Cytotoxic activity of abietane diterpenoids from roots of Salvia sahendica by HPLC-based activity profiling

Screening of medicinal plants from Iranian flora against human cancer cell-lines have shown that an hexane extract from roots of Salvia sahendica Boiss. & Buhse, Lamiaceae, is active against human cervical cancer (HeLa) and colorectal adenocarcinoma (Caco-2) cell-lines at the test concentration of 100 μg/ml (100% inhibition). Cytotoxicity of the extract was localized with the aid of HPLC-time-based activity profiling adapted to the tetrazolium colorimetric bioassay. Four abietane-type diterpenoids in active time-windows were identified as cytotoxic compounds namely: sahandone (1), sahandol (2), 12-deoxy-salvipisone (3) and sahandinone (4). Compound 1 showed the highest toxicity against HeLa cells (IC50 = 5.6 ± 0.1 μg/ml), which was comparable with betulinic acid (IC50 = 4.3 ± 1.2 μg/ml), the positive control. Compound 2 was active against the HeLa cells (IC50 = 8.9 ± 0.7 μg/ml) but not the Caco-2 cell-line. Compounds 1, 3 and 4 exhibited moderate activity (IC50 = 22.9–41.4 μg/ml) against the Caco-2 cells. This study reveals that the HeLa cells are more sensitive to all tested compounds than the Caco-2 cells. In silico molecular docking study showed a rigid binding of the compounds to tyrosine kinase pp60src, and proved their cytotoxic activity.