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Biomarkers derived from heterolytic and homolytic cleavage of allylic hydroperoxides resulting from alkenone autoxidation

DRS at CSIR-National Institute of Oceanography

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Title Biomarkers derived from heterolytic and homolytic cleavage of allylic hydroperoxides resulting from alkenone autoxidation
 
Creator Rontania, J.F.
Harji, R.
Volkmanc, J.K.
 
Subject biomarkers
pollution indicators
marine pollution
incubation
lipids
suspended particulate matter
Emiliania huxleyi
 
Description Laboratory incubation of alkenone mixtures with tert-butyl hydroperoxide and di-tert-butyl nitroxide (radical initiator) in hexane, as a means to simulate alkenone autoxidation processes, rapidly led to the formation of allylic hydroperoxides, whose presence was recently demonstrated in Emiliania huxleyi cells. After incubation in seawater and subsequent reduction with NaBH4 (to reduce residual hydroperoxides before analysis), these reaction products quickly disappeared and were replaced by complex mixtures of n-alcohols, fatty acids, alkyldiols and hydroxyacids. Methyl alkenones produced saturated n-alkan-l-ols and fatty acids ranging from C sub(13) to C sub(16) and two series of C sub(13) - C sub(16) (w-1) hydroxyacids and (1,w-1)-diols. Ethyl alkenones also afforded C sub(13) - C sub(16) saturated n-alkan-1-ols and fatty acids, accompanied by the production of C sub(14) - C sub(17) (w-2) hydroxyacids and (1,w-2)-diols. Deuterium labelling allowed us to show that most of the n-alkan-1-ols, hydroxyacids and alkyldiols resulted from the reduction during the NaBH4 treatment of the corresponding aldehydes, ketoxyacids and ketoxyaldehydes formed from heterolytic or hemolytic cleavages of allylic hydroperoxyl groups resulting from the oxidation of the double bonds of di- and triunsaturated alkenones. Amongst these products, the (w-1) - and (w-2) hydroxyacids formed after NaBH4 reduction of the (w-1) - and (w-2) - ketoxyacids were selected as potential biomarkers for alkenone autoxidation. Re-examination of lipid extracts of post-bloom seawater particulate matter samples from the DYFAMED station in the Ligurian Sea (where strong autoxidative alteration of the lipid distributions had previously been detected) showed the presence of significant amounts of 12-hydroxytetradecanoic, 13 -hydroxytetradecanoic, 14-hydroxyhexadecanoic and 15-hydroxyhexadecanoic acids thus providing good evidence that these autoxidative processes occur in natural samples.
 
Date 2008-01-30T12:41:29Z
2008-01-30T12:41:29Z
2007
 
Type Journal Article
 
Identifier Marine chemistry, Vol.107; 230-243p.
http://drs.nio.org/drs/handle/2264/674
 
Language en
 
Publisher Elsevier