Generation of isoprenoid compounds,notably prist-1-ene,via photo- and autoxidative degradation of vitamin E |
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Authors: | Mina Nassiry Claude Aubert Abdelkrim Mouzdahir Jean-François Rontani |
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Institution: | 1. Laboratoire de Microbiologie de Géochimie et d’Ecologie Marines (UMR 6117), Centre d’Océanologie de Marseille, F-13288 Marseille, France;2. Laboratoire de Chimie Bioorganique, Université Chouaïb Doukkali, 24000 El Jadida, Morocco;3. Laboratoire de Pharmacocinétique et Toxicocinétique (UPRES 3286), Faculté de Pharmacie, 13385-Marseille, France |
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Abstract: | In order to mimic the photodegradation of vitamin E during phytoplankton senescence and study the behaviour of the resulting photoproducts during cell lysis, vitamin E dispersed in seawater was irradiated with solar light in the presence of hematoporphyrin as sensitizer. Under these conditions, singlet oxygen-mediated photooxidation and free radical oxidation (autoxidation) acted simultaneously on the substrate, affording 4,8,12-trimethyltridecanal, 4,8,12-trimethyltridecanoic acid, 6,10,14-trimethylpentadecan-2-one, α-tocopherylquinone, 4,8,12,16-tetramethylheptadecan-4-olide, 2,3-epoxy-α-tocopherylquinone and 5,6-epoxy-α-tocopherylquinone as minor products. Different mechanisms were proposed to explain the formation of these different isoprenoids. The main products (85% of the degraded substrate) appeared to be previously described diastereoisomeric trimeric oxidation products of vitamin E, whose pyrolysis during gas chromatography–mass spectrometry (GC–MS) afforded 2,6,10,14-tetramethylpentadec-1-ene (prist-1-ene). On the basis of their greater ability to produce prist-1-ene during pyrolysis than intact vitamin E and their highly favoured production in phytoplanktonic cells, these trimers are proposed as likely sources of this isoprenoid alkene, previously identified in many pyrolysates from immature kerogens. |
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