Mycosporine–like amino acids (MAAs) are a class of UV-absorbing compounds synthesized by a variety of marine and freshwater algae and cyanobacteria with absorption maxima between 310 - 360 nm. To date, ~25 different MAAs have been characterized with several new compounds identified each year. A major difficulty in the analysis of MAAs is the lack of commercial standards. Thus far, MAAs have been identified by their retention time and UV absorption after separation via high performance liquid chromatography (HPLC). Complementing the HPLC method with the use of mass spectrometry (LC-MS) offers greater sensitivity and reduces the hindrance standard unavailability presents by providing detailed molecular information (molecular weight and fragmentation patterns). The molecular weight information adds one more level to our ability to characterize MAAs and any new UV-absorbing compounds discovered. The fragmentation patterns obtained via LC-MS-MS also contributes diagnostic information for structure elucidation and identification. LC/MS analysis has been used to examine UV-absorbing compounds in methanolic extracts from Phaeocystis antarctica. When samples were analyzed using isocratic HPLC elution, several UV-absorbing peaks were eluted. However, molecular weight and fragmentation patterns of some UV-absorbing compounds were not commiserate with those expected for MAAs. Additionally, palythenic acid was detected rather than mycosporine-glycine:valine as had been previously reported for this organism. Gradient elution provided further separation into MAA and ‘unknown’ groupings. The unknown UV-absorbing component has longer retention times and different mass spectral characteristics with wavelength maxima between 315-325 nm. This study benefited immensely by the addition of MS techniques, as many of the compounds would have remained either misidentified or entirely unidentified. The increased analytical capability afforded by LC-MS allows us to further investigate the structural diversity and biochemistry of MAAs aiding our study of the role MAAs play as sunscreen agents.

Key words: LC-MS, MAAs, mass spectra, mycosporine-like amino acids, Phaeocystis antarctica, UV-absorbing compounds