An efficient method for improving the stability of Monascus pigments using ionic gelation.

BACKGROUND: Monascus pigments (Mps) are easily impacted by heating, pH and light, resulting in degradation. In this study, Mps were encapsulated by the ionic gelation method with sodium alginate (SA) and sodium caseinate (SC), as well as CaCl2 as a crosslinker. The encapsulated Mps SA/SC in four proportions (SA/SC: 1/4, 2/3, 3/2, 4/1, w/w). Then, the encapsulation efficiency and particle size of the SA/SC-Mps system were evaluated to obtain the optimal embedding conditions. Finally, the effects of heating, pH, light and storage on the stability of non-capsulated Mps and encapsulated Mps were assessed. RESULTS: SA/SC = 2/3 (AC2) had higher encapsulation efficiency (74.30%) of Mps and relatively small particle size (2.02 mm). The AC2 gel beads were chosen for further investigating the stability of encapsulated Mps to heating, pH, light and storage. Heat stability experiments showed that the degradation of Mps followed first-order kinetics, and the encapsulated Mps had lower degradation rates than non-capsulated Mps. Encapsulation could reduce the effect of pH on Mps. The effects of ultraviolet light on the stability of Mps were considered, and showed that the retention efficiency of encapsulated Mps was 22.01% higher than that of non-capsulated Mps on the seventh day. Finally, storage stability was also evaluated under dark refrigerated conditions for 30 days, and the results indicated that encapsulation could reduce the degradation of Mps. CONCLUSION: This study has proved that AC2 gel beads can improve the stability of Mps. Thus, the ionic gelation method is a promising encapsulation method to improve the stability of Mps. © 2023 Society of Chemical Industry.

Hybrid Hydrogel Electrolyte Based on Metal-Organic Supermolecular Self-Assembly and Polymer Chemical Cross-Linking for Rechargeable Aqueous Zn-MnO2 Batteries.

Multifunctional metal-organic supramolecular hydrogels have achieved great progress nowadays. However, their applications in aqueous batteries for flexible energy storage devices remain limited due to their unsatisfactory mechanical properties. Here, we report a rapid formation of supramolecular hydrogel by adenosine 5'-monophosphate (AMP) and manganese ions (Mn2+). Additionally, the AMP-Mn hydrogel is combined with chemical cross-linking poly(vinyl alcohol) (PVA) polymer networks to form an AMP-Mn/PVA hybrid hydrogel, which effectively solves the problems with regard to the mechanical properties and stability of metal-organic supramolecular hydrogels as well as self-healing of tough chemical cross-linking polymer networks. The AMP-Mn/PVA hybrid hydrogel served as the hydrogel electrolyte to fabricate flexible Zn-MnO2 batteries, which exhibit fast ion conductivity, excellent electrochemical stability, and robust mechanical strength, indicating feasible practical application prospects. This investigation provides a promising opportunity for the application of metal-organic supramolecular hydrogels in the field of energy storage.

Nitrogen-doped porous carbon sphere supported Pt nanoparticles for methanol and ethanol electro-oxidation in alkaline media.

A simple method for the preparation of porous nitrogen-doped carbon spheres (MNCS) with honeycomb-like structures through the self-assembly of colloidal silica by using polyaniline as the nitrogen source and a carbon precursor is reported. The BET surface area calculated from N2 adsorption/desorption measurement of the MNCS is up to 882 m2 g-1. The synthesized MNCS were employed as a support for Pt nanoparticles for the oxidation of methanol and ethanol in alkaline media. Compared to Pt supported on commercial Vulcan XC-72R carbon (Pt/C), Pt/MNCS exhibit higher electro-catalytic performance and greater stability, indicating that MNCS have potential application prospects as electro-catalyst supports for alcohol oxidation in alkaline media. This enhancement in performance is due to the honeycomb-like porous structure of the MNCS and the doping with nitrogen.

Hydrogen bonding and π-π stacking in nicotinamide/H2O mixtures.

The interactions between nicotinamide (NA) and H2O were studied using UV-visible spectra (UV-Vis), cyclic voltammetry (CV), nuclear magnetic resonance (NMR), density functional theory (DFT) and atoms in molecules (AIM) analysis. According to the changes of the UV-Vis spectra and the oxidation and reduction potentials in cyclic voltammograms of NA in aqueous solution, it was found that hydrogen bonding occurred between NA and H2O molecules. Quantum chemistry calculations and AIM analysis further confirmed the existence of hydrogen bonding between H2O molecules and the amide group, the nitrogen atom, and hydrogen atoms on the pyridine ring of NA molecules. In addition, the NMR results demonstrated that the π-π stacking between NA pyridine rings could be formed at higher concentrations.

Experimental and theoretical study on the hydrogen bonding between dopamine hydrochloride and N,N-dimethyl formamide.

The hydrogen bonding between dopamine hydrochloride (DH) and N,N-dimethyl formamide (DMF) were investigated by UV-visible spectra (UV-Vis), cyclic voltammetry (CV) and density functional theory (DFT). It was found that the position of UV-Vis absorption band and the anodic/cathodic peak potentials of DH were all affected by the concentrations of DH in DMF. It was suggested that hydrogen bonding were formed between DH and DMF, which was confirmed by the DFT results. AIM analyses were performed to elucidate the nature of the hydrogen bonding in the mixtures.

A combined experimental and theoretical study on vibrational spectra of 2-acetylpyridine.

The molecular geometries, FT-IR and Raman spectra of 2-acetylpyridine were studied using Density functional theory (DFT-B3LYP) with the large basis sets. Theoretical calculations indicate the cis conformer of 2-acetylpyridine is most stable though this conformation was seldom found in the crystal structures of coordinated compounds. Based on the stable conformer, comprehensive assignments of the experimental bands were made. The observed and calculated positions are found to be in good agreement with an average deviation of <4 cm(-1). The assignments provide valuable information for the fingerprint and identification of 2-acetylpyridine.

Molecular structure and vibrational spectra of N4-acetylcytosine.

The infrared and FT-Raman spectra of N4-acetylcytosine in the solid phase have been recorded, and the molecular geometrical parameters were optimized using B3LYP and MP2 methods with 6-311++G(d,p) basis set. The theoretical calculations indicate the presence of four stable conformers of N4-acetylcytosine, and the one containing an intramoleuclar six-membered ring is the most stable. The vibrational wavenumbers, infrared intensities, Raman scattering activities and the corresponding assignments of the observed bands based on the most optimized conformer were performed by B3LYP methods using the aug-cc-pvtz basis set. The observed and calculated frequencies are found to be in good agreement.

Mathematic modeling for optimum conditions on aflatoxin B1degradation by the aerobic bacterium Rhodococcus erythropolis.

Response surface methodology was employed to optimize the degradation conditions of AFB1 by Rhodococcus erythropolis in liquid culture. The most important factors that influence the degradation, as identified by a two-level Plackett-Burman design with six variables, were temperature, pH, liquid volume, inoculum size, agitation speed and incubation time. Central composite design (CCD) and response surface analysis were used to further investigate the interactions between these variables and to optimize the degradation efficiency of R. erythropolis based on a second-order model. The results demonstrated that the optimal parameters were: temperature, 23.2 °C; pH, 7.17; liquid volume, 24.6 mL in 100-mL flask; inoculum size, 10%; agitation speed, 180 rpm; and incubation time, 81.9 h. Under these conditions, the degradation efficiency of R. erythropolis could reach 95.8% in liquid culture, which was increased by about three times as compared to non-optimized conditions. The result by mathematic modeling has great potential for aflatoxin removal in industrial fermentation such as in food processing and ethanol production.

Quantum chemical studies of FT-IR and Raman spectra of methyl 2,5-dichlorobenzoate.

In this paper, experimental and theoretical studies on the molecular structure and vibrational spectra of methyl 2,5-dichlorobenzoate (MDCB) are presented. Fourier transform infrared and Raman spectra of the title molecule in the solid phase were recorded and analyzed. The geometrical parameters were calculated using DFT (B3LYP) with 6-311G(d,p) and 6-311++G(d,p) basis sets, and compared with the experimental data. The vibrational frequencies, infrared intensities and Raman scattering activities were also reported. The detailed assignments were given based on the total energy distribution of the vibrational modes, calculated with scaled quantum mechanics method. The observed and calculated frequencies are found to be in good agreement.

(2,9-Dimethyl-1,10-phenanthroline-κN,N')(4-hydroxy-benzoato-κO,O')(nitrato-κO)copper(II).

In the title compound, [Cu(C(7)H(5)O(3))(NO(3))(C(14)H(12)N(2))], the Cu(II) ion is five-coordinated in a slightly distorted square-pyramidal geometry by one O atom of a nitrate anion, two O atoms of a 4-hydroxy-benzoate anion, and two N atoms from a bidentate 2,9-dimethyl-1,10-phenanthroline (dmphen) ligand. In the crystal structure, inversion-related mol-ecules are linked into dimers by O-H⋯O hydrogen bonds. The packing is further stabilized by π-π inter-actions involving the benzene rings of the dmphen and hydroxy-benzoate units, with centroid-centroid distances of 3.4930 (14) or 3.5727 (14) Å.

(2,9-Dimethyl-1,10-phenanthroline-κN,N')bis-(2-hydroxy-benzoato-κO)copper(II).

The Cu(II) atoms in the two independent mol-ecules of the title compound, [Cu(C(7)H(5)O(3))(2)(C(14)H(12)N(2))], are each coordinated by a bidentate 2,9-dimethyl-1,10-phenanthroline (dmphen) mol-ecule and two monodentate 2-hydroxy-benzoate anions in a distorted tetra-hedral geometry. The crystal packing is stabilized by intra-molecular hydrogen bonding and π-π inter-actions between the dmphen rings of neighboring mol-ecules, with distances between their ring planes of 3.5670 (4) and 3.5181 (9) Å.

Diaqua-(2,9-dimethyl-1,10-phenanthroline-κN,N')(4-hydroxy-benzoato-κO,O')cobalt(II) nitrate dihydrate.

In the title compound, [Co(C(7)H(5)O(3))(C(14)H(12)N(2))(H(2)O)(2)]NO(3)·2H(2)O, the Co(II) ion is six-coordinated by two N atoms of a 2,9-dimethyl-1,10-phenanthroline (dmphen) ligand, two carboxyl-ate O atoms of one 4-hydroxy-benzoate anion and two O atoms of two water mol-ecules, in a distorted octa-hedral environment; the two water mol-ecules occupy the apical positions. In the crystal structure, the ionic units and water mol-ecules are linked through O-H⋯O hydrogen bonds, leading to the formation of a three-dimensional network. In addition, π-π inter-actions between a pyridine ring of the dmphen ligand and the benzene ring of the hydroxy-benzoate anion [centroid-centroid separation = 3.6861 (3) Å] are observed.

[Studies on chemical constituents from Elsholtzia bodinieri Vaniot].

OBJECTIVE: To study the chemical constituents from Elsholtza bodinieri Vaniot. METHOD: The chemical constituents were isolated and repeatedly purified on silica gel column and the structures were elucidated by the NMR spectra and physico-chemical properties. RESULTS: Seven compounds were obtained and they are identified as 5,7-dihydroxyflavone, 5,7,3',4-tetrahydroxyflavone, 5,3',4'-trihydroxy-7-O-beta-D-glucoside, acacetin, oleanolic acid, beta-sitosterol, daucosterol. CONCLUSION: All the compounds were obtained from Elsholtzia bodinieri Vaniot for the first time.