Isolation and structural elucidation of novel antimicrobial compounds from maggots of Chrysomyis megacephala Fabricius

The excretions/secretions from the maggot of Chrysomyis megacephala Fabricius are traditionally used to treat serious infections in China. In this study, bioassay-guided fractionation led to the isolation of three novel antibacterial compounds (1–3), including important fluorinated compounds (3 and 5), together with other nine known compounds from 70% methanol extract of C. megacephala. The structures of the new compounds were elucidated by NMR spectroscopic analysis and high-resolution mass spectroscopy. The antibacterial activities of the isolated compounds were evaluated using agar disc diffusion method. New compounds 1 and 2 exhibited moderate activity against Bacillus subtilis with a minimum inhibitory concentration (MIC) of 250 μg mL^− 1. The most active compounds 3 and 5 displayed a broad spectrum of antimicrobial activity with an MIC of 125 μg mL^− 1 against G⁺ and G⁻  bacteria. The structure of the above-mentioned novel compounds and their antimicrobial activities are herein reported for the first time from the natural product of insects.