Isolation of the Acetylcholinesterase Inhibitor Ungeremine from Nerine bowdenii by Preparative HPLC Coupled On-Line to a Flow Assay System

Abstract

In an attempt to isolate the active compound while detecting acetylcholinesterase inhibitory activity, we applied a fluorometric flow assay system to an on-line coupled preparative HPLC. The MeOH extract of Nerine bowdenii showed a strong inhibitory peak in the on-line assay, and the active compound was isolated by CPC and HPLC. It was identified as ungeremine by analysis of its ¹H-NMR, 2D-NMR, and NOESY spectra. The assignment of the active N. bowdenii constituent was also confirmed by co-TLC, co-HPLC, and co-¹H-NMR experiments using an authentic sample of synthetic ungeremine. The IC₅₀ value of ungeremine was 0.35 μM, showing stronger activity than galanthamine (2.2 μM).