Isolation and identification of seven microcystins from a cultured M.TN-2 strain of Microcystis aeruginosa

Seven microcystins (MCYSTs), three major and four minor ones, were isolated from a cultured Microcystis aeruginosa strain M.TN-2 isolated from an eel pond in southern Taiwan in the summer of 1993. Microcystins were separated by a column separation of LH-20 gel filtration chromatography, a subsequent silica gel flash column chromatography, and then purified by a reversed ph ase high performance liquid chromatography. MCYST-LR, -RR, -RA, -FR, -WR, [ D-Asp(3)] MCYST-FR, and [D-Asp(3)] MCYST-WR were characterized and determin ed by amino acid analysis, MALDI-TOF mass spectrometry, H-1 and DQF-COSY nu clear magnetic resonance spectroscopy and UV spectroscopy. Among them, [D-A sp(3)] MCYST-FR and [D-Asp(3)] MCYST-WR, two new compounds, were the desmet hyl variants of MCYST-FR and MCYST-WR, respectively.