Untargeted Metabolomics Reveals the Effect of Carbon Dots on Improving the Shelf Life of Postharvest Goji Berries (Lycium barbarum L.)

Lycium barbarum L. (goji berry) undergoes rapid quality deterioration after harvest owing to its high water activity and abundant reactive oxygen species (ROS). Carbon-dot-mediated photodynamic treatment (CD-PDT) has recently been shown to extend shelf life by modulating ROS-scavenging and defense enzymes, yet the global metabolic reprogramming that supports this protection remains unresolved. Here, we applied ultra-high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS)-based untargeted metabolomics to decode the metabolic footprint of CD-PDT in freshly harvested goji berries. Our results revealed a total of 17,603 differentially expressed metabolites between the treatment and control groups under both positive- and negative-ion modes. Principal component analysis indicated that CD-mediated PDT significantly altered the metabolic profile of fresh goji berries. The treatment activated the phenylpropanoid biosynthesis pathway, promoting the accumulation of compounds such as kaempferol-3-sophoroside, kaempferol-3-O-β-D-glucoside, and galactoside, thereby enhancing the antioxidant capacity of the fruit. Furthermore, CD-mediated PDT induced the tricarboxylic acid cycle, providing sufficient energy to support the phenylpropanoid biosynthesis pathway. In conclusion, these findings provide the systems-level evidence that CD-PDT orchestrates a coordinated activation of primary and secondary metabolism in postharvest goji berries, establishing a mechanistic framework for preservation of horticultural products.