Actinoplanones C, D, E, F and G, new cytotoxic polycyclic xanthones from Actinoplanes sp.

Our previous finding of strong cytotoxic polycyclic xanthones, actinoplanones A (1) and B (2), in the culture broth of Actinoplanes sp. R-304 stimulated us to isolate further five new cytotoxic polycyclic xanthones which were named actinoplanones C (3), D (4), E (5), F (6) and G (7) from the broth. Actinoplanones C (3) and G (7) showed very strong cytotoxicity against HeLa cells at less than 0.00004 microgram/ml dosage (IC50). The structures of 3-7 were varieties of 1 for the N-2 and C-4 substituents. All or several actinoplanones showed strong antimicrobial activities against bacteria and the rice blast fungus. Actinoplanone A (1) was tested for cytotoxicity against various tumor cells and for inhibitory effect on HeLa cell macromolecular synthesis, and 1 exhibited strong cytotoxicity against the cells and inhibitory action on DNA synthesis.