Phytochemical investigation of the seeds of Alpinia katsumadai (Zingiberaceae) led to the isolation and identification of six new diarylheptanoid derivatives, katsumains D-G ( 1- 4), 3-(acetyloxy)-alpinikatin ( 5), and 5-(acetyloxy)alpinikatin ( 6). The structures of 1- 6 were elucidated by spectroscopic data analysis including 1D- and 2D-NMR experiments.