Cytotoxic clerodane diterpenoids from the roots of Mast.

A study of diterpenoids as active ingredients against cancer from the active roots extract of Mast. (IC = 1.57 μg mL) led to the isolation of six new clerodane diterpenoids, named as barterins A-F (1-6) alongside seven known compounds, caseamembrin A, caseamembrin E, casearlucin A, graveospene G, -feruloyltyramine, -feruloytyramine and sitosterol-3--β--(6--palmitoyl)-glucopyranoside. Their structures were elucidated based on NMR spectroscopic data and mass spectrometry. The absolute configurations of 1-6 were established by the time-dependent density functional theory (TDDFT), electronic circular dichroism (ECD) calculations and experimental data analysis. The cytotoxic effects of compounds 1-6 were evaluated against a human cervix carcinoma cell line -3-1. Barterins A-D (1-4) showed cytotoxic effects against the -3-1 cell line with IC values ranging from 1.34-4.73 μM.