Interaction of phenolic compounds with bovine serum albumin (BSA) and α-amylase and their relationship to astringency perception

Abstract

The ability of grape seed extracts to bind to bovine serum albumin (BSA) and α-amylase was studied by fluorescence quenching of protein intrinsic fluorescence and nephelometry. The influence of grape seed ripeness on astringency was also evaluated. From the spectra obtained, the modified Sterm-Volmer (K(app)) and the bimolecular quenching constants were calculated. Results showed that grape seed extracts had good affinity for proteins. The association strength of tannin-protein interactions varied with changes in tannin structure associated with the degree of ripeness affecting the binding/quenching process. In all cases studied, higher values of K(app) were obtained in samples at harvest which have greater ability to bind to proteins than have samples at post-veraison time. Nephelometric assays show the same trend as do fluorescence quenching studies. A possible explanation for this is that, as seeds ripen, their tannins increase in molecular mass, which relates to an increase in hydrophobicity of the molecules, and this increases protein affinity. However, that is contrary to the reported decrease in astringency of grape seeds during maturity. This indicates that tannin-protein interactions are not the only explanation for the complex sensations of astringency of grape seeds.

The mechanism of interactions between tea polyphenols and porcine pancreatic alpha‐amylase: Analysis by inhibition kinetics, fluorescence quenching, differential scanning calorimetry and isothermal titration calorimetry

“…apparent static quenching . The modified form of the Stern–Volmer equation describing this situation is as follows : …”

Evaluation of the potential astringency of the skins and seeds of different grape varieties based on polyphenol/protein binding

“…Electrophoresis was performed on a DYCZ-24DN electrophoresis apparatus (Beijing, China) using a DYY-6C power supply (Beijing, China) according to previous reports (Ferrer-Gallego et al, 2012;Rinaldi et al, 2015). Human saliva was combined with the grape skin or seed extracts from eight different grape varieties at a ratio of 4:1 ratio, keep the reaction for 5 min at 25 °C, then centrifuged the reaction mixtures (300 μL of HS and 150 μL of sample) for 10 min at 3000 r/min.…”

“…Fluorescence spectra were recorded using a 970 CRT fluorescence spectrophotometer (Shanghai, China) (Ferrer-Gallego et al, 2012;Pinto et al, 2010). The extracts of grape skins or seeds were appropriately diluted and added to the BSA solution (BSA was dissolved in 1 mol/L Tris-HCl buffer (pH 7.4), then mixed with 0.5 mol/L NaCl and distilled water to make up 1.0×10 -6 mol/L BSA solution).…”

Effect of in vitro gastrointestinal digestion on the composition and bioactivity of anthocyanins in the fruits of cultivated Lycium ruthenicum Murray

“…Both the plots of F 0 /F against anthocyanins concentration concave towards the y axis (Figure 4(c,d)), indicating that both the anthocyanins quenched the enzyme fluorescence through an apparent static or a sphere-of-action mechanism (Castanho & Prieto, 1998). The quenching constant, K FQ , indicates the binding affinity of a quencher to an enzyme, and a higher K FQ value suggests stronger affinity of a quencher to enzyme (Ferrer-Gallego et al, 2012). The order of K FQ values for the anthocyanins was consistent with that of the inhibition activities (Table 4), suggesting that CLM anthocyanins obtained from Hedong CLM might be more effective in inhibition of α-glucosidase than these from other samples.…”