One- and two-dimensional stop-flow HPLC-NMR experiments were applied to investigate a root extract of Ancistrocladus likoko (Ancistrocladaceae). Three new naphthylisoquinoline alkaloids with a 5,8' coupling pattern were found. The constitutions and relative configurations were elucidated by application of H,H-TOCSY and ROESY experiments carried out in the stop-flow mode. This example demonstrates the potential of HPLC-NMR as an efficient coupling technique for plant screening studies in phytochemical analysis. Copyright (C) 1999 John Wiley & Sons, Ltd.