Mechanism of dsDNA binding, enzyme inhibition, antioxidant activities, and molecular docking studies of taxifolin, daidzein, and S-equol.

Abstract

This study investigated the binding mechanism of taxifolin (TA), daidzein (DA), and S-equol (SQ) flavonoids with fish sperm double helix DNA (dsDNA) under the simulated physiological pH condition using UV-Vis and photoluminescence spectroscopy, as well as viscometric methods. Binding constants (K_b) for the flavonoids to dsDNA were determined as 1.8 × 10⁴ M^-1 for SQ, 1.6 × 10⁴ M^-1 for DA and 1.7 × 10⁴ M^-1 for TA, indicating moderate affinity. The groove binding mode was confirmed by competitive binding studies with ethidium bromide or rhodamine B, UV-Vis spectrophotometry and viscosity evaluation. Additionally, the compounds showed high cholinesterase (ChE) inhibitory activity, with TA being the most potent, particularly against BChE (IC₅₀ = 2.93 μM) and AChE (IC₅₀ = 6.42 μM). Antioxidant activities were also evaluated using DPPH and ABTS assays, with TA showing the lowest IC₅₀ values. Additionally, molecular docking studies were performed to assess the interactions and binding affinities of all compounds with AChE and BChE enzymes. As a result, the studied compounds were found to prefer minor groove binding. This research analyzed the contribution of the structure-activities of natural flavones in terms of their biological properties, which is important for their future application against diseases.