Isoprenylated flavonoids from the roots and rhizomes of Sophora tonkinensis

Two new flavanones, tonkinochromanes A (1) and B (2), and a new chalcone. tonkinochromane C (3), were isolated from the roots and rhizomes of Sophora tonkinensis. Their structures were elucidated by spectroscopic methods including 2D-NMR and MS experiments. Of the three isoprenyl substituents in these compounds on rings A and B, one to two were found to be ring-fused in the form of either dihydro- or regular 2,2-dimethyl-2H-pyran moieties.