The Non-Covalent Interactions and In Vitro Radical Scavenging Activities of the Caseinate-Galangin and Caseinate-Genistein Complexes

Abstract

Non-covalent interactions and in vitro radical scavenging activities of the complexes formed by the commercial milk protein product caseinate and one of the two polyphenols (galangin and genistein) were assessed by the multi-spectroscopic techniques, molecular docking, and detection of scavenging activities against the 1,1–diphenyl-2-picryl-hydrazyl (DPPH), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and hydroxyl radicals. The caseinate bound with the two polyphenols showed conformational changes and increased scavenging activities, compared with original caseinate. The caseinate-polyphenol binding was driven by the hydrophobic interaction and hydrogen-bonds, while hydrophobic interaction was the main binding force. Meanwhile, sodium dodecyl sulfate and urea could damage the essential hydrophobic interaction and hydrogen-bonds, respectively, and thus led to decreased apparent binding constants for the caseinate-polyphenol binding. Based on the measured values of several apparent thermodynamic parameters like ΔH, ΔS, ΔG, and donor–acceptor distance as well as the detected radical scavenging activity, galangin having more planar stereochemical structure and random B-ring rotation always had higher affinity for caseinate than genistein having location isomerism and twisted stereochemical structure, while the caseinate-galangin complex showed higher radical scavenging activity than the caseinate-genistein complex. It is thus concluded that both chemical and stereochemical structures of polyphenols are crucial to the affinity of polyphenols for protein and antioxidant activities of the protein-polyphenol complexes.

Study on the interaction mechanism between luteoloside and xanthine oxidase by multi‐spectroscopic and molecular docking methods

“…With the increase of luteoloside concentration, the absorption peak intensity of XO at 280 nm increased and the blue shift occurred, 56 indicating that there was an interaction between luteoloside and XO and the polarity of protein amino acid residues decreased and the hydrophobicity increased, as shown in Figure 6. In the study of the interaction between dihydromyricetin and bovine lactoferrin, Ma et al found that the absorption peak intensity of bovine lactoferrin increased at 280 nm with the addition of dihydromyricetin, indicating the interaction occurred between bovine lactoferrin and dihydromyricetin 57 . The absorption peak intensity of bovine lactoferrin was also 280 nm, which was similar to our study.…”

“…found that the absorption peak intensity of bovine lactoferrin increased at 280 nm with the addition of dihydromyricetin, indicating the interaction occurred between bovine lactoferrin and dihydromyricetin. 57 The absorption peak intensity of bovine lactoferrin was also 280 nm, which was similar to our study.…”