This website has changed. We hope you can find what you need easily, but items have moved around. If you have trouble finding what you are looking for please let us know.

Contact us

Novel toxins produced by the dinoflagellate Karenia brevisulcata

Abstract

Karenia brevisulcata (Chang), a new toxic dinoflagellate of the genus Karenia was isolated from a harmful algal bloom that occurred in Wellington Harbour, New Zealand in 1998. The bloom severely affected most marine biota resulting in long-term ecological damage and causing respiratory distress in harbour bystanders. Cultures of K. brevisulcata produced a range of novel toxins including ten lipid-soluble K. brevisulcata toxins (KBTs) and six water-soluble brevisulcatic acids (BSXs). Brevetoxins were not detected. KBT-F, KBT-G, BSX-1 and BSX-2 were isolated from 1450 L of bulk cultures and purified in mg quantities. Preliminary chemical and toxicological investigations show that KBT-F (M 2054 C107H160O38) and KBT-G (M 2084 C108H162O39) are complex polycyclic ethers with UVmax at 227 nm. NMR data gave characteristics of ladder frame polyether structures and a 2-methylbut-2-enal side chain, similar to gymnocins. The mouse i.p. LD50s for KBT-F and -G were 0.032 and 0.040 mg kg−1, respectively. These KBTs were also highly cytotoxic and haemolytic. BSX-1 (M 916 C49H72O16) and BSX-2 (M 872 C47H68O15) are polycyclic ether dicarboxylates with UVmax 196 nm. BSX-4 and BSX-5, the lactone ring-closed analogues and the presumed primary toxins in the algal cells, were isolated in smaller quantities. Preliminary structural information from NMR and MS showed a carboxylated side chain and some similarities to brevetoxin-A. However, the structures have not yet been fully elucidated due to conformers confounding the NMR. The mouse i.p. LD50 for BSX-1 was 3.9 mg kg−1 while no deaths were seen in mice injected with BSX-2 at 6.6 mg kg−1. The LD50s for the lactones BSX-4 and -5 were 1.4 and 1.6 mg kg−1 respectively. BSX-4 and -5 were agonists of voltage-gated sodium channels but only weakly haemolytic. Activities in the Neuro-2a cytotoxicity assay were ca 10% of dihydrobrevetoxin-2 and were fully antagonised by saxitoxin.

view journal