Study On Preparation And Character Of UV-absorbing Compound In Seaweeds

MAAs (mycosporine-like amino acids) are a class of small, water-soluble UV-absorbing compounds.They are distributed in red algae and brown algae which are breeded widely in China. MAAs have high molar absorptivities, so they have important significance in protecting biological and non-biological materials. Red algae (Porphyra yezoensis,Gracilaria chilensis, Eucheuma cottonii) and brown algae (Sargassum fusiforme, Macrocystis pyrifera) are used as materials and studied as follows:1)Extraction, identification and analysis of MAAs. It was found that there are MAAs only in Porphyra yezoensis and Gracilaria chilensis among six kinds of alga. The content of MAAs in Porphyra yezoensis is higher than in Gracilaria chilensis. Two kinds of MAAs, Shinorin and Porphyra-334, were found in Porphyra yezoensis. Three kinds of MAAs, Shinorine, palythinol and Porphyra-334 were found in Gracilaria chilensis.2)Technics of extraction of the main MAAs - porphyra-334 was optimized. It was found that the best extract technics is as follows: the materials are extracted two times at 50℃, each time for 1.5 hours and liquid-solid ratio is 1:5.3)The study on characters of MAAsThe pH value has some effect on the properties and stability of UV absorbing compounds. In high acid condition, the absorption maximum of porphyra-334 showed hypsochromic shift to shorter wavelength, the absorbance also decreased. In alkaline condition, mycosporine-like amino acids are stable.In the range of pH3-9, there is almost no effect on the absorption spectrum. In high acidic conditions, pH≤2, both pH and temperature have effect on absorbance and the absorption maximum. In high alkaline conditions, pH≥10, absorbance decrease obviously as the increasing of temperature and pH, and the effect of pH is more obvious.Ionic strength has no effect on UV absorbing properties and stability of mycosporine-like amino acids.4) MAAs from porphyra yezoensis and Gracilaria chilensis are found to be able to prevent the oxidation of hydroxyl radical (OH·), superoxide anion (O2·ˉ), and phosphatidylcholine (PC). Porphyra yezoensis extracts have moderately stronger inhibition activity, as the content of porphyra-334 in mycosporine-like amino acicds from porphyra yezoensis is higher.5) MAAs were added into cosmetic for application. The best techics of sunscreen cosmetic adding mycosporine-like amino acicds are as follows: emulsification temperature is 90℃and MAAs are added in the sunscreen cosmetic at 50℃. Indexes of the sunscreen cosmetic were studied by testing the colour, smoothness,stability and irritability and proved to be eligible. Results showed that the sunscreen cosmetic made in the experient can protect skin from ultraviolet radiation effectively and better than the sunscreen cosmetic for sale.