Abstract
Mycosporine-like amino acids (MAAs) are the natural ultraviolet (UV)-absorbing compounds from micro- and macro-algae. The MAAs in algae change with the environmental conditions and seasons. We previously determined an efficient extraction method of MAAs from red alga dulse in Usujiri (Hokkaido, Japan) and revealed monthly variation of MAA in 2019. Dulse samples in 2019 for MAA preparation were suitable from late February to April. In this study, to confirm the suitable timings to extract MAAs from Usujiri dulse, we also investigated the monthly (from January to May) variation of MAA content in 2020. There were the most MAAs in the sample on 18 March (6.696 µmol g−1 dry weight) among the samples from January to May 2020. From two years of investigation, we deduce that samples of Usujiri dulse from late February to early April were suitable for MAA preparation. The UV stability of the two major purified MAAs in Usujiri dulse—palythine and porphyra-334—was tested. The two MAAs and 2-hydroxy-4-methoxybenzophenone were stable for up to 12 h under a 312 nm lamp at 200 µW cm−2, but 2-ethylhexyl-4-methoxycinnamate formed a cis/trans-mixture in a short time. The data in this study show the suitable sampling period for Usujiri dulse and the possible application for UV protection from food and cosmetics.
Highlights
Sunlight is essential for photosynthesis in plants, it contains harmful ultraviolet (UV) for organisms
We determined the quantity of each Mycosporine-like amino acids (MAAs) by High Performance Liquid Chromatography (HPLC) (Table 1)
The quantities of MAAs in 1 g of dry-weight dulse increased from January to March and decreased in April and May 2020
Summary
Sunlight is essential for photosynthesis in plants, it contains harmful ultraviolet (UV) for organisms. Some agents may cause oxygen radical production, cancer, and photoallergic skin inflammation [8,9,10], while some cause coral bleaching even in low concentrations [11]. Alternative compounds such as polyphenols and flavonoids from natural products have been used as UV protection agents [12,13,14], and natural UV protection products with a high molar extinction coefficient are in demand. We investigated the monthly variation of MAAs in Usujiri, Hokkaido, from January to May 2020 to clarify the suitable dulse sampling periods. To demonstrate the suitable application of MAAs as UV protection materials, we evaluated the UV stability of two purified MAAs, palythine and porphyra-334, in strong UV conditions
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