Production of Functionally Active Palytoxin-like Compounds by Mediterranean Ostreopsis cf. siamensis

Background and purpose: Dinoflagellates from the genus Ostreopsis have been related to the production of palytoxin and analogues. Based on that, this paper describes functional studies of crude extracts from Ostreopsis cf. siamensis collected in the Mediterranean Sea in order to biochemically characterize their toxic compounds. Methods: We compared the effects of 5 crude dinoflagellates extracts with a commercially available palytoxin and a purified Ostreopsis ovata extract on metabolic activity, membrane potential, and cytosolic calcium levels by using fluorescent dyes. Results: All the extracts resulted to be neurotoxic. In addition, all of them induced a membrane depolarization and a calcium increment that were abolished when preincubating with ouabain, an inhibitor of the Na+/K+ pump. Conclusion: The effects observed were quite close to those induced by palytoxin and the Ostreopsis ovata extract as well, suggesting that Ostreopsis cf. siamensis is actually producing palytoxin-like compounds that are highly toxic and functionally active. Copyright (C) 2009 S. Karger AG, Basel