Metabolic Profiling on Alternaria Toxins and Components of Xinjiang Jujubes Incubated with Pathogenic Alternaria alternata and Alternaria tenuissima via Orbitrap High-Resolution Mass Spectrometry

Xinjiang jujubes (Zizyphus rhamnaceae) are important agro-economical foods with the highest planting area and yields in China; however, black spot disease and contaminated Alternaria toxins have unfortunately caused a decline or loss of jujube nutritional quality in recent years. In this study, we used ultrahigh-performance liquid chromatography coupled to Orbitrap high-resolution mass spectrometry to profile both Alternaria toxins and components in three representative Xinjiang jujubes, Hami Huang, Hetian Jun, and Ruoqiang Hui. Before liquid chromatography–mass spectrometry analysis, jujubes were inoculated with two main pathogens of Alternaria alternata (Aa) and Alternaria tenuissima (At). Different combinations of jujube varieties with pathogenic isolates display different metabolic profiles, as expected. Moreover, four major Alternaria toxins, alternariol, alternariol monomethyl ether, altenuene, and tenuazonic acid, were detected in all samples. The inoculation of both pathogens significantly decreased the levels of nutrients and metabolites in jujube, including four saponins, three organic acids, and three alkaloids, whereas it increased the level of several glycerol phosphates. The flavonoid profiles are diverse. Lastly, inoculation of Aa changes more metabolites in jujubes than At. Our data provide insights to better understand the detrimental contamination of Alternaria pathogens in Xinjiang jujubes and improve food safety of jujubes.