Application of untargeted tandem mass spectrometry with molecular networking for detection of enniatins and beauvericins from complex samples

Abstract

An untargeted LC-MS/MS-based molecular networking method was established for the automatic determination of variants of enniatin and beauvericin from both fungal cultures and naturally contaminated samples. Using this method, a large number of samples can be efficiently analyzed for the presence of enniatin- and beauvericin-related compounds. As proof of concept, 26 cultures, derived from 13 fungal strains in the genera of Fusarium, Beauveria, and Diaporthe, as well as 46 food samples were analyzed. Four enniatin- and three beauvericin-producing fungi were newly discovered. Among them, the production of beauvericin by Fusarium sp. 190-20-2 was further confirmed by the presence of a beauvericin biosynthesis gene cluster in its genomic sequence. Additionally, 17 enniatin congeners, including one new isomer of enniatin A, and three previously unreported bassianolide analogues were detected from an enniatin-producing fungus, Fusarium sp. 17-048, and a beauvericin-producing fungus, Beauveria sp. 186-069, respectively. The structures of the detected compounds were tentatively determined by a series of product ions of their sodium adducts. The new isomer of enniatin A was further confirmed by NMR spectra. A preliminary survey of food samples showed that enniatins were prevalent in the tested wheat flour and noodle samples, whereas beauvericin was only discovered in cornflour powder samples.