4.4.3. Metabolite Identification

Based on the public database of metabolite information and the MVDB V2.0 database of Wuhan Metware Biotechnology Co., Ltd. (Wuhan, China), qualitative analysis of the primary and secondary mass spectrometry data was performed by referencing the existing mass spectrometry databases such as MassBank, KNAPSAcK, HMDB and METLIN; thus, the structural analysis of metabolites was determined. Regarding the quantitative analysis of the metabolites, MRM was used, and PCA and OPLS-DA were then carried out to identify differential metabolites. A VIP ≥ 1 and a fold change ≥ 2 or ≤0.5 were set for metabolites with significant difference.

#### *4.5. Illumina Sequencing*
