RESUMO
Reline, which is composed of choline chloride (ChCl) and urea, is the first and most widely used deep eutectic solvent (DES) described by Abbot and co-workers. Due to the hygroscopic feature, traces of water are unavoidable, which significantly affect the physicochemical properties of reline. At present, the local structure of molecules and the impact from the presence of water are still the most significant questions in this field. Herein, reline and six aqueous dilutions with a controlled amount of water (from 3.2 to 50.0 wt %) were studied mainly by using a combination of nuclear magnetic resonance (NMR) techniques. According to 1D 35Cl NMR, 1D 15N NMR, and 2D 1H-15Cl heteronuclear Overhauser effect spectroscopy, we probed the interactions of urea···Cl- and Ch+···Cl- in pure reline, which gradually dissociated in the presence of water. Moreover, it was revealed that the dissociation rate altered when the water content reached 9.0 wt %, which is ascribed to the higher preference of hydration for Cl- ion compared to other species in the system. Furthermore, selected cross peaks in 1H-1H correlation spectroscopy spectra were analyzed. Accordingly, an enhanced correlation was observed for urea···Ch+ at a lower water fraction within 9.0 wt %. When the water content increased to 24.9 wt %, the water solvation of Ch+ and urea was also observed in COSY spectra. The interaction of H2O···Ch+ got continuously stronger when the water content increased from 24.9 to 50.0 wt %, while H2O···urea got enhanced when the water content reached 33.3 wt % and then diminished gradually from 33.3 to 50.0 wt %. 1H-1H nuclear Overhauser effect spectroscopy and 1H-1H rotating frame Overhauser effect spectroscopy experiments were also conducted for dynamics investigation. The τc value for the species in 9.0 wt % aqueous reline is very close to τccrit of 0.44 ns. For pure reline and the aqueous reline with a water fraction of less than 9.0 wt %, the τc value of the species is longer than 0.44 ns, while for the sample with water of 24.9 wt %, the τc value is much shorter than 0.44 ns. Based on our NMR study, we revealed that with the water amount increasing from 0 to 50.0 wt %, the species involved in the system behaved as the large molecules or molecules in viscous liquids transiting to the medium-sized molecules in nonviscous liquids and finally to small molecules in nonviscous liquids.
RESUMO
Penta-O-galloyl-ß-d-glucose (PGG) was prepared from tannic acid methanolysis products based on HSCCC, and its protective effects and mechanism on the glucose-induced glycation were investigated for the first time. PGG was confirmed to exhibit strong anti-AGEs effects in bovine serum albumin (BSA)-glucose (Glu) and BSA-methylglyoxal (MGO) glycation systems. It was showed that PGG could inhibit the AGEs formation by blocking glycated intermediates (fructosamine and α-dicarbonyl compounds), eliminating radicals, and chelating metal-ions. In-depth mechanism analysis proved that PGG could prevent BSA from glycation by hindering the accumulation of amyloid fibrils, stabilizing the BSA secondary structures, and binding the partial glycation sites. Furthermore, PGG exhibited a prominent trapping capacities on the reactive intermediate MGO by generating PGG-mono-MGO adduct. This research indicated that PGG could be an effective agent to block Glu/MGO-triggered glycation and offered new insights into PGG as a functional ingredient in food materials for preventing diabetic syndrome.