Abstract: 【Objective】The objective of this study is to establish an efficient method to investigate the differences between different varieties of oranges, and to find their differential metabolites, which will serve the citrus metabolomics and provide reference for the identification of oranges and orange juice. 【Method】 8 orange cultivars from the same area were chosen to obtain the methanol extracts of their peels, and then based on ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QToF-MS), the LC-MS fingerprints of the 8 oranges were obtained with obvious differences. Combined with the software Progenesis QI, the differential metabolites were screened in positive and negative modes through principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) as well as loadings plots and VIP (variable importance for projection) values. Furthermore, the differential metabolites were identified based on retention times, accurate mass, MS/MS fragments, reference standards and public databases.【Result】Based on the established method, differential metabolites of the 8 orange cultivars were screened. 17 compounds had been identified and among them, and 6 compounds were confirmed by comparison with their commercial standards. 3-Hydroxy-5,7,3',4'-tetramethoxyflavone and luteolin-7-O-neohesperidoside were the characteristic metabolites of Xuecheng. Hesperidin was the marker compound of S26 Jincheng. Narirutin-4'-glucoside and Isosinensetin could act as the characteristic metabolites of 8045 Tiancheng. 【Conclusion】 The method was versatile and suitable for the analysis of sample differences caused by varieties, geographical origins and maturity.

Key words: ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry, orange, Progenesis QI, metabolites