Production of goniodomin A by the planktonic, chain-forming dinoflagellate Alexandrium monilatum (Howell) Balech isolated from the Gulf Coast of the United States

Abstract

The chain-forming dinoflagellate Alexandrium monilatum has been reported to be associated with widespread discolored water and increased fish mortality in the Mississippi Sound and off the eastern and western coasts of Florida. Previous studies over the last 60–70 years have determined that A. monilatum produces a harmful substance(s) that is predominantly contained in the cell mass as exhibited by apparent increased toxicity when the organism cytolyses. The current research in our lab corroborated earlier research demonstrating that A. monilatum produces a lipophilic toxin, unlike its Alexandrium relatives noted for their production of saxitoxin-like toxins. Using sophisticated chemical, chromatographic, and analytical techniques, we have successfully purified and identified the molecular structure of the toxin produced by A. monilatum. We utilized a 500 MHz NMR to carry out a number of experiments (i.e., 1H, 13C, COSY, HSQC, and HMBC) to unambiguously determine the molecular structure of the toxin. In addition, we report mass analysis of the toxin utilizing electrospray ionization-mass spectrometry (ESI-MS), matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS), and Q-TOF mass spectral techniques. The toxin is representative of a polyether macrolide with an empirical formula of C 43H 60O 12. This toxic compound is shown to be identical to a Japanese tidepool toxin identified as goniodomin A, which is produced by another Alexandrium species.