Furong Sun

Isolation of linear peptides related to the hepatotoxins nodularin and microcystins

Abstract Linear peptide 2 , Adda-D-Glu(γ)-Mdhb-D-MeAsp(β)-L-Arg-OH, was isolated from cultured Nodularia spumigena and was analyzed in the cells after one weeks ( 1:2 : 30:1) to eight weeks (>100:1) cultivation. Three linear peptides, Adda-D-Glu(γ)-Mdha-D-Ala-L-Leu-D-MeAsp(β)-L-Arg-OH ( 3 ), L-Leu-D-MeAsp(β)-L-Arg-Adda-D-Glu(γ)-Mdha-D-Ala-OH ( 4 ), and L-Phe-D-MeAsp(β)-L-Arg-Adda-D-Glu(γ)-Mdha-D-Ala-OH ( 5 ) were obtained from a water bloom of Microcystis spp. collected from Homer Lake (Illinois). Some of these linear peptides ( 2 , 3 ) are thought to be biogenetic precursors of nodularin and microcystins. Linear peptides 2 , 3 , and 4 did not show apparent toxicity at 1.0, 1.1, and 2.25 mg/kg, respectively, in a mouse bioassay (ip). Feeding experiments using 13 C-labeled precursors established that the 2-, 6- and 8-methyl and 9-methoxy carbons of the unusual (2 S ,3 S ,8 S ,9 S )-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyl-4,6-decadienoic acid (Adda) unit of 1 were clearly derived from L-methionine.

Isolation and structures of microcystins from a cyanobacterial water bloom (Finland)

A hepatotoxic cyanobacterial (blue-green algal) water bloom was collected from a constructed water reservoir in Finland. The water bloom contained two cyanobacterial species, Microcystis aeruginosa and Aphanizomenon flos-aquae. Two hepatotoxins, 1 and 2, were isolated from extracts of lyophilized cells. The structures of 1 and 2 were assigned based upon their amino acid analyses on a Waters Pico Tag HPLC system and a chiral GC capillary column (Chirasil Val III), fast atom bombardment mass spectrometry (FABMS), high resolution FABMS, and tandem FABMS data. Toxin 1 was identical to a previously reported compound, [D-Asp3]microcystin-RR. Toxin 2 was new and was assigned the structure [D-Asp3]microcystin-YR.

Two new l-serine variants of microcystins-LR and -RR from Anabaena sp. strains 202 A1 and 202 A2

Two new microcystins, [L-Ser7]microcystin-LR (1) and [L-Ser7]microcystin-RR (2), were isolated from a filamentous fresh water cyanobacterium (blue-green alga), Anabaena sp. strain 202 A1, along with the two major toxins, [Dha7]microcystin-LR (3) and [Dha7]microcystin-RR (4) and their minor components the D-Asp variants [D-Asp3,Dha7]microcystin-LR (5) and [D-Asp3,Dha7]microcystin-RR (6). Anabaena sp. strain 202 A1 also produced another new toxin, whose structure is tentatively proposed as [D-Asp3,L-Ser7]microcystin-XR (7), where X is a leucine homologue. Anabaena sp. strain 202 A2 produced one new microcystin, 1, and three known microcystins, 3, 4, and 5. The structures of the toxins were assigned based on their amino acid analyses, and fast atom bombardment mass spectrometry data.

Isolation of <Glu-Asn-Phe-His-Leu-Arg-Pro-NH2 (Antho-RPamide II), a novel, biologically active neuropeptide from sea anemones

Using a radioimmunoassay against the C-terminal sequence Arg-Pro-NH2 (RPamide) we have isolated the neuropeptide <Glu-Asn-Phe-His-Leu-Arg-Pro-NH2 (Antho-RPamide II) from extracts of the sea anemone Anthopleura elegantissima. Addition of low concentrations of Antho-RPamide II to a tentacle preparation of sea anemones inhibited the spontaneous, rhythmic contractions, suggesting that the peptide is a neurotransmitter or neuromodulator.