The unprecedented iridal lactone and adducts of spiroiridal and isoflavonoid from Belamcanda chinensis

Abstract

Five novel iridal-type triterpenoid derivatives, including three unprecedented adducts of spiroiridal and isoflavonoid, named belamcandanins A-C (1-3), one unprecedented iridal lactone, named belamcanolide A (4), and one new and rare iridal epoxide, named belamcanoxide A (5), have been isolated from the rhizomes of Belamcanda chinensis, along with five known compounds. Their structures were elucidated on the basis of extensive spectroscopic analysis. Compounds 1-3 represent the first meroterpenoids composed of an isoflavonoid linked to a spiroiridal-triterpenoid. To the best of our knowledge, compound 4 is the first example of 5/6-fused bicyclic iridal lactone. Compounds 1-8 were evaluated for their in vitro cytotoxicity against five tumor cell lines. Among them, compounds 5-8 showed moderate cytotoxic activities against five cancer cell lines with IC50 values from 3.26 to 8.63 μM.