Rapid Screening for Mycosporine-like Amino Acids (MAAs) of Irish Marine Cyanobacteria and Their Antioxidant Potential

The present study evaluated 53 Irish marine cyanobacteria intending to identify potential producers of mycosporine-like amino acids (MAAs) to meet the increasing demand for replacing chemical sunscreen with bio-sunscreen. The biodiscovery analysis using absorption spectra of methanolic extracts identified eight cyanobacteria as potential MAAs producers with a specific content of 0.114–0.511 A* mg DW⁻¹. Leptolyngbya tenuis SABC010201 was found to possess notably higher MAAs content. LC-MS analysis identified a total of eight different types of known MAAs (mycosporine-glutamicol, mycosporine-glutaminol-glucoside, mycosporine-serinol, mycosporine-taurine, palythine, palythine-threonine-sulphate, porphyra-334, and usujirene) in eight cyanobacteria, while four compounds were considered unknown UV-absorbing compounds with specific mass and absorption maximum. For example, two unknown compounds with, respectively, [M-H]^- values of 219.0557 and 289.0730 and lambda max of 314 and 326 nm, were detected in three cyanobacteria Leptolyngbya tenuis SABC010201, Phormidium angustissimum SABC020801, and Schizothrix sp. SABC022401. These two unknown compounds were named M-314 and M-326, respectively. Antioxidant activities of total MAAs of all cyanobacteria showed considerable amounts of DPPH, FRAP, and ORAC activities. Considering the specific MAAs content and antioxidant activities, Leptolyngbya africana SABC021601 was considered the best producer of MAAs.