The First Detection of Phthalimides in Sediments as Novel Biomarkers for Photosynthetic Organisms

Abstract

We detected a homologous series of phthalimides in organic solvent extracts of Cretaceous to Quaternary sediments. 2-Ethyl-3-methylmaleimide has been found in present-day sediments as a degradation product of chlorophylls; therefore, an authentic sample was heated, affording phthalimide and its homologs as well as homologs of maleimide. The heating products showed a similar molecular distribution of phthalimide and methylphthalimides to those found in the sediments analyzed. These results suggest that the phthalimides found in old sediments are derived from chlorophylls via 2-ethyl-3-methylmaleimide by geochemical transformation.

Maleimide index: a paleo-redox index based on fragmented fossil-chlorophylls obtained by chromic acid oxidation

“…Porphyrins and their related substances are commonly found in sedimentary rocks, crude oils, and recent sediments. 1–21 These compounds are considered to be degradation products of the chlorophylls possessed by photosynthetic organisms that lived in the past. 1–22…”

“…1–21 These compounds are considered to be degradation products of the chlorophylls possessed by photosynthetic organisms that lived in the past. 1–22…”

“…1–5 Since each photoautotroph possesses a different type of chlorophyll, 23 determination of the source chlorophyll from analysis of the porphyrin in geological samples can lead to an estimation of past photosynthetic organism distributions. 1–21 The information related to dominant photosynthetic organisms has been previously employed for paleoenvironmental reconstructions, since the paleoenvironment can be estimated from such habitat characteristics. 6–10…”

“…1–21 The information related to dominant photosynthetic organisms has been previously employed for paleoenvironmental reconstructions, since the paleoenvironment can be estimated from such habitat characteristics. 6–10…”

“…The information related to dominant photosynthetic organisms has been previously employed for paleoenvironmental reconstructions, since the paleoenvironment can be estimated from such habitat characteristics. [6][7][8][9][10] The majority of porphyrins present in sedimentary rocks are trapped within an insoluble and amorphous polymer known as kerogen, [13][14][15][16][17][18][19][20][21][22] and so their extraction with common solvents is challenging. To address this issue, the analysis of maleimides (1H-pyrrole-2,5-diones, Mis) derived from the pyrrole skeletons of porphyrins, is promising, since these soluble compounds can be easily extracted and analyzed by gas chromatography-mass spectrometry (GC-MS).…”