Characterization of the Anticholinesterase and Antioxidant Properties of Phytochemicals from Moringa oleifera as a Potential Treatment for Alzheimer’s Disease

<b>Background/Objectives:</b> Alzheimer's disease (AD) is the most prevalent form of dementia and is characterized by a decline in cognition that may be due, in part, to deficient cholinergic signalling. Cholinesterase inhibitors (ChEIs) are the first-line pharmacotherapies for treating the diminished cholinergic function in AD patients. Plant phytochemicals may provide useful ChEIs and mitigate other elements of AD pathology, including oxidative stress. <b>Methods</b>: Herein, the phytochemicals present in <i>Moringa oleifera</i> aqueous and methanolic extracts were identified by LC-MS/MS and the potential of several phytochemicals (4-<i>O</i>-caffeoylquinic acid (4-CQA), quercetin 3-β-D-glucoside (Q3-β-D), chlorogenic acid (CGA), and rutin) to act as ChEIs and antioxidants was assessed. <b>Results</b>: The phytochemicals inhibited human acetylcholinesterase (AChE) in the following order of potency: 4-CQA > Q3-β-D > CGA > rutin; for AChE from <i>Electrophorus electricus</i>, the order of potency was Q3-β-D > 4-CQA > CGA > rutin. For human butyrylcholinesterase (hBuChE), the order of potency was rutin > 4-CQA > Q3-β-D > CGA and for equine serum BuChE, it was 4-CQA > Q3-β-D > rutin > CGA. Molecular docking validated the binding of the phytochemicals to cholinesterases, with binding affinities comparable to or higher than those of ChEI drugs. All the phytochemicals displayed potent radical-scavenging and antioxidant activities across six assays. 4-CQA was the most effective antioxidant in three of the assays. <b>Conclusions</b>: <i>M. oleifera</i> contains phytochemicals with weak ChEI activity and potent antioxidant capacity, with potential use as nutraceuticals to treat the cholinergic signalling deficit and oxidative stress that typifies AD pathology.