A significant acetylcholinesterase inhibitory activity was observed for the ethyl acetate and methanol extracts from the leaves and the fruits of MYRISTICA CRASSA. Three new dimeric acylphenols, giganteone C ( 5), maingayones B and C ( 6 and 7) were isolated together with the known malabaricones B and C ( 2 and 3) and giganteone A ( 4). Compounds 2 and 3 possess significant inhibitory activity on acetylcholinesterase. LC/MS study was particularly useful to discriminate structures of compounds 6 and 7.