Preincubation format for a sensitive immunochromatographic assay for monocrotaline, a toxic pyrrolizidine alkaloid

Introduction: Monocrotaline (MCT), which is classified as a 1,2-dehydropyrrolizidine alkaloid (DHPA), is a toxic compound that is mainly produced by Crotalaria spp. MCT contamination in cereals and herbs leads to hepatitis, gastroenteritis, pulmonary vasculitis and hypertension, and different types of cancer. The current analytical methods for MCT are complicated and expensive using liquid chromatography equipped with mass spectrometry detection. Objective: The aim of this study was to develop a simple and sensitive preincubation format for an immunochromatographic assay (PI-ICA) for MCT detection. Methodology: We conducted the PI-ICA via incubation of an MCT-containing sample with an anti-MCT monoclonal antibody conjugated with colloidal gold before strip dipping. We compared the PI-ICA detection sensitivity with that of the conventional ICA (Conv-ICA) format. Results: The PI-ICA was sensitive with a limit of detection (LOD) of 0.61 ng/mL, which is a 16-fold improvement over the Conv-ICA format. These results indicated that the PI-ICA method exhibits high binding specificity for MCT and low cross-reactivity towards retronecine, retrorsine, senecionine and heliotrine. Sample solutions from plants containing MCT and related DHPAs produced positive results via PI-ICA analysis. Conclusions: The proposed PI-ICA system provides a highly sensitive method compared to Conv-ICA. In addition, the developed PI-ICA method is simple and highly effective for detecting MCT contamination.