Two novel alkaloids, trigonoine A containing a 2,8-diazabicyclo[3.3.1]nonane ring system and trigonoine B formed by a combination of a 2,3-dihydroquinolin-4-one and 3H-pyrrolo[2,3-c]quinoline rearranged from B-carboline skeleton were isolated from the leaves of Trigonostemon lii. Their structures were elucidated by 10 and 20 NMR spectroscopic methods. (C) 2011 Elsevier Ltd. All rights reserved.