Preparation of antioxidants from Red Algae, a low-use resource
Rangkaan topik
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In the previous course "Development of UV-protectants from Red Algae, a Low-Use Resource," it was introduced that red algae, which are constantly exposed to UV light, contain mycosporin-like amino acids (MAAs) as UV-protectants. This compound is highly stable, but is known to be decomposed when heated to high temperatures such as 100°C. Now, it is known that MAAs are decomposed when heated to high temperatures such as 100°C. Now, what kind of compounds do MAAs become when decomposed?
In this study, we prepared MAAs from the low-utilized resource red algal dulse and investigated what kind of compounds they become upon heating and their antioxidant activity as one of their functionalities (Figure 1).
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Two MAAs, porphyra-334 and parisin, were prepared from red alga Dalus. The MAAs exhibited absorption maxima between 310 and 360 nm, whereas the heat-treated MAAs lost these wavelengths and exhibited absorption maxima between 210 and 225 nm. In high-performance liquid chromatography (HPLC), differences were also observed in the elution times of the compounds (Figure 2).
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The spectral analysis and HPLC elution time showed that the structure of MAAs is changed by heating. Therefore, we performed structural analysis using mass spectrometry and NMR. The structure of heat-treated paricin was estimated to be that of paricin with the loss of the hydroxy group from the fifth carbon atom (Fig. 3).
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The MAAs had antioxidant activity in addition to UV-protection. Heat-treated MAAs lost their UV-protective activity, but we examined whether they had antioxidant activity (Table 1). The results showed that the antioxidant activity increased after heat treatment compared to before treatment. In particular, the antioxidant activity of MAAs was weaker on the acidic side compared to ascorbic acid, but after heat treatment, MAAs showed antioxidant activity comparable to ascorbic acid over a wide range of pH.
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We have identified UV-protection and antioxidant activity as the functional properties of MAAs. Heat-treated MAAs lost their UV-protective activity, but were transformed into compounds with strong antioxidant activity over a wide range of pH. In a previous study, a similar compound was produced from laver porphyra-334.
（https://www.sciencedirect.com/science/article/pii/S0308814608010650）。
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-Exploring red algae rich in MAAs
-Exploration of functionalities of MAAs other than UV-protection
-Preparation of MAAs polymers
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