OBJECTIVE:To study the chemical constituents of Zhizi(Fructus Gardeniae) and their antiamnesic effect in a mouse model of Alzheimer's disease.METHODS:Ameliorating effects of the extracts,fractions and constituents on scopolamine-induced memory impairment in vivo using a passive avoidance task system and their inhibitory activities on acetylcholinesterase(AChE) in vitro were examined.The isolation of components was performed by chromatographic techniques and their structures were identified on the basis of spectral analysis.RESULTS:Activity-guided fractionation of the total extracts resulted in the isolation of two glycosides,geniposide and crocin from the n-butanol fraction and genipin and crocetin from the ethylacetate fraction.Among the fractions tested,n-butanol fraction showed the strongest AChE inhibition(43.4% at a final dose of 0.03 mg/mL) and also exhibited outstanding efficacy(65.9% at a dose of 250 mg/kg) in an experimental model of amnesia.Geniposide showed a 22.8% AChE inhibitory activity and a potent ameliorating effect on scopolamine-induced memory impairment in amnesic mice of 93.4% as compared to the control group.CONCLUSION:Geniposide,a main constituent of gardenia should be considered a candidate for further clinical study for the purpose of developing a cognition activator and its mechanism of action may be mediated,at least in part,by the acetylcholine enhancing cholinergic nervous system.