Headspace solid-phase microextraction applied to the simultaneous determination of sorbic and benzoic acids in beverages

A new analytical procedure was developed using headspace solid-phase microextraction (HS-SPME) for the simultaneous determination of sorbic and benzoic acids in beverages. The sample were processed depending on their nature, either only diluted with water, or treated with a NaOH solution and filtered through a 0.45-μm membrane filter. The samples were heated in a vial in the presence of sulfuric acid and anhydrous sodium sulfate and the analytes were collected from the headspace by using a 65-μm polydimethylsiloxane-divinylbenzene (PDMS-DVB) coated fiber and determined by gas chromatography with flame ionization detector (GC-FID). To enhance the sensitivity of HS-SPME, the temperature and time of the extraction and desorption, the acidity and salt concentration of the extraction solution were optimized. Linear range of the analytes was found to be between 0.1 and 20 mg/L with regression coefficients (R²) of 0.9998 for sorbic acid and 0.9980 for benzoic acid. Limits of detection (LOD) were 5.83 μg/L and 11.4 μg/L for sorbic and benzoic acids, respectively. Relative standard deviation (R.S.D.) for six replicate analyses within 3 days (two times/day) was found to be lower than 8.62% at three concentration levels (2, 6, 10 mg/L). Recoveries ranged from 81.20% to 108.1% for real samples. The results demonstrate the suitability of the HS-SPME technique to analyze sorbic and benzoic acids in a variety of beverages.     

Molecular structure and microbiological activity of alkali metal 3,4-dihydroxyphenylacetates

The changes in physical, chemical and biological properties of chemical compounds decide about their biological activity. In this paper the molecular structure of alkali metal 3,4-dihydroxyphenylacetates is studied in comparison to 3,4-dihydroxyphenylacetic acid (3,4-DHPAA) using FT-IR, FT-Raman and UV–Vis spectroscopy as well as density functional theory (DFT) calculations. The B3LYP/6-311++G⁷ method is used to calculate optimized geometrical structures of studied compounds, atomic charges (Mulliken, APT, NBO), dipole moments, energies as well as the wavenumbers and intensities of the bands in vibrational spectra. Theoretical parameters are compared to the experimental data. The relationship between spectroscopic parameters of studied compounds and their biological activity is analyzed. Antioxidant activity is studied using FRAP and DPPH methods. IC₅₀ parameter is also calculated. Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli and Klebsiella oxytoca are used in microbiological analysis of 3,4-DHPAA as well as its sodium and potassium salts.     

Synthesis,characterization, antimicrobial,and nuclease activity studies of some metal Schiff-base complexes

A Schiff base (L) is prepared by condensation of cuminaldehyde and L-histidine, and characterized by elemental analysis, IR, UV-Vis, ¹H-NMR, ¹³C-NMR, and mass spectra. Co(II), Ni(II), Cu(II), and Zn(II) complexes of this Schiff-base ligand are synthesized and characterized by elemental analysis, molar conductance, mass, IR, electronic spectra, magnetic moment, electron spin resonance (ESR), CV, TG/DTA, powder XRD, and SEM. The conductance data indicate that all the complexes are 1 : 1 electrolytes. IR data reveal that the Schiff base is a tridentate monobasic donor, coordinating through azomethine nitrogen, imidazole nitrogen, and carboxylato oxygen. The electronic spectral data and magnetic measurements suggest that Co(II) and Ni(II) complexes are tetrahedral, while Cu(II) complex has distorted square planar geometry. XRD and SEM show that Co(II), Cu(II), and Zn(II) complexes have crystalline nature, while the Ni(II) complex is amorphous and the particles are in nanocrystalline phase. The in vitro biological activities of the synthesized compounds were tested against the bacterial species, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and Staphylococcus aureus; and fungal species, Aspergillus niger, Aspergillus flavus, and Candida albicans by the disc diffusion method. The biological study indicates that complexes exhibit more activity than the ligand. The nuclease activity of the ligand and its complexes are assayed on CT DNA using gel electrophoresis in the presence and the absence of H₂O₂. The Cu(II) complex shows increased nuclease activity in the presence of an oxidant when compared to the ligand, Co(II) and Ni(II) complexes.     

High pressure effects on benzoic acid dimers: Vibrational spectroscopy

To understand pressure effects on dimer structure stability, Raman and FTIR spectroscopies were used to examine changes in H-bonded dimers of benzoic acid (BA). Experiments were performed on single crystals compressed to 33 GPa in a diamond anvil cell (DAC). Several changes in Raman spectra were observed in the range 6–8 GPa indicating modification in the dimer structure suggesting the lowering of molecular symmetry. Pressure increase above 15 GPa induced strong luminescence and a gradual change of the crystal color from white to yellow/brownish. FTIR measurements on the sample released from 33 GPa indicated formation of a new compound. It is proposed that molecules of this compound are composed of the hydroxyl group associated with alcohol, carbonyl group associated with ketone, and the sp³ hydrocarbon groups. This study demonstrates that sufficient high pressure compression and subsequent decompression can lead to significant changes in the H-bonded dimer structure, including the breaking of bonds and formation of new chemical compound.     

FTIR study of ion solvation and ion-pair formation in alkaline and alkaline earth metal salt solutions in acetonitrile

The IR spectra of alkaline and alkaline earth metal perchlorate and of lithium bromide solutions in acetonitrile, obtained with the help of FTIR measurements in the region of the C-N stretching mode of the solvent, reveal bands produced by acetonitrile molecules in the solvation shells and bands of ClO ₄ ^– ions in contact and solvent separated ion pairs. The shift and the attenuation of the C-N stretching band of acetonitrile at 2254 cm^–1 is used for the calculation of cation solvation numbers for Li⁺(4), Na⁺(4), Mg²⁺(6), Ca²⁺(6), and Ba²⁺(6). No solvation is assumed for the contact ion pairs of LiClO₄, LiBr, NaClO₄, Mg(ClO₄)₂, Ca(ClO₄)₂, and Ba(ClO₄)₂. The association constants of the symmetrical electrolytes are compared to those obtained from other methods.     

Synthesis, spectroscopic, antimicrobial, DNA binding and cleavage studies of some metal complexes involving symmetrical bidentate N, N donor Schiff base ligand

The Schiff base ligand, N,N′-bis-(4-isopropylbenzaldimine)-1,2-diaminoethane (L), obtained by the condensation of 4-isopropylbenzaldehyde and 1,2-diaminoethane, has been used to synthesize the complexes of the type [ML₂X₂] [M = Co(II), Ni(II) and Zn(II); X = Cl and OAc]. The newly synthesized ligand (L) and its complexes have been characterized on the basis of elemental analyses, mass, ¹H and ¹³C-NMR, molar conductance, IR, UV–vis, magnetic moment, CV and thermal analyses, powder XRD and SEM. IR spectral data show that the ligand is coordinated to the metal ions in a bidentate manner. The geometrical structures of these complexes are found to be octahedral. Interestingly, reaction with Cu(II) ion with this ligand undergoes hydrolytic cleavage to form ethylenediamine copper(II) complex and the corresponding aldehyde. The antimicrobial results indicate that the chloro complexes exhibit more activity than the acetato complexes. The complexes bind to CT–DNA by intercalation modes. Novel chloroform soluble ZnL₂Cl₂ complex exhibits tremendous antimicrobial, DNA binding and cleaving properties.     

Synthesis,characterization and antimicrobial screening of quinoline based quinazolinone-4-thiazolidinone heterocycles

In an attempt to find new pharmacologically active molecules, we report here the synthesis and in vitro antimicrobial activity of various 2-(2-chloro-6-methyl(3-quinolyl))-3-[2-(4-chlorophenyl)-4-oxo(3-hydroquinazolin-3-yl)]-5-[(aryl)methylene]-1,3-thiazolidin-4-ones. In vitro antimicrobial activity of the title compounds are screened against two Gram positive bacteria (Staphylococcus aureus, Streptococcus pyogenes), two Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and three strains of fungi (Candida albicans, Aspergillus niger, Aspergillus clavatus) using broth micro dilution method. Some derivatives bearing chloro or hydroxy group exhibited very good antimicrobial activity.     

Sorbic Acid as an Alkylating Agent

A kinetic study of the alkylating potential of the sorbic acid + NaOH and sorbic acid + KOH systems was performed in 7:3 (volume/volume) water + dioxane solvent mixtures. The following conclusions were drawn. First, the sorbic acid + sorbate system shows alkylating activity on the nucleophile 4-(p-nitrobenzyl)pyridine (NBP), which is used as a trap for alkylating agents having nucleophilic characteristics similar to DNA bases. Second, the maximum alkylating capacity is observed in the pH = 5.0 to 6.5 range. Third, the alkylation reactions comply with the rate equation r=k _alk[H⁺][S][NBP]/(K _a +[H⁺]), with K _a being the dissociation constant of sorbic acid. Fourth, an enthalpy–entropy (ΔH ^#/ΔS ^#) compensation effect for activation quantities is observed by comparing NBP alkylation reactions due to sorbic acid + NaOH, sorbic acid + KOH, as well as potassium sorbate + HCl mixtures. Fifth, the results may help to establish suitable expiration times for products preserved with sorbic acid.     

Silica Sulfuric Acid: An Efficient,Reusable, Heterogeneous Catalyst for the One-Pot,Five-Component Synthesis of Highly Functionalized Piperidine Derivatives

A series of highly functionalized piperidine derivatives was synthesized through one-pot, five-component reaction of aldehydes, amines, and β-ketoesters. Silica sulfuric acid efficiently catalyzes the reaction to afford the corresponding piperidine derivatives in good yields. As a representative example, heating of 4-methylaninle, 4-fluorobezaldehyde, and methyl-acetoacetate in methanol in the presence of silica sulfuric acid furnished the corresponding ethyl 2,6-bis(4-fluorophenyl)-1-p-tolyl-4-(p-tolylamino)-1,2,5,6-tetrahydropyridine-3-carboxylate in excellent yield (85%). Most of the synthesized compounds were screened in vitro for their antibacterial and antifungal activities. Most of compounds showed significant antibacterial activity.     

Vibrational study on the cobalt binding mode of Carnosine

The Co(II)-l-Carnosine (Carnos) system was investigated at different pH and metal/ligand molar ratios by Raman and IR spectroscopy. Raman spectra present some marker bands yielding information on the ability of the Co(II)/Carnos system to bind molecular oxygen and to identify the metal co-ordination site of the imidazole ring (N_π or N_τ atom) of Carnos.The existence of different oxygenated species is greatly affected by pH and the structure of the predominant complexes depends on the available nitrogen atoms. Under basic conditions, binuclear complexes binding molecular oxygen are the predominant species and two forms (monobridged and dibridged) were identified by the Raman νO-O band (750-850 cm⁻¹).Decreasing pH to 7, the species present in the system are less able to bind oxygen. Hydrogen peroxide and a Co(III) chelate not binding O₂, were formed with a significant conversion of peroxo into superoxo complexes. A slight excess of Carnos does not enhance metal chelation.In slightly acidic conditions, the formation of H₂O₂ and superoxo species is more enhanced than at pH 7 and another Co(III) chelate is probably formed.     

Vibrational spectra and density functional study of propylgermane

Raman and infrared spectra of propylgermane, CH₃CH₂CH₂GeH₃, and its Ge-deuterated analog, CH₃CH₂CH₂GeD₃, were investigated in their gaseous, liquid and solid states. The normal coordinate treatment was carried out by density functional theory (DFT) calculation, using B3LYP/6-31G^* and 6-311++G^** basis sets, and the corresponding fundamental vibrations were assigned. The trans (T) and gauche (G) forms around the central C–C bond coexisted in the gaseous and liquid states and only the T form existed in the solid state. From the temperature dependent measurements of the Raman spectra in the liquid state, the enthalpy difference was found to be ΔH(T−G)=−0.36±0.02 kcalmol⁻¹ with the T form being more stable. The energy differences between the isomers obtained by DFT calculations were ΔE(T−G)=−0.46 kcalmol⁻¹ and ΔE(T−G)=−0.87 kcalmol⁻¹ by the 6-31G^* basis set and 6-311++G^** basis set, respectively.     

New N1-(4-aryloxybenzyl)uracils containing N3-positioned 4-(trimethyleneoxy)benzoic acid moiety,and study of their antiviral activity against SARS-CoV-2 and influenza virus

New title uracil derivatives, 4-{3-[2,6-dioxo-3-(4-aryl-oxybenzyl)-3,6-dihydropyrimidin-1(2H)-yl]propoxy}benzoic acids and their butoxy homologues, were obtained in three steps using 2,4-bis(trimethylsilyloxy)pyrimidine, 4-aryloxy-benzyl bromides and methyl 4-(ω-bromoalkoxy)benzoates as the key reactants. The compounds were studied as inhibitors of H1N1 influenza virus and SARS-CoV-2 R replication in MDCK and Vero E6 cell cultures, respectively, which revealed that the tested compounds had high levels of anti-SARS-CoV-2 activity.     

Synthesis,characterization and biological studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes with pyrral-l-histidinate

The Schiff base ligand, pyrral-l-histidinate(L) and its Co(II), Ni(II), Cu(II) and Zn(II) complexes were synthesized and characterized by elemental analysis, mass, molar conductance, IR, electronic, magnetic measurements, EPR, redox properties, thermal studies, XRD and SEM. Conductance measurements indicate that the above complexes are 1:1 electrolytes. IR data show that the ligand is tridentate and the binding sites are azomethine nitrogen, imidazole nitrogen and carboxylato oxygen atoms. Electronic spectral and magnetic measurements indicate tetrahedral geometry for Co(II) and octahedral geometry for Ni(II) and Cu(II) complexes, respectively. The observed anisotropic g values indicate the presence of Cu(II) in a tetragonally distorted octahedral environment. The redox properties of the ligand and its complexes have been investigated by cyclic voltammetry. Thermal decomposition profiles are consistent with the proposed formulations. The powder XRD and SEM studies show that all the complexes are nanocrystalline. The in vitro biological screening effects of the synthesized compounds were tested against the bacterial species, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus; fungal species, Aspergillus niger, Aspergillus flavus and Candida albicans by the disc diffusion method. The results indicate that complexes exhibit more activity than the ligand. The nuclease activity of the ligand and its complexes were assayed on CT DNA using gel electrophoresis in the presence and absence of H₂O₂.     

α,β-不饱和羰基化合物抗菌作用和机理的研究

采用全略微分重叠法对丁烯二酸及其酯类的量子化学参数进行了计算，并对该类化合物的分子结构特征与抗菌活性间的关系进行了相关分析．结果表明，丁烯二酸及其酯类抗菌活性依分子流水性能增强而提高，依分子内基团间作用力的增强而降低；随分子最低空轨道能量的降低，抗菌生物活性极显著上升（p＜0．01），抗代谢性能显著提高（p＜0．02）．α，β-不饱和羰基结构是该类化合物的抗菌功能域，其活性中心在β-碳和羰基氧。     

Amino acid derivatives, VIII [1]: synthesis and antimicrobial evaluation of α-amino acid esters bearing an indole side chain

A series of peptide and dipeptide derivatives conjugated with an indole residue were synthesized. The prepared compounds were tested for antimicrobial activity against two different bacterial and one antifungal species displaying different degrees of antimicrobial activities or inhibitory actions. Correspondence: Adel A.-H. Abdel-Rahman, Department of Chemistry, Faculty of Science, Menoufia University, Shebin El-Koam, Egypt.     

Amino acid derivatives,IX [1]: synthesis and antimicrobial evaluation of α-amino acid esters bearing a tryptophane side chain

A series of peptide and dipeptide derivatives conjugated with a tryptophane residue were synthesized. The prepared compounds were tested for antimicrobial activity against four different bacterial species displaying different degrees of antibacterial activities or inhibitory actions. Correspondence: Adel A.-H. Abdel-Rahman, Department of Chemistry, Faculty of Science, Menoufia University, Shebin El-Koam, Egypt; Wael A. El-Sayed, National Research Centre, Department of Photochemistry, Cairo, Egypt.     

New superior bioactive metal complexes of ligand with N,O donor atoms bearing sulfadiazine moiety: Physicochemical study and thermal behavior for chemotherapeutic application

Sulfadiazine is a drug famous for its anti-inflammatory, antimicrobial, and antitumor effects. Remarkably, its biological activity can be further enhanced upon incorporating a suitable metal ion. However, these metal-comprising complexes are not widely available. In the current study, a sulfadiazine Schiff base derivative was exploited as a ligand for synthesizing new complexes utilizing Cu(II), Co(II), Ni(II), Fe(III), and Cr(III) metals. The structural and analytical characteristics of the ligand and the newly prepared complexes were elucidated using various spectral and thermal investigations. Also, the biological activity of the ligand and the metal complexes, including the cytotoxic effect on normal cells and on liver malignant cells and the antimicrobial activity, was examined. The infrared spectra demonstrated that the ligand coordinated to all the added metal ions in a neutral form. It behaved in a bidentate manner in all mononuclear complexes. The new complexes exhibited octahedral geometry. Evaluating the biological activities revealed that the ligand and its novel metal-containing complexes had moderate antimicrobial activity, while the metal complexes, especially those comprising of Cr(III), Fe(III), and Cu(II), displayed a superior chemotherapeutic effect on HepG2 cell line in comparison to the ligand with very week or rare cytotoxic effects on normal human cells. Efficiently, new sulfadiazine Schiff base derivative-containing metal complexes with enhanced therapeutic potential were manufactured and could be applied on experimental models for the treatment of various types of infections and malignancies.     

Synthesis and Antimicrobial Activities of Some 1-[(N,N-Disubstitutedthiocarbamoylthio)acetyl]-3,5-diaryl-2-pyrazolines

The increasing clinical importance of drug-resistant fungal and bacterial pathogens has lent additional urgency to microbiological research and new antimicrobial compound development. For this purpose, new pyrazoline derivatives were synthesized and evaluated for antimicrobial activity.

Some 1-[(N, N-disubstitutedthiocarbamoylthio)acetyl]-3,5-diaryl-2-pyrazolines derivatives were synthesized by reacting 1-(chloroacetyl)-3,5-diaryl-2-pyrazolines with appropriate potassium salts of secondary amine dithiocarbamic acids. The chemical structures of the compounds were elucidated by IR, ¹ H-NMR, and FAB⁺-MS spectral data. Their antimicrobial activities against Staphylococcus aureus (B-767), Escherichia coli (B-3704), Pseudomonas aeruginosa (ATCC 27853), Proteus vulgaris (NRLL B-123), and Candida albicans (NRRL-27077) were investigated. The results showed that some of the compounds have notable activity against S. aureus and C. albicans.     

芳香基苯并咪唑衍生物的合成、表征及抑菌活性研究

在微波辐射下,通过二茂铁磺酰氯和相应的苯并咪唑合成了4种芳香基苯并咪唑衍生物。经^1H NMR、MS及元素分析确证产物结构。通过X线衍射测定了化合物4a的晶体结构。用琼脂稀释法测定化合物抑菌活性,并与对照药剂50%多菌灵可湿性粉剂比较,结果表明化合物4a～4d对番茄早疫病菌、烟草赤星病菌和小麦赤霉病菌有与对照药剂近似的抑菌活性。