Inhibition potential against butyrylcholinesterase of stilbenes, bibenzyls, and dihydrophenanthrenes from Pholidota chinensis

Butyrylcholinesterase (BuChE, EC 3.1.1.8) inhibitors have promising application prospects as they can alleviate cognitive impairment and have a positive impact on some pathological features of Alzheimer’s disease. In this study, two new phenolic glycosides (1 and 2), pholidotosins B and C, together with two bibenzyls (3 and 5), two stilbenes (4 and 6), and two dihydrophenanthrenes (7 and 8) were isolated from Pholidota chinensis Lindl.. Among them, thunalbene (4) and lusianthridin (8) exhibited the strongest inhibitory effects, with IC₅₀ values of 11.01 ± 0.26 μM and 10.49 ± 0.34 μM, respectively. The structure-activity relationship analysis indicated that the BuChE inhibitory activity of the isolated compounds 3–8 was influenced by the substituted position and number of hydroxy and methoxy groups in the two benzene ring skeletons, as well as the connection mode of the two benzene rings. In silico predictions of physicochemical properties, drug-likeness, and pharmacokinetics were performed. The isolated compounds 3–8 obeyed the rule of five by Lipinski and had better oral bioavailability. Furthermore, the Boiled-Egg chart revealed that thunalbene possessed favorable blood-brain barrier permeability and did not serve as a substrate for P-glycoprotein. The results of enzyme kinetic studies indicated that thunalbene reversibly inhibited BuChE in a mixed-type manner. The molecular docking results demonstrated that thunalbene bind to BuChE with a docking energy of −6.10 kcal/mol, potentially inducing conformational changes in the enzyme’s active structure. These findings highlight the potential of thunalbene as a natural BuChE inhibitor for the treatment of neurodegenerative diseases.