Anthraquinone-benzisochromanquinone dimers from the roots of Berchemia floribunda.

Four novel anthraquinone-benzisochromanquinone dimers, named floribundiquinones A, B, C, and D (1-4), along with six known anthraquinones, 10-(chrysophanol-7'-yl)-10-hydroxychrysophanol-9-anthrane (5), physcion (6), chrysophanol (7), 1,5,8-trihydroxy-3-methyl-anthraquinone (8), aloe-emodin (9), and xanthorin (10), were isolated from the roots of Berchemia floribunda. Their structures including the absolute axial stereochemistry were elucidated on the basis of spectroscopic methods. Floribundiquinones represent a novel carbon skeleton with an anthraquinone-benzisochromanquinone unit. Hepatoprotective activities were evaluated against D-galactosamine-induced toxicity in WB-F344 rat hepatic epithelial stem-like cells.