Metabolomics of Lonicera caerulea fruit during ripening and its relationship with color and antioxidant activity

• Metabolite profiling of L. caerulea fruits were studied at seven ripening stages.
• Fructose and glucose affecting fruit taste were increased during ripening.
• Malic and citric acids affecting development were decreased during ripening.
• The level of anthocyanins related of fruit color was increased after stage four.
• L. caerulea fruits at stage six possessed high antioxidant activity, TFC, and TPC.

We performed mass spectrometry-based metabolites profiling in Lonicera caerulea fruits according to seven ripening stages. During ripening, fruit color significantly changed from green to red, with sugars, organic acids, phenolic acids, anthocyanins, and flavonoids significantly altered. In particular, the contents of cyanidin-3-glucoside, peonidin-glucoside, peonidin-3-rutinoside and cyanidin-3-rutinoside, which are closely associated with color, were elevated from stages four to seven. The changes of antioxidant activity during ripening were similar to those of total phenolic and flavonoid contents. L. caerulea fruits at stage six (pale-purple) had higher antioxidant activity and total phenolic and flavonoid contents with higher cyanidin-3,5-diglucoside contents than those at stage seven (fully purple). From this study, we revealed the changes in the contents of primary and secondary metabolites with antioxidant properties during ripening, and these results could be helpful to determine the optimal harvest stage of L. caerulea fruit.