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Search for β -Secretase and Acetylcholinesterase Inhibitors from Plants
The number of patients of dementia is increasing and has been considered as a serious social problem. In our research program for searching novel agents for prevention and treatment of dementia, we focused on β-secretase and acetylcholinesterase inhibition, which are now recognized as a promising therapeutic target. We have already discovered caryophyllenes, curcumins and piperine as β-secretase inhibitors which were found in leaves of Murraya koenigii, rhizomes of Curcuma longa and fruits of Piper nigrum, respectively. Our consecutive research led to determine 4-methoxycinnamic acid ethyl ester (IC50= 0.68 mM) and pipataline (0.30 mM) as novel inhibitors from rhizomes of Kaempferia galanga and fruits of P. longum, respectively. As for acetylcholinesterase inhibitor, we focused on ginseng, which has been utilized as a panax in east Asia. Hexane and ethylacetate extracts of ginseng showed inhibitory activities at 250 µg/ml. Activity guided fractionation led us to determine novel polyacetylenes, 9-trans-homopanaxynol (0.27 mM) and homopanaxydol (> 0.50 mM) as active principles. Structure-activity relationship studies are now underway in order to create more suitable agent for medicinal use.