Two undescribed constituents from Salvia castanea Diels and evaluation of their cytotoxic activity

One previously undescribed abietane diterpene alkaloid containing an oxazole ring (1), one unreported abietane diterpene (2), and nine known abietane diterpenes (3-11) were isolated from the roots and rhizomes of Salvia castanea Diels. Their structures and absolute configurations were elucidated by a combination of HRESIMS, 1D and 2D NMR, and ECD. All compounds were evaluated for their cytotoxic activity against several human cancer cell lines (HepG2, A549, H460, MCF7, PC3, and Hela). The results showed that 1 exhibited a moderate cytotoxic effect on HepG2 cells (IC₅₀: 14.22 ± 1.05 μM) and was able to inhibit the cell growth of MCF7 and Hela cells by 35.08% and 47.26% respectively, at a concentration of 20 μM, while other compounds showed low cytotoxic activity.