A method development for improving the stability of vegetable polyphenol complexes for semi-finished minced meat products with antioxidant effect

Polyphenolic vegetable complexes are active antioxidants and play an important role in the processes of free radicals quenching in the human body. The aim of the work was to develop an immobilization method as a way for improving the stability of polyphenols in dried cowberry squeezing extract (DCSE) and to develop semi-finished minced meat products with antioxidant effect without changing their nutritional value. Experiments were carried out to study the nutritional value of DCSE. The presence of a large number of polyphenolic compounds in DCSE and a high radical-binding ability of the extract were revealed. Based on the mathematical planning method, an offal paste composition was obtained, which was used to obtain pellets, and the formulation of semi-finished minced meat products with pellets was optimized. It was established that preliminary immobilization of DCSE on offal pellets components allows to increase the level of total antioxidant content in the minced meat. Subsequent heat treatment of semi-finished minced meat products produced from such minced meat showed an increase in stability and, thus, bioavailability of antioxidants and the possibility of obtaining a finished product with antioxidant effect. The antioxidant effect of cowberry squeezing extract in the meat system is proved: accumulation of lipid oxidative decomposition products in the meat system during storage of frozen semi-finished minced meat products was inhibited to a greater extent when using offal pellets with immobilized compounds of cowberry squeezing extract. This work was carried out as part of the State Assignment of the Ministry of Education and Science of the Russian Federation No. 19.5486.2017/BCh and the «Young Scientists of ESSTU‑2019» grant.

Synthesis of MCM-41 Immobilized (Phenoxy)Imine Palladium(II) Complexes as Recyclable Catalysts in the Methoxycarbonylation of 1-Hexene

The immobilization of 2-phenyl-2-((3(tryethoxysicyl)propyl)imino)ethanol (HL1) and 4-methyl-2-(((3(triethoxysilyl)propyl)imino)methyl)phenol (HL2) on MCM-41 afforded the respective ligands HL1-MCM-41 (HL3) and HL2-MCM-41 (HL4). The treatment of complexes Pd(L1)2 and Pd(L2)2 with MCM-41 afforded the immobilized complexes (Pd(L1)2)-MCM-41 (1) and (Pd(L2)2)-MCM-41 (2) respectively. Separately, the reactions of HL3 and HL4 with Pd(NCMe)2Cl2 produced the immobilized complexes Pd(HL3)Cl2 (3) and Pd(HL4)Cl2 (4) respectively. The immobilized compounds were characterized by FT-IR, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), energy-dispersive X-ray (EDX), Thermogravimetric Analysis (TGA) and X-ray Powder Diffraction (XRD). All the complexes (1–4) formed active catalysts in the methoxycarbonylation of 1-hexene to give linear and branched esters. The catalysts were recycled four times without the loss of catalytic activity. Hot filtration experiments established the absence of leaching, and the heterogeneous nature of the active species was derived from mercury drop experiments.

Photo-click chemistry strategies for spatiotemporal control of metal-free ligation, labeling, and surface derivatization

Three photo-click ligation strategies described in this account provide scientists with efficient and selective tools for derivatization of various molecules, polymers, and surfaces. Fast photochemical reactions that are utilized in these techniques permit spatiotemporal control of the process. The absence of activating reagents and catalysts, as well as compatibility with aqueous media, makes photo-click ligations suitable for biomedical applications. The first of these approaches relies on the photochemical decarbonylation of cyclopropenones to produce cyclooctynes. The latter undergo rapid catalyst-free strain-promoted azide–alkyne cycloaddition (SPAAC) to azide-tagged substrates. The second method is based on a very fast (>104 M–1 s–1) light-triggered hetero-Diels–Alder reaction and permits efficient derivatization of substrates bearing vinyl ether moiety. An even faster reaction between photochemically generated naphthoquinone methides (oNQMs) and thiols (~2 × 105 M–1 s–1) serves as a basis for a third method. This thiol photo-click chemistry allows for the selective derivatization of thiol-functionalized substrates or labeling of free cysteine residues in proteins. The thioether linkage produced by the reaction of oNQMs and a thiol is stable under ambient conditions, but can be cleaved by UV irradiation, regenerating free thiol. This feature permits the removal or replacement of immobilized compounds, as well as traceless substrate release.

Synthesis, characterization and catalytic behavior of iron porphyrins immobilized in layered double hydroxides

We report the synthesis, characterization and catalytic behavior of iron(III) porphyrins immobilized in layered double hydroxides (LDH). A combination of EPR, UV-visible spectroscopy and powder X-ray diffraction (PXRD) was used to characterize the products. Three different procedures were used to perform the immobilization of iron porphyrin: a) adsorption into the LDH powder, b) co-precipitation and c) rehydration of calcined LDH. Several different porphyrins ( Fe ( TSPP ), Fe ( TCPP ), Fe ( TPP ) and Fe ( TDFSPP )) were employed in the study. After characterization, the isolated powders were investigated in the oxidation reaction of cyclohexane by iodosylbenzene and hydrogen peroxide in heterogeneous catalysis in comparison to homogeneous media. Some of these immobilized compounds were very good catalysts for this oxidation reaction, stimulating the future investigation of other substrates.