Isolation of the acetylcholinesterase inhibitor ungeremine from Nerine bowdenii by preparative HPLC coupled on-line to a flow assay system.

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 (1)H-NMR, 2D-NMR, and NOESY spectra. The assignment of the active N. bowdenii constituent was also confirmed by co-TLC, co-HPLC, and co-(1)H-NMR experiments using an authentic sample of synthetic ungeremine. The IC(50) value of ungeremine was 0.35 microM, showing stronger activity than galanthamine (2.2 microM).