Analysis of Metabolites in Rhodiola crenulata Seedlings under Different Light Intensities

To systematically analyze the changes in the metabolome of seedlings cultivated under different light intensities, root and rhizome samples of Rhodiola crenulata were collected from the H and L treatment groups, with four replicates per treatment. The plant samples were first freeze-dried and ground into powder. A 50 mg aliquot of the freeze-dried powder was dissolved in methanol solution (70%). The samples were then centrifuged and filtered for subsequent UPLC-MS/MS analysis. A 4 μL volume of the above extract was injected into the UPLC-ESI-MS/MS system. Differentially expressed metabolites (DEMs) between the different groups were identified based on variable importance in projection (VIP) and fold change (FC) values using ESI-triple quadrupole linear ion trap (QTRAP)-MS. VIP values were obtained from the OPLS-DA model. Metabolites with VIP values ≥ 1 and FC values ≥ 2 or ≤ 0.5 were identified as differentially expressed metabolites. Functional annotation and pathway analysis of the differentially expressed metabolites were performed based on the KEGG database (http://www.kegg.jp/kegg/compound/).