Integrated GC–MS and UPLC-Q-Orbitrap MS untargeted metabolomics for the comprehensive identification of metabolites and characterization of metabolic pathways in key tissues of Cinnamomum cassia

<i>Cinnamomum cassia</i>, a commercially valuable aromatic medicinal plant, is widely used in the food, pharmaceutical and perfume industries. Here, we characterizd the metabolites and metabolic pathways in <i>C. cassia</i> bark, fruits and leaves using integrated GC-MS and UPLC-Q-Orbitrap MS techniques. A total of 71 volatile and 2882 non-volatile metabolites were identified, with terpenoids as the dominant class. Bark exhibited the highest volatile oil content (2.30%), which was dominated by <i>trans</i>-cinnamaldehyde (937 mg/g of oil). Tissue-specific biomarkers were screened from differential metabolites. Specifically, fruits accumulated higher levels of fatty acids, terpenoids and alkaloids relative to leaves, while bark was enriched in carbohydrates, phenylpropanoids, and terpenoids. Furthermore, a putative acetyl-CoA-centered inter-tissue metabolite exchange network was proposed, which might link photosynthate-derived acetyl-CoA from leaves to bark and fruits. This study advances our understanding of <i>C. cassia</i> metabolism and provides novel insights for its quality evaluation and comprehensive utilization of multi-tissue resources.