The present invention relates to pharmaceutical composition comprising the naturally occurring compounds selected from (±) Marrnesin, Columbianetin, Dihydroxanthyletin and substituted coumarin derivatives of 7-allyloxy coumarin, 7-benzyloxy coumarin, 7 -methoxycoumarin, 7-acetyloxy coumarin, 4-methyl-7-hydroxy coumarin and 4-methyl-7-acetyloxy coumarin. The said compositions possess a high degree of acetylcholinesterase inhibitory (AChE) property.