Cognitive and memory enhancing activities of tannins on scopolamine-induced learning and memory impairment in rats

The precise pathological mechanism of AD is unknown, but amyloid-rich plaques are known neuropathologic hallmark, and acetylcholine esterase (AChE) inhibitor is generally used as primary therapeutic agents for neurodegenerative disease. In our screening for the new drug development of AD from natural plant, it showed that tannins (tannic acid, ellagic acid and catechin) have significant inhibitory action on AChE activity, but their cognitive and memory enhancing effects are not known. We studied effects of these three tannins on cognition and memory enhancing in scopolamine induced amnesia rat model. Experiments were carried out to determine the cognitive and memory enhancing actions of these tannins on passive/active avoidance task and water maze task. It showed that all tannins had significant AChE inhibitory activity in concentration-dependent manners, but their activities were less than donepezil. Tannic acid, catechin and ellagic acid significantly inhibited AChE activity. Tannins had significant cognitive and memory enhancing activities, but their activity was less than piracetam on passive/active avoidance task and water maze task. These results indicated that tannins might have useful effects for neurodegenerative diseases like AD and show the possibility as a new agent.