Isolation and structural elucidation of novel antimicrobial compounds from maggots of <i>Chrysomyis megacephala</i> Fabricius

<div><p>The excretions/secretions from the maggot of <i>Chrysomyis megacephala</i> 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 (<b>1</b>–<b>3</b>), including important fluorinated compounds (<b>3</b> and <b>5</b>), together with other nine known compounds from 70% methanol extract of <i>C. megacephala</i>. 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 <b>1</b> and <b>2</b> exhibited moderate activity against <i>Bacillus subtilis</i> with a minimum inhibitory concentration (MIC) of 250 μg mL^− 1. The most active compounds <b>3</b> and <b>5</b> 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.</p></div

Simultaneous determination of chloramphenicol, florfenicol and florfenicol amine in ham sausage with a hybrid chemiluminescent immunoassay

<div><p>A novel chemiluminescent immunoassay utilising two types of primary antibodies (murine monoclonal antibody and rabbit polyclonal antibody) and two types of horseradish peroxidase–labelled secondary antibodies was established for simultaneously detecting multiple amphenicol residues in ham sausage. After combining the extract procedure of the target amphenicol into one simplified method, this hybrid chemiluminescent immunoassay could screen chloramphenicol (CAP), florfenicol (FF) and its metabolite florfenicol amine (FFA) at the same time by adding the corresponding secondary antibody. Ham sausage samples were analysed by using this hybrid immunoassay, with LODs of CAP being 0.01 μg kg⁻¹, of FF being 2.8 μg kg⁻¹ and of FFA being 3.0 μg kg⁻¹. The applicability of the proposed method has been validated by determining CAP, FF and FFA in ham sausage samples with satisfactory results. Good recoveries and high correlation with traditional enzyme-linked immunosorbent assay and LC-MS/MS results illustrated that the developed hybrid chemiluminescent immunoassay could screen high-throughput ultra-trace amphenicol residues effectively at one time.</p></div