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.