Cytotoxicity and NMR spectral assignments of ergolide and bigelovin.

Two potent cytotoxic sesquiterpene lactones, ergolide (1) and bigelovin (2) were isolated from Inula hupehensis and I. helianthus-aquatica and their structures and NMR data were assigned unambiguously by using a combination of one- and two-dimensional NMR techniques and computer modeling calculations.