Abietane-Type Diterpenoids From Salvia kiangsiensis: Isolation, Semisynthesis, and Cytotoxicity of Their Oxime Ester Derivatives.

Systematic phytochemical investigation of whole plant of Salvia kiangsiensis led to the isolation of three undescribed abietane diterpenoids (1-3) and 24 known analogues (4-27), while compounds 2 and 3 belong to the 20-norabietane skeleton. Four derivatives (24a-24d) were also obtained through structural optimization. Their structures were elucidated by a combination of spectroscopic data, chemical methods, and x-ray diffraction. Cytotoxicity screening indicated that 24c, an oxime ester derivative of 24, exerted the most potent activity against the non-small-cell lung cancer (NSCLC) cell line H1975, with higher potency than the positive control cisplatin. Mechanism study revealed that 24c could promote cell-cycle arrest in S phase and induce cell apoptosis.