Ali_2019_Chem.Biol.Interact_309_108707

Alzheimer's disease (AD) is a slow but progressive neurodegenerative disease. One of the pathological hallmarks of AD is the progressive accumulation of beta-amyloid (Abeta) in the form of senile plaques, and Abeta insult to neuronal cells has been identified as one of the major causes of AD onset. In the present study, we investigated the anti-AD potential of four flavonoids, naringenin, didymin, prunin, and poncirin, by evaluating their ability to inhibit acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and beta-site amyloid precursor protein cleaving enzyme 1 (BACE1). All four flavonoids displayed promising inhibitory activity against AChE, BChE, and BACE1. Structure-activity relationships suggested that glycosylation of naringenin at sugar moieties, and at different positions of the glycosidic linkage, might be closely associated with anti-AD potential. Kinetic and docking studies showed the lowest binding energy and highest affinity for the mixed, competitive, and non-competitive type inhibitors didymin, prunin, and poncirin. Hydrophobic interactions and the number of hydrogen bonds determined the strength of the protein-inhibitor interaction. We also examined the neuroprotective mechanisms by which flavonoids act against Abeta25-35-induced toxicity in PC12cells. Exposure of PC12cells to 10muMAbeta25-35 for 24h resulted in a significant decrease in cell viability. In addition, pretreatment of PC12cells with different concentrations of flavonoids for 1h significantly reversed the effects of Abeta. Furthermore, treatment with the most active flavonoid, didymin, significantly reduced BACE1, APPsbeta, and C99 expression levels in a dose-dependent manner, without affecting amyloid precursor protein (APP) levels in the amyloidogenic pathway. Together, our results indicate that flavonoids, and in particular didymin, exhibit inhibitory activity in vitro, and may be useful in the development of therapeutic modalities for the treatment of AD.