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A Customizable Approach for the Enzymatic Production and Purification of Diterpenoid Natural Products
Published on: October 4, 2019
Structure elucidation and tentative formation pathway of a red colored enzymatic oxidation product of caffeic acid
Fabian Weber1, Garwin Hagen Engelke1, Andreas Schieber1
1Institute of Nutritional and Food Sciences, Molecular Food Technology, University of Bonn, Endenicher Allee 19b, D-53115 Bonn, Germany.
Abstract:
A red colored caffeic acid trimer was synthesized in model solution by enzymatic oxidation. The structure was elucidated by mass spectrometry and NMR spectroscopy and consisted of four carbon rings and two unsaturated acyl side chains. A formation pathway is suggested which includes the formation of a caffeic acid ortho-quinone followed by a Michael-type reaction, and radical coupling of a semiquinone of the formed dimer and a third caffeic acid molecule. The final structure is formed by decarboxylation and cyclisation. Results of ESI-MSn analysis can be explained by the presence of two carboxylic acid groups and a tetracyclic structure. The relative configuration of the central chiral carbons was deduced by NOESY experiments.
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