Two New Types of Bisindole Alkaloid from Trigonostemon lutescens

Six unprecedented bisindole alkaloids, trigolutesins A and B (1-2) with a unique polycyclic skeleton and trigolutes A-D (3-6) with another polycyclic skeleton, were isolated from the twigs of Trigonostemon lutescens. Their structures and relative configurations were elucidated by spectroscopic data and single-crystal X-ray diffraction crystallography. Trigolutesin A (1) showed weak AChE inhibitory activity.