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A new series of steryl chlorin esters: Pheophorbide a steryl esters in an oxic surface sediment

Riffé-Chalard, Catherine
Published in Organic Geochemistry. 2000, vol. 31, no. 12, p. 1703-1712
Abstract Investigation of chlorins in the oxic surface sediment of a small eutrophic alpine lake (Motte lake) revealed the presence of a new series of steryl chlorin esters containing the pheophorbide a nucleus, together with their pyropheophorbide a steryl ester counterparts previously observed in the anoxic surface sediment of the same lake. Identification of the pheophorbide a steryl esters was based on comparison of spectroscopic, chromatographic and mass spectrometric characteristics of the compounds with those of a synthetic standard and of pyropheophorbide a steryl esters. Combined liquid chromatography-mass spectrometry analysis confirmed the absence of pheophorbide a steryl esters in the anoxic sediment but allowed their detection in traces in the water column, indicating that pheophorbide a steryl esters are, like their pyropheophorbide a analogs, formed in the water column. The distribution of sterols released by hydrolysis of the pheophorbide a steryl esters shows close similarities to that of the free sterols in the water column and of the sterols of the pyropheophorbide a steryl esters. It appears that, like their pyropheophorbide a counterparts, pheophorbide a steryl esters incorporate mainly sterols of phytoplanktonic origin. Their formation probably involves the same mechanism as for pyropheophorbide a steryl ester formation, i.e. metabolism by zooplankton grazing on phytoplankton. The presence of pheophorbide a steryl esters in the oxic sediment and their absence from the anoxic sediment is probably due to a lower stability of compounds containing a carbomethoxy substituent in the anoxic environment.
Keywords Steryl chlorin estersSterolsPheophorbide aPyropheophorbide aSedimentsLC–MS
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Research group Groupe Gülaçar
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RIFFÉ-CHALARD, Catherine, VERZEGNASSI, Ludovica, GULACAR, Fazil. A new series of steryl chlorin esters: Pheophorbide a steryl esters in an oxic surface sediment. In: Organic Geochemistry, 2000, vol. 31, n° 12, p. 1703-1712. https://archive-ouverte.unige.ch/unige:3210

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Deposited on : 2009-09-21

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