Owing to the various beneficial properties
of the popular spice
saffron, the interaction of safranal, a secondary metabolite of the
former, with hen egg white lysozyme was investigated. The formation
of a complex was evidenced by UV–visible spectroscopy. Fluorescence
quenching experiments were also performed to understand the binding
mechanism and to evaluate the forces involved in binding. The strong absorption of safranal in the range
of excitation and emission wavelengths of lysozyme fluorescence required
the correction of the inner filter effect for fluorescence spectra
to obtain the apparent extent of binding. There was a considerable
difference between the observed spectra and corrected spectra, and
a similar observation was found in the case of synchronous fluorescence
spectra. From the analysis of quenching data, it was found that the
mechanism involved in quenching was static with 1:1 binding between
them. The interaction was found to be driven, mainly, by hydrophobic
forces and hydrogen bonding. Safranal had negligible impact on the
secondary structure of lysozyme. The interaction was also studied
by molecular docking, and the results were in good agreement with
the results obtained experimentally. The binding site of safranal
was in the big hydrophobic cavity of lysozyme. The amino acids involved
in the interaction were Asp52, Ile58, Gln57, Asn59, Trp62, Trp63,
Trp108, Ile98, Asp101, and Ala107.