Untitled Analysis of Metabolites in <i>Rhodiola crenulata</i> Seedlings under Different Light IntensitiesItem

Leaf samples of R. crenulata from the H and L treatments were collected for metabolomic analysis, with four biological replicates per treatment. Plant samples were first freeze-dried and ground into powder. Subsequently, 50 mg of freeze-dried powder was extracted with 70% methanol. The extracts were centrifuged and filtered prior to UPLC–MS/MS analysis. A volume of 4 μL of the extract was injected into the UPLC–ESI–MS/MS system. Differentially expressed metabolites (DEMs) between treatments were identified using an electrospray ionization triple quadrupole linear ion trap mass spectrometer (ESI-QTRAP-MS/MS). Metabolites were screened based on variable importance in projection (VIP) values and fold change (FC). VIP values were obtained from the orthogonal partial least squares discriminant analysis (OPLS-DA) model. Metabolites with VIP ≥ 1 and FC ≥ 2 or ≤ 0.5 were defined as differential metabolites. Functional annotation and pathway enrichment analysis of DEMs were conducted based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) database (http://www.kegg.jp/kegg/compound/).