A new biflavonoid from Aristolochia contorta.

From the fruits of Aristolochia contorta Bge, beside the known aristolochic acids IVa and VII, aristolactam-N-β-D-glucopyanoside, aristoloctam la M-β-D-glucopyanoside, pinitol and daucosterol, a new biflavonoid was isolated. Its structure was determined as (′)-2"R,3"R-dihydro-3"-hydroxyamentoflavone (1) by means of spectral methods including 1D-, 2D-NMR and HR-ESIMS and the known compounds were identified on the basis of comparing their NMR data with those of the corresponding compounds in the literature.