Coumarins from opopanax chironium. New dihydrofuranocoumarins and differential induction of apoptosis by imperatorin and heraclenin

Opopanax chironium is a rich source of furano- and dihydrofuranocoumarins, whose accumulation in all plant parts and especially the roots is presumably responsible for the poisonous properties of the species. The presence of two distinct chemotypes was evidenced, with the one from Sicily affording the new dihydrofuranocoumarins 5d and 5e, while extracts from the Sardinian chemotype showed powerful apoptotic activity, which was traced to the prenylated furanocoumarins heraclenin (2a) and imperatorin (2b). Despite a close structural similarity, compounds 2a and 2b induced apoptosis in Jurkat leukemia cells in mechanistically different ways.