Furanocoumarins from the Root of Angelica dahurica

Five furanocoumarins including a new one were isolated from the root of Angelica dahurica by repeated silica gel column chromatography. Their chemical structures were determined to be isoimperatorin (1), oxypeucedanin hydrate-3"-butyl ether (2), imperatorin (3), knidilin (4), and oxypeucedanin hydrate (5). This represents the first study in which the compound 2 has been isolated and identified, The long-range coupling ($^{5}J$) in the $^1H$-NMR spectrum observed in the linear furanocoumarin skeleton was also investigated in detail.