A. Gavin McInnes

HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY OF DOMOIC ACID, A MARINE NEUROTOXIN, WITH APPLICATION TO SHELLFISH AND PLANKTON*

Abstract A recent outbreak of poisoning resulting from the consumption of cultured blue mussels (Mytilus edulis L.) from a localized area in Eastern Canada has been attributed to the presence of domoic acid (1), a relatively rare neurotoxic amino acid, previously found only in some algae of the family Rhodomelaceae. Studies on aqueous extracts of shellfish tissue indicated that the toxin and several of its isomers could be separated (and isolated in sufficient amounts for subsequent structural identification) by reversed-phase high-performance liquid chromatography (HPLC) with ultraviolet (UV) diode array detection (DAD). Aqueous acetonitrile containing 0.1% v/v trifluoroacetic acid was used as mobile phase. As the retention time and characteristic UV absorption spectrum of 1 (λmax = 242 nm) permit unequivocal identification, the HPLC-DAD procedure was refined with a microbore column to provide a rapid (5 min), sensitive (0.3 ng detection limit) and reproducible assay method for the determination of 1 in ...

Jadomycin, a novel 8H-benz[b]oxazolo[3,2-f]phenanthridine antibiotic from from streptomyces venezuelae ISP5230.☆

In a galactose-isoleucine medium at 37 °C, Streptomyces venezuelae ISP5230 produces jadomycin (1), the first 8H-benz[b]oxazolo[3,2]phenanthridine derivative to be isolated from natural sources. The structure of 1 was assigned by interpretation of the spectral data.

Biosynthesis of hydrocarbons by algae: Decarboxylation of stearic acid to N-heptadecane inAnacystis nidulans determined by13C- and2H-labeling and13C nuclear magnetic resonance

The distribution of isotopic labels inn-heptadecane enriched from [1,2-13C] and [2-13C, 2-2H3) acetates byAnacystis nidulans has been determined by13C nuclear magnetic resonance (13C NMR). Labeling with [1,2-13C] acetate is consistent with assembly from13C−13C units derived from an acetate “starter” group and 8 malonate units, as in fatty acid biosynthesis, followed by production of a methyl group through bond cleavage of the terminal13C−13C unit. A comparison of the hydrocarbon with palmitic acid (the only fatty acid produced in sufficient amount for NMR analysis) enriched from [2-13C,2-2H3]acetate by the same culture shows that they have retained the same fraction of2H at corresponding sites, and have therefore undergone identical biosynthetic and hydrogen-deuterium exchange processes, as would be expected ifn-heptadecane originates from de novo-synthesized stearic acid.

1H- and 13C-n.m.r. spectra of the methyl mono-, di-, and tri-O-acetyl-α- and -β-d-xylopyranosides

Abstract The 1 H- and 13 C-n.m.r. data for the mono- O -acetyl derivatives of methyl α- and β- d -xylopyranoside are compared with those for the parent compounds, to determine the effect of the acetyl groups on the chemical shifts of the methine protons and the skeletal carbons, and on the one-bond 1 H- 13 C, coupling constants. These substituent effects were used to confirm the assignments in the spectra of the di- and tri- O -acetyl derivatives of methyl α- and β- d -xylopyranoside.

A new secalonic acid. Linkage between tetrahydroxanthone units determined from deuterium isotope 13C chemical shifts

Abstract The previously unknown secalonic acid G has been isolated from Pyrenochaeta terrestris , and its structure determined by circular dichroism and 13 C nmr techniques including deuterium isotope 13 C chemical shift measurements to identify the linkage between the tetrahydroxanthone units.

Tenellin and bassianin, metabolites of Beauveria species. Structure elucidation with 15N- and doubly 13C-enriched compounds using 13C nuclear magnetic resonance spectroscopy

13 C n.m.r. spectroscopy and biosynthetic labelling with [15N]nitrate and [1,2-13C]acetate proved to be valuable adjuncts to established chemical and spectroscopic methods in elucidating the structures of tenellin and bassianin as 3-acyl derivatives of 1,4-dihydroxy-5-p-hydroxyphenyl-2(1H)-pyridone.

Comparative biochemistry of fatty acid and macrolide antibiotic (brefeldin a). Formation in penicillium brefeldianum

Abstract The stereochemistry of the D labeling of mycelial steric ( 3 ) and oleic acids ( 4 ) by 13 C 2 H 3 CO 2 H in vivo in Penicillium brefeldianum is the same at their even numbered, nonstarting group positions as found for saturated fatty acid biosynthesis in two other eukaryotes. This conclusion was reached by comparing the D labeling at C-10 of methyl stearate with that of methyl oleate as determined by 13 C NMR spectroscopy. Since brefeldin A ( 1 ) is labeled by CD 3 CO 2 H at C-6 and C-8 with the enantiotopic configurational result, the stereochemistry of antibiotic formation either differs at two points from fatty acid formation; or the C-6 and C-8 configuration of 1 is determined by some process unique to cyclopentane ring formation, but not by reduction of enolylthioester intermediates of its carbon chain assembly process.

New techniques in biosynthetic studies using 13C nuclear magnetic resonance spectroscopy. The biosynthesis of tenellin enriched from singly and doubly labelled precursors

13 C n.m.r. spectroscopy was used for the dual purpose of assessing the relative merits of singly and doubly labelled precursors while establishing the biosynthesis of tenellin from 13C-labelled acetate, phenylalanine, and methionine; precursors in which two adjacent sites are labelled can provide superior information, and may prove useful for obtaining enrichment data at low incorporations.

Differential hydrogen exchange during the biosynthesis of fatty acids in Anacystis nidulans: the incorporation of [2,2,2-2H3, 2-13Co;1] acetate☆

13C NMR studies (with simultaneous 1H, 2H-decoupling) of 13C, 2H-labelled methyl palmitate showed a gradation of 2H-retention along the acyl chain. The results are rationalized within the known steps of fatty acid biosynthesis.

6-Ethyl-5-hydroxy-2,7-dimethoxy-1,4-naphthoquinone from Hendersonula toruloidea: A biosynthetic study using 13C labels detected by nuclear magnetic resonance and 14C tracers

Abstract Production of 6-ethyl-5-hydroxy-2,7-dimethoxy-1,4-naphthoquinone was obtained by growth of Hendersonula toruloidea on Czapek-Dox broth supplemented with malt extract. Stationary cultures were grown at 28°C for 21–22 days yielding about 6 mg of metabolite per 700 ml of culture fluid. The best incorporations of isotopic tracers were obtained by addition at the 20th day of growth, followed by harvest 24–48 hr later. With [2- 14 C]acetate, incorporation values were in the range of 0.1–0.3% with dilution values from 2000 to 5900. With [1- 14 C]propionate, incorporations were much lower (0.04%) and dilutions much higher (120,000). Activity from [ 14 CH 3 ]methionine was incorporated only into the OCH 3 groups (incorporation values, 0.5–0.7%). Nuclear magnetic resonance studies confirmed that propionate was not a precursor. Using [1,2- 13 C]acetate, substantial enrichments were obtained at all carbon atoms except those of the OCH 3 groups. The following pairs of carbon atoms were shown to be derived from acetate units: C-1 + 2, C-3 + 4, C-5 + 10, C-6 + 7, C-8 + 9, C-11 + 12. The biosynthetic pathway is clearly that of acetate plus polymalonate. Experiments with [2- 13 C 2 H 3 ]acetate suggested that the “starter” acetate unit was located at positions C-12 + 11.