In the course of screening plants used in natural medicines as memory enhancers, a 70% ethanol extract of the aerial parts of Leonurus heterophyllus showed significant AChE inhibitory activity. Bioassay‐guided fractionation and repeated column chromatography led to the isolation of a new labdane‐type diterpenoids (1), named leoheteronin F, and six known compounds (2–7). The chemical structures of isolated compounds were elucidated based on extensive 1D and 2D NMR spectroscopic data. The isolates 1–7 were investigated in vitro for their anticholinesterase activity using mouse cortex AChE enzyme. Leoheteronin A (5) and leopersin G (7), which possess a 15,16‐epoxy group at the side chain, were found to be potent in the inhibition of AChE. Copyright © 2010 John Wiley & Sons, Ltd.