Abstract:The EtOH extract of the root of the Chinese herb Achyranthes bidentata B1. was subjected to column chromatography to obtain abidenine (1), a new isoquinoline alkaloid. 1 is bright needle crystals, m. p. 200℃ (dec). Its structure was elucidated through spectroscopic methods as 5,6-dihydro-2,3,10,11-tetramethoxy-dibenzo [a,g] quino-lizinium (1).