Development of a flow injection method for monitoring cell membrane damage of wine lactic acid bacteria

A flow injection analysis (FIA) system was developed for the determination of phosphate efflux from wine lactic acid bacteria (Oenococus oeni and Lactobacillus hilgardii) as an indication of cell membrane damage. The system allowed the direct injection of the cell suspension, avoiding the filtration step, with minimum sample treatment and minimized reagent consumption. The developed system is characterized by a linear concentration zone between 3.23 × 10⁻⁵ and 4.84 × 10⁻⁴ mol L⁻¹ PO₄ ³⁻ and repeatability better than 2.9%. Bacterial suspensions were exposed to a chemical stress with phenolic acids and injected in the FIA system at regular intervals. The extracellular concentration of phosphate was measured spectrophotometrically. The experimental results obtained indicate that hydroxycinnamic acids (p-coumaric, ferulic and caffeic) induced faster phosphate leakage rates than hydroxybenzoic acids (vanillic and p-hydroxybenzoic) in both strains tested, which could be related to their higher lipophilic character.     

Application of solid-phase extraction for determination of phenolic compounds in barrique wines

A fast, selective and sensitive chromatographic method has been developed for determination of gallic, protocatechuic, p-hydroxybenzoic, vanillic, caffeic, syringic, p-coumaric, benzoic, ferulic, sinapic, cinnamic, and ellagic acids and p-hydroxybenzaldehyde, vanillin, syringaldehyde, 2-furfural, 5-methylfurfural, and 5-methoxyfurfural. The compounds from untreated wine samples were pre-concentrated and cleaned using solid-phase extraction on RP-105 polymeric sorbent. The cartridge was conditioned with methanol and water. Co-extracted ballast substances were rinsed from the sorbent with 0.1 mol L^–1 hydrochloric acid–methanol, 1:4 (v/v). Retained phenolic compounds were selectively eluted with diethyl ether. A linear mobile phase gradient containing 0.3% acetic acid and methanol was used for final baseline chromatographic separation on a Hypersil BDS C18 column. Limits of detection (LOD=3s_bl) in the range 5.2 to 181.2 g L^–1, resolution (R) better than 1.7, and repeatability of 2.7–5.1% (RSD for real samples) were achieved. The method was applied for quantification of individual phenolic compounds in barrique wines.     

Some observations on the spectrophotometric determination of amino acids via interaction with p-benzoquinone

Spectrophotometric quantitative determination of amines and sulfa drugs via interaction with p-benzoquinone was extended to determination of amino acids, whereby the colored products obtained display maximum absorption at λ = 490–500 nm, E₁ cm^1% in the range 160–480, and a concentration range of 1.5–34.0 μg/ml. The effects of time, concentration, temperature, and cooling on the nature of the reaction product were investigated. The reaction proved to be irreversible. A monosubstituent compound is more easily formed in the presence of excess p-benzoquinone. A linear relation between the formation constant (K_f) and pK_α for the tested amino acids has been observed. Determination of adrenaline by this method is considered to offer an indirect means of determination of tyrosine.     

Chiral recognition and enantiomer assays of N-(3,5-dinitrobenzoyl)amino acid derivatives using electrospray ionization–mass spectrometry

A pair of pseudoenantiomers, anilide derivatives of N-pivaloylproline were prepared and used as chiral selectors for enantiomer discrimination of amides or esters of N-(3,5-dinitrobenzoyl)amino acids in single-stage electrospray ionization/mass spectrometric experiments. Addition of a chiral analyte to a solution of the two pseudoenantiomeric chiral selectors affords selector–analyte complexes in the electrospray ionization mass spectrum where the ratio of these complexes is dependent on the enantiomeric composition of the analyte. The relationship between the ratio of the selector–analyte complexes in the electrospray ionization mass spectrum and the enantiomeric composition of the analyte can be used to relate the extent of the measured enantioselectivity and for quantitative enantiomeric composition determinations. Effects of the added cationic ions (H⁺, Li⁺, Na⁺ and K⁺) and instrument conditions on the selector–analyte ion intensity and the enantioselectivity (α_MS) were investigated. The percent ratio of the sum of the selector–analyte ion counts and the total ion counts decreases accordingly with the increase of the desolvation temperature for H⁺, Na⁺ and K⁺. The ratio for Li⁺ kept almost constant. The best α_MS was observed at a desolvation temperature of 200 °C with the added H⁺. The cone voltage has little effects on the α_MS values though the intensities of selector–analyte complexes are decreased at higher cone voltages. The observed MS enantioselectivities are comparable to the HPLC enantioselectivities and the sense of chiral recognition by MS is consistent with what is observed chromatographically. Quantitative enantiomeric composition determinations for five different samples of N-(3,5-dinitrobenzoyl)leucinyl butylamide at four different concentrations were performed. The average % difference between the HPLC and MS enantiomer determinations is 6.8% and 3.7% for the calibration lines constructed at a concentration of the analyte of 125 μM and 12.5 μM, respectively.     

Indice de liaison en méthode CNDO. Relation entre indice de liaison et distance de liaison

The use of p_AB = Σ_μ^A Σ_ν^B _μν S_μν as bond index in the CNDO approximation is theoretically justified as it is an elaborated form of Coulson's bond order and an approximation of Roby's shared electron density. This bond index correlates with diatomic energy E_AB, a measure of binding energy, and with interatomic distance R_AB, for several bonds involving hydrogen and atoms of the n = 2 period. As an example of utilization of p_AB bond lengths in butadiene and a series of ethylenic compounds are determined.     

A Simple and Highly Efficient One-Pot Procedure for the Synthesis of Amides via Beckmann Rearrangements Using 1-Tosylimidazole (TsIm)

A facile and highly efficient method for one-pot Beckmann rearrangement of ketoximes into N-substituted amides using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, ketoximes are refluxed with TsIm and Cs₂CO₃ in the presence of SiO₂ as a recyclable catalyst in DMF affording the corresponding amides in high yields. This methodology is highly efficient and regioselective for various structurally diverse ketoximes including symmetrical and unsymmetrical as well as cyclic oximes. The results of quantum mechanical studies used to rationalize the experimental outcomes are discussed.     

Fragmentation characteristics of hydroxycinnamic acids in ESI‐MSn by density functional theory

This work aims to analyze the electrospray ionization multistage mass spectrometry (ESI‐MSⁿ) fragmentation characteristics of hydroxycinnamic acids (HCAs) in negative ion mode. The geometric parameters, energies, natural bond orbitals and frontier orbitals of fragments were calculated by density functional theory (DFT) to investigate mass spectral fragmentation mechanisms. The results showed that proton transfer always occurred during fragmentation of HCAs; their quasi‐molecular ions ([M − H]⁻) existed in more than one form and were mainly with the lowest energy. The fragmentation characteristics included the followings: (1) according to the different substitution position of phenolic hydroxyl group, the ring contraction reaction by CO elimination from benzene was in an increasingly difficult order: m‐phenolic hydroxyl > p‐phenolic hydroxyl > o‐phenolic hydroxyl; and (2) ortho effect always occurred in o‐dihydroxycinnamic acids (o‐diHCAs), i.e. one phenolic hydroxyl group offered H⁺, which combined with the other one to lose H₂O. In addition, there was a nucleophilic reaction during ring contraction in diHCAs that oxygen atom attacked the carbon atom binding with the other phenolic hydroxyl to lose CO₂. The fragmentation characteristics and mechanism of HCAs could be used for analysis and identification of such compounds quickly and effectively, and as reference for structural analogues by ESI‐MS. Copyright © 2017 John Wiley & Sons, Ltd.     

Bioactive Components,Volatile Profile and In Vitro Antioxidative Properties of Taxus baccata L. Red Arils

This study aimed at assessing the composition of bioactive compounds, including ascorbic acid, carotenoids and polyphenols, the volatile compound profile and the antioxidant activity of red arils (RAs) of Taxus baccata L. grown in diverse locations in Poland. Among the carotenoids assayed in high quantities (3.3–5.42 μg/g), the lycopene content (2.55–4.1 μg/g) was remarkably higher than that in many cultivated fruits. Samples collected from three sites were distinguished by higher amounts of ascorbic acid (125 mg/100 g, on average) than those found in many cultivated berries. Phenylpropanoids quantitatively dominated among the four groups of phenolic compounds. Chromatographic separation enabled the detection of two phenylpropanoid acids: ferulic and p-coumaric. Irrespectively of the growth site, RAs contained substantial amounts of (-)-epicatechin (1080 μg/100 g, on average). A higher ability to scavenge DPPH^● and ABTS^●+ radicals was found in the hydrophilic fraction of RAs from two sites (Warsaw and Koszalin) compared with the other two sites. The volatile compound profile of RAs was dominated by alcohols, followed by ketones, esters and aldehydes. The presence of some volatiles was exclusively related to the specific growth site, which may be regarded as a valuable indicator. The combination of bioactive and volatile compounds and the fairly good antioxidant potential of RAs render them an attractive source for preparing functional foods.     

Quenching Behavior of the Electrochemiluminescence of Ru(bpy)32+/TPrA System by Phenols on a Smartphone-Based Sensor

Phenolic compounds such as vanillic and p-coumaric acids are pollutants of major concern in the agro-industrial processing, thereby their effective detection in the industrial environment is essential to reduce exposure. Herein, we present the quenching effect of these compounds on the electrochemiluminescence (ECL) of the Ru(bpy)₃²⁺/TPrA (TPrA=tri-n-propylamine) system at a disposable screen-printed carbon electrode. Transient ECL profiles are obtained from multiple video frames following 1.2 V application by a smartphone-based ECL sensor. A wide range of detection was achieved using the sensor with limit of detection of 0.26 μM and 0.68 μM for vanillic and p-coumaric acids, respectively. The estimated quenching constants determined that the quenching efficiency of vanillic acid is at least two-fold that of p-coumaric acid under the current detection conditions. The present ECL quenching approach provided an effective method to detect phenolic compounds using a low-cost, portable smartphone-based ECL sensor.     

Combined microwave-assisted isolation and solid-phase purification procedures prior to the chromatographic determination of phenolic compounds in plant materials

A fast, sensitive and selective procedure employing a combination of microwave-assisted extraction (MAE) and solid phase extraction (SPE) was applied prior to liquid chromatographic identification and quantification of phenolic compounds in plant materials. MAE has been tested and optimized for the isolation of phenolic acids (gallic, protocatechuic, p-hydroxybenzoic, chlorogenic, vanilic, caffeic, syringic, p-coumaric, ferulic, sinapic, benzoic, m-coumaric, o-coumaric, rosmarinic, cinnamic acids) and 3,4-dihydroxybenzaldehyde, syringaldehyde, p-hydroxybenzaldehyde, and vanillin in various plants. The effects of experimental conditions on MAE efficiency, such as solvent composition, temperature, extraction time, have been studied. The extraction efficiencies were compared with those obtained by computer-controlled, two-step Soxhlet-like extractions. Plant extracts were purified and phenolic compounds were pre-concentrated using SPE on polymeric RP-105 SPE sorbent prior to HPLC analysis. Chromatographic separation was carried out on a Hypersil BDS C₁₈ column using a mobile phase consisted of 0.3% (v/v) acetic acid in water (solvent A) and methanol (solvent B) at flow rate 0.6 ml min⁻¹ and column temperature 30 °C with gradient elution.     

Synthesis of novel N-protected β-amino nitriles: study of their hydrolysis involving a nitrilase-catalyzed step

Several commercially available nitrilases were investigated with regard to their potential to hydrolyze N-protected β³-amino nitriles into their corresponding N-protected β³-amino acids.The biotransformations were obtained in different proportions depending on the nitrilase involved. The best hydrolysis results were achieved for the N-Cbz-β³-amino nitrile from l-alanine using the NIT-107, in a phosphate buffer at 0.05 M. However, no biotransformation into the corresponding acids was observed for the N-sulfonylamide β³-amino nitriles. Two simple and efficient procedures to prepare the β³-amino nitriles from their analogous α-amino acids are described. Thirty four new substances were synthesized and characterized over the course of this work.     

Nipecotic Acid Derivatives as Potent Agents against Neurodegeneration: A Preliminary Study

Alzheimer’s Disease (AD) is a common neurodegenerative disorder characterized by memory loss and cognitive impairment. Its pathology has not been fully clarified and therefore highly effective treatments have not been obtained yet. Almost all the current treatment options aim to alleviate only the symptoms and not to eliminate the disease itself. Acetylcholinesterase inhibitors are the main therapeutic agents against AD, whereas oxidative stress and inflammation have been found to be of great significance for the development and progression of neurodegeneration. In this work, ethyl nipecotate (ethyl-piperidine-3-carboxylate), a heterocyclic carboxylic acid derivative, which acts as a GABA reuptake inhibitor and has been used in research for diseases involving GABAergic neurotransmission dysfunction, was amidated with various carboxylic acids bearing antioxidant and/or anti-inflammatory properties (e.g., ferulic acid, sinapic acid, butylated hydroxycinnamic acid). Most of our compounds have significant antioxidant potency as lipid peroxidation inhibitors (IC₅₀ as low as 20 μΜ), as oxidative protein glycation inhibitors (inhibition up to 57%), and act as DPPH reducing agents. Moreover, our compounds are moderate LOX inhibitors (up to 33% at 100 μΜ) and could reduce rat paw edema induced by carrageenan by up to 61%. Finally, some of them possessed inhibitory activity against acetylcholinesterase (IC₅₀ as low as to 47 μΜ). Our results indicate that our compounds could have the potentiality for further optimization as multi-targeting agents directed against AD.     

Synthesis and reactivity of neodymium(III) amido-tethered N-heterocyclic carbene complexes

The reaction of the heteroleptic Nd(III) iodide, [Nd(L′)(N″)(μ-I)] with the potassium salts of primary aryl amides [KN(H)Ar′] or [KN(H)Ar^*] affords heteroleptic, structurally characterised, low-coordinate neodymium amides [Nd(L′)(N″)(N(H)Ar′)] and [Nd(L′)(N″)(N(H)Ar^*)] cleanly (L′ = t-BuNCH₂CH₂[C{NC(SiMe₃)CHNt-Bu}], N″ = N(SiMe₃)₂, Ar′ = 2,6-Dipp₂C₆H₃, Dipp = 2,6-Prⁱ₂C₆H₃, Ar^* = 2,6-(2,4,6-Prⁱ₃C₆H₂)₂C₆H₃). The potassium terphenyl primary amide [KN(H)Ar^*] is readily prepared and isolated, and structurally characterised. Treatment of these primary amide-containing compounds with alkali metal alkyl salts results in ligand exchange to give alkali metal primary amides and intractable heteroleptic Nd(III) alkyl compounds of the form [Nd(L′)(N″)(R)] (R = CH₂SiMe₃, Me). Attempted deprotonation of the Nd-bound primary amide in [Nd(L′)(N″)(N(H)Ar^*)] with the less nucleophilic phosphazene superbase Bu^tNP{NP(NMe₂)₃}₃ resulted in indiscriminate deprotonations of peripheral ligand CH groups.     

Application of a Glassy Carbon Electrode Modified with Poly(Glutamic Acid) in Caffeic Acid Determination

Glassy carbon electrodes were coated with films of poly(glutamic acid) (PG), and the modified electrode proved to be very effective in the oxidation of caffeic acid. The performance of the film was also tested with ascorbic acid, coumaric acid, ferulic acid, sinapic acid and chlorogenic acid. At pH 5.6, all the hydroxycinnamic acids yield a higher peak current intensity when oxidized after incorporation in the PG-modified electrode, and only the oxidation of ascorbic acid exhibits overpotential reduction. At pH 3.5 only caffeic and chlorogenic acid are incorporated in the modified electrode and exhibit a well-defined oxidation wave at +0.51 V and +0.48 V, which is the base for their determination. Linear calibration graphs were obtained from 9 × 10⁻⁶ mol L⁻¹ to 4 × 10⁻⁵ mol L⁻¹ caffeic acid by linear voltammetric scan and from 4 × 10⁻⁶ mol L⁻¹ to 3 × 10⁻⁵ mol L⁻¹ by square wave voltammetric scan. The method was successfully applied to the determination of caffeic acid in red wine samples without interference from other hydroxycinnamic acids or ascorbic acid.     

Antioxidative properties of hydroxycinnamic acid derivatives and a phenylpropanoid glycoside. A pulse radiolysis study

Spectral and redox properties of the phenoxyl radicals from hydroxycinnamic acid derivatives and one selected component of phenylpropanoid glycosides, verbascoside, were studied using pulse radiolysis techniques. On the basis of the pH dependence of phenoxyl radical absorptions, the pK_a values for deprotonation of sinapic acid radical and ferulic acid radical are 4.9 and 5.2. The rate constants of one electron oxidation of those antioxidants by azide radical and bromide radical ion were determined at pH 7. The redox potentials of those antioxidants were determined as 0.59–0.71 V vs NHE at pH 7 with reference standard 4-methoxyphenol and resorcinol.     

Colorimetric determination of palladium (II) by means of promazine hydrochloride

In acetate buffer medium palladium(II) ions form with promazine hydrochloride (PM) two complexes: an orange one of a formula [Pd(C₁₇H₂₀N₂S)]²⁺ (λ_max = 460 nm, ε = 4.5 × 10³, at 20 °C and pH = 2) and a violet one of a formula [Pd(C₁₇H₂₀N₂S)₂]²⁺ (λ_max = 540 nm, ε = 8.8 × 10³ at 20 °C and pH = 2).The values for instability constants determined by Bjerrum's method amount to pK₁ = 3.95; pK₂ = 3.07; pβ₁ = 3.95; pβ₂ = 7.02, respectively.A colorimetric method of the determination of palladium(II) has been elaborated. The method consists in a measurement of the absorbance of the violet complex of palladium(II) with promazine hydrochloride at λ = 540 nm. The method permits the determination of 2–17 μg Pd/ml with an error of ±2%. The time of the determination is 20 min. Iron(III), Ce(IV), Pt(IV), V(V), Cr(VI), and HNO₃ interfere with the determination.     

Salicylaldoxime in manganese(III) carboxylate chemistry: Synthesis, structural characterization and physical studies of hexanuclear and polymeric complexes

The use of salicylaldehyde oxime (H₂salox) in manganese(III) carboxylate chemistry has yielded new members of the family of hexanuclear compounds presenting the [Mn₆(μ₃-O)₂(μ₂-OR)₂]¹²⁺ core, complexes [Mn^III₆(μ₃-O)₂(O₂CPh)₂(salox)₆(L₁)₂(L₂)₂] (L₁ = py, L₂ = H₂O (1); L₁ = Me₂CO, L₂ = H₂O (2); L₁ = L₂ = MeOH (3)). Addition of NaOMe to the acetonitrile reaction mixture, afforded the 1D complex [Mn^III₃Na(μ₃-O)(O₂CPh)₂(salox)₃(MeCN)]_n (4), whereas addition of NaClO₄ to the acetone reaction mixture afforded an analogous 1D complex [Mn^III₃Na(μ₃-O)(O₂CPh)₂(salox)₃(Me₂CO)]_n (5). The structures of 1–3 present the [Mn₆(μ₃-O)₂(μ₂-OR)₂]¹²⁺ core and can be described as two [Mn₃(μ₃-O)]⁷⁺ triangular subunits linked by two μ₂-oximato oxygen atoms of the salox²⁻ ligands, which show the less common μ₃-κ²O:κO′:κN coordination mode. The benzoato ligands are coordinated through the usual syn,syn-μ₂-κO:κO′ mode. The 1D polymeric structures of 4 and 5 consist of alternating [Mn₃(μ₃-O)]⁷⁺ subunits and Na⁺ atoms linked through two μ₃-κ²O:κO′:κN and one μ₄-κ²O:κ²O′:κN salox²⁻ ligands as well as one syn,anti-μ₂-κO:κO′ benzoato ligand. DC and AC magnetic susceptibility studies on 1 revealed the stabilization of an S = 4 ground state, and indications of single-molecule magnetism behavior, whereas the DC experimental data from polycrystalline sample of 5 are indicative of antiferromagnetic interactions within the [Mn₃] subunit. Solid state ¹H NMR data of 1 were used to probe the spin-lattice relaxation of the system.     

Separation ofcis andtrans isomers of naturally occurring hydroxycinnamic acids by high-pressure liquid chromatography

Summary The separation of hydroxycinnamic acids has been investigated by high-pressure liquid chromatography using a micro C₁₈ bonded phase. Irradiation oftrans-ferulic and sinapic acids readily gave a mixture ofcis-trans isomers which can be also separated with the system described.     

C carbide ligand in the trigonal prismatic environment of rheniums in [Re12CS17(CN)6] complexes

The electronic state of carbon in trigonal prismatic environment in [Re₁₂CS₁₇(CN)₆]ⁿ⁻ complexes with variable redox state n = 6 ↔ 8 was studied by molecular orbital method and electron localization function. The state is characterized by sp²-hybridisation and oxidation state −4. A weak long-distance interaction between μ₆-С and μ₂-S in the group [(μ₆-С)(μ₂-S)₃] was discovered for n = 6, the interaction disappears for n = 8.     

Host–guest complexation of antioxidative caffeic and ferulic acid amides with a functionalized cyclophane

Host?guest complexation has been studied by ¹H NMR on the benzyl and phenethyl amides of ferulic and caffeic acids as the guests in chloroform and acetonitrile; the counter host is a cyclophane which integrates four phenylene rings, amino and amide groups in the macrocyclic framework and bears four pendant methyl acetate ester arms. CAPE, one of the best known natural antioxidants, also has been studied for comparison. Among the guests studied, ferulic acid benzyl amide shows NMR shifts due to the formation of a host?guest complex in chloroform. The complexation occurs in two steps with the formation constants K ₁?=?[HG]/[H][G]?=?6?M^?1 and β ₂?=?[HG₂]/[H][G]²?=?87?M^?2. Two guest molecules are bound on the surface of the macrocyclic framework of a host molecule by two hydrogen bonds, NH(host amide)···O=C(guest amide) and C=O(host ester)···HO(guest phenol). The latter hydrogen bond may protect the bioactive site, i.e., phenol OH, of guest molecules captured in the complex against undesirable oxidation. This feature is observed only for ferulic acid benzyl amide in chloroform; the cyclophane ester interacts with this amide, distinctively from the other hydroxycinnamic acid derivatives.