Preparative purification and characterization of [Dha7] microcystin RR
微囊藻毒素［Dha7］MCRR的制备及鉴定

One variant of microcystins was isolated and purified with cyanobacteria natural bloom as the starting material, which was collected in Dianchi Lake, China. The separation protocol involved extraction of cyanobacterial cells by 75% aqueous methanol, isolation by reversed-phase flash chromatography, and purification by reversed-phase semipreparative HPLC. The structure and purity of purified microcystin was identified with electrospray ionization mass spectrometry, UV spectrophotometer, and analytical HPLC. The purified microcystin was assigned as Dha7]MCRR (purity >95%), which was a demethylated variant of MCRR. The structure of purified microcystin was identified as cyclo-(Ala-Arg-MeAsp-Arg-Adda-Glu-Dha) with molecular weight of 1023. There was a maximum absorbance at 239nm in its UV spectrum (200~300nm). This variant of microcystins occurred frequently, and sometimes could become the main variant in waterbloom from Dianchi Lake.