Determination of microcystin variants and related peptides present in a water bloom of Planktothrix (Oscillatoria) rubescens in a Spanish drinking water reservoir by LC/ESI-MS

6 pages, 3 figures, 2 tables.-- PMID: 15530970 [PubMed].-- Printed version published Dec 15, 2004.A water bloom of Planktothrix (Oscillatoria) rubescens was observed in a drinking water reservoir in central Spain in 2003. Microcystins where analysed by LC/ESI-MS in 21 samples collected from this reservoir in five different days between March and May. A demethylated variant of microcystin-RR was identified as the major microcystin in most samples. Trace levels of microcystin-LR, -RR and -YR were detected in some samples. Four less common microcystins, with [M+H]+ ions at m/z 960, 981, 1045 and 1053, were also found. Total extracellular microcystin concentration varied from 0.010 to 19.126 μg l−1. Furthermore, anabaenopeptins B and F as well as Oscillamide Y were also identified in these samples.This work has been supported by Canal de Isabel II. The authors would also like to thank this institution for having supplied the samples and authorised the publication of the results.Peer reviewe