Westalsan: A New Acetylcholine Esterase Inhibitor from the Endophytic FungusWesterdykella nigra

Abstract A new cytochalasan alkaloid, westalsan ( 1 ), along with two known cytochalasan compounds, phomacin B ( 2 ) and 19‐hydroxy‐19,20‐dihydrophomacin C ( 3 ), were isolated from the solid rice culture of Westerdykella nigra , a marine‐derived endophytic fungus, isolated from the roots of mangrove Avicennia marina (Forssk.) Vierh. The structures of compounds 1 – 3 were established on the basis of extensive 1D and 2D NMR spectroscopic techniques in combination with HR‐ESI‐MS. The ability of the isolated compounds to inhibit acetylcholine esterase activity was evaluated. Compound 3 showed the highest acetylcholine esterase inhibitory activity (IC 50 0.056±0.003 μM), followed by compound 1 (IC 50 0.088±0.005 μM) and compound 2 (IC 50 0.140±0.007 μM) compared to donepezil (IC 50 0.035±0.002 μM). This was further confirmed by molecular docking experiment.