A new rearranged abietane diterpene from Clerodendrum inerme with antioxidant and cytotoxic activities

Abstract

Eight compounds were isolated from the leaves of Clerodendrum inerme, including one new rearranged abietane diterpene, crolerodendrum B (1). Their structures were determined by means of spectroscopic methods including one-dimensional and two-dimensional nuclear magnetic resonance (1-D and 2-DNMR), high-resolution electrospray ionisation mass spectrometry (HR-ESI-MS) and circular dichroism (CD). The DPPH radical scavenging and cytotoxic activities of isolated compounds against MCF7 (breast), HCT116 (colon) and B16F10 (melanoma) cancer cell lines were evaluated. Compounds 1, 3 and 4 exhibited strong DPPH radical-scavenging effects (ED₅₀ values of 17.6 ± 2.1, 10.1 ± 0.8 and 11.3 ± 0.3 μM, respectively) and 4 showed strong cytotoxicity against the HCT116 cell line (IC₅₀ = 3.46 ± 0.01 μM).

Keywords:

• Clerodendrum inerme
• Verbenaceae
• abietane diterpene
• crolerodendrum B
• antioxidant
• cytotoxic

Acknowledgements

The authors are grateful to the Institute of Chemistry, VAST for measurement of the NMR spectra and Dr. Bui Huu Tai, Institute of Marine Biochemistry, VAST for measurement of the CD spectra.