Novel cytotoxic seco-abietane rearranged diterpenoids from Salvia prionitis

Six novel 4,5-seco-rearranged abietane diterpenoids, including one tetracyclic diterpenoid, prionoid A (1), two tricyclic diterpenoids, prionoids B (2) and C (3), and three dicyclic diterpenoids, prionoids D (4), E (5), and F (6), were isolated from the roots of Salvia prionitis Hance (Labiatae). Their structures were elucidated using spectroscopic analysis. The structure of 1 was further confirmed by a single-crystal X-ray diffraction determination. Moreover, it was found that 4 (IC50 = 0.41 microM) and 5 (IC50 = 0.72 microM) showed significant cytotoxic activity against P-388 and A-549 cell lines, respectively.