IDENTIFICATION AND CHARACTERIZATION OF MICROCYSTIN-LY FROM MICROCYSTIS-AERUGINOSA (STRAIN-298)

Two toxins, a main component A and a minor component B, were isolated from the freshwater cyanobacterium Microcystis aeruginosa (strain 298) and characterized in their chemical structure by amino-acid analysis, configurational analysis, by FAB-MS and H-1-NMR spectroscopy. The aci d hydrolysate yielded for toxin A as constituent amino acids D-Ala, L- Leu, D-Glu, erythro-D-beta-Me-Asp and L-Arg, and for toxin B the amino acids D-Ala, L-Leu, D-Glu, erythro-D-beta-Me-Asp and L-Tyr. ID and 2D H-1-NMR spectroscopy of the toxins A and B in DMSO-d6 allowed to char acterize them as cyclic heptapeptides containing both the unusual beta -amino acid Adda -methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic ac id) and N-methyldehydroalanine (Mdha) as additional constituent residu es. Toxin A was found to correspond to the known and structurally well characterized microcystin-LR and toxin B to microcystin-LY. The prese nce of this variant has already been proposed, but its primary structu re could be confirmed in this study.