Widely targeted metabolomics reveal the distribution of primary and secondary metabolites in pomegranate fruit.

The pomegranate fruit is valued for its nutritional and medicinal properties, and the composition and content of primary and secondary metabolites are the main factors impacting its nutritional and medicinal properties. However, a deep understanding of metabolites in different parts of fruit is still lacking. Here, the peel, aril, and seed of mature pomegranate fruits were analyzed separately to compare metabolic component differences using UPLC/MS-MS. A total of 858 metabolites belonging to 11 classes were identified, of which flavonoids, such as delphinidin-3-O-glucoside and cyanidin-3-O-glucoside; tannins, such as ellagic acid and punicalin; and terpenoids, such as corosolic acid and madasiatic acid, were upregulated in the peel. Lipids, such as punicic acid, methyl linolenate, and linoleic acid; alkaloids, such as indole and choline; nucleotides and derivatives mainly including 2-deoxyribose-1-phosphate and 9-(arabinosyl)-hypoxanthine, were upregulated in seeds. Phenolic acids, such as 1-O-galloyl-4,6-(S)-HHDP-β-D-glucose and 1,7-di-O-galloyl-D-sedoheptulose, and flavonoids, such as cyanidin-3-O-glucoside, cyanidin-3-O-(2″-O-xylosyl) galactoside, and delphinidin-3-O-glucoside, were upregulated in aril. The flavone and flavonol biosynthesis (ko00944) pathways were significantly enriched between the peel and seed, as were the anthocyanin biosynthesis (ko00944) pathways between the aril and seed and the flavonoid biosynthesis (ko00941) pathways between the peel and aril. Additionally, functional antioxidants, such as 10,16-dihydroxypalmitic acid, 3-O-methylellagic acid, and 3,3'-O-dimethylellagic acid, were first identified in pomegranate fruits. Our results revealed the composition and abundance of primary and secondary metabolites in pomegranate fruit, which can lay the foundation for further elucidation of its nutritional and medicinal properties.