2-Ethyl-3-methylmaleimide in Tokyo Bay Sediments Providing the First Evidence for its Formation from Chlorophylls in the Present Photic and Oxygenic Zone

A new method for the rapid analysis of 1H-Pyrrole-2,5-diones (maleimides) in environmental samples by two-dimensional gas chromatography time-of-flight mass spectrometry

“…Maleimides have also been detected in environmental samples, where they have been used as indicators of algal productivity, water column properties (i.e. redox conditions, stratification, chemocline depth) and depositional conditions [19,20,[26][27][28][29][30][31][32][33][34][35]. However, the precursors of many maleimides have still not been fully identified, the processes leading to their formation are incompletely understood and their environmental significance needs further investigation [29].…”

1:1 Co-crystal of 3-ethyl-4-methyl-3-pyrrolin-2-one and 3-ethyl-4-methyl-3-pyrroline-2,5-dione

“…We attempted to crystallize 3ethyl-4-methyl-3-pyrrolin-2-one from a 20-year-old commercial source (Aldrich), but upon solving the structure, it was determined that the compound crystallized as a 1:1 cocrystal with its oxidized derivative, 3-ethyl-4-methyl-3-pyrrolin-2,5-dione, C 7 H 9 NO 2 (2), which is also known as 2-ethyl-3-methylmaleimide. The source of this maleimide is unclear, though it is reported to form through certain aerobic photoxidation pathways, for example from chlorophyls (Xian et al, 2006;Kozono et al, 2002), and therefore aerobic oxidation cannot be ruled out.…”

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…”