Helikaurolides A-D with a Diterpene-Sesquiterpene Skeleton from Supercritical Fluid Extracts of Helianthus annuus L. var. Arianna

Four novel compounds (1-4) with an unprecedented skeleton that combines a sesquiterpene lactone and a-kaurane diterpene acid were isolated from Helianthus annuus L. var. Arianna extract, which was obtained under supercritical conditions. The structures of 1 4 were elucidated by NMR and MS analyses. The biosynthetic routes involve sesquiterpene lactones and kauranic acid, both of which were previously isolated from this species.