Direct Depolymerization Coupled to Liquid ExtractionSurface Analysis-High-Resolution Mass Spectrometry for the Characterizationof the Surface of Plant Tissues

摘要

The cuticle, the outermost layer covering the epidermis of most aerial organs of land plants, can have a heterogeneous composition even on the surface of the same organ. The main cuticle component is the polymer cutin which, depending on its chemical composition and structure, can have different biophysical properties. In this study, we introduce a new on-surface depolymerization method coupled to liquid extraction surface analysis (LESA) high-resolution mass spectrometry (HRMS) for a fast and spatially resolved chemical characterization of the cuticle of plant tissues. The method is composed of an on-surface saponification, followed by extraction with LESA using a chloroform–acetonitrile–water (49:49:2) mixture and direct HRMS detection. The method is also compared with LESA-HRMS without prior depolymerization for the analysis of the surface of the petals of Hibiscus richardsonii flowers, which have a ridged cuticle in the proximal region and a smooth cuticle in the distal region. We found that on-surface saponification is effective enough to depolymerize the cutin into its monomeric constituents thus allowing detection of compounds that were not otherwise accessiblewithout a depolymerization step. The effect of the depolymerizationprocedure was more pronounced for the ridged/proximal cuticle, whichis thicker and richer in epicuticular waxes compared with the cuticlein the smooth/distal region of the petal.