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.