Chemical Characterization and Toxicity of Dihydro Derivatives of Nodularin and Microcystin-LR, Potent Cyanobacterial Cyclic Peptide Hepatotoxins

Michio Namikoshi, Byoung Wook Choi, Furong Sun, Kenneth L. Rinehart, William R. Evans, Wayne W. Carmichael

Research output: Contribution to journalArticlepeer-review

Abstract

Dihydro derivatives of nodularin (1) and microcystin-LR (4), potent cyclic peptide hepatotoxins isolated from Nodularia spumigena and Microcystis aeruginosa, respectively, were prepared by sodium borohydride reduction of the dehydroamino acid residues. The two stereoisomers of both dihydronodularin (2 and 3) and dihydromicrocystin-LR (5 and 6), isolated by reversed-phase HPLC, showed similar toxicity to each other [ip in mice, LD50 = 150 (2), 150 (3), 85 (5), and 100 (6) µg/kg]. The stereochemistries of the reduced amino acids obtained by acid hydrolysis of dihydronodularin and dihydromicrocystin-LR [respectively, α-(methylamino)butyric acid and N-methylalanine] were determined by GC on a permethylated β-cyclodextrin capillary column as their trifluoroacetyl methyl ester derivatives. Authentic l- and dl-N-methylamino acids were prepared to compare directly with the natural amino acids. Deuterated derivatives were also prepared using sodium borodeuteride (98 atom % D), and the location (β) and percentage (78–84%) of the deuterium incorporation were determined.

Original languageEnglish (US)
Pages (from-to)151-158
Number of pages8
JournalChemical Research in Toxicology
Volume6
Issue number2
DOIs
StatePublished - 1993

ASJC Scopus subject areas

  • Toxicology

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