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In the course of screening plants used in Korean folk medicine as memory enhancers, a 70% ethanol extract of tuber from Corydalis turtschaninovii Besser (Papaveraceae) showed significant acetylcholinesterase (AChE) inhibitory activity. Repeated column chromatography led to the isolation of a new aporphine alkaloid, oxoglaucidaline (9), and a new protoberberine, pseudodehydrocorydaline (13) together with 14 known compounds (1-8, 10-12, and 14-16). The chemical structures of isolated compounds were elucidated base on extensive 1D and 2D NMR spectroscopic data. Compounds 1-16 were investigated in vitro for their anti-cholinesterase activity using the mice cortex AChE enzyme. In further study, the anti-amnesic activities of pseudoberberine (16) in mice on the learning and memory impairments induced by scopolamine (1.0 mg/kg, i.p.) were examined. This alkaloid (5.0 mg/kg, p.o.) administration significantly reversed cognitive impairments in mice by passive avoidance test (P<0.05). It also reduced escape latencies in training trials and prolonged swimming times in the target quadrant during the probe trial in the water maze task (P<0.05). These results indicated that Corydalis turtschaninovii due to its alkaloids have anti-cholinesterase activity and pseudoberberine and other alkaloids have anti-amnesic activities that may be useful for cognitive impairment treatment.

Methanolic extracts of seven herbs (Acorus calamus, Acorus gramineus, Bupleurm facaltum, Dioscorea batatas, Epimedium koreanum, Poria cocos and Zizyphi jujuba) used in traditional Korean medicine for improvement of memory and cognition in old age were tested for cholinesterase inhibitory properties using the Ellman colorimetric method. Significant inhibition of the enzyme at 200 microg/ml was observed for extracts from A. calamus and E. koreanum. The possible bases for the reputation of these and the other herbs tested are discussed in the light of previous investigations into their chemistry and biological activity.