Determination of the absolute configuration and evaluation of the in vitro antitumor activity of dilospirane B

The absolute configuration of dilospirane B (1), a diterpene featuring a novel carbon framework recently isolated from the brown alga Dilophus spiralis, was established on the basis of theoretical calculations of its electronic circular dichroism spectra applying the time-dependent density functional theory method. Metabolite 1, evaluated for its in vitro antitumor activity against six human cancer cell lines displaying various levels of sensitivity to pro-apoptotic stimuli, exhibited growth inhibitory activity with a mean IC50 value of 66 mu M. Quantitative videomicroscopy analyses indicated that 1 initially displays cytostatic effects which later become cytotoxic. (C) 2012 Published by Elsevier B.V. on behalf of Phytochemical Society of Europe.