Antibiotic and Antimalarial Quinones from Fungus-Growing Ant-Associated Pseudonocardia sp.

Three new members of the angucycline class of antibiotics, pseudonocardones A-C (1-3), along with the known antibiotics 6-deoxy-8-O-methylrabelomycin (4) and X-14881 E (5) have been isolated from the culture of a Pseudonocardia strain associated with the fungus-growing ant Apterostigma dentigerum. Compounds 4 and 5 showed antibiotic activity against Bacillus subtilis 3610 and liver-stage Plasmodium berghei, while 1-3 were inactive or only weakly active in a variety of biological assays. Compound 5 also showed moderate cytotoxicity against HepG2 cells.