| Abstract
| - Phenolic compounds are responsible for major organoleptic characteristics of plant-derived food andbeverages; these substances have received much attention, given that the major function of thesecompounds is their antioxidant ability. In the context of this study, our major aim was study the bindingof several phenolic compounds such as (+)-catechin, (−)-epicatechin, (−)-epicatechin gallate,malvidin-3-glucoside, tannic acid, procyanidin B4, procyanidin B2 gallate, and procyanidin oligomersto different proteins (bovine serum albumin and human α-amylase) by fluorescence quenching ofprotein intrinsic fluorescence. From the spectra obtained, the Stern−Volmer, the apparent static,and the bimolecular quenching constants were calculated. The structure of polyphenols revealed tosignificantly affect the binding/quenching process; in general, the binding affinity increased with themolecular weight of polyphenol compounds and in the presence of galloyl groups. For catechinmonomer and procyanidin dimer B4, the KSV was 14100 and 13800 M-1, respectively, and for galloylderivatives, the KSV was 19500 and 21900 M-1, respectively. Tannic acid was shown to be the majorquenching molecule for both proteins. However, comparing different proteins, the same polyphenolshowed different quenching effects, which are suggested to be related to the three-dimensionalstructure of the proteins studied. For (+)-catechin and BSA, the KSV was 8700 M-1, and withα-amylase, it was 14100 M-1; for tannic acid, the KSV was 100548 and 110674 M-1, respectively.From the results obtained, besides the main binding analysis performed, we conclude that thistechnique is more sensitive than thought because we can detect several interactions that have notbeen proven by other methods, namely, nephelometry. Overall, fluorescence quenching has provento be a very sensitive technique with many potentialities to analyze the interaction between polyphenolsand proteins. Keywords: Polyphenols; bovine serum albumin; human salivary α-amylase; fluorescence quenching
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