Hydrogen–Deuterium exchange kinetics in β-lactoglobulin (−)-epicatechin complexes studied by FTIR spectroscopy

Preparation and characterization of zein-lecithin-total flavonoids from Smilax glabra complex nanoparticles and the study of their antioxidant activity on HepG2 cells

Total flavonoids from Smilax glabra (TFSG) exhibit several biological activities; however, their poor stability limits their application. In this work, zein-lecithin-TFSG complex nanoparticles (Z-L-TFSG NPs) were prepared using the anti-solvent coprecipitation technique. The prepared Z-L-TFSG NPs were spherical with an encapsulation efficiency of 98.0%. Differential scanning calorimetry, Fourier transform infrared spectroscopy, and morphology tests revealed that the TFSG were successfully encapsulated by Z-L NPs. Z-L-TFSG NPs showed superior stability and better controlled release characteristics in simulated gastrointestinal digestion. The encapsulation of TFSG by Z-L NPs could improve their antioxidant capacity in vitro. Moreover, Z-L-TFSG NPs could enhance the protective effects of TFSG against H₂O₂-induced oxidative damage to HepG2 cells. The results indicated that the Z-L self-assembled NPs could serve as a promising drug delivery system through the integrated encapsulation of multiple flavonoids.

Fabrication of Zein-Lecithin-EGCG complex nanoparticles: Characterization, controlled release in simulated gastrointestinal digestion

The Zein-Lecithin-Epigallocatechin gallate (EGCG) complex nanoparticles were fabricated by anti-solvent coprecipitation method. The Zein-Lecithin (Z-L) nanocomplexes exhibited great encapsulation efficiency of 68.5% for EGCG, and the encapsulated EGCG still had good antioxidative capacity. The cumulative release of EGCG in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) were 19% and 92%, respectively, and the release was closest to Fick release in SGF and First release in SIF. Fluorescence spectroscopy (FL), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) experiments revealed that the EGCG was successfully encapsulated by Z-L nanocomplexes through electrostatic, hydrophobic and hydrogen bonding interactions. The Zein-Lecithin-EGCG complex nanoparticles exhibited excellent stability and great sustained-release performance, which will be the alternative for potential application in the food industry.

Normal mode calculation and infrared spectroscopy of proteins in water solution: Relationship between amide I transition dipole strength and secondary structure

Dipole Strength (DS) of the amides has gained a renewed interest in chemical physics since it provides an important tool to disclose the on-site vibrational energy distributions. Apart from earlier experimental efforts on polypeptides, little is still known about DS in complex proteins. We accurately measured the Fourier Transform Infrared absorption spectra of nine proteins in water solution obtaining their Molar Extinction Coefficient in the amide I and II spectral region. Our results show that the amide I DS value depends on the protein secondary structure, being that of the α-rich and unstructured proteins lower by a factor of 2 than that of the β-rich proteins. The average DS for amino acids in α and β secondary structures confirms this finding. Normal Mode calculation and Molecular Dynamics were performed and used as tools for data analysis and interpretation. The present outcomes corroborate the hypothesis that antiparallel β-sheet environment is more prone to delocalize the on-site CO stretching vibration through coupling mechanisms between carbonyl groups, whereas α-helix structures are energetically less stable to permit vibrational mode delocalization.