Synthesis Conditions And Characteristic Of MAAs In Nostoc Flagellifome

Mycosporine-like amino acids （MAAs）， comprise a diverse family ofsmall-molecular weight, colourless, water-soluble secondary metabolites found inalgae，such prokaryotic and eukaryotic organisms. They can absorb UV radiation in thewavelength from310nm to360nm. MAAs may serve as UV screening, osmoticsubstance and antioxidant molecules, et al. This paper aims to explore the change ofMAAs under the simulation of habitat conditions （UV-B radiation，salt concentrationand temperature） about Nostoc flagelliforme in wild. The reducing power, freeradical-scavenging capacity of MAAs was detected after the N. flagelliforme extractwas dry and explored the biosynthetic pathway of MAAs. The main researchconclusions are as follows:1. The production of MAAs increased slowly and reached the maximum after12hwith31.32mg/g and32.26mg/g under UV-B exposure at1W/m2and5W/m2. Afterlong time and high intensity of UV-B, MAAs content decreased and degraded. HPLCprofiles showed the second, fifth, eighth and ninth peaks in cell treatment by1W/m2and5W/m2for12h were higher than the initial MAAs. At the same time, two new peaks（tenth and eleventh） appeared, but the sixth and seventh disappeared.2. MAAs content changed with the treatment of NaCl or NH₄Cl. MAAs contentwas maximizing treated by50mmol NaCl and NH₄Cl, and the results were45.09mg/gand35.14mg/g, respectively. After that, MAAs content began to decrease with the saltconcentrations increased. HPLC profiles showed the third and fifth peaks weredisappeared and the first peak redured in both treatments compared to the control. In thetreatment of NH₄Cl, the forth, sixth, seventh and ninth peaks increased. In the NaCltreatment, the second, sixth, seventh and ninth peaks increased.3．MAAs content changes in N. flagelliforme cells under different temperature of5℃and45℃. Under the treatment of45℃, the content of MAAs changed little and thenumber of MAAs was16.00mg/g after7days, while the initial number was19.05mg/g.Low temperature （5℃） could inhibit the synthesis of MAAs and the content was7.19mg/g after7days. HPLC profiles also showed the peaks of MAAs in N. flagelliformecells had a downward trend with the temperature treatment. The first and eighth peaksreduced in45℃treatment and the first, forth and eighth peaks reduced in5℃treatment.4. The methanol extract of N. flagelliforme was white, powder solid after freeze drying. The antioxidant capacity of MAAs product was detected and their reducing power, freeradical-scavenging capacity increased with the concentration of MAAs increased. Whenthe concentration was0.32mg/, the absorbance was0.32at700nm. And the clearancerate of ultra oxygen anion and hydroxyl free radical were59.01%and78.64%with theconcentration of MAAs was7.05mg/mL and30.78mg/mL, respectively. In order toanalysis the UV screening ability, MAAs was mixed into sunscreen products at the massratio of1:1and1:2. The result showed sunscreen products had absorption maximaranging from280nm to320nm. Added MAAs to sunscreen products, the ability ofmixture absorbing UV rose.5. Glyphosate and aromatic amino acids are the inhibitors of shikimic acid pathway.In this experiment, MAAs were decreased under the condition of the culture containedglyphosate and aromatic compounds （tyrosine, tryptophan and phenylalanine）,respectively. The results suggested the synthesis of MAAs is restrained treated byglyphosate. In the treatment of aromatic amino acid, the inhibition on the MAAssynthesis of tyrosine is obvious, followed by tryptophan, and phenylalanine had noinfluence. Above two experimental results showed that the synthesis of MAAs may become from the way of shikimic acid. In another experiment, tricyclazole also couldaffect the synthesis of MAAs. With an extension of tricyclazole treatment, the ability ofMAAs synthesis reduced. This suggests that polyketone way may be involved in thesynthesis of MAAs.