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Natural Product Discovery with LC-MS/MS Diagnostic Fragmentation Filtering: Application for Microcystin Analysis
Published on: May 31, 2019
[D-Leu(1)] microcystin-LR, a new microcystin isoplated from waterbloom in a Canadian prairie lake
H Park1, M Namikoshi, S M Brittain
1Department of Environmental Sciences, Faculty of Science, Shinshu University, Matsumoto 390-8621, Japan.
Abstract:
A previously undescribed cyclic heptapeptide hepatotoxin was isolated from a cyanobacteria waterbloom collected in Pakowki Lake, Alberta, Canada (49 degrees 20'N and 110 degrees 55'W). The compound was characterized by amino acid analysis, ESIMS/CID/MS, (1)H and (13)C NMR, and UV spectroscopy. Structure of the new microcystin was assigned as [D-Leu(1)]microcystin-LR (1). The amino acid composition is the same as microcystin-LR (2) except for D-Leu and L-Leu in 1 instead of D-Ala and L-Leu in 2. This is the first microcystin identified, among the 64 known microcystins, that has both a D- and L-Leu amino acid. Toxicity as measured by the protein phosphatase inhibition activity of 1 is similar to microcystin-LR. The presence of microcystins in waterblooms from this lake is discussed in relation to the almost yearly bird mortalities that have occurred there since 1995.
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