Metabolic Profiles of Pomegranate Juices during Fruit Development and the Redirection of Flavonoid Metabolism

The pomegranate (Punica granatum L.) fruit is favorable for its nutrient-rich benefits to human health. However, the global metabolic profiles of pomegranate juice and the metabolic mechanisms of its essential metabolites are poorly understood. In this study, we conducted a widely targeted metabolome, integrated with the transcriptome of juices (edible parts) of pomegranate fruits at 50, 95, and 140 days after flowering (DAF) to comprehensively investigate the metabolic profiles and potential metabolism of essential metabolites. Five hundred and nine metabolites, including 11 sugar and sugar alcohols, 17 common organic acids, 20 essential amino acids, and a variety of flavonoids, were detected in pomegranate juices. Among them, metabolites in the flavonoid biosynthesis pathway greatly changed during fruit development. Notably, the redirection of metabolite flux from catechin and its derivative synthesis to anthocyanin synthesis occurred at the later developmental stages. The increased expression of Pgr021399.1 encoding dihydroflavonol 4-reductase (DFR), Pgr017842.1 encoding anthocyanidin synthesis (ANS), Pgr015322.1 encoding anthocyanidin 3-O-glucosyltransferase (BZ1), Pgr000447.1 encoding UTG75C1, and the decreased expression of Pgr024128.1 encoding leucoanthocyanidin reductase (LAR) may trigger redirection. The results of this study provide a global view of the metabolic profiles of pomegranate juices and valuable information on the molecular mechanisms underlying the redirection of flavonoid metabolism. It also sheds light on the genetic regulation of flavonoid metabolism in pomegranate juices.