Manual annotation combined with untargeted metabolomics for chemical characterization and discrimination of two major crataegus species based on liquid chromatography quadrupole time-of-flight mass spectrometry.

Hawthorn is a popular functional food. In China, Crataegus pinnatifida Bunge. and C. pinnatifida Bge. var. major N. E. Brown are two major species that are used for the preparation of hawthorn products. Accordingly, it is crucial to explore the chemical differences between these two species for the market standardization of hawthorn products. In this study, we integrated manual annotation with untargeted metabolomics based on ultra-high performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry for compound characterization and discrimination of the two hawthorn species. We characterized 78 compounds in the two species including saccharides, glycosides, organic acids, phenols, flavonoids and triterpenoids. Moreover, 47 differential compounds and 17 false positive ions were recognized and fully reviewed. The 47 identified compounds were then used to build a partial least squares discriminant analysis model that successfully discriminated C. pinnatifida Bge. and C. pinnatifida Bge. var. major N.E.Br.