Surface molecularly imprinted polymers prepared by two-step precipitation polymerization for the selective extraction of oleanolic acid from grape pomace extract.

Surface molecularly imprinted polymers were successfully prepared by a novel two-step precipitation polymerization method. The first-step allowed the formation of 4-vinylpyridine divinylbenzene and trimethylolpropane trimethacrylate copolymeric microspheres. In the second-step precipitation polymerization, microspheres were modified with a molecularly imprinting layer of oleanolic acid as template, methacrylic acid as functional monomer, and divinylbenzene/ethylene glycol dimethacrylate as cross-linker. The obtained polymers had an average diameter of 4.43 µm and a polydispersity index of 1.011; adsorption equilibrium was achieved within 40 min, with adsorption capacity reaching 27.4 mg/g. Subsequently, the polymers were successfully applied as the adsorbents of molecularly imprinted solid-phase extraction to separate and purify the oleanolic acid from grape pomace. The content of oleanolic acid in the grape pomace extract was enhanced from 13.4 to 93.2% after using the molecularly imprinted solid-phase extraction process. This work provides an efficient way for effective oleanolic acid separation and enrichment from complex matrices, which is especially valuable in industrial production.

Computer-aided design of magnetic dummy molecularly imprinted polymers for solid-phase extraction of ten phthalates from food prior to their determination by GC-MS/MS.

Magnetic dummy molecularly imprinted polymers (MDMIPs) were prepared by combining the surface imprinting technique with computer simulation for selective recognition of phthalate esters (PAEs). A computational study based on the density functional theory was performed to evaluate the template-monomer geometry and interaction energy in the prepolymerization mixture. The MDMIPs were characterized by transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometry, X-ray diffraction, and Fourier transform infrared spectroscopy. They exhibited (a) high saturation magnetization of 53.14 emu g-1 (leading to fast separation), and (b) large adsorption capacity, fast binding kinetics, and high selectivity for PAEs. Subsequently, a molecularly imprinted solid-phase extraction procedure followed by GC-MS was established for selective extraction and determination of 10 PAEs in food samples. Under the optimal experimental conditions, the response (peak area) was linear in the 0.5-100 ng mL-1 concentration range. The limits of detection ranged from 0.15 to 1.64 ng g-1. The method was applied to the determination of PAEs in spiked real samples. The recoveries for 10 PAEs from various foods were in the range of 73.7%-98.1%, with relative standard deviations of 1.7%-10.2%. Graphical abstract Magnetic dummy molecularly imprinted polymers (MDMIPs) were prepared and successfully were applied as a special sorbent for the selective recognition and fast enrichment of 10 PAEs from different complex matrix.

Preparation and characterization of monodisperse molecularly imprinted polymers for the recognition and enrichment of oleanolic acid.

Monodisperse molecularly imprinted polymers for oleanolic acid were successfully prepared by a precipitation polymerization method using oleanolic acid as a template, methacrylic acid as a functional monomer, and divinylbenzene/ethylene glycol dimethacrylate as a crosslinker in a mixture of acetonitrile and ethanol (3:1, v/v). The imprinted polymers and nonimprinted polymers were characterized by using scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The resulting imprinted polymers had average diameters of 3.15 µm and monodispersity values of 1.024. The results clearly demonstrate that use of ethanol as a cosolvent is indeed exceedingly effective in promoting the dissolution of oleanolic acid and in obtaining uniform microspheres. Molecular recognition properties and binding capability to oleanolic acid were evaluated by adsorption testing, which indicated that the imprinted polymers displayed optimal binding performance with a maximum adsorption capacity of 17.3 mg/g and a binding saturation time of 80 min. Meanwhile, the produced imprinted polymers exhibited higher selectivity to oleanolic acid than that for ursolic acid and rhein. Herein, the studies can provide theoretical and experimental references for the oleanolic acid molecular imprinted system.

Magnetic-nanobead-based competitive enzyme-linked aptamer assay for the analysis of oxytetracycline in food.

This study presents a novel analytical method for the detection of oxytetracycline (OTC) in complex food matrices based on a direct competitive enzyme-linked aptamer assay and magnetic separation technology. In this protocol, free OTC competed with horseradish peroxidase labeled OTC (OTC-HRP) for binding to the OTC aptamer immobilized on magnetic beads. The parameters that can affect the response, such as avidin concentration, aptamer concentration, OTC-HRP concentration, incubation temperature, incubation time, blocking agent, and binding buffer, were optimized. Under the optimal conditions, the linear range for the OTC concentration detection is 0.5-100 ng mL(-1), with a concentration of OTC needed to obtain 50 % of the maximum signal of 14.47 ng mL(-1). The limit of detection and the limit of quantitation were 0.88 and 3.40 ng mL(-1), respectively. There was no obvious cross-reactivity with most of the tetracycline pesticides. The recovery rates ranged from 71.0 to 91.2 % for the food samples, including chicken, milk, and honey, and the relative standard deviation was less than 15.0 %. The proposed method was applied to measure OTC in real samples, and was validated using high-performance liquid chromatography. This method has the advantages of magnetic separation and the concentration effect of magnetic nanoparticles, the specificity of the aptamer, and the high-throughput of microtiter plates; it offers a promising approach for the screening of OTC because it is simple, rapid, highly sensitive, and has low cost.

Assessment of antibacterial properties and the active ingredient of plant extracts and its effect on the performance of crucian carp (Carassius auratus gibelio var. E'erqisi, Bloch).

BACKGROUND: In this study, the antibacterial properties and active ingredient of plant extracts and its effect on the performance of crucian carp (Carassius auratus gibelio var. E'erqisi, Bloch) were assessed. RESULTS: The transmission electron microscopy and flow cytometric analysis showed that the antibacterial activity of plant extracts is due to the disruption of the cell membrane and the leakage of cytoplasmic contents. The UPLC-MS/MS analysis showed that the contents of gallic acid, (-)-epigallocatechin, (+)-catechin, (-)-epigallocatechin gallate, (-)-epicatechin gallate, aloe-emodin, rhein, emodin, chrysophanol, and physcion, were 5.27%, 3.30%, 1.08%, 19.32%, 5.46%, 0.23%, 0.56%, 1.28%, 0.75% and 0.39% in plant extracts, respectively. Results of feeding experiment showed that feeding crucian carp with 1.0% and 2.0% plant extracts significantly enhanced specific growth rate, serum total protein, lysozyme, catalase and superoxide dismutase activities, and decreased the feed conversion rate, malondialdehyde contents and the mortality rate (P < 0.05). CONCLUSION: It can be concluded that plant extracts added to fish feed can act as natural antimicrobial and immunostimulants to prevent pathogenic infection, enhance immune response, and promote growth of the fish.

Curculigo orchioides polysaccharide COP70-1 stimulates osteogenic differentiation of MC3T3-E1 cells by activating the BMP and Wnt signaling pathways.

The crude polysaccharide CO70 isolated from Curculigo orchioides could alleviate ovariectomy-induced osteoporosis in rats. To clarify the bioactive components, a new heteropolysaccharide (COP70-1) was purified from CO70 in this study, which was consisted of ß-D-Manp-(1→, →4)-α-D-Glcp-(1→, →4)-ß-D-Manp-(1→, →3,4)-ß-D-Manp-(1→, →4,6)-ß-D-Manp-(1→, and →4,6)-α-D-Galp-(1→. COP70-1 significantly promoted the osteoblastic differentiation of MC3T3-E1 cells through improving alkaline phosphatase activity, the deposition of calcium as well as up-regulating the expression of osteogenic markers (RUNX2, OSX, BSP, OCN, and OPN). Furthermore, COP70-1 stimulated the expression of critical transcription factors of the BMP and Wnt pathways, including BMP2, p-SMAD1, active-ß-catenin, p-GSK-3ß, and LEF-1. In addition, LDN (BMP pathway inhibitor) and DKK-1 (Wnt pathway inhibitor) suppressed the COP70-1-induced osteogenic differentiation of MC3T3-E1 cells. Therefore, COP70-1 was one of the bioactive constituents of C. orchioides for targeting osteoblasts to treat osteoporosis by triggering BMP/Smad and Wnt/ß-catenin pathways.

Impact of Thyme Microcapsules on Histamine Production by Proteus bacillus in Xinjiang Smoked Horsemeat Sausage.

Here, we explored the influences of thyme microcapsules on the growth, gene expression, and histamine accumulation by Proteus bacillus isolated from smoked horsemeat sausage. RT-qPCR was employed to evaluate the gene expression level of histidine decarboxylase (HDC) cascade-associated genes. We used HPLC to monitor histamine concentration both in pure culture as well as in the processing of smoked horsemeat sausage. Results showed that histamine accumulation was suppressed by thyme microcapsule inhibitory effect on the histamine-producing bacteria and the reduction in the transcription of hdcA and hdcP genes. Besides, compared with thyme essential oil (EO), thyme microcapsules exhibited higher antibacterial activity and had a higher score for overall acceptance. Therefore, the addition of thyme microcapsules in Xinjiang smoked horsemeat sausage inhibits histamine accumulation.

Degradation of pendimethalin by the yeast YC2 and determination of its two main metabolites.

In this study, we isolated a yeast strain, YC2, by enrichment culture from pendimethalin-contaminated soil. The analysis of its phenotypic features and 26S rRNA sequence confirmed that the strain YC2 is Clavispora lusitaniae. According to the kinetics of pendimethalin degradation, YC2 could degrade 74% of 200 mg L-1 pendimethalin in CMB liquid culture over 8 days. LC-MS/MS was used to identify the metabolites of pendimethalin after degradation. This study confirmed that its metabolites consist of 1,2-dimethyl-3,5-dinitro-4-N(buta-1,3-dien-2-yl)-dinitrobenzenamine-N-oxide and 1,2-dimethyl-3,5-dinitro-4-N(prop-1-en-2-yl)-dinitrobenzenamine-N-oxide, which were broken down by a series of enzymatic reactions to produce CO2 and H2O. Thus, the study herein sheds light on the role of yeast in the degradation of pendimethalin.