Characterization of Allelopathic Compounds Produced by Akashiwo sanguinea.
LaTasha Amisial1,2, Peter Moeller 1,3, and Alan Lewitus 1,2,4
1 Marine Biomedicine and Environmental Sciences Center, Medical University of South Carolina, Charleston, SC
2 Hollings Marine Laboratory, Charleston, SC, USA
3 Toxin Chemistry, National Ocean Services (NOS), Charleston, SC, USA
4 Baruch Institute, University of South Carolina, and Marine Resources Research Institute, Charleston, SC, USA
Akashiwo sanguinea (formerly Gymnodinium sanguineum, Gynodinium nelsonii, Gymnodinium splendens) is a dinoflagellate common to coastal marine and estuarine waters where it forms blooms. Although these blooms have been associated with harmful effects to fish and shellfish, the mechanism for toxicity has scantly been examined up tell now and as such is still unknown. Evidence that A. sanguinea produces allelopathic compounds was obtained during a 1980 bloom off southern California, from which macrozooplankton avoidance and reduced grazing were observed. However, chemical characterization and isolation of these allelopathic compounds was not attempted. This thesis research seeks to identify the allelopathic compounds produced by a local South Carolina strain of A. sanguinea, and characterize the mechanism for toxicity. Based on toxins associated with other free-living phototrophic dinoflagellates, the allelopathic compounds are most likely to be protein phosphatases, carbohydrate derivatives, polyethers, and/or polyunsaturated fatty acids. The identification of these compounds will proceed by extracting and isolating the compounds from the A. sanguinea cultures. Every aqueous and organic extract fraction will be tested for toxic activity using a MTT cell viability assay and a standard marine toxicity assay. Once the active fractions have been identified, further purification will be done via HPLC, prep TLC, and column chromatography. The purified compound(s) will then be chemically characterized using NMR, Mass Spectrometry, and elemental analysis. Along with chemical characterization, the LC50 value of the active compound(s) will be determined using a standard marine toxin assay (e.g. abalone larvae mortality). Lastly the species will be tested for the polyketide synthase (PKS) gene, commonly found in other toxic dinoflagellates. Our goal is to establish the mechanism and parameters of toxicity for A. sanguinea. This will assist in the over all understanding of how this common dinoflagellate impacts on ecosystems and natural resources around the world.