Masayuki Satake

Brevetoxin B3, a new brevetoxin analog isolated from the greenshell mussel perna canaliculus involved in neurotoxic shellfish poisoning in new zealand

Abstract A new brevetoxin analog, brevetoxm B3 (BTXB3 1 ). was isolated from the greenshell mussel, Perna canaliculus from New Zealand. In BTXB3 the brevetoxin B skeleton is modified by cleavage of ring D. esterification of the resulting alcohol, and oxidation of the aldehydic terminus.

Total synthesis and structural confirmation of brevisamide, a new marine cyclic ether alkaloid from the dinoflagellate Karenia brevis.

The first total synthesis of brevisamide (1) has been accomplished in 21 linear steps starting from cis-but-2-ene-1,4-diol. A synthetic highlight is the Suzuki-Miyaura coupling between an ether ring fragment and a dienol side chain. This result confirmed the structure of 1 isolated from the dinoflagellate Karenia brevis.

Absolute configuration of brevisamide and brevisin: confirmation of a universal biosynthetic process for Karenia brevis polyethers.

The discovery of brevisin, the first example of an interrupted polycyclic ether, obtained from the dinoflagellate Karenia brevis, posed some important questions regarding the mechanism of the cyclization process. Consequently, we have established absolute configurations of brevisin and its related metabolite brevisamide using a modified Moshers esterification method. For brevisin, analysis was carried out on both the 31-monokis- and the 10,31-bis-MTPA esters. The results suggest that both metabolites, like other polyethers from K. brevis, result from polyepoxide precursors with uniform (S, S) configurations for all epoxides and provide further support for a universal stereochemical model for dinoflagellate polyether formation.

Brevisulcenal-F: a polycyclic ether toxin associated with massive fish-kills in New Zealand.

A novel marine toxin, brevisulcenal-F (KBT-F, from karenia brevisulcata toxin) was isolated from the dinoflagellate Karenia brevisulcata. A red tide of K. brevisulcata in Wellington Harbour, New Zealand, in 1998 was extremely toxic to fish and marine invertebrates and also caused respiratory distress in harbor bystanders. An extract of K. brevisulcata showed potent mouse lethality and cytotoxicity, and laboratory cultures of K. brevisulcata produced a range of novel lipid-soluble toxins. A lipid soluble toxin, KBT-F, was isolated from bulk cultures by using various column chromatographies. Chemical investigations showed that KBT-F has the molecular formula C(107)H(160)O(38) and a complex polycyclic ether nature. NMR and MS/MS analyses revealed the complete structure for KBT-F, which is characterized by a ladder-frame polyether scaffold, a 2-methylbut-2-enal terminus, and an unusual substituted dihydrofuran at the other terminus. The main section of the molecule has 17 contiguous 6- and 7-membered ether rings. The LD(50) (mouse i.p.) for KBT-F was 0.032 mg/kg.

Two new indole alkaloids, 2-(3,3-dimethylprop-1-ene)-costaclavine and 2-(3,3-dimethylprop-1-ene)-epicostaclavine, from the marine-derived fungus Aspergillus fumigatus.

Two new indole alkaloids, 2-(3,3-dimethylprop-1-ene)-costaclavine (1) and 2-(3,3-dimethylprop-1-ene)-epicostaclavine (2), together with the known compounds costaclavine (3), fumgaclavine A (4) and C (5), were isolated from the marine-derived fungus Aspergillus fumigatus. The planar structures of the two new compounds were elucidated on the basis of chemical and physicochemical evidence including MS, UV, IR and NMR spectra. Their stereochemistry was studied by NOESY, 1H–1H coupling constant and CD spectra. The compounds 1, 2, 3 and 5 showed weak cytotoxicity against a mouse leukemia cell line (P388).

Total Synthesis of (–)-Brevisin: A Concise Synthesis of a New Marine Polycyclic Ether

The first and highly efficient total synthesis of (-)-brevisin has been achieved. The title compound was synthesized in only 29 steps (longest linear sequence) from commercially available starting materials. The synthesis provided over 70 mg of a marine polycyclic ether compound.

Prorocentrol, a Polyoxy Linear Carbon Chain Compound Isolated from the Toxic Dinoflagellate Prorocentrum hoffmannianum

A polyoxy linear carbon chain compound, prorocentrol (1), was isolated from cultured cells of the dinoflagellate Prorocentrum hoffmannianum, which produces a polyether carboxylic acid, okadaic acid. The structure of 1 was elucidated by detailed analyses of 2D NMR spectra. Compound 1 possesses 30 hydroxy groups, 1 ketone, and 8 double bonds on the C65-linear carbon chain. Its partial relative configuration was deduced by the proton-proton and long-range carbon-proton coupling constants, and compound 1 showed moderate cytotoxicity and antidiatom activity.

Origins of oxygen atoms in a marine ladder-frame polyether: evidence of monooxygenation by 18O-labeling and using tandem mass spectrometry.

Yessotoxin is a ladder-frame polyether produced by the dinoflagellate Protoceratium reticulatum. Previous labeling experiments using (13)C-acetate established the unique assembly of the carbon chain from intact and cleaved acetate units. The origins of ether and hydroxy oxygens in the molecule, which would yield further information regarding the assembly of the ladder-frame structure, have yet to be established. In this study, we describe the incorporation of (18)O in one experiment where the dinoflagellate was cultured under (18)O(2) atmosphere and in a second where the culture media was supplemented with [(18)O(2)]acetate. Labeled yessotoxin obtained from these experiments was subjected to collision-induced dissociation tandem mass spectrometry to determine the positions of (18)O-incorporation pattern in the molecule. Detailed analyses of product ions from the fragmentation processes led to the identification of (18)O-labeled positions and the incorporation ratios. The data revealed that the ether oxygens were labeled from (18)O(2) and the hydroxy oxygen on C32 was derived from [(18)O(2)]acetate. These results support a proposed biosynthetic mechanism of marine ladder-frame polyethers that a polyene precursor was oxidized by a monooxygenase after acetate condensation.

A sensitive LC-MS/MS assay for brevisulcenal and brevisulcatic acid toxins produced by the dinoflagellate Karenia brevisulcata

A toxic dinoflagellate, Karenia brevisulcata, devastated almost all marine life in Wellington Harbour, New Zealand during the late summer of 1998. Brevisulcatic acids (BSXs) and brevisulcenals (KBTs), both polycyclic ether toxins, have been identified as the causative agents. A liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the sensitive and specific determination of BSXs and KBTs in culture medium, seawater and shellfish. Acidified algal culture, or seawater, was extracted using reverse phase solid phase extraction cartridges. Shellfish tissue homogenate was blended with methanol-water (9:1) and partitioned with hexane to remove non-polar lipids. This extraction protocol is similar to that used for analysis of lipophilic shellfish toxins. LC-MS/MS (triple quadrupole) was used for quantitative analysis with gradient elution (acidic buffer), positive electrospray ionization and multiple-reaction monitoring. Purified toxins were available for 4 KBTs (KBT-F, -G, -H and -I) and 4 BSXs (-1, -2, -4, and -5), and were used to calibrate the instrument responses. Relative response factors were used for semi-quantitative analysis of BSX-3 and BSX-6, using BSX-1 and BSX-4 respectively. Calibration curves for all toxins monitored were linear over the concentration range tested (5-200xa0ngxa0mL(-1)) with r(2) values >0.99. The method limit of quantitation was determined to be 2xa0ngxa0mL(-1) for BSXs and KBTs, except KBT-I, which was 5xa0ngxa0mL(-1). Validation data was generated for culture medium and shellfish. Toxin recoveries were typically >70% with relative standard deviations <20% across all of the matrices tested. In addition, toxins specific to K. brevisulcata were able to be detected in seawater at a cell concentration of 10,000xa0cellsxa0L(-1), which represents the suggested trigger level for this harmful algal species. This method shows suitable performance characteristics to be regarded a useful tool to monitor toxin levels in a variety of sample matrices during future bloom events.

Brevisulcatic acids, marine ladder-frame polyethers from the red tide dinoflagellate Karenia brevisulcata in New Zealand.

The isolation and structural determination of new marine ladder-frame polyethers, brevisulcatic acids-1 (1) and -4 (2) are reported. Brevisulcatic acids were isolated from the dinoflagellate Karenia brevisulcata, which was identified as the causative species of a major red tide event in New Zealand in 1998. The ether ring composition and a β-hydroxy, γ-methylene valeric acid side chain of 1 and 2 are common, but 2 has a γ-lactone as the 5-membered A-ring while 1 is the seco acid analogue. Compound 2 has structural and bioactivity similarities to brevetoxin A.