(+)-/(−)-Angelignanine, a pair of neolignan enantiomers with an unprecedented carbon skeleton from an aqueous extract of the Angelica sinensis root head

A pair of 2,7′-cyclo-8,9′-neolignan enantiomers with an unprecedented carbon skeleton and hypnotic effect were isolated and structurally characterized from an aqueous extract of the Angelica sinensis root heads (guitou). Biogenetically, the carbon skeleton is postulated from coupling between ferulic acid and coniferyl alcohol. [Display omitted] A pair of neolignan enantiomers with an unprecedented carbon skeleton, (+)-/(−)-angelignanine [(+)-/(−)-1], was isolated as minor components of an aqueous extract of the Angelica sinensis root heads (guitou). Their structures were determined by spectroscopic data analysis and the absolute configurations were assigned by the circular dichroism (CD) exciton chirality method as well as electronic CD quantum calculations. The enantiomers represent the first 2,7′-cyclo-8,9′-neolignans, of which biosynthetic pathways originating from precursors ferulic acid and coniferyl alcohol is proposed. In an in vivo test, both the enantiomers showed significant hypnotic effects at a dose of 10 mg/kg (i.g.).