The racemic trimeric quinone and polycyclic quinones isolated from the aerial parts of Morinda umbellata L
Four undescribed racemic quinones, umbellatas Q-T, were isolated from the aerial parts of Morinda umbellata L. All enantiomers were separated on a chiral HPLC column, and their structures were elucidated by UV spectroscopy, IR spectroscopy, HR-ESI-MS, 1D and 2D NMR spectroscopy, DP4+ NMR calculations, ECD spectroscopy, and X-ray diffraction. Three of the racemes are polycyclic anthraquinones, and one is a rare racemic trimer of naphthoquinone-bisnaphthohydroquinones. (+)-Umbellata S exhibited potent cytotoxicity (IC