Glycosylated Porphyra-334 and Palythine-Threonine from the Terrestrial Cyanobacterium Nostoc commune

Mycosporine-like amino acids (MAAs) are water-soluble UV-absorbing pigments, and structurally different MAAs have been identified in eukaryotic algae and cyanobacteria. In this study novel glycosylated MAAs were found in the terrestrial cyanobacterium Nostoc commune (N. commune). An MAA with an absorption maximum at 334 nm was identified as a hexose-bound porphyra-334 derivative with a molecular mass of 508 Da. Another MAA with an absorption maximum at 322 nm was identified as a two hexose-bound palythine-threonine derivative with a molecular mass of 612 Da. These purified MAAs have radical scavenging activities in vitro, which suggests multifunctional roles as sunscreens and antioxidants. The 612-Da MAA accounted for approximately 60% of the total MAAs and contributed approximately 20% of the total radical scavenging activities in a water extract, indicating that it is the major water-soluble UV-protectant and radical scavenger component. The hexose-bound porphyra-334 derivative and the glycosylated palythine-threonine derivatives were found in a specific genotype of N. commune, suggesting that glycosylated MAA patterns could be a chemotaxonomic marker for the characterization of the morphologically indistinguishable N. commune. The glycosylation of porphyra-334 and palythine-threonine in N. commune suggests a unique adaptation for terrestrial environments that are drastically fluctuating in comparison to stable aquatic environments.     

Efficient Isolation of Mycosporine-Like Amino Acids from Marine Red Algae by Fast Centrifugal Partition Chromatography

Marine rhodophyta are known to synthesize specific secondary metabolites, mycosporine-like amino acids (MAAs), to protect themselves from harmful UV-radiation. Shinorine and porphyra-334 are among the most abundant representatives of this compound class. In the present work, a novel approach for their isolation is described. As a first step, a fast centrifugal partition chromatography method, with an aqueous two-phase system comprising water, ethanol, ammonium sulfate and methanol in ascending mode, was developed to isolate the two MAAs from crude aqueous-methanolic extracts of three algal species within 90 min. The compounds could be isolated when just one of them was present in a sample or also both at the same time. By employing solid phase extraction as a second purification step, the individual MAAs were obtained in high purity and good quantity within a much shorter time frame than the established purification protocols, e.g., semi-preparative HPLC. For example, from 4 g Porphyra sp. (Nori) crude extract, 15.7 mg shinorine and 36.2 mg porphyra-334 were isolated. Both were highly pure, as confirmed by TLC, HPLC-MS and NMR analyses.     

复合单体TEGDMA/MAA接枝真丝纱线的工艺条件及试样的性能表征

为提高真丝接枝体系中的单体利用率,在真丝接枝体系中添加反应活性较高的三乙二醇二甲基丙烯酸酯(TEGD-MA)单体,与常用接枝单体甲基丙烯酰胺(MAA)复合,对真丝纱线进行化学接枝。经过单因素试验得出适宜的接枝工艺条件:TEGDMA/MAA复合单体用量为真丝纱线质量的70%,其中TEGDMA与MAA的质量比为1∶9,引发剂过硫酸钾(KPS)的浓度为5 mmol/L,pH≈2.5,反应温度80℃,反应时间60 min,吐温-80的质量浓度为0.2 g/L,浴比为1∶20。在此工艺条件下,TEGDMA/MAA复合接枝体系可获得约58%的接枝率,较相同接枝条件下的MAA接枝纱线提高了约16个百分点,同时其单体利用率达到83%,较MAA单体利用率提高了23个百分点。通过扫描电子显微镜观察发现接枝后的真丝纱线表面分布有接枝聚合物,接枝真丝纱线的红外光谱显示在1 700～1 800 cm-1处具有较宽的TEGDMA分子结构中CO双键的伸缩振动吸收峰,热重分析显示在500℃下接枝真丝纱线出现不同于MAA接枝纱线的失重速率峰,说明TEGDMA与MAA 2种单体分子均参与了接枝反应。