The present invention relates to a pharmaceutical composition containing, as active ingredients, epitulipinolide and costunolide extracted from the bark of Liriodendron tulipifera. More specifically, the present invention relates to a pharmaceutical composition for treating the gastrointestinal tract, the composition containing, as active ingredients, epitulipinolide and costunolide, which are the active ingredients of the extract from the bark of Liriodendron tulipifera, and to the use thereof as a therapeutic agent for gastrointestinal diseases.