Phenolic Derivatives with Anti‐Acetylcholinesterase Inhibitory Activities fromGaleola nudifoliain Vietnam

Abstract

A new phenolic derivative, galeomalate A (1), together with five known structurally related compounds (2‐6), was isolated from the ethyl acetate extract of Galeola nudifolia collected in Vietnam. The structures were elucidated by various spectroscopic methods, including 1D and 2D NMR, HR‐ESI‐TOF‐MS, and CD data, and chemical conversion of the sugar moiety. All isolated compounds possessed acetylcholinesterase (AChE) inhibitory activities in a dose‐dependent manner. Among them, compounds 2 and 3 exhibited the first and second highest inhibitory activity on AChE with IC50 values of 122.13 and 125.49 μM, respectively. Compounds 1 and 4–6 inhibited the AChE activity by mixed modes of action comprising competitive and non‐competitive modes, whereas 2 and 3 exerted their inhibitory activities in a competitive manner. Molecular docking analyses suggested that the phenyl‐β‐D‐glucopyranoside unit of 2 and 3 bound to the active site of AChE for the competitive inhibitory activities, while the mixed inhibitory activity of 4 was due to the two binding patterns in the active‐site and the active‐site entrance of AChE. Furthermore, the docking studies indicated that 1, 5, and 6 would inhibit AChE in a mixed inhibitory manner by adopting three distinct binding patterns of the additional phenyl‐β‐D‐glucopyranoside unit at the active‐site entrance.