Analysis of Primary Metabolites in Three Plum Varieties Using Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry

The primary metabolites in Fengtang, Kongxin and Cuihong plum fruits were qualitatively and quantitatively analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The differential metabolites among varieties were identified by principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA), and the differential metabolic pathways were analyzed through KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis. The results showed that a total of 307 metabolites belonging to 12 categories were detected, including amino acids and derivatives, nucleotides and derivatives, organic acids, sugars, alcohols, and free fatty acids. There were 70 differential metabolites between Fengtang and Cuihong plum, among which, 43 (61.43%) were up-regulated and 27 (38.57%) were down-regulated. Five significantly differential metabolic pathways were recognized, including metabolic pathways, aminoacyl-tRNA biosynthesis, valine, leucine and isoleucine degradation, glucosinolate biosynthesis and lysine degradation. In total, 96 differential metabolites were found between Fengtang and Kongxin plum, of which, 84 (87.50%) were up-regulated and 12 (12.50%) were down-regulated, and only one significantly differential metabolic pathway was identified, namely tryptophan metabolism. A total of 75 differential metabolites were found between Kongxin and Cuihong plum, of which, 19 (25.33%) were up-regulated and 56 (74.67%) were down-regulated, and two significantly differential metabolic pathways were identified, including purine metabolism and glucosinolate biosynthesis.