Neo-clerodane diterpenoids with cytotoxic activity from Salvia ozolotepecensis

Chemical investigation of the aerial parts of Salvia ozolotepecensis J.G. González & Fragoso led to the isolation of two undescribed neo-clerodane-type diterpenoids, ozolotepensin A (1) and ozolotepensin B (2), along with already known salvimicrophylline B (3), and the neoclerodane glucoside 4. Structures of 1 and 2 were elucidated by careful analysis of their 1D/2D NMR data, and the absolute configuration of 1 was established by single-crystal X-ray diffraction. Cytotoxic activity of the isolated compounds was evaluated against human cancer cell lines (MCF-7, HCT-116 and HeLa). Compound 2 exhibited cytotoxic activity (HeLa, IC₅₀ = 0.26 μM) comparable to vinblastine (HeLa, IC₅₀ = 0.13 μM). These findings contribute to the chemistry of members of the Salvia subgenus Calosphace.