BACE1 and cholinesterase inhibitory activities of Nelumbo nucifera embryos

The aim of the present study was to evaluate the comparative anti-Alzheimer's disease (AD) activities of different parts of Nelumbo nucifera (leaves, de-embryo seeds, embryos, rhizomes, and stamens) in order to determine the selectivity and efficient use of its individual components. Anti-AD activities of different parts of N. nucifera were evaluated via inhibitory activities on acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) along with scavenging activity on peroxynitrite (ONOO^-). Among the evaluated parts of N. nucifera, the embryo extract exhibited significant inhibitory potential against BACE1 and BChE as well as scavenging activity against ONOO^-. Thus, the embryo extract was selected for detailed investigation on anti-AD activity using BACE1- and ChEs-inhibitory assays. Among the different solvent-soluble fractions, the dichloromethane (CH₂Cl₂), ethyl acetate (EtOAc), and n-butanol (n-BuOH) fractions showed promising ChEs and BACE1 inhibitory activities. Repeated column chromatography of the CH₂Cl₂, EtOAc and n-BuOH fractions yielded compounds 1-5, which were neferine (1), liensinine (2), vitexin (3), quercetin 3-O-glucoside (4) and northalifoline (5). Compound 2 exhibited potent inhibitory activities on BACE1, AChE, and BChE with respective IC₅₀ values of 6.37 ± 0.13, 0.34 ± 0.02, and 9.96 ± 0.47 μM. Likewise, compound 1 showed potent inhibitory activities on BACE1, AChE, and BChE with IC₅₀ values of 28.51 ± 4.04, 14.19 ± 1.46, and 37.18 ± 0.59 μM, respectively; the IC₅₀ values of 3 were 19.25 ± 3.03, 16.62 ± 1.43, and 11.53 ± 2.21 μM, respectively. In conclusion, we identified potent ChEs- and BACE1-inhibitory activities of N. nucifera as well as its isolated constituents, which may be further explored to develop therapeutic and preventive agents for AD and oxidative stress related diseases.