In the present study, we assessed the effects of gluco-obtusifolin, isolated from the seeds of Cassia obtusifolia L., and its aglycone, obtusifolin, on the learning and memory impairments induced by scopolamine using the passive avoidance and the Morris water maze tasks in mice. Gluco-obtusifolin (1, 2, and 4 mg/kg, p.o.) and obtusifolin (0.25, 0.5, 1, and 2 mg/kg, p.o.) significantly reversed scopolamine-induced cognitive impairments in the passive avoidance test (P<0.05). Moreover, gluco-obtusifolin (2 mg/kg, p.o.) and obtusifolin (0.5 mg/kg, p.o.) improved escape latencies, swimming times in the target quadrant, and crossing numbers in the zone where the platform previously existed in the Morris water maze test. In the acetylcholinesterase assay, gluco-obtusifolin and obtusifolin were found to inhibit acetylcholinesterase activity in vitro (IC(50) = 37.2 and 18.5 microM, respectively) and ex vivo. These results suggest that gluco-obtusifolin and its aglycone may be useful for the treatment of cognitive impairment, and that its beneficial effects are mediated, in part, by the enhancement of cholinergic signaling.