Inclusion complexes of tea polyphenols with HP-ß-cyclodextrin:Preparation, characterization, molecular docking, and antioxidant activity.

The purpose of this study was to prepare and characterize inclusion complexes between tea polyphenol (TP) and hydroxypropyl-ß-cyclodextrin (HP-ß-CD), and to evaluate their antioxidant properties. Freeze-drying was used to prepare the inclusion complex of TP/HP-ß-CD at different component ratios (1:0.5, 1:1, and 1:2). The supermolecular structure of the TP/HP-ß-CD complex was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Molecular docking was used to simulate the positions and interactions of the binding sites of TP/HP-ß-CD inclusion complexes and target protein receptors. In addition, the effects of TP/HP-ß-CD inclusion complexes on myofibrillar protein (MP) from lamb tripe were observed under oxidative conditions. Results showed that TP was encapsulated in the cavity of HP-ß-CD to form an optimal complex with 1:2 molar ratio of stoichiometry, while the FTIR, TGA, and SEM studies also support the inclusion process. Molecular modeling results were systematically analyzed to determine the stability of inclusion complexes and protein. Furthermore, the addition of an appropriate concentration (5 to 105 µmol/g) of TP/HP-ß-CD inclusion complex decreased the carbonyl content, hydrophobicity, and protein aggregation of MP from lamb tripe, whereas it increased the sulfhydryl content. This improved antioxidant activity and bioavailability of the inclusion complexes will be beneficial for its potential applications in food. PRACTICAL APPLICATION: Tea polyphenol was an antioxidant with potential for the field of food. In this study, the unstable properties of tea polyphenols were evaluated and were improved by inclusion of HP-ß-cyclodextrin. The binding mode of the inclusion complex with protein was revealed via the molecular docking method, and the application of inclusion complex to control protein oxidation was studied. Results showed that the inclusion complex could effectively inhibit protein oxidation, which can provide a reference for the application of polyphenols in meat products and the improvement of protein properties.

Preparation and Characterisation of Polyphenol-HP-ß-Cyclodextrin Inclusion Complex that Protects Lamb Tripe Protein against Oxidation.

Grape seed extract (GSE) displays strong antioxidant activity, but its instability creates barriers to its applications. Herein, three HP-ß-CD/GSE inclusion complexes with host-guest ratios of 1:0.5, 1:1, and 1:2 were successfully prepared by co-precipitation method to improve stability. Successful embedding of GSE in the HP-ß-CD cavity was confirmed by fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) analyses. The Autodock Tools 1.5.6 was used to simulate the three-dimensional supramolecular structure of the inclusion complex of 2-hydroxypropyl-ß-cyclodextrin and grape seed extract (HP-ß-CD/GSE) by molecular docking. The MALDI-TOF-MS technology and chemical database Pubchem, and structural database PDB were combined to reconstitute the three-dimensional structure of target protein. The binding mode of the HP-ß-CD/GSE inclusion complex to target protein was studied at the molecular level, and the antioxidant ability of the resulting HP-ß-CD/GSE inclusion complexes was investigated by measuring 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging. The effects of HP-ß-CD/GSE on myofibrillar protein from lamb tripe were also investigated under oxidative conditions. The positions and interactions of the binding sites of HP-ß-CD/GSE inclusion complexes and target protein receptors were simulated by molecular docking. The results showed that HP-ß-CD/GSE inclusion complexes were successfully prepared, optimally at a molar ratio of 1:2. At low (5 µmol/g) to medium (105 µmol/g) concentrations, HP-ß-CD/GSE inclusion complexes decreased the carbonyl content, hydrophobicity, and protein aggregation of myofibrillar protein from lamb tripe, and increased the sulphydryl content. Furthermore, high concentration (155 µmol/g) of HP-ß-CD/GSE inclusion complexes promoted protein oxidation.