Towards new ligands of nuclear receptors. Discovery of malaitasterol A, an unique bis-secosterol from marine sponge Theonella swinhoei

Malaitasterol A, an unprecedented bis-secosterol, was isolated from a Solomon collection of Theonella swinhoei. The structure was elucidated on the basis of a combination of comprehensive 1D and 2D NMR analysis, high-resolution mass spectrometry and DFT C-13 chemical shift calculations. The biological characterization of malaitasterol A provided evidence that this compound is a potent agonist of pregnane-X-receptor and its putative binding mode to PXR has been obtained through docking calculations.