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-β-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.