title: C(25) highly branched isoprenoid alkenes from the marine benthic diatom Pleurosigma strigosum.
abstract: The hydrocarbon composition of the marine diatom Pleurosigma strigosum isolated from coastal Mediterranean sediments is described. A suite of five C(25) highly branched isoprenoid (HBI) alkenes with 2-5 double bonds were detected together with n-C(21:4) and n-C(21:5) alkenes and squalene. The analysis by (1)H and (13)C NMR spectroscopy of two isolated HBI alkenes allowed the structural identification of a novel C(25) HBI triene (2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadeca-5E,13-diene) and the first identification in diatom cells of 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5E-ene, an HBI previously detected in marine sediments and particulate matter. The other minor C(25) HBIs detected were a tetraene and a pentaene that have been previously identified in other diatoms from the genera Haslea and Rhizosolenia, and one other C(25) tetraene that could not be structurally identified. The structures of the HBI alkenes of P. strigosum were compared with those of C(25) homologues previously identified in three other Pleurosigma sp. (Pleurosigma intermedium, Pleurosigma planktonicum and Pleurosigma sp.). Unlike most structures previously reported, none of the HBI alkenes produced by P. strigosum showed an unsaturation at C7-C20, or E/Z isomerism of the trisubstituted double bond at C9-C10 (whenever present).
authors.affiliation: Laboratoire de Microbiologie, Géochimie et Ecologie Marines, UMR 6117 CNRS, Centre d'Océanologie de Marseille, OSU, Campus de Luminy, case 901, F-13288 Marseille, France. grossi@com.univ-mrs.fr
authors.forename: Vincent
authors.initials: V
authors.lastname: Grossi
authors.forename: Béatriz
authors.initials: B
authors.lastname: Beker
authors.forename: Jan A J
authors.initials: JA
authors.lastname: Geenevasen
authors.forename: Stefan
authors.initials: S
authors.lastname: Schouten
authors.forename: Danielle
authors.initials: D
authors.lastname: Raphel
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Fontaine
authors.forename: Jaap S
authors.initials: JS
authors.lastname: Sinninghe Damsté
mesh_terms: D017377:Diatoms / Q000737:chemistry*; D004777:Environment; D008401:Gas Chromatography-Mass Spectrometry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013729:Terpenes / Q000032:analysis*
chemical_list: D013729:Terpenes