Preparation of Antioxidant Peptide by Microwave- Assisted Hydrolysis of Collagen and Its Protective Effect Against H2O2-Induced Damage of RAW264.7 Cells.

Antioxidant peptides have elicited interest for the versatility of their use in the food and pharmaceutical industry. In the current study, antioxidant peptides were prepared by microwave-assisted alkaline protease hydrolysis of collagen from sea cucumber (Acaudina molpadioides). The results showed that microwave irradiation significantly improved the degree of hydrolysis of collagen and the hydroxyl radical (OH⋅) scavenging activity of hydrolysate. The content and OH⋅ scavenging activity of collagen peptides with molecular weight ≤ 1 kDa (CPS) in the hydrolysate obtained at 250 W increased significantly compared with the non-microwave-assisted control. CPS could scavenge OH⋅ and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical in a dose-dependent manner. The scavenging activity of OH⋅ and DPPH radical was 93.1% and 41.2%, respectively, at CPS concentration of 1 mg/mL. CPS could significantly promote RAW264.7 cell proliferation and reduce the Reactive Oxygen Species (ROS) level of H2O2-induced damage in RAW264.7 cells in a dose-dependent manner. Furthermore, all CPS-treated groups exhibited an increase in superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and a decrease in malondialdehyde (MDA) level compared with the control. These results showed that CPS could effectively protect RAW264.7 cells from H2O2-induced damage, implying the potential utilization of CPS as a natural antioxidant for food and pharmaceutical applications.

Fabrication of Carboxymethylcellulose/Metal-Organic Framework Beads for Removal of Pb(II) from Aqueous Solution.

The ability to remove toxic heavy metals, such as Pb(II), from the environment is an important objective from both human-health and ecological perspectives. Herein, we describe the fabrication of a novel carboxymethylcellulose-coated metal organic material (MOF-5⁻CMC) adsorbent that removed lead ions from aqueous solutions. The adsorption material was characterized by Fourier-transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, and X-ray photoelectron spectroscopy. We studied the functions of the contact time, pH, the original concentration of the Pb(II) solution, and adsorption temperature on adsorption capacity. MOF-5⁻CMC beads exhibit good adsorption performance; the maximum adsorption capacity obtained from the Langmuir isotherm-model is 322.58 mg/g, and the adsorption equilibrium was reached in 120 min at a concentration of 300 mg/L. The adsorption kinetics is well described by pseudo-second-order kinetics, and the adsorption equilibrium data are well fitted to the Langmuir isotherm model (R² = 0.988). Thermodynamics experiments indicate that the adsorption process is both spontaneous and endothermic. In addition, the adsorbent is reusable. We conclude that MOF-5⁻CMC is a good adsorbent that can be used to remove Pb(II) from aqueous solutions.

Preparation and Evaluation of Peptides with Potential Antioxidant Activity by Microwave Assisted Enzymatic Hydrolysis of Collagen from Sea Cucumber Acaudina Molpadioides Obtained from Zhejiang Province in China.

The present study was focused on the preparation and characterization of the antioxidant peptides by microwave-assisted enzymatic hydrolysis of collagen from sea cucumber Acaudina molpadioides (ASC-Am) obtained from Zhejiang Province in China. The results exhibited the effects of microwave irradiation on hydrolysis of ASC-Am with different protease. Neutrase was selected from the four common proteases (papain, pepsin, trypsin, and neutrase) based on the highest content and DPPH scavenging activity of hydrolysate Fa (Molecular weight < 1 kDa). The content and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity of Fa obtained by hydrolysis of neutrase increased by 100% and 109% respectively at a microwave power of 300 W compared with no microwave irradiation. Five subfractions were obtained after performing the gel filtration chromatography, and the Fa.2 exhibited the highest DPPH scavenging activity. The amino acid analysis showed that the contents of Glutamic acid, Alanine, Tyrosine, and Phenylalanine in fraction Fa.2 increased significantly, but an obvious decrease in the content of Glycine was observed compared to Fa. Four peptides (Fa.2-A, Fa.2-B, Fa.2-C, and Fa.2-D) were purified from Fa.2 by high performance liquid chromatography, and Fa.2-C showed the highest DPPH scavenging activity. The sequence of Fa.2-C was identified as Phenylalanine-Leucine- Alanine-Proline with a half elimination ratio (EC50) of 0.385 mg/mL. The antioxidant activity of Fa.2-C was probably attributed to the small molecular sizes and the presence of hydrophobic amino acid residues in its sequence. This report provided a promising method for the preparation of antioxidant peptides from collagen for food and medicinal purposes.

Enhancement of epoxide hydrolase production by 60 Co gamma and UV irradiation mutagenesis of Aspergillus niger ZJB-09103.

An effective epoxide hydrolase (EH) production strain was mutagenized using 60 Co gamma and UV irradiation. Among positive mutant strains, the EH activity of C2-44 reached 33.7 U/g, which was 267% as much as that of the original Aspergillus niger ZJB-09103. Compared with the wild type, there were significant changes in morphology for C2-44, including the color of mycelia on the slants and the shape of conidial head. In addition, glucose and soybean cake were the optimal carbon and nitrogen source in terms of EH activity for the mutant C2-44 instead of soluble starch and peptone for the wild-type strain. The reaction time required to reach 99% enantiomeric excesses of (S)-epichlorohydrin from racemic substrate was shortened significantly by the mutant C2-44. This phenomenon was probably explained by the higher Vmax for hydrolysis of racemic epichlorohydrin by C2-44 compared with Aspergillus niger ZJB-09103.

Analysis of flumequine enantiomers in rat plasma by UFLC-ESI-MS/MS.

In this study the analysis and confirmation of flumequine enantiomers in rat plasma by ultra-fast liquid chromatography coupled with electron spray ionization mass spectrometry (using propranolol as an internal standard [IS]) was developed and validated. Plasma samples were prepared by liquid-liquid extraction using methyl tert-butyl ether as the extraction solvent. Direct resolution of the R- and S-isomers was performed on a CHIRALCEL OJ-RH column (4.6 × 150 mm, 5 µm) using acetonitrile / 0.1% formic acid / 1 mM ammonium acetate as the mobile phase. Detection was operated by electron spray ionization in the selected ion monitoring and positive ion mode. The target ions at m/z 262.1 and m/z 260.1 were selected for the quantification of the enantiomers and IS, respectively. The linear range was 0.5-500 ng/mL. The precisions (coefficient of variation, CV%) and recoveries were 1.43-8.68 and 94.24-106.76%, respectively. The lowest quantitation limit for both enantiomers is 0.5 ng/mL, which is sensitive enough to be applied to sample analysis in other related studies.

Validation of a Chiral Liquid Chromatographic Method for the Degradation Behavior of Flumequine Enantiomers in Mariculture Pond Water.

In this work, flumequine (FLU) enantiomers were separated using a Chiralpak OD-H column, with n-hexane-ethanol (20:80, v/v) as the mobile phase at a flow rate of 0.6 mL/min. Solid phase extraction (SPE) was used for cleanup and enrichment. The limit of detection, limit of quantitation, linearity, precision, and intra/interday variation of the chiral high-performance liquid chromatography (HPLC) method were determined. The developed method was then applied to investigate the degradation behavior of FLU enantiomers in mariculture pond water samples. The results showed that the degradation of FLU enantiomers under natural, sterile, or dark conditions was not enantioselective. Chirality 28:649-655, 2016. © 2016 Wiley Periodicals, Inc.

Synthesis and Characterization of Magnetic Molecularly Imprinted Polymer for the Enrichment of Ofloxacin Enantiomers in Fish Samples.

A new method for the isolation and enrichment of ofloxacin enantiomers from fish samples was developed using magnetic molecularly imprinted polymers (MMIPs). These polymers can be easily collected and rapidly separated using an external magnetic field, and also exhibit a high specific recognition for ofloxacin enantiomers. The preparation of amino-functionalized MMIPs was carried out via suspension polymerization and a ring-opening reaction using rac-ofloxacin as a template, ethylenediamine as an active group, glycidyl methacrylate and methyl methacrylate as functional monomers, divinylbenzene as a cross-linker, and Fe3O4 nanoparticles as magnetic cores. The characteristics of the MMIPs were assessed using transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM) measurements. Furthermore, the adsorption properties were determined using Langmuir and Freundlich isotherm models. The conditions for use of these MMIPs as magnetic solid-phase extraction (MSPE) sorbents, including pH, adsorption time, desorption time, and eluent, were investigated in detail. An extraction method using MMIPs coupled with high performance liquid chromatography (HPLC) was developed for the determination of ofloxacin enantiomers in fish samples. The limits of quantitation (LOQ) for the developed method were 0.059 and 0.067 µg∙mL(-1) for levofloxacin and dextrofloxacin, respectively. The recovery of ofloxacin enantiomers ranged from 79.2% ± 5.6% to 84.4% ± 4.6% and ofloxacin enantiomers had good linear relationships within the concentration range of 0.25-5.0 µg∙mL(-1) (R² > 0.999). The obtained results demonstrate that MSPE-HPLC is a promising approach for preconcentration, purification, and simultaneous separation of ofloxacin enantiomers in biomatrix samples.

Composition and anti-inflammatory effect of polysaccharides from Sargassum horneri in RAW264.7 macrophages.

Sulfated polysaccharides extracted from brown marine algae have been shown to possess a variety of biological activities. We assessed the potential activity of the sulfated polysaccharide from Sargassum horneri (SP) and its isolated two major components (fraction-1 (F1) and fraction-2 (F2)), on anti-inflammatory activity in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. In the present study, analysis of polysaccharide chemical composition found that the constituent ratios of sulfate ester and fucose in SP and F1 were 4.95% vs 7.6%, and 4.48% vs 55.9%, respectively, suggesting that F1 may be a major sulfated polysaccharide containing fucose. Meanwhile, our findings demonstrated that TNF-α secretion levels were significantly (P<0.05) decreased by SP and F1 treatments in LPS-stimulated RAW264.7 cells in a dose-dependent manner under the preventive and repair experimental models. Pro-/anti-inflammatory (TNF-α/IL-10) cytokines secretion ratios by LPS-stimulated RAW264.7 macrophages were significantly (P<0.05) inhibited by SP and F1 treatments, particularly by F1 (at high dose, 200µg/ml). Moreover, NO release and iNOS activity were significantly (P<0.05) inhibited by F1. Collectively, the present study suggested that purified component, F1 from SP, had strong anti-inflammatory effects on LPS-stimulated RAW264.7 macrophages in the preventive and repair manner through inhibiting TNF-α secretion levels and NO release.

Enantioselective hydrolysis of epichlorohydrin using whole Aspergillus niger ZJB-09173 cells in organic solvents.

The enantioselective hydrolysis of racemic epichlorohydrin for the production of enantiopure (S)-epichlorohydrin using whole cells of Aspergillus niger ZJB-09173 in organic solvents was investigated. Cyclohexane was used as the reaction medium based on the excellent enantioselectivity of epoxide hydrolase from A. niger ZJB- 09173 in cyclohexane. However, cyclohexane had a negative effect on the stability of epoxide hydrolase from A. niger ZJB-09173. In the cyclohexane medium, substrate inhibition, rather than product inhibition of catalysis, was observed in the hydrolysis of racemic epichlorohydrin using A. niger ZJB-09173. The racemic epichlorohydrin concentration was markedly increased by continuous feeding of substrate without significant decline of the yield. Ultimately, 18.5% of (S)-epichlorohydrin with 98 percent enantiomeric excess from 153.6 mM of racemic epichlorohydrin was obtained by the dry cells of A. niger ZJB-09173, which was the highest substrate concentration in the production of enantiopure (S)-epichlorohydrin by epoxide hydrolases using an organic solvent medium among the known reports.

Nitrite-mediated synthesis of chiral epichlorohydrin using halohydrin dehalogenase from Agrobacterium radiobacter AD1.

In the current study, the haloalcohol dehalogenase HheC gene from Agrobacterium radiobacter AD1 was synthesized and expressed in Escherichia coli. After purification using Ni-nitrilotriacetic acid affinity chromatography, HheC was used in the synthesis of chiral epichlorohydrin in the presence of NO2⁻. The optimal pH, temperature, and NO2⁻ concentration for enantioselectivity are 5.0, 37°C, and 60 mM, respectively. The maximum velocity and Michaelis constant values for (S)-epichlorohydrin are 714.3 µmol min⁻¹ mg⁻¹ and 17.2 mM, respectively, whereas those for (R)-epichlorohydrin are 166.8 µmol min⁻¹ mg⁻¹ and 29.0 mM, respectively. Under optimal conditions, (R)-epichlorohydrin with 99% enantiomeric excess was obtained after an 18 Min reaction; the yield reached 41%, which is the highest amount obtained for chiral epichlorohydrin synthesis using haloalcohol dehalogenase. In addition, (R)-epichlorohydrin with 99% enantiomeric excess was successfully obtained from 1,3-dichloro-2-propanol by the ring opening of racemic epichlorohydrin in the presence of NO2⁻ after the ring closure of 1,3-dichloro-2-propanol with HheC. To the best of our knowledge, the current study is the first report on the kinetic resolution of epichlorohydrin with NO2⁻ and synthesis of chiral epichlorohydrin with 99% enantiomeric excess from 1,3-dichloro-2-propanol by combining ring closure of 1,3-dichloro-2-propanol and ring opening of racemic epichlorohydrin.