Inhibition of flavonoids on acetylcholine esterase: binding and structure-activity relationship.

The inhibitory effects of flavonoids on acetylcholinesterase (AChE) have attracted great interest among researchers. However, few reports have focused on the structure-activity relationship for AChE inhibition of flavonoids. This work mainly concerns the structural aspects of inhibitory activities and binding affinities of flavonoids as AChE inhibitors. The results show that hydroxyl groups in the A ring of flavonoids are favorable for inhibiting AChE, and the hydroxylation increases the affinities for AChE. However, methoxylation may decrease or increase the activities depending on the class of flavonoids. The glycosylation decreases the AChE inhibitory activities of flavonoids and lowers the affinities for AChE by 1 to 5 times depending on the conjunction site and the type of sugar moiety. The hydrogenation of the C2-C3 double bond of apigenin decreases both the affinity for AChE and AChE inhibition. The molecular property-affinity relationship reveals that the hydrogen bond force plays an important role in binding flavonoids to AChE. The AChE inhibitions generally increase with the increasing affinities of flavonoids within the class, especially for flavones and flavonols.