Comparative studies on interactions of baicalein, baicalin and scutellarin with lysozyme

The interactions of baicalein, baicalin and scutellarin with lysozyme (LYSO) were studied by fluorescence and UV spectroscopy. The results showed that all the three flavones can quench the fluorescence of LYSO via static quenching with the distance between the donor and acceptor less than 7 nm. The hydroxyl at B-ring gave flavones an advantage to binding with LYSO. Electrostatic forces played a major role in stabilizing baicalein–LYSO complex and baicalin–LYSO complex, whereas hydrophobic interactions in scutellarin–LYSO. Furthermore, the presence of pantothenic acid can increase the binding constant and the number of binding sites between flavones and LYSO.

Contour spectra of (a) LYSO, (b) Baicalein–LYSO, (c) Baicalin–LYSO, and (d) Scutellarin–LYSO; C (LYSO) = 1.0 × 10−6 M, C(Baicalein) = C(Baicalin) = C(Scutellarin) = 7.0 × 10−6 M. Peak 1 is the Rayleigh scattering peak (λex = λem), peak 2 mainly reveals the spectral behavior of Trp residues, and peak 3 the fluorescence characteristic of polypeptide backbone structures. In the presence of baicalein, Trp residues were located in a more hydrophobic environment, while Trp residues were brought to a more hydrophilic environment in the presence of baicalin or scutellarin. The three flavones can change polarity of hydrophobic cavity, thereby influencing the conformation of LYSO. Figure optionsDownload as PowerPoint slideHighlights
► The paper showed the effect of pantothenic acid on flavone–LYSO binding.
► The flavones quenched LYSO fluorescence via static quenching with r less than 7 nm.
► The hydroxyl and steric hindrance of flavones influenced the binding interactions.
► Pantothenic acid decreased Ka and n of the flavones to LYSO.
► It provided a support for activity of antibiotics enhanced by pantothenic acid.