Purification of closely eluting hydrophobic microcystins (peptide cyanotoxins) by normal-phase and reversed-phase flash chromatography

Two closely eluting hydrophobic peptides, microcystin-LW and -LF had proved in the past to be particularly difficult to purify by reversed-phase HPLC. Initial extraction by reversed-phase flash chromatography provided a good method of concentrating microcystins and also partially purifying them, alt hough the separation of closely eluting variants was not possible. The use of normal-phase flash chromatography after initial reversed-phase extractio n was found to be a suitable method for achieving high purity and gave a go od yield of both microcystins. However, a final reversed-phase flash step w as necessary to eliminate trace contaminants. The method described provides a simple three step flash chromatography extraction and purification elimi nating the need to use preparative HPLC. (C) 1999 Elsevier Science B.V. All rights reserved.