Identification and fingerprint analysis of novel multi-isomeric Lycibarbarspermidines and Lycibarbarspermines from Lycium barbarum L. by liquid chromatography with high-resolution mass spectrometry (UHPLC-Orbitrap)

Abstract Goji berry (Lycium barbarum) is largely consumed in Asia as a supplement and functional food, being rapidly introduced worldwide. Its phytochemical constituents include polysaccharides, phenolics, flavonoids, lipids and carotenoids. The myriad of compounds also includes polyamines (spermidine), conjugated with caffeic and dihydrocaffeic acids, that are O-glycosylated. In the present investigation, an extensive chromatographic and spectrometric approach has been employed to characterize these molecules, allowing identification of novel isomers of glucosyl-caffeoylspermidine, including novel tetraglucosides. Besides of these novel structures, we described a novel class of glycosides present in L. barbarum, that contains the spermine as polyamine core, rather than spermidine. As in the caffeoylspermidines, in these novel caffeoylspermines, the glycosylation patterns yield several isomers, which makes their analysis a particularly challenging. The degrees of glycosylation, ranging from 1 to 4 glucose units, could not be explained the number of novel isomers, considering only monosaccharides attached to the caffeoyl moieties, as previously reported. Nevertheless, mass spectrometry and methylation analyses revealed that the glucosyl moieties can produce oligosaccharides chains, augmenting the number of isomers. Thus, considering the presence of novel glycan chains and novel polyamine core linked to caffeic and/or dihydrocaffeic acids, we found and characterized approximately one hundred different structures.