β-Amyloid peptide (Aβ) with a length of 39-43 amino acid residues exists in human plasma and cerebrospinal fluid as a naturally occurring component(1). Soluble Aβ monomers can self-associate to small oligomers, protofibrils and finally to the rigid insoluble fibrils, which are characterized with cross β-sheet conformation (2). It was found that Aβ fibrils constitute the major component of senile plaques in the brain of patients suffering from Alzheimer's disease (AD) (3). Recent research has shown that small Aβ oligomers are associated with the pathogenesis of AD (4, 5). Inhibition of the aggregation of Aβ monomers to oligomers and fibrils might be a promising way to treat AD.
Several small molecules have been identified that inhibit or reverse amyloid fibril formation, such as nicotine, β-cyclodextrin, Congo red and rifampicin (6). Furthermore, naturally occurring flavonoids were reported to prevent β-amyloid-induced cell death in cultured pheochromocytoma PC12 cells (7). Flavonoids are a ubiquitous group, which are abundant in wine, tea and bark, flowers and roots of vegetables and herbs. We studied the use of various spectroscopic methods to monitor the effects of myricetin (Figure 1), one of the flavonoids, on Aβ aggregation and secondary structure, as well as the vibrational modes of the aromatic side chains.