Cytotoxic abietane-derivative diterpenoids of Salvia lachnostachys

A bioassay-guided fractionation of Salvia lachnostachys Benth leaf extract led to the isolation of three known diterpenes, namely fruticuline A (1), fruticuline B (2) and 7,20-dihydrofruticuline A (3), together with two new compounds, 4 and 5. The structures were mainly elucidated by 1D and 2D NMR spectroscopy and HRESIMS. The cytotoxic activity of the crude ethanol extract, the semi-purified fractions (A-E) and compounds 1, 2 and 4 were evaluated against seven human cancer cell lines and the normal cell line HaCat. The ethanol extract showed activity against all tested cell lines (GI(50) 25.0-44.0 mu g/mL). Among the fractions, the greatest activity was exhibited by fraction A (eluted with hexane), which inhibited the growth of all tested cell lines with GI(50) of 3.9-19.5 mu g/mL. Compounds 1 and 4 were the most active, inhibiting the growth of U251, MCF-7, NCI-ADR/RES, 786.0, NCI-H460, PC-3, OVCAR-03 and HaCat cell lines with GI(50) < 10 mu M. Compound 2 showed moderate activity against MCF-7, NCI-H460, OVCAR-03, K562 and HaCat, with GI(50) varying 19.9-29.3 mu M. (C) 2016 Phytochemical Society of Europe. Published by Elsevier Ltd. All rights reserved.