Ionones and lignans from the fresh roots of Rehmannia glutinosa.

Nine undescribed compounds, together with 21 known components, were isolated from the fresh roots of Rehmannia glutinosa. Their structures were elucidated based on spectroscopic data analysis, and the absolute configurations of undescribed compounds were determined by comparison of their calculated and experimental electronic circular dichroic (ECD) spectra and interpretation of their optical rotation data. The α-glucosidase inhibitory effects of the isolated compounds were investigated and all of them exhibited slightly inhibitory activities.