Cytotoxic clerodane diterpenoids from the roots of Casearia barteri Mast.

ABSTRACT

A study of diterpenoids as active ingredients against cancer from the active roots extract of Casearia barteri Mast. (IC50 = 1.57 µg mL-1) 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, N-trans-feruloyltyramine, N-cis-feruloytyramine and sitosterol-3-O-ß-D-(6-O-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 KB-3-1. Barterins A-D (1-4) showed cytotoxic effects against the KB-3-1 cell line with IC50 values ranging from 1.34-4.73 µM.