Chemical characterization of dicaffeoyl polyamine derivatives to understand specific secondary metabolites in goji berry

Goji berries are among the most valuable edible and medicinal crops worldwide due to their richness in healthy compounds. Dicaffeoyl polyamine derivatives (DCPAds) contain a considerable number of isomers and are prominent specialized metabolites in goji berries. Very little has been achieved thus far in the evaluation of these compounds because of the lack of standards. The characterization and natural variation of DCPAds in goji berry remain unclear. The present study focused on the comprehensive characterization and quantitative analysis of DCPAds in goji berries using liquid chromatography-mass spectrometry. A strategy was developed to determine the fragmentation patterns of authentic standards. Three diagnostic ions were used as characteristic markers to quickly identify these compounds in goji berries. Furthermore, the natural variation and differential spatiotemporal accumulation patterns of seven DCPAds in 94 goji berry batches were revealed. In addition, principal component analysis of metabolomics data grouped the wild and cultivated samples, while green samples and those at other developmental stages could also be discriminated. These results improve our understanding of DCPAds in goji berries, which can provide essential data for chemical insight into further phytochemical studies, metabolite identification, and quality control of goji berries.