title: Seven new microcystins possessing two L-glutamic acid units, isolated from Anabaena sp. strain 186.
abstract: Electrospray ionization mass spectrometry has been applied to the structure assignment of seven new microcystins (1-7), obtained from cultured Anabaena sp. strain 186. The seven new microcystins contain the dehydroalanine (Dha) or L-Ser unit instead of the N-methyldehydroalanine unit and the L-Glu and/or its delta-methyl ester [E(OMe)] units at the two variable L-amino acid units, and the structures were assigned as [Dha7]microcystin-E(OMe)E(OMe) (1), [D-Asp3,Dha7]microcystin-E(OMe)E(OMe) (2), [L-Ser7]microcystin-E(OMe)E(OMe) (3), [D-Asp3,L-Ser7]microcystin-E(OMe)E(OMe) (4), [Dha7]microcystin-EE(OMe) (5), [D-Asp3,Dha7]microcystin-EE(OMe) (6), and [L-Ser7]microcystin-EE(OMe) (7). These microcystins are the first examples containing dicarboxylic amino acids at the two variable L-amino acid units in microcystins.
authors.affiliation: Department of Ocean Sciences, Tokyo University of Fisheries, Japan. namikosh@tokyo-u-fish.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Namikoshi
authors.forename: M
authors.initials: M
authors.lastname: Yuan
authors.forename: K
authors.initials: K
authors.lastname: Sivonen
authors.forename: W W
authors.initials: WW
authors.lastname: Carmichael
authors.forename: K L
authors.initials: KL
authors.lastname: Rinehart
authors.forename: L
authors.initials: L
authors.lastname: Rouhiainen
authors.forename: F
authors.initials: F
authors.lastname: Sun
authors.forename: S
authors.initials: S
authors.lastname: Brittain
authors.forename: A
authors.initials: A
authors.lastname: Otsuki
mesh_terms: D017033:Anabaena / Q000737:chemistry*; D001427:Bacterial Toxins / Q000032:analysis / Q000302:isolation & purification*; D018698:Glutamic Acid / Q000032:analysis / Q000737:chemistry*; D013058:Mass Spectrometry; D010456:Peptides, Cyclic / Q000032:analysis / Q000302:isolation & purification*
chemical_list: D001427:Bacterial Toxins; D010456:Peptides, Cyclic; D018698:Glutamic Acid