Rapid determination of nucleosides, nucleobases and free amino acids in brown seaweeds using ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry

In this study the contents of nucleosides, nucleobases and free amino acids (FAAs) in common brown seaweeds Saccharina japonica, Sargassum pallidum, S. fusiforme, S. thunbergii and S. muticum from major production areas in China were determined by ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-TQ-MS). The total contents of nucleosides and nucleobases varied from 48.46 to 4,105.00 mu g g(-1). Among the five seaweeds, levels of nucleosides and nucleobases in S. japonica were higher than the other species. The contents of ribonucleosides in these brown seaweeds were higher than those of deoxynucleosides. Uridine was the predominant constituent in all samples while 2'-deoxycytidine was the least in most samples. FAAs contents ranged from 0.14 to 22.76 mg g(-1). Among the five seaweeds, levels of FAAs in S. muticum were higher than the other species. Essential amino acids accounted for 3.26-51.49 % of total FAAs contents in different species. Glutamic acid was the major constituent in most samples. Four non-protein amino acids, gamma-aminobutyric acid, taurine, hydroxyproline and citrulline, were found in the seaweed samples. Furthermore, principal component analysis (PCA) showed that chemical profiles of nucleosides, nucleobases and FAAs in S. pallidum and S. fusiforme were different from S. muticum, S. thunbergii and S. japonica. Common brown seaweeds could be promising natural sources for future industrial research into nucleosides, nucleobases and FAAs with potential benefits for human health.