Goondolinones A and B: Terpenyl-quinolin-4(1H)-ones from an Australian Volcanic Crater Soil-Derived Actinomadura sp., with Selective Activity against Dirofilaria immitis (Heartworm).

A chemical investigation of the Australian pasture soil-derived Actinomadura sp. S4S-00245B09, supported by chemical, bioactivity and cultivation profiling, yielded a new class of terpenyl-quinolin-4(1H)-ones, goondolinones A and B (1 and 2), featuring an unprecedented fused seven-membered ether. Structures were assigned to 1 and 2 on the basis of detailed spectroscopic analysis, including X-ray analysis of 1, and biosynthetic considerations. Goondolinone A (1) lacks antibacterial or antifungal properties, is noncytotoxic to two human carcinoma cell lines, but exhibits selective inhibition of the motility of heartworm Dirofilaria immitis microfilaria (EC50 5.1 μM) and L4 larvae (EC50 21.4 μM). As a new anthelmintic scaffold, future understanding of the structure activity relationship and mechanism of action of 1 could inform the discovery of new treatments for heartworm and other filarial diseases, capable of safeguarding the health and welfare of companion animals.