Exploiting Redox-Complementary Peptide/Polyoxometalate Coacervates for Spontaneously Curing into Antimicrobial Adhesives.

Recently, there has been a wave of reports on the fabrication of peptide-based underwater adhesives with the aim of understanding the adhesion mechanism of marine sessile organisms or creating new biomaterials beyond nature. However, the poor shear adhesion performance of the current peptide adhesives has largely hindered their applications. Herein, we proposed to sequentially perform the interfacial adhesion and bulk cohesion of peptide-based underwater adhesives using two redox-complementary peptide/polyoxometalate (POM) coacervates. The oxidative coacervates were prepared by mixing oxidative H5PMo10V2O40 and cationic peptides in an aqueous solution. The reductive coacervates consisted of K5BW12O40 and cysteine-containing reductive peptides. Each of the individual coacervate has well-defined spreading capacity to achieve fast interfacial attachment and adhesion, but their cohesion is poor. However, after mixing the two redox-complementary coacervates at the target surface, effective adhesion and spontaneous curing were observed. We identified that the spontaneous curing resulted from the H5PMo10V2O40-regulated oxidization of cysteine-containing peptides. The formed intermolecular disulfide bonds improved the cross-linking density of the dual-peptide/POM coacervates, giving rise to the enhanced bulk cohesion and mechanical strength. More importantly, the resultant adhesives showcased excellent bioactivity to selectively suppress the growth of Gram-positive bacteria due to the presence of the polyoxometalates. This work raises further potential in the creation of biomimetic adhesives through the orchestrating of covalent and noncovalent interactions in a sequential fashion.

Discovery and Targeted Isolation of Phenylpropanoid-Substituted Ester-Catechins Using UPLC-Q/TOF-HRMS/MS-Based Molecular Networks: Implication of the Reaction Mechanism among Polyphenols during Green Tea Processing.

Tea is an important beverage source of dietary polyphenols and well known for containing phenolic structure diversity. A series of phenylpropanoid-substituted catechins, flavonols, flavan-3-hexoside, and proanthocyanidin are present in different herbs with various biological activities, inspiring our exploration of phenylpropanoid-substituted ester type of catechins (PSECs) due to the enrichment of galloylated catechins in tea. In this study, we used a guiding-screening-location-isolation integrated route including creating a hypothesized PSEC dataset, MS/MS data acquiring, construction of molecular networks, and traditional column chromatography and preliminarily identified 14 PSECs by MS/MS spectrum. Two of these PSECs were further purified and elucidated by NMR and CD spectra. Further MS detection in tea products and fresh leaves suggests that the production of the two new compounds was enhanced during tea processing. The synthesis mechanism was proposed to obtain these types of components for further investigation on their roles in human health protection. This study provides an example for the exploration of new functional ingredients from food sources guided by MS/MS data-based networking, and also new insights into the reaction mechanism to form new catechin conjugates among polyphenols in green tea.

Detection and quantification of flavoalkaloids in different tea cultivars and during tea processing using UPLC-TOF-MS/MS.

Flavoalkaloids have been found from tea. However, there is limited information about their content in different teas. Herein, 51 tea samples were screened for flavoalkaloid content. Twelve teas with relatively higher contents of flavoalkaloids were further quantified by UPLC-TOF-MS/MS. The cultivars Yiwu and Bulangshan had the highest levels, with total flavoalkaloid contents of 3063 and 2727 µg g-1, respectively. Each of the six flavoalkaloids were at levels > 198 µg g-1 in these cultivars. Of the flavoalkaloids, etc-pyrrolidinone A had the highest content in the teas, reaching 835 µg g-1 in Yiwu. The content of the flavoalkaloids varied among tea cultivars and with processing procedures, particularly heating. The potential of using flavoalkaloids to discriminate grades of Keemun black tea was studied and discussed. The teas identified in this work with high levels of flavoalkaloids can be used in the future to study the mechanisms by which flavoalkaloids are synthesized in tea.

Magnesium Citrate Protects Against Vascular Calcification in an Adenine-induced Chronic Renal Failure Rat Model.

BACKGROUND: Hypomagnesemia was identified as a strong risk factor for cardiovascular disease in patients with chronic renal failure (CRF). However, the effects of magnesium (Mg) on vascular calcification (VC) have not been fully elucidated. Thus, we aim to determine the effects of Mg citrate (MgCit) on VC in CRF rats. METHODS: Rats were divided into 5 groups: group 1 (normal diet), group 2 (normal diet with MgCit), group 3 (the VC model of CRF induced by 0.75% adenine and 0.9% phosphorus diet from day 1 to day 28), group 4 (group 3 treated with low-dose MgCit from day 1 to day 42), and group 5 (same as group 3 except the high-dose MgCit). All rats were killed at day 43 with collection of blood and aortas. Then, serum biochemical parameters, VC-related staining, calcium and P contents, alkaline phosphatase contents and activity, expression of alpha smooth muscle actin, and runt-related transcription factor 2 (RUNX2) in aortas were assessed. RESULTS: Group 3 had extensive VC. The VC degree decreased in groups 4 and 5 in a dose-depended manner with reduced calcium content, P levels, alkaline phosphatase content and activity, and protein levels of RUNX2 and increased protein levels of alpha smooth muscle actin in aortas. CONCLUSIONS: MgCit exerted a protective role in VC in adenine-induced CRF rats; thus, it may be a potential drug for the prevention of VC in patients with CRF.