Carboxylic Acid Moiety Research Articles

Chemical Derivatization of Commercially Available Condensed and Hydrolyzable Tannins.

Novel valorization routes for tannins were opened by the development of a simple, straightforward, robust, and flexible approach to the selective functionalization of condensed and hydrolyzable tannins. Irrespective of the different degrees of polymerization, different commercial tannins were efficiently functionalized by the generation of an ether linkage bound to a short linker carrying the desired functional group. Functionalizations could be realized at varying degrees of technical loadings, i.e., amounts of introduced tannin-alien functionalities per number of phenolic hydroxyl groups. The same strategy was found suitable for the synthesis of polyethylene glycol-functionalized tannin copolymers. Condensed tannins functionalized with carboxylic acid moieties could be converted into a tannin–oligopeptide hybrid.

Physico-chemical characterization of bilirubin-10-sulfonate and comparison of its acid\u2013base behavior with unconjugated bilirubin

Unconjugated bilirubin (UCB) is the end-product of heme catabolism in the intravascular compartment. Although beneficial for human health when mildly elevated in the body, when present at greater than a critical threshold concentration, UCB exerts toxic effects that are related to its physico-chemical properties, particularly affecting the central nervous system. The aim of the present study was to characterize bilirubin-10-sulfonate (ranarubin), a naturally occurring bile pigment, including determination of its mixed acidity constants (pKa*). Thanks to the presence of the sulfonic acid moiety, this compound is more polar compared to UCB, which might theoretically solve the problem with an accurate determination of the UCB pKa* values of its propionic acid carboxylic groups. Bilirubin-10-sulfonate was synthesized by modification of a previously described procedure; and its properties were studied by mass spectrometry (MS), nuclear magnetic resonance (NMR), infrared (IR), and circular dichroism (CD) spectroscopy. Determination of pKa* values of bilirubin-10-sulfonate and UCB was performed by capillary electrophoresis with low pigment concentrations in polar buffers. The identity of the synthesized bilirubin-10-sulfonate was confirmed by MS, and the pigment was further characterized by NMR, IR, and CD spectroscopy. The pKa values of carboxylic acid moieties of bilirubin-10-sulfonate were determined to be 5.02, whereas those of UCB were determined to be 9.01. The physico-chemical properties of bilirubin-10-sulfonate were partially characterized with low pKa* values compared to those of UCB, indicating that bilirubin-10-sulfonate cannot be used as a surrogate pigment for UCB chemical studies. In addition, using a different methodological approach, the pKa* values of UCB were found to be in a mildly alkaline region, confirming the conclusions of a recent critical re-evaluation of this specific issue.

Discoveries and Syntheses of Highly Potent Antimalarial Troponoids.

Novel derivatives of puberulic acid were synthesized and their antimalarial properties were evaluated in vitro against the Plasmodium falciparum K1 parasite strain, cytotoxicity against a human diploid embryonic cell line MRC-5, and in vivo efficacy using a Plasmodium berghei-infected mouse model. From previous information that three hydroxy groups on the tropone framework were essential for antimalarial activity, we converted the carboxylic acid moiety into the corresponding esters, amides, and ketones. These derivatives showed antimalarial activity against chloroquine-resistant Plasmodium in vitro equivalent to puberulic acid. We identified that the pentane-3-yl ester, cyclohexyl ester, iso-butyl ketone, cyclohexyl methyl ketone all show an especially potent antiparasitic effect in vivo at an oral dose of 15 mg/kg without any apparent toxicity. These esters were more effective than the existing commonly used antimalarial drug, artesunate.

Molecular docking-guided synthesis of NSAID-glucosamine bioconjugates and their evaluation as COX-1/COX-2 inhibitors with potentially reduced gastric toxicity.

Non-steroidal anti-inflammatory drugs (NSAIDs) are a powerful class of inhibitors targeting two isoforms of the family of cyclooxygenase enzymes (COX-1 and COX-2). While NSAIDs are widely used in the management of pain, in particular as a treatment for osteo- and rheumatoid arthritis, their long-term use has been associated with numerous on- and off-target effects. As the carboxylic acid moiety present in common NSAIDs is responsible for some of their adverse effects, but is not required for their anti-inflammatory activity, we sought to mask this group through direct coupling to glucosamine, which is thought to prevent cartilage degradation. We report herein the conjugation of commonly prescribed NSAIDs to glucosamine hydrochloride and the use of molecular docking to show that addition of the carbohydrate moiety to the parent NSAID can enhance binding in the active site of COX-2. In a preliminary, in vitro screening assay, the diclofenac-glucosamine bioconjugate exhibited 10-fold greater activity toward COX-2, making it an ideal candidate for future in vivo studies. Furthermore, in an intriguing result, we observed that the mefenamic acid-glucosamine bioconjugate displayed enhanced activity toward COX-1 rather than COX-2.

Intramolecular Photo-Oxidation as a Potential Source to Probe Biological Electron Damage: A Carboxylated Adenosine Analogue as Case Study.

A carboxylated adenosine analog (C-Ado−) has been synthesized and probed via time-resolved photoelectron spectroscopy in order to induce intra-molecular charge transfer from the carboxylic acid moiety to the nucleobase. Intra-molecular charge transfer can be exploited as starting point to probe low-energy electron (LEE) damage in DNA and its derivatives. Time-dependent density functional theory (TD-DFT) calculations at the B3LYP-6311G level of theory have been performed to verify that the highest occupied molecular orbital (HOMO) was located on carboxylic acid and that the lowest occupied molecular orbital (LUMO) was on the nucleobase. Hence, the carboxylic acid could work as electron source, whilst the nucleobase could serve the purpose of electron acceptor. The dynamics following excitation at 4.66 eV (266 nm) were probed using time-resolved photoelectron spectroscopy using probes at 1.55 eV (800 nm) and 3.10 eV (400 nm). The data show rapid decay of the excited state population and, based on the similarity of the overall dynamics to deoxy-adenosine monophosphate (dAMP–), it appears that the dominant decay mechanism is internal conversion following 1ππ* excitation of the nucleobase, rather than charge-transfer from the carboxylic acid to the nucleobase.

Large screening of DNA-compatible reaction conditions for Suzuki and Sonogashira cross-coupling reactions and for reverse amide bond formation

Progress in DNA-encoded chemical library synthesis and screening crucially relies on the availability of DNA-compatible reactions, which proceed with high yields and excellent purity for a large number of possible building blocks. In the past, experimental conditions have been presented for the execution of Suzuki and Sonogashira cross-coupling reactions on-DNA. In this article, our aim was to optimize Suzuki and Sonogashira reactions, comparing our results to previously published procedures. We have tested the performance of improved conditions using 606 building blocks (including boronic acids, pinacol boranes and terminal alkynes), achieving >70% conversion for 84% of the tested molecules. Moreover, we describe efficient experimental conditions for the on-DNA synthesis of amide bonds, starting from DNA derivatives carrying a carboxylic acid moiety and 300 primary, secondary and aromatic amines, as amide bonds are frequently found in DNA-encoded chemical libraries thanks to their excellent DNA compatibility.

Ice Nucleation Activity of Perfluorinated Organic Acids.

Perfluorinated acids (PFAs) are widely used synthetic chemical compounds, highly resistant to environmental degradation. The widespread PFA contamination in remote regions such as the High Arctic implies currently not understood long-range atmospheric transport pathways. Here, we report that perfluorooctanoic acid (PFOA) initiates heterogeneous ice nucleation at temperatures as high as −16 °C. In contrast, the eight-carbon octanoic acid, perfluorooctanesulfonic acid, and deprotonated PFOA showed poor ice nucleating capabilities. The ice nucleation ability of PFOA correlates with the formation of a PFOA monolayer at the air–water interface, suggesting a mechanism in which the aligned hydroxyl groups of the carboxylic acid moieties provide a lattice matching to ice. The ice nucleation capabilities of fluorinated compounds like PFOA might be relevant for cloud glaciation in the atmosphere and the removal of these persistent pollutants by wet deposition.

Elucidating the anti-biofilm and anti-quorum sensing potential of selenocystine against respiratory tract infections causing bacteria: in vitro and in silico studies.

Bacteria are increasingly relying on biofilms to develop resistance to antibiotics thereby resulting in their failure in treating many infections. In spite of continuous research on many synthetic and natural compounds, ideal anti-biofilm molecule is still not found thereby warranting search for new class of molecules. The current study focuses on exploring anti-biofilm potential of selenocystine against respiratory tract infection (RTI)-causing bacteria. Anti-bacterial and anti-biofilm assays demonstrated that selenocystine inhibits the growth of bacteria in their planktonic state, and formation of biofilms while eradicating preformed-biofilm effectively. Selenocystine at a MIC50 as low as 42 and 28μg/mL effectively inhibited the growth of Klebsiella pneumonia and Pseudomonas aeruginosa. The antibacterial effect is further reconfirmed by agar cup diffusion assay and growth-kill assay. Selenocystine showed 30-60% inhibition of biofilm formation in K.pneumonia, and 44-70% in P.aeruginosa respectively. It also distorted the preformed-biofilms by degrading the eDNA component of the Extracellular Polymeric Substance matrix. Molecular docking studies of selenocystine with quorum sensing specific proteins clearly showed that through the carboxylic acid moiety it interacts and inhibits the protein function, thereby confirming its anti-biofilm potential. With further validation selenocystine can be explored as a potential candidate for the treatment of RTIs.

Hydrothermal synthesis of two-dimensional cadmium(II) micro-porous coordination material based on Bi-functional building block and its application in highly sensitive detection of Fe3+ and Cr2O72−

Metal-organic framework (MOFs), also known as porous coordination polymers (PCPs), is a new kind of crystalline porous materials, which has received extensive attention in the past few decades. As a new type of sensing material, MOFs stand out from many other traditional fluorescence sensors because of its crystal characteristics, structural diversity, stable porosity and adjustable functional characteristics. In this work, the bi-functional building block containing aromatic carboxylic acid and triazole moieties, namely 3-(1H-1,3,4-triazol-1-yl) benzoic acid, was selected as the linker to synthesize {[Cd(µ5-L)⋅I}n (1, HL = 3-(1H-1,3,4-triazol-1-yl)benzoic acid) by hydrothermal method with transition CdII metal centers. Firstly, the preliminary characterization of 1 was carried out by means of PXRD, FT-IR, and then the UV and fluorescence tests were conducted to study the fluorescence properties of 1. The crystal structure analysis indicates that CdII is the center and the ligand is bridged to form a two-dimensional porous structure. In addition, 1 has good selectivity for Fe3+ and Cr2O72−, meanwhile, it has high detection sensitivity (Ksv quenching efficiency for Fe3+: 1.2 × 104 M−1 and Cr2O72− 1.85 × 104 M−1) and low detection limit (Fe3+: 19.21 μM and Cr2O72−: 12.46 μM). The results of photoluminescence test show that 1 can detect cations and anions with high sensitivity, resist the interference of other ions, and have good reusability. As far as we know, 1 is the first example of ultra-stable two-dimensional (2D) Cadmium (II) microporous coordination material as a fluorescence sensor for Fe3+ and Cr2O72−.

Fabrication of flexible blend films using a chitosan derivative and poly(trimethylene carbonate)

To modify the flexibility of chitosan (CS), poly(trimethylene carbonate) (PTMC) and its derivatives and copolymers were blended with a chitosan derivative, N,N,N-trimethylchitosan (TM-CS). The tensile strength of the CS and TM-CS films blended with PTMC was found to cause brittleness, but a PTMC derivative copolymer bearing carboxylic acid improved the elongation properties of TM-CS. A softer film was obtained for a blend film composed of TM-CS with 25% consisting of an added PTMC derivative copolymer bearing a 10% carboxylic acid moiety on the side chain. This film showed an elongation at break of 20.6 ± 9.3% with a tensile strength of 2.2 ± 0.83 MPa, while the original CS and TM-CS films showed an elongation at break of 7.4 ± 3.4% and 9.2 ± 1.6% with a tensile strength of 13.6 ± 1.0 MPa and 3.7 ± 0.35 MPa, respectively. This is the first report of the modification of CS using polymers with a PTMC backbone. Poly(trimethylene carbonate) (PTMC) based polymers were blended with N,N,N-trimethylchitosan (TM-CS). The tensile strength of the chitosan (CS) and TM-CS films blended with PTMC was found to cause brittleness, but a PTMC derivative copolymer bearing carboxylic acid improved the elongation properties of TM-CS. A softer film was obtained for a blend film composed of TM-CS with 25% consisting of an added PTMC derivative copolymer bearing a 10% carboxylic acid moiety on the side chain. This is the first report of the modification of CS using polymers with a PTMC backbone.

Reversible Solvatochromism of Polydiacetylenes Based on Extensively Hydrogen-Bonded Tubular Arrays

Since the pioneering discovery by Wagner, polydiacetylenes (PDAs) and their solvatochromic properties (typically blue-to-red or purple transitions) have been the subject of extensive research efforts. Without exception, PDAs have been found to undergo irreversible solvent-induced color changes, and no cases exist in which initial blue states of the PDAs are regenerated after solvent removal. Herein, we describe the first example of a reversibly solvatochromic PDA that is derived from a macrocyclic diacetylene (MCDA) containing four carboxylic acid moieties. Infrared spectroscopic studies confirmed the synergetic interplay of intra- and intermolecular hydrogen-bonding interactions to control the reversibility. The weak intramolecular hydrogen bonds allowed a solvent-induced distortion of the PDA backbone (purple state) by releasing unpolymerized monomers, while the strong and networked intermolecular hydrogen-bonding interactions ensured the rigidity of the tubular channels and served as the driving forces for the recovery of the initial conformation (blue state).

Insight into the mechanochemistry of the Maillard reaction: degradation of Schiff bases via 5-oxazolidinone intermediate

With the emergence of mechanochemistry as a fast and efficient synthetic methodology, we reported earlier that ball milling of glucose with histidine leads to the formation of reaction mixtures rich in Schiff bases. Upon subsequent thermal treatments, these mixtures exhibited enhanced reactivity generating more browning and pyrazine-rich volatiles, compared to non-milled samples. To rationalize these observations, we further investigated the mechanochemistry of the Maillard reaction using glycolaldehyde and histidine or phenylalanine as model systems. The conversion of Schiff bases into reactive 5-oxazolidinone in these model systems was proposed as the basis of the observed enhanced reactivity. Furthermore, the formation of 5-oxazolidinone in the ball-milled samples was verified through direct spectroscopic observation of its characteristic FTIR absorption band between 1780 cm−1 and 1810 cm−1 and through the identification of its specific degradation products. The important role of the carboxylic acid moiety in enabling the formation of reactive 5-oxazolidinone intermediate that facilitates its subsequent decarboxylation and formation of downstream degradation products such as dihydropyrazines and Strecker aldehydes were elucidated.

Metabolism, excretion, and pharmacokinetics of [14C]mirogabalin, a novel α2δ ligand, in healthy volunteers following oral administration

The metabolism, excretion, and pharmacokinetics of mirogabalin were investigated following a single oral administration of [14C]mirogabalin at 30 mg/5.55 MBq to six healthy male subjects. The mean recovery values of radioactivity in urine and faeces were 96.85 and 1.21%, respectively. The main component of radioactivity in the plasma, urine, and faeces was mirogabalin. A204-4455 (lactam form), mirogabalin N-glucuronide, and glucuronide of oxidized A204-4455 were detected as minor components in the specimens. Renal clearance of mirogabalin was higher than the glomerular filtration rate of the human kidneys, indicating renal secretion is involved in the clearance. In vitro studies revealed that UDP-glucuronosyltransferase produced two metabolites: A204-4455, formed via mirogabalin acylglucuronide, and a ring-opened form of mirogabalin N-glucuronide. Mirogabalin was absorbed almost completely, and was eliminated via urine. A part of the orally administered dose of mirogabalin was metabolized through glucuronidation at the amine and carboxylic acid moiety, which represents the primary metabolic pathway.

Synthesis of Alkaline-soluble Triazine-based Poly(phenylene sulfide)s with Single/Double Pendant Carboxylic Acid Moieties and Their Application to Refractive Index Contrast Materials

Abstract The design, synthesis, and optical characterization of refractive-index-contrast (RIC) triazine-based poly(phenylene sulfide)s (PPSs) are investigated. Indeed, novel PPSs with two pendant groups, either tert-butyl (tBu) ester or carboxylic acid groups, at each monomer repeating unit (PPS-2E or PPS-2CA, respectively) were successfully synthesized. PPS-2CA showed high refractive index (n) values of 1.6964 (633 nm) and 1.6714 (940 nm) as well as high δn (increase in the n value by the deprotection of PPS-2E) values of +0.062 (633 nm) and +0.058 (940 nm).

Synthesis, characterization and photophysicochemical properties of peripherally tetra-substituted phthalocyanines bearing carboxylic acid moieties

In the present study, peripherally tetra-substituted metal-free (H2Pc), Mg(II) (MgPc) and In(III)CI (InPc) phthalocyanine compounds containing carboxylic acid moieties were synthesized and characterized by various spectroscopic techniques. Photophysical, photochemical and aggregation properties of these compounds, which are show good solubility in DMSO, DMF and THF, were investigated. Aggregation behaviors of these phthalocyanines were investigated using DMSO and DMF in different concentrations. The photophysicochemical properties including fluorescence spectra and quantum yield, singlet oxygen generation and photodegradation behavior were researched in DMSO and DMF to clarify the usability of these compounds as a photosensitizers. In addition, the effects of the presence and absence of metal ion on photochemical and photophysical properties of these phthalocyanines are also examined. The metallo phthalocyanines (Mg(II) and In(III)CI) showed high singlet oxygen generation efficiency compared to metal-free phthalocyanine derivative. According to singlet oxygen generation efficiency, we can say that the presence of metal ion on phthalocyanine ring increases singlet oxygen generation. The results show that these compounds may have potential to be used as a photosensitizers in photodynamic therapy (PDT) applications.

Perceptual Quality of Nonesterified Fatty Acids Varies with Fatty Acid Chain Length.

Nonesterified fatty acids (NEFA) are effective taste stimuli. The quality they impart has not been well characterized. Sourness, and "fattiness" have been reported, but an irritation component has also been described and how these transition with gradations of aliphatic chain length has not been systematically studied. This study examined intensity and quality ratings of NEFA ranging from C2 to C18. Oral sites and the time course of sensations were also monitored. Given all NEFA contain carboxylic acid moieties capable of donating hydrogen ions, the primary stimulus for sour taste, testing was conducted with and without sour adaptation to explore the contribution of sour taste across the range of NEFA. Short-chain NEFA (C2-C6) were rated as predominantly sour, and this was diminished in C2 and C4 by sour adaptation. Medium-chain NEFA (C8-C12) were rated as mainly irritating with long-chain NEFA (C18) described mostly as bitter. The latter may reflect the lack of "fatty" lexicon to describe the sensation. Short-chain NEFA were mostly localized to the anterior tongue and were of rapid onset. The sensation from medium-chain NEFA was attributed to the lateral tongue, whereas medium- and long-chain NEFA sensations were predominantly localized to the back of the tongue and throat and had a longer lag time. The findings indicate there is a systematic transition of NEFA taste quality and irritation with increments in chain length and this is consistent with multiple modes of transduction.

Translational isomers of N-sulfonylated [3]catenane: synthesis and isomerization

N-Sulfonylated [3]catenanes, which exist as two translational isomers, were synthesized. The X-ray crystal structure of the distal isomer of [3]catenane, which has higher symmetry, revealed hydrogen bonds involving the carboxylic acid moieties on the terminal rings. The thermodynamic parameters of the isomerization revealed that this hydrogen bonding influenced the isomerization process.

Synthesis of bis-azobenzene derivatives with reactive bromohexyl unit and carboxylic acid group based on Disperse Yellow 7

In this work, two types of azobenzene derivatives based on Disperse Yellow 7 (DY7, 4-[4-(phenylazo)phenylazo]-o-cresol) were synthesized, which are bis-azobenzenes bearing flexible functional 6-bromohexyl chain or carboxylic acid moiety. The first one was synthesized by alkylation of DY7 with an excess of 1,6-dibromohexane in the presence of a mild base (K2CO3). The second one (azo dye with carboxylic acid functionality) was obtained by the alkaline hydrolysis of the ester bond of the newly obtained DY7 derivative with the ethoxycarbonyl group. The synthesized compounds were characterized by different spectral analytical techniques such as 1H NMR, 13C NMR, FT-IR, and UV-Vis. They can be employed for the synthesis of a wide variety of azo-based materials, which may be suitable for photochromic systems and molecular electronics applications.

Elucidation of Gut Microbiota-Associated Lipids Using LC-MS/MS and 16S rRNA Sequence Analyses.

SummaryHost-microbiota interactions create a unique metabolic milieu that modulates intestinal environments. Integration of 16S ribosomal RNA (rRNA) sequences and mass spectrometry (MS)-based lipidomics has a great potential to reveal the relationship between bacterial composition and the complex metabolic network in the gut. In this study, we conducted untargeted lipidomics followed by a feature-based molecular MS/MS spectral networking to characterize gut bacteria-dependent lipid subclasses in mice. An estimated 24.8% of lipid molecules in feces were microbiota-dependent, as judged by > 10-fold decrease in antibiotic-treated mice. Among these, there was a series of unique and microbiota-related lipid structures, including acyl alpha-hydroxyl fatty acid (AAHFA) that was newly identified in this study. Based on the integrated analysis of 985 lipid profiles and 16S rRNA sequence data providing 2,494 operational taxonomic units, we could successfully predict the bacterial species responsible for the biosynthesis of these unique lipids, including AAHFA.

Di-tert-butylsilylene as a protecting group for substituted salicylic acids

The use of di-tert-butylsilyl bis(trifluoromethanesulfonate) has been used to form cyclic protecting groups for substituted salicylic acids. The reaction works well in the presence of a variety of electron-donating groups (EDG) affording the protected compounds in moderate to excellent yields (70–99%) in most cases. In addition, a handful of electron-withdrawing groups (EWG) also provided the corresponding protected silylene derivatives in good yields (77–83%). However, substrates bearing additional ortho -substitution of the carboxylic acid moiety as well as strongly deactivating groups on the aromatic ring did not undergo reaction.