Structural and molecular aspects of flavonoids as ligands for serum transferrin

Novel O-Methylglucoside Derivatives of Flavanone in Interaction with Model Membrane and Transferrin

“…The plots for all compounds showed the linear behavior and the calculated parameters are listed in Table 1 . The binding constant values obtained for MFA, MFB, and MFC compounds are about 3–4 times smaller than values published for other flavonoids, for example: apigenin (6.7 × 10 4 M −1 ), flavanone (6.9 × 10 4 M −1 ), 3-hydroxyflavone (7.6 × 10 4 M −1 ), and luteolin (8.2 × 10 4 M −1 ) [ 34 , 36 , 37 ]. It is considered that the binding ability generally increases with the increasing number of hydroxyl groups in flavonoid molecules [ 37 ].…”

“…In order to determine the compound–HTF interaction, the fluorescence quenching method was used. This method provides insight into the binding mechanism, driving forces, binding constant, intermolecular distances between ligands and proteins, and also the microenvironment of the chromophore groups in proteins [ 34 ]. A decrease in the quantum yield of fluorescence from a fluorophore is due to a variety of molecular interactions, and a mechanism of this quenching is usually classified as either dynamic or static quenching.…”

“…When HTF is excited at 280 nm, the fluorescence comes from both tryptophan and tyrosine residues. In this study, HTR was excited at 295 nm, and the observed fluorescence emission originates only from its tryptophan residues [ 34 ]. The fluorescence spectra of HTF in phosphate buffer (pH 7.4) in the absence and presence of 6-methylflavone biotransformation products showed strong fluorescence emission with a peak at 328 nm ( Figure 6 ).…”

“…These values are much higher than the maximum scatter collision quenching constant of dynamic quenching (2 × 10 10 M − 1 s − 1 ), which suggests that there is a specific interaction between HTF and the 6-methylflavanone glucosides and indicates that the static quenching mechanism occurred. The literature data also showed that the quenching mechanism between different flavonoids and HTS is static and occurs via complex formation [ 34 , 36 , 37 ]. The same type of interaction was also observed between bovine serum albumin (BSA) and various flavonoids [ 35 , 38 ] studied by fluorescence quenching methods.…”

“…In the case of static quenching presses, the binding constant (K a ) and the number of binding sites (n) may be calculated from the regression curve based on the Scatchard equation [ 34 ]: where F 0 —fluorescence intensity of HTF, F—fluorescence intensity of HTF in the presence of the tested compounds, K a —binding constant, Q—concentration of the quencher, n—binding sites per HTF molecule.…”