Mycosporine-like amino acids (MAAs) are the ultraviolet (UV)-absorbable compounds, which are naturally produced by cyanobacteria and algae. Not only these algae but also marine organisms utilize MAAs to protect their DNA from UV-induced damage. On the other hand, the content of MAAs in algae was changed by the environmental condition and season. In addition to the UV-protected function, the antioxidant capacity of MAAs can apply to the cosmetic sunscreen materials and anti-cancer for human health. In this study, we developed the efficient extraction method of MAAs from red alga dulse in Usujiri (Hokkaido, Japan) and investigated the monthly variation. We also evaluated the antioxidant capacity. We employed the successive extraction method of water and then methanol extraction. Spectrophotometric and HPLC analyses revealed that the yield of MAAs by 6 h water extraction was the highest among the tested conditions, and the content of MAAs in the sample of February was the most (6.930 µmol g-1 dry weight) among the sample from January to May in 2019. Antioxidant capacity of MAAs such as crude MAAs, the purified palythine and porphyra-334 were determined by 2,2'-azinobis(3-ethylbenzothiazoline 6-sulfonic acid) (ABTS) radical scavenging and ferrous reducing power assays in various pH conditions, showing that the highest scavenging activity and reducing power were found at alkaline condition (pH 8.0).
Keywords: antioxidant capacity; dulse; monthly variation; mycosporine-like amino acids; red alga.