n-Nonacosadienes from the marine haptophytes Emiliania huxleyi and Gephyrocapsa oceanica

The hydrocarbons in cultures of marine haptophytes Emiliania huxleyi NIES837 and Gephyrocapsa oceanica NIES1315 were analyzed, and nonacosadienes and hentriacontadienes were detected as the major compounds in both strains. C-29 and C-31 monoenes and di-, tri- and tetra-unsaturated C-33 alkenes were also detected as minor compounds but not C-37 and C-38 alkenes. The positions of the double bonds in the C-29 and C-31 alkenes were determined by mass spectrometry of their dimethyl disulfide (DMDS) adducts. Among the four C-29 alkenes identified, the most abundant isomer was 2,20-nonacosadiene, and the other three compounds were 1,20-nonacosadiene, 3,20-nonacosadiene and 9-nonacosene, respectively. Hitherto, 2,20-nonacosadiene and 3,20-nonacosadiene were unknown to be natural products. The double bond at the n-9 (omega 9) position in these C-29 alkenes is hypothesized to be derived from precursors of unsaturated fatty acids possessing an n-9 double bond, such as (9Z)-9-octadecenoic acid. Nonacosadienes have the potential for being used as distinct haptophyte biomarkers. (C) 2015 Elsevier Ltd. All rights reserved.