Effects of lactic acid bacteria on antioxidant activity in vitro and aroma component of Eucommia ulmoides tea.

Eucommia ulmoides tea is a popular functional health drink in Asian countries, but its unique herbal aroma is difficult for consumers to accept. The effects of four lactic acid bacteria strains (Lactobacillus plantarium, Lactobacillus bulgaricus, Lactobacillus acidophilus and Streptococcus thermophilus) fermentation on the physicochemical property, antioxidant activity in vitro and aroma component of E. ulmoides leaves were studied. Within the four strains, the sample by L. bulgaricus fermentation showed the higher concentrations of chlorogenic acid, geniposidic acid and stronger antioxidant activity in vitro. Moreover, the sample by L. bulgaricus fermentation produced a stronger fruity and floral flavor. These results suggested that L. bulgaricus was the best strain for fermentation E. ulmoides tea. The differences between different strains should be considered when selecting lactic acid bacteria for raw material fermentation of fruits and vegetables.

Improved matrix purification using a graphene oxide-coated melamine sponge for UPLC-MS/MS-based determination of 37 veterinary drugs in milks.

A rapid and highly sensitive method was established for the analysis of 37 veterinary drug residues in milk using a modified QuEChERS method based on a reduced graphene oxide-coated melamine sponge (rGO@MeS) coupled with UPLC-MS/MS. Under optimal chromatographic and mass spectrometric conditions, the effects of different dehydrated salts (MgSO4 and Na2SO4) and metal chelating agents (Na2EDTA) on extraction efficiency were first investigated. Next, the influence of a dynamic and static purification mode was evaluated in terms of drug recoveries. Calibration curves of 37 veterinary drugs were constructed in the range 0.6-500 µg kg-1, and good linearities were obtained with all determination coefficients (R2) ≥0.992. The limits of detection (LODs) and quantitation (LOQs) were in the range 0.3-1.1 µg kg-1 and 0.6-3.5 µg kg-1, respectively. The recoveries of all compounds were in the range 61.3-118.2% at three spiked levels (20, 100, and 200 µg kg-1) with RSDs ≤15.4% for both intra- and inter-day precisions. Compared to pristine melamine sponges and commercial adsorbents (C18, PSA, and GCB), rGO@MeS demonstrated an equal or even better purification performance in terms of recoveries, matrix effects, and matrix removal efficiency. This method is rapid, simple, efficient, and appropriate for the qualitative and quantitative analyses of 37 veterinary drug residues in milk, providing a new detection strategy and technical support for the routine analysis of animal-derived food.

A facile fluorescent sensor based on nitrogen-doped carbon dots derived from Listeria monocytogenes for highly selective and visual detection of iodide and pH.

Sensitive and visual analysis of iodide (I-) and pH is significant in environmental and food applications. Herein, we present a facile fluorescent sensor for highly selective and visual detection of I- and pH based on nitrogen-doped carbon dots derived from Listeria monocytogenes (NCDs-LM). The NCDs-LM-based fluorescent sensor showed a good linear relationship to I- concentrations, and the detection limit was calculated as 20 nmol L-1. The developed sensor was successfully applied to the detection of I- in drinking water and milk samples. Meanwhile, the as-synthesized NCDs-LM sensor can be used to detect pH, achieving a wide linear pH range. Furthermore, fluorescent test papers based on NCDs-LM were designed for semi-quantitative detection of I- and pH via the naked-eye colorimetric assay. The present work indicates that the NCDs-LM-based fluorescent sensor has high potential for use in environmental monitoring and food analysis.

Application of silanized melamine sponges in matrix purification for rapid multi-residue analysis of veterinary drugs in eggs by UPLC-MS/MS.

Fast and convenient matrix purification is an important prerequisite for high-throughput analysis of drug multiresidues in food. In this study, a silanized melamine sponge was prepared and first applied in the rapid determination of multiclass veterinary drugs in eggs by ultrahigh-performance liquid chromatography-tandem mass spectrometry. Within five seconds, fast, convenient and efficient matrix separation could be achieved through simple soaking and squeezing. Compared to other matrix adsorbents, the developed material demonstrated equivalent or better purification performance. Good validation results were obtained in terms of drug recoveries (61.5%~97.0%, relative standard deviation (RSD) ≤ 10.8%), and linearities (R2 ≥ 0.999), as well as low limits of quantitation (0.3 ~ 10.9 µg·kg-1) and detection (0.1 ~ 3.8 µg·kg-1). By analyzing 52 egg samples, high concentrations of ofloxacin, trimethoprim, metronidazole, and dimetridazole were found at 542.9, 121.2, 66.1 and 58.0 µg·kg-1, respectively. The silanized melamine sponge has shown its great potential for rapid analysis of multiclass residues in food safety.

Development of a modified quick, easy, cheap, effective, rugged, and safe method based on melamine sponge for multi-residue analysis of veterinary drugs in milks by ultra-performance liquid chromatography tandem mass spectrometry.

The purpose of this study was to develop a modified QuEChERS method based on melamine sponge for rapid determination of multi-class veterinary drugs in milks by UPLC-MS/MS. Through simple infiltration and extrusion, fast and convenient matrix purification could be achieved within several seconds, and there was no need of extra phase separation operations. Good linearity with correlation coefficient (R2) ≥0.999 was obtained for all drugs in the range of 2~500 µg·kg-1. The obtained matrix effects were within ±20% for all monitored drugs. The recoveries of all monitored drugs ranged from 60.7% to 116.0% at three spiked levels (50, 100, and 200 µg·kg-1), with relative standard deviations less than 7.4%. Comparatively low LODs and LOQs were obtained in the ranges of 0.1~3.8 µg·kg-1 and 0.2~6.3 µg·kg-1, respectively. Compared with conventional purification adsorbents, melamine sponge yielded an equal or higher purification performance with matrix removal rate as high as 52.5% and acceptable recoveries in range of 60%-120% for all monitored drugs. The satisfactory results have demonstrated the good potential of melamine sponge in matrix purification for rapid determination of multiclass residues in food safety.

Magnetic porous aromatic framework with a core-shell structure as a sorbent for rapid extraction of phenols and their quantitation in urine by HPLC-UV.

A porous aromatic framework (PAF) is shown to be a viable sorbent for the adsorption of phenols. To overcome the difficulty of quick adsorption and enrichment by phenols from the matrix, a sorbent material consisting of porous aromatic framework magnetic nanoparticles (PAF MNPs) with a core-shell structure was fabricated by an in situ growth method. The PAF MNP sorbent was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy and other techniques. The factors affecting enrichment performance including the amount of PAF-6 MNPs, sample pH, extraction time and elution conditions were optimized. Under the optimal conditions, a method utilizing high-performance liquid chromatography with an ultraviolet detector (HPLC-UV) was developed to quantify phenols in urine. The method showed good linearity (r ≥ 0.998), good precision (RSD ≤ 9.9%, n = 6) and a low limit of detection (1.0-2.0 ng/mL, S/N = 3), with recoveries performed in urine matrix ranging from 76.7% to 113.2%. The method is simple, time-saving and sensitive. Moreover, compared with traditional mass spectrometry detection methods, this method has advantages in terms of low cost and repeatability. Graphical abstract.

Antioxidant epoxydon and benzolactone derivatives from the insect-associated fungus Phoma sp.

One new epoxydon ester (1) and a new benzolactone derivative (2), along with four known compounds (3-6), were isolated from the insect-associated fungus Phoma sp. Their structures were confirmed by extensive MS and NMR spectroscopic analysis and their absolute configurations were determined by a combination of modified Mosher method and Mo2(OCOCH3)4-induced electronic circular dichroism (ECD) experiments. Compounds 1 and 5 were revealed to have potent antioxidant activities, which were approximate to the potency of the positive control trolox. In addition, 1 also exhibited moderate cytotoxic effect against human MGC-803 tumor cell line.[Formula: see text].