Iridal-type triterpenoids with ichthyotoxic activity from belamcanda chinensis

Ichthyotoxic activity-guided fractionation of the hexane and ether extracts of Belamcanda chinensis (Iridaceae) has resulted in the isolation of eleven iridal-type triterpenoids including six new compounds, 3-O-tetradecanoyl-16-O-acetylisoiridogermanal (4), 3-O-decanoyl-16-O-acetylisoiridogermanal (5), belachinal (7), anhydrobelachinal (9), epianhydrobelachinal (10), and isoanhydrobelachinal (11). Structures of the new iridals were determined by spectral and chemical methods. The absolute configuration of isoiridogermanal (1) at C-16 was determined to be R by the modified Mosher's method. Of these compounds, 16-O-acetylisoiridogermanal (3), 7, and spiroiridal (12) exhibited potent ichthyotoxic activity against killie-fish (Oryzias latipes).