Objective To investigate the trace amounts of furanocoumarin dimers from Angelica dahurica var. formosana. Methods Using an LC-MS guided separation method, the furanocoumarin dimers were isolated by silica gel, Sephadex LH-20 column chromatography, and semi-preparative HPLC. The structures of the isolated dimeric coumarins were identified by NMR spectroscopy, and their preliminarily acetylcholinesterase (AChE) inhibitory activities were evaluated. Results Three furanocoumarin dimers were isolated from the ethyl acetate fraction of the ethanol extract of A. dahurica var. formosana, namely 9-{[4-(3-methylbut-2-en-1-yl)-7-oxo-7H-furo[3,2-g]chromen-9-yl]oxy}-4-[(2-methylbut-3-en-2-yl)oxy]-7H-furo[3,2-g]chromen-7-one (1), dahuribiethrin E (2) and dahuribiethrin B (3). Conclusion Compound 1 is a new compound, namely dahuribiscoumarin A. Compounds 2 and 3 are isolated from A. dahurica var. formosana for the first time. Compound 2 exhibits acetylcholinesterase inhibitory activity with a median inhibition concentration (IC₅₀) value of (71.37 ± 1.26) μmol/L.

Angelica dahurica (Fisch. ex Hoffm.) Benth. et Hook. f. var. formosana (Boiss.) Shan et Yuan  /  furanocoumarin  /  coumarin dimer  /  LC-MS  /  acetylcholinesterase inhibitory activity  /  dahuribiscoumarin A  /  dahuribiethrin E