Interaction between baicalein and amyloid-β fibrils studied by fluorescence spectroscopy

Abstract

The interaction between baicalein and amyloid-β(Aβ) polypeptide was investigated by fluorescence and UV-Vis absorbance spectroscopy. The absence of the characteristic peak of tyrosinate(Tyr) in the absorption spectra of Aβ-baicalein complexes provided evidence that the sole Tyr residue in Aβ is not bound to baicalein, but remains close to it. The intrinsic fluorescence of Tyr residues in Aβ 1–42 aggregates was quenched strongly by the excited-state ionization of baicalein. In this complex the hydroxyl group was not ionized, but to ionize immediately upon excitation. Absorbance, fluorescence and synchronous spectroscopies show that the formation of Schiff base between the quinone of baicalein and the lysine(Lys) side chains of Aβ 1–42 is another major reason in the depolymerization of Aβ 1–42 aggregates by baicalein. It is desirable that our research would offer some valuable reference for the application of flavonoid derivants in Alzheimer’s disease(AD) treatment.