

Diatoms are able to react to biotic and abiotic stress, such as competition, predation and unfavorable growth conditions, by producing bioactive compounds including polyunsaturated aldehydes (PUAs). PUAs have been shown to act against grazers and either enhance or inhibit the growth of different phytoplankton and bacteria both in culture and in the field. Presence of nanomolar concentrations of dissolved PUAs in seawater has been reported in the North Adriatic Sea (Mediterranean), suggesting that these compounds are released in seawater following diatom cell lysis. However, the origin of the PUAs and their effects on natural phytoplankton assemblages remain unclear. Here we present data from four oceanographic cruises that took place during diatom blooms in the northern Adriatic Sea where concentrations of particulate and dissolved PUAs were monitored along with phytoplankton cell lysis. Cell lysis was positively correlated with both concentrations of particulate and dissolved PUAs (R = 0.69 and R = 0.77, respectively), supporting the hypothesis that these compounds are released by cell lysis. However, the highest concentration of dissolved PUAs (2.53 nM) was measured when cell lysis was high (0.24 d−1) but no known PUA-producing diatoms were detected, suggesting either that other organisms can produce PUAs or that PUA-producing enzymes retain activity extracellularly after diatom cells have lysed. Although in situ concentrations of dissolved PUAs were one to three orders of magnitude lower than those typically used in laboratory culture experiments, we argue that concentrations produced in the field could induce similar effects to those observed in culture and therefore may help shape plankton community composition and function in the oceans.

Investigating the Molecular Determinants for Substrate Channeling in BphI–BphJ, an Aldolase–Dehydrogenase Complex from the Polychlorinated Biphenyls Degradation Pathway

BphI-BphJ, an aldolase-dehydrogenase complex from the polychlorinated biphenyls (PCBs) degradation pathway, cleaves 4-hydroxy-2-oxoacids to pyruvate and an aldehyde. The enzyme complex was shown to exhibit substrate channeling, whereby linear aldehydes of up to 6 carbons long and branched isobutyraldehyde were directly channeled from the aldolase to the dehydrogenase with greater than 80% efficiency. BphI variants G322F, G322L, and G323F were created and were found to block aldehyde channeling. The dehydrogenase cofactor NADH was able to activate the catalytic activity of the aldol cleavage reaction in these variants, suggesting that activation of BphI by BphJ cofactors is not solely due to faster aldehyde release. A G323L variant was able to channel acetaldehyde but not the larger propionaldehyde while the G323A variant was able to channel butyraldehyde but not its isomer isobutyraldehyde, confirming that the restricted channeling of aldehydes in these glycine variants are due to steric blockage of the channel. Substitution of His-20 and Tyr-290 in BphI led to significant reductions in aldehyde channeling efficiencies. A mechanism of substrate channeling involving these two gating residues is proposed.

Structure and Mechanism of Human UDP-glucose 6-Dehydrogenase

Elevated production of the matrix glycosaminoglycan hyaluronan is strongly implicated in epithelial tumor progression. Inhibition of synthesis of the hyaluronan precursor UDP-glucuronic acid (UDP-GlcUA) therefore presents an emerging target for cancer therapy. Human UDP-glucose 6-dehydrogenase (hUGDH) catalyzes, in two NAD+-dependent steps without release of intermediate aldehyde, the biosynthetic oxidation of UDP-glucose (UDP-Glc) to UDP-GlcUA. Here, we present a structural characterization of the hUGDH reaction coordinate using crystal structures of the apoenzyme and ternary complexes of the enzyme bound with UDP-Glc/NADH and UDP-GlcUA/NAD+. The quaternary structure of hUGDH is a disc-shaped trimer of homodimers whose subunits consist of two discrete α/β domains with the active site located in the interdomain cleft. Ternary complex formation is accompanied by rigid-body and restrained movement of the N-terminal NAD+ binding domain, sequestering substrate and coenzyme in their reactive positions through interdomain closure. By alternating between conformations in and out of the active site during domain motion, Tyr14, Glu161, and Glu165 participate in control of coenzyme binding and release during 2-fold oxidation. The proposed mechanism of hUGDH involves formation and breakdown of thiohemiacetal and thioester intermediates whereby Cys276 functions as the catalytic nucleophile. Stopped-flow kinetic data capture the essential deprotonation of Cys276 in the course of the first oxidation step, allowing the thiolate side chain to act as a trap of the incipient aldehyde. Because thiohemiacetal intermediate accumulates at steady state under physiological reaction conditions, hUGDH inhibition might best explore ligand binding to the NAD+ binding domain.

Synthesis of amphiphilic copolymer having acid‐labile bicyclo bisoxazolidine in the side chain for controlled release of fragrance aldehyde

AbstractA metharylate monomer having an octanal‐derived bicyclo bisoxazolidine (BBOX) moiety was synthesized and was radically copolymerized with a methacrylate having a hydrophilic poly(ethylene glycol) chain to obtain an amphiphilic copolymer having the BBOX moieties as hydrophobic side chains. The BBOX moieties were stable for 7 days at pH 7.0, whereas they were gradually hydrolyze at pH 5.0 to release octanal continuously for 7 days, confirming the potential applicability of the copolymer to a polymeric pro‐fragrance that can release aldehyde‐type fragrance molecules slowly for a long period. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Conversion of Pyruvate Decarboxylase into an Enantioselective Carboligase with Biosynthetic Potential

Pyruvate decarboxylase (PDC) catalyzes the decarboxylation of pyruvate into acetaldehyde and CO(2) and requires the cofactors thiamin diphosphate and Mg(2+) for activity. Owing to its catalytic promiscuity and relaxed substrate specificity, PDC catalyzes carboligation side reactions and is exploited for the asymmetric synthesis of 2-hydroxy ketones such as (R)-phenylacetyl carbinol, the precursor of (-)-ephedrine. Although PDC variants with enhanced carboligation efficiency were generated in the past, the native reaction, i.e., formation of aldehydes, is heavily favored over carboligation side reactions in all these biocatalysts. We characterized an active site variant (Glu473Gln) in which partitioning between aldehyde release versus carboligation is inverted with an up to 100-fold preference for the latter pathway. Due to a defective protonation of the central carbanion/enamine intermediate, substrate turnover stalls at this catalytic stage and addition of external aldehydes leads to quantitative and enantioselective formation of 2-hydroxy ketones as shown for (R)-phenylacetyl carbinol, which is afforded with unmatched yields, rates, and purity. This protein variant thus constitutes an example for the rational design of biocatalysts with greatly enhanced accidental catalytic promiscuity by selective blockage of the native reaction and accumulation of reactive intermediates under steady-state turnover conditions.

Synthesis of amphiphilic polyacetal by polycondensation of aldehyde and polyethylene glycol as an acid‐labile polymer for controlled release of aldehyde

AbstractA new acid‐labile polymer having acetal moieties in the main chain was synthesized by polycondensation of poly (ethylene glycol) (PEG) and lilial, an aldehyde widely used in fragrance applications. The hydrophobicity of the resulting acetal moiety and the hydrophilicity of the PEG chain allowed the polyacetal to exhibit amphiphilicity. The polyacetal derived from PEG having weight average molecular weight (Mw) of 1000 (PEG1000) was soluble in water and self‐associated to form associates in water. The polyacetals were hydrolyzed in acidic aqueous solutions to release hydrophobic lilial from the systems. The release rate of aldehyde from the polyacetal derived from PEG1000 was higher than that from the polyacetal derived from PEG having Mw of 400 (PEG400). These results supported that the release rate of lilial can be controlled by the chain length of PEG, on which hydrophilicity of polyacetal depends. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

A new water‐soluble branched poly(ethylene imine) derivative having hydrolyzable imidazolidine moieties and its application to long‐lasting release of aldehyde

AbstractA new water‐soluble poly(ethylene imine)‐derivative having imidazolidine moieties was developed. With using branched poly(ethylene imine) (BPEI) as a precursor, it was modified by Michael addition reaction of its primary amino group to an acrylate having poly(ethylene glycol) (PEG) chain. The modified BPEI was reacted with octanal to give the corresponding BPEI derivative having octanal‐derived imidazolidine moieties. The obtained polymer inherited the high hydrophilicity of the attached PEG chains to allow hydrolysis of the imidazolidine moieties under homogeneous conditions in aqueous media, leading to long‐lasting release of octanal. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

Synthesis of an amphiphilic polymer having hydrophobic acetal and hydrophilic pyrrolidone moieties and its application to persisting release of aldehyde as a pro‐fragrance

AbstractA polymer having acetal moiety in the side chain was synthesized by a reaction of 1,3‐diol structure of poly(vinyl alcohol‐co‐N‐vinylpyrrolidone) and octanal. The hydrophobicity of the resulting acetal moiety and the hydrophilicity of the pyrrolidone moiety allowed the polymer to exhibit amphiphilicity. The polymer released octanal by hydrolysis of the acetal side chains under acidic conditions. The release of octanal was enhanced by the increased hydrophilicity of the polymer because of the presence of pyrrolidone moiety. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3816–3822, 2010

Amphiphilic Copolymer Having Acid-Labile Acetal in the Side Chain as a Hydrophobe: Controlled Release of Aldehyde by Thermoresponsive Aggregation−Dissociation of Polymer Micelles

Statistical amphiphilic copolymers of polymethacrylate having a lilial-derived acetal moiety as a hydrophobic side chain and poly(ethylene glycol) (PEG) as a hydrophilic side chain were synthesized with different unit ratios (3a (x:y = 100:0), 3b (x:y = 73:27), and 3c (x:y = 24:76)). In aqueous media the polymer 3c (x:y = 24:76) formed its micelles, whose particle diameter was ranged mainly from 10 to 220 nm and averaged diameter was 35 nm. Polymer 3c in aqueous media exhibited aggregation−dissociation behavior which was dependent sharply and reversibly on temperature in the presence of NaCl. The aggregation of the polymer micelles inhibited hydrolysis of the acid-labile acetal side chain and release of the resulting lilial, while its dissociation removed the inhibition. This responsive behavior by simply heating and cooling could control hydrolysis of the acid-labile acetal side chain and release of the resulting lilial.