Evaluation of seafood toxicity in the Australes archipelago (French Polynesia) using the neuroblastoma cell-based assay.

Ciguatera fish poisoning (CFP), a disease caused by consuming fish that have accumulated ciguatoxins (CTXs) in their tissue, is regarded as the most prevalent form of intoxication in French Polynesia. Recently, the Australes, one of the least affected archipelago until the early 1980s, has shown a dramatic increase in its incidence rates in 2009 with unusual CFP cases. In the present work, potential health hazards associated with the proliferation of various marine phytoplankton species and the consumption of fish and marine invertebrates highly popular among local population were assessed in three Australes islands: Raivavae, Rurutu and Rapa. Extracts from the marine dinoflagellates Gambierdiscus, Ostreospis and mat-forming cyanobacteria as well as fish, giant clams and sea urchin samples were examined for the presence of CTXs and palytoxin (PLTX) by using the neuroblastoma cell-based assay (CBA-N2a). Cytotoxic responses observed with both standards (Pacific CTX-3C and PLTX) and targeted marine products indicate that CBA-N2a is a robust screening tool, with high sensitivity and good repeatability and reproducibility. In Rurutu and Raivavae islands, our main findings concern the presence of CTX-like compounds in giant clams and sea urchins, suggesting a second bio-accumulation route for CFP toxins in the ciguatera food chain. In Rapa, the potential CFP risk from Gambierdiscus bloom and fish was confirmed for the first time, with levels of CTXs found above the consumer advisory level of 0.01 ng Pacific CTX-1B g(-1) of flesh in three fish samples. However, despite the presence of trace level of PLTX in Ostreopsis natural assemblages of Rapa, no sign of PLTX accumulation is yet observed in tested fish samples. Because this multi-toxinic context is likely to emerge in most French Polynesian islands, CBA-N2a shows great potential for future applications in the algal- and toxin-based field monitoring programmes currently on hand locally.

Protective effect of Heliotropium foertherianum (Boraginaceae) folk remedy and its active compound, rosmarinic acid, against a Pacific ciguatoxin.

ETHNOPHARMACOLOGICAL RELEVANCE: Senescent leaves of Heliotropium foertherianum Diane & Hilger (Boraginaceae) are traditionally used in the Pacific region to treat Ciguatera Fish Poisoning. This plant contains rosmarinic acid that is known for its multiple biological activities. In the present study, H. foertherianum aqueous extract, rosmarinic acid and its derivatives were evaluated for their capacity to reduce the effect of ciguatoxins. MATERIALS AND METHODS: Aqueous extract of H. foertherianum leaves was prepared and studied for its effects against a Pacific ciguatoxin (P-CTX-1B) in the neuroblastoma cell assay and the receptor binding assay. Rosmarinic acid and six derivatives were also evaluated by means of these bioassays. For this purpose, we have developed an improved synthetic route for caffeic acid 3,4-dihydroxy-phenethyl ester (CADPE). RESULTS: Both the aqueous extract of H. foertherianum leaves and rosmarinic acid showed inhibitory activities against a Pacific ciguatoxin in the above bioassays. Among all the molecules that were evaluated, rosmarinic acid was the most active compound. CONCLUSION: These results confirm further the potential of H. foertherianum in the treatment of Ciguatera Fish Poisoning.

First evidence of palytoxin and 42-hydroxy-palytoxin in the marine cyanobacterium Trichodesmium.

Marine pelagic diazotrophic cyanobacteria of the genus Trichodesmium (Oscillatoriales) are widespread throughout the tropics and subtropics, and are particularly common in the waters of New Caledonia. Blooms of Trichodesmium are suspected to be a potential source of toxins in the ciguatera food chain and were previously reported to contain several types of paralyzing toxins. The toxicity of water-soluble extracts of Trichodesmium spp. were analyzed by mouse bioassay and Neuroblastoma assay and their toxic compounds characterized using liquid chromatography coupled with tandem mass spectrometry techniques. Here, we report the first identification of palytoxin and one of its derivatives, 42-hydroxy-palytoxin, in field samples of Trichodesmium collected in the New Caledonian lagoon. The possible role played by Trichodesmium blooms in the development of clupeotoxism, this human intoxication following the ingestion of plankton-eating fish and classically associated with Ostreopsis blooms, is also discussed.