The Sundarbans mangrove forest has a rich biodiversity of flowering plants and many of these have been used in traditional medicine although the flora remains comparatively uninvestigated scientifically. Xylocarpus granatum, Xylocarpus moluccensis and Excoecaria agallocha methanolic extract showed a central nervous system depressant activity on the hole cross and open field test at 800 mg/kg dose level. The most significant depressant activity was observed in Xylocarpus granatum followed by Xylocarpus moluccensis and Excoecaria agallocha. There was no depressant activity observed in the models for Sarcolobus globosus. Further studies are required to confirm the activity and to explain the mechanism.