Endiandrin A, a Potent Glucocorticoid Receptor Binder Isolated from the Australian Plant Endiandra anthropophagorum

Bioassay-guided fractionation of the DCM extract from the roots of Endiandra anthropophagorum resulted in the isolation of a new cyclobutane lignan, endiandrin A (1), together with the known natural products nectandrin B (2) and (−)-dihydroguaiaretic acid (3). The structure of 1 was determined by extensive 1D and 2D NMR and MS data analyses. Acetylation and methylation of 1 yielded di-O-acetylendiandrin A (4) and di-O-methylendiandrin A (5), respectively. All compounds were tested in a glucocorticoid receptor binding assay and displayed IC50 values ranging from 0.9 to 35 μM.