This work was developed with the financial support of the Picardie Region Research Council (project COMET).

Cell wall localized heterogeneous polyesters are widespread in land plants. The composition of these polyesters, such as cutin, suberin, or more plant specific forms such as the flax seed coat lignan macromolecule, can be determined after total hydrolysis of the ester linkages. The main bottleneck in the structural characterization of these macromolecules, however, resides in the determination of the higher order monomer sequences. Partial hydrolysates of the polyesters release a complex mixture of fragments of different lengths, each present in low abundance and therefore challenging to structurally characterize.

Here, a method is presented by which liquid chromatography‐mass spectrometry (LC‐MS) profiles of such partial hydrolysates are searched for pairs of related fragments. LC‐MS peaks that show a mass difference corresponding to the addition of one or more macromolecule monomers were connected in a network. Starting from the lowest molecular weight peaks in the network, the annotation of the connections as the addition of one or more polyester monomers allow the prediction of consecutive and increasingly complex adjacent peaks.

MSn experiments further help to reject, corroborate, and sometimes refine the structures predicted by the network. As a proof of concept, this procedure was applied to partial hydrolysates of the flax seed coat lignan macromolecule, and allowed to characterize 120 distinct oligo‐esters, consisting of up to 6 monomers, and containing monomers and linkages of which the incorporation in the lignan macromolecule had not been described before. These results show the capacity of the approach to advance the structural elucidation of complex plant polyesters.

Benjamin Thiombiano, Eric Gontier, Roland Molinié, Paulo Marcelo, François Mesnard, Rebecca Dauwe