Kibdelones are natural aromatic polyketides first isolated from an actinomycete, Kibdelosporangium. They exhibit potent and selective cytotoxicity against a panel of human tumor cell lines. Kibdelones also display significant antibacterial and nematocidal activity. Kibdelone B is a member of this group that undergoes facile equilibration to kibdelones A-C under mild conditions. Its mode of action and pharmacology have not been studied.