Chemical characterization and toxicity of dihydro derivatives of nodularin and microcystin-LR, potent cyanobacterial cyclic peptide hepatotoxins.
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) micrograms/kg]. The stereochemistries of the reduced amino acids obtained by acid hydrolysis of dihydronodularin and dihydromicrocystin-LR [respectively, alpha-(methylamino)butyric acid and N-methylalanine] were determined by GC on a permethylated beta-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 (beta) and percentage (78-84%) of the deuterium incorporation were determined.
Namikoshi
M
M
Roger Adams Laboratory, University of Illinois, Urbana 61801.
Choi
B W
BW
Sun
F
F
Rinehart
K L
KL
Evans
W R
WR
Carmichael
W W
WW
D000818:Animals; D056486:Chemical and Drug Induced Liver Injury / Q000209:etiology* / Q000378:metabolism; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D000458:Cyanobacteria / Q000276:immunology / Q000378:metabolism; D000087522:Cyanobacteria Toxins; D006868:Hydrolysis; D007928:Lethal Dose 50; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000633:toxicity*; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D000087522:Cyanobacteria Toxins; D010456:Peptides, Cyclic; C064961:dihydromicrocystin LR; C080847:dihydronodularin