Asymmetric Mannich Reaction of Isatin-Derived Ketimines with α-Fluoroindanones Catalyzed by a Chiral Phase-Transfer Catalyst.

A highly enantioselective Mannich reaction of α-fluoroindanones with isatin-derived N-Boc-ketimines catalyzed by a quinine-derived phase-transfer catalyst was developed. A variety of 3-substituted 3-amino-2-oxindoles bearing fluorine-containing, vicinal, tetrasubstituted stereocenters were constructed using this protocol in high yields (83-95%), with moderate to excellent enantioselectivities (66-91%) and high diastereoselectivities (up to >99:1).

Active Antioxidant Packaging from Essential Oils Incorporated Polylactic Acid/Poly(butylene adipate-co-terephthalate)/Thermoplastic Starch for Preserving Straw Mushroom.

The short-term shelf life of straw mushrooms (Volvariella volvacea) is a major challenge, hampering their wide distribution. Thus, the aim of this work was to develop a novel active packaging composed of essential oils (EOs), particularly clove oil (CO) and peppermint oil (PO), to reduce autolysis of straw mushrooms. The morphological characterizations, mechanical properties, barrier properties, and antioxidant activities of the films were characterized. The suppressive effects of the EOs on straw mushroom autolysis were estimated during storage at 16 ± 1 °C for 96 h. The results indicated that the addition of EOs weakened the mechanical and barrier properties of the films. The radical-scavenging activities of polylactic acid/poly(butylene adipate-co-terephthalate)/thermoplastic starch-peppermint oil (PLA/PBAT/TPS-PO) and polylactic acid/poly(butylene adipate-co-terephthalate)/thermoplastic starch-clove oil (PLA/PBAT/TPS-CO) films for 2,2-diphenyl-1-picrylhydrazyl were 56.0% and 91.3%, respectively. However, the PLA/PBAT/TPS-PO film was more effective in reducing polyphenol oxidase activity and maintaining the total phenol content of straw mushrooms, demonstrating better antioxidative activity. Mushrooms packaged with the PLA/PBAT/TPS-PO film exhibited the lowest autolysis rate (42.29%, p < 0.05) after 96 h of storage. Thus, PO is a good preservative agent for straw mushroom.

Controlled moisture permeability of thermoplastic starch/polylactic acid/poly butylene adipate-co-terephthalate film for the autolysis of straw mushroom Volvariella volvacea.

Straw mushrooms are prone to autolyze, leading to a high requirement of environmental humidity. In this work, thermoplastic starch/polylactic acid/poly (butylene adipate-co-terephthalate) (TPS/PLA/PBAT) film was produced by extrusion. The moisture permeability of the film was controlled by adjusting the content of TPS, which could be expected to further control humidity of the microenvironment in the package. Results revealed that the water vapor transmission rate of the film linearly increased from 612.31 g/m2·24 h to 1082.50 g/m2·24 h with the increase in the TPS concentration. The TPS/PLA/PBAT film with 30 wt% TPS showed the strongest inhibition on the autolysis of straw mushrooms compared with other groups, effectively delaying the increase in the free water, soluble solid content, rate of weight loss, and polyphenol oxidase of straw mushrooms and extending the shelf life of straw mushrooms from 24 h to 72 h.

Visualizing the spatial distribution of metabolites in Clausena lansium (Lour.) skeels using matrix-assisted laser desorption/ionization mass spectrometry imaging.

Clausena lansium (Lour.) Skeels (Rutaceae) is a natural bioactive plant. Its roots, stems, leaves, and seeds are widely used in Chinese traditional and folk medicine. Although the characterization and functional analysis of bioactive components in Clausena lansium (Lour.) Skeels has been widely reported, the spatial distribution of these compounds within the main plant tissues remains undefined. Here, we adopted matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) to reveal the spatial distribution of active alkaloids, coumarins, sugars and organic acids in C. lansium. Using a combined wet and dry matrix covering method to enhance sensitivity, we detected alkaloids throughout the fruit including 3-methylcarbazole and murrastinine which were especially rich in the kernel tissues but were restricted to the stem xylem and medulla and in the leaf epidermal region. Interestingly, murrayanine and heptaphylline were mainly found in pulp tissues with very low content in the stems and leaves while girinimbine was only distributed within the outer kernel skin. Coumarins were mainly distributed in the fruit pericarp and leaf vein tissues but with no clear spatial specificity in stems. Lastly, hexoses were mainly evident in the fruit pulp, although sucrose was also found in the pericarp, pulp, and pulp fibers with citric acid being distributed throughout the fruit. The accurate spatial and chemical information obtained provides new insights into the specific accumulation of metabolites in individual tissues.

Solid phase extraction using magnetic core mesoporous shell microspheres with C18-modified interior pore-walls for residue analysis of cephalosporins in milk by LC-MS/MS.

A fast and effective extraction method has been developed for measuring the residue of cephalosporins (cefalexin, cefazolin, cefoperazone) in milk by using magnetic core-mesoporous shell microspheres with C18-functionalized interior pore-walls (C18-Fe3O4@mSiO2) as adsorbent. With no need for any protein precipitation procedure, the cephalosporins were directly adsorbed onto the C18-Fe3O4@mSiO2 microspheres through hydrophobic interaction with C18-groups (Octadecyl functional groups) functionalized in the interior walls of mesopore channels while the abundant proteins in milk sample were excluded out of the channel due to the size exclusion effect. Thereafter, the cephalosporins-absorbed C18-Fe3O4@mSiO2 microspheres were rapidly isolated by placing a magnet, and followed by liquid chromatography-tandem mass spectrometry analysis after eluted by methanol. Various parameters which could affect the extraction performance were optimised. The newly developed extraction method was successfully applied in determination of cephalosporin residues in milk samples, offering a valuable alternative to simplify and speed up the sample preparation step.