A novel antimicrobial epoxide isolated from larval Galleria mellonella infected by the nematode symbiont, Photorhabdus luminescens (Enterobacteriaceae).

A novel antimicrobial epoxide, 2-isopropyl-5-(3-phenyl-oxiranyl)-benzene-1,3-diol (1), was identified from larval Galleria mellonella infected by a symbiotically associated bacterium-nematode complex (Photorhabdus luminescens C9-Heterorhabditis megidis 90). Its structure was determined with spectroscopic analysis and confirmed by chemical synthesis starting from a known antibiotic, 2-isopropyl-5-(2-phenylethenyl)-benzene-1,3-diol (2). Epoxide 1 was active against Bacillus subtilis, Escherichia coli, Streptococcus pyogenes, and a drug-resistant, clinical strain of Staphylococcus aureus (RN4220) with minimum inhibitory concentrations in the range of 6.25-12.5 microg/ml. Epoxide 1 was cytotoxic against human cancer cell lines, MCF-7 wt, H460, and Jurkat, with GI(50) of 2.14, 0.63, and 0.42 microM, respectively, but was less toxic on normal, mouse splenic lymphocytes with a GI(50) of 45.00 microM.