Analysis of the Binding Mechanism of Bioactive Coumarins with Ovalbumin: Further Investigation into the Inhibitory Effects toward Protein Fibrillation

Abstract

Two bioactive coumarin derivatives, 7-hydroxycoumarin (7-HC) and 4-methyl-7-hydroxycoumarin (4-Me-7-HC), were used to investigate the molecular interactions with the main food allergen from egg white, ovalbumin (OVA), along with their inhibitory effects on OVA aggregation. The mechanism of binding interaction was elucidated by multispectroscopic and computational methods. Circular dichroism (CD) and Fourier transform infrared (FT-IR) experiments confirmed the ligand-induced conformational changes of OVA. The fluorescence spectroscopic experiments demonstrated that the quenching mechanism was an unusual static quenching method with binding constants (K b) in the range of 104 M–1, indicating a moderate nature of binding between OVA and coumarins. Thioflavin T (ThT) and Congo red (CR) binding assays confirmed the production of OVA fibrils, and the aggregation was shown to be inhibited by the coumarin derivatives in vitro. Thermodynamic parameters for OVA-7-HC/4-Me-7-HC interactions showed positive ΔH and ΔS values, indicating hydrophobic forces predominated in the binding processes and a negative ΔG value, implying the spontaneity of the complex formation, which was then further confirmed by computational studies.

Construing the Interactions of Coumarin Derivatives with the Main Protease of Stomach Pepsin Using Spectroscopic and Computational Analyses: Insights into the Binding Thermodynamics, Antifibrillation Studies, and Enzymatic Assay

“…However, the absorption intensity is lower in the presence of UMB and 4-MU compared to F-pepsin alone, indicating reduced aggregate formation. This suggests that coumarin derivatives effectively act as an antifibrillating agent, consistent with previous research on ovalbumin protein, where UMB and 4-MU also demonstrated antifibrillation potential …”

“…The Rule of Five (RO5) addresses the relationship between active compounds and specifies four basic pharmacokinetic parameters: molecular weight, log P (partition coefficient), the number of H-bond donors, and the number of H-bond acceptors . As previously reported by the BOILED-Egg analysis, it was observed that both ligands are situated within the yolk region, this suggests that UMB and 4-MU are likely to have the capacity to penetrate the brain . As indicated in Table S6, both ligands fell within the acceptable molecular weight range and their H-bond donor and H-bond acceptor were also within the specified range of less than 5 and 10 respectively.…”

Binding Interaction of Coumarin Derivative Daphnetin with Ovalbumin: Molecular Insights into the Complexation Process and Effects of Metal Ions and pH in the Binding and Antifibrillation Studies

“…Previous studies have reported comparable findings with coumarin derivatives as an antifibrillating agent when investigated alongside pepsin and OVA protein fibrils. 96,97 3.11. Utilizing Molecular Docking Analyses to Identify the Potential Binding Site.…”