AN UNUSUAL POLYUNSATURATED C‐27 HYDROCARBON FROM THE MARINE DINOFLAGELLATE PYROCYSTIS LUNULA

Abstract

Leblond, J. D.1 & Chapman, P. J.2 1Department of Biology, Middle Tennessee State University, Murfreesboro, TN 37132. 2US EPA (NHEERL), Gulf Ecology Division, 1 Sabine Island Dr., Gulf Breeze, FL 32561Studies of the lipids of different algal species have revealed a diversity of fatty acids, sterols, and hydrocarbons, of which several are considered useful biomarkers, with potential for characterizing phytoplankton community composition. To extend this approach and characterize the lipids and lipid classes of laboratory‐cultured marine dinoflagellates, a silicic acid fractionation system was developed to obtain compositional data for sterols and hydrocarbons of over forty species. In the course of this work, a neutral fraction obtained from a lipid extract of Pyrocystis lunula was found to contain an abundant quantity of a long‐chain polyunsaturated hydrocarbon, along with previously reported keto‐steranes. The hydrocarbon molecular weight (364) and retention time obtained by gas chromatography/mass spectrometry analysis suggested a C27 compound, which was confirmed by reduction (Adams catalyst) to give the straight chain alkane, n‐heptacosane. The presence of eight double bonds was established by deuteration to give a product with molecular weight 396. While the positions of double bonds have not been established, the carbon number of this hydrocarbon and the number of double bonds strongly suggest formation by decarboxylation of the recently described, long‐chain polyunsaturated C28 fatty acid shown to be a constituent of phospholipids. This hydrocarbon was not found in any other genus of the examined dinoflagellates, and appears to be one of the first identifications of a hydrocarbon in this class of algae. The function(s) of this compound in P. lunula is currently unclear.