Structurally Diverse Diterpenoids from the Roots of Salvia deserta Based on Nine Different Skeletal Types

Twenty-four diterpenoids (1-24), classified into nine diverse carbon skeletal types, 8-nor-7(8→14),9(8→7)-di-abeo-abietane (1, 2, and 13), 7(8→14),9(8→7)-di-abeo-abietane (3 and 4), 6-nor-6,7-seco-abietane (5 and 6), 6,7-seco-abietane (7 and 11), 9,10-seco-abietane (8), abietane (9, 10, and 14-21), 11(9→8),20(10→11)-di-abeo-abietane (12), 15(13→12)-abeo-abietane (22 and 23), and 4,5-seco-20(10→5)-abeo-abietane (24), respectively, were isolated from the roots of Salvia deserta. The structures of 10 new diterpenoids, named salviadesertins A-J (1-10), were elucidated by spectroscopic data interpretation, quantum-chemical calculations including calculated ¹³C NMR-DP4+ analysis and electronic circular dichroism as well as X-ray crystallography analysis. The absolute configurations of compounds 1-3, 7, 14, and 22 were defined by single-crystal X-ray diffraction analysis. All the isolated diterpenoids 1-24 were evaluated for their cytotoxicity against five cancer cell lines, and 6-hydroxysalvinolone (14) showed micromolar potencies against MCF-7, A-549, SMMC-7721, and HL-60 cells, whereas the other diterpenoids were inactive (half-maximal inhibitory concentration greater than 10.0 μM).