Cutin extraction and composition determined under differing depolymerisation conditions in cork oak leaves

Abstract

Introduction: Cutin is a biopolyester involved in waterproofing aerial plant organs, including leaves. Cutin quantification and compositional profiling require depolymerisation, namely by methanolysis, but specific protocols are not available.Objectives: Investigate how different methanolysis conditions regarding catalyst concentration effect cutin depolymerisation and monomer release, to better define protocols for cutin content determination and composition profiling.Material and Methods: Cork oak (Quercus suber) dewaxed leaves were reacted with five sodium methoxide (NaOMe) concentrations. Extracts were analysed: glycerol by high-performance liquid chromatography (HPLC) and long-chain lipids by gas chromatography-mass spectrometry (GC-MS).Results: Cutin was completely removed by 3% NaOMe (8.4% of dewaxed leaves), while mild 0.1% and 0.01% NaOMe methanolysis only depolymerised 14% of total cutin. Reactivity of cutin ester bonds is not homogeneous and glyceridic ester bonds are more easily cleaved, releasing the existing glycerol already under the mildest conditions (0.53% with 0.01% NaOMe and 0.41% with 3% NaOMe). The composition of cutin extracts varies with depolymerisation extent, with easier release of alkanoic acids and alkanols, respectively, 34.9% and 8.8% of total monomers at 0.1% NaOMe, while ω-hydroxyacids (49.3% of total monomers) and α,ω-diacids (9.0% of the monomers) are solubilised under more intensive reactive conditions. Conclusion:Cutin of Quercus suber leaves is confirmed as a glyceridic polyester of ω-hydroxyacids and alkanoic acids, with minor content of α,ω-diacids, and including coumarate moieties. The protocol for the determination of cutin content and compositional profiling was established regarding catalyst concentration. The molar composition of cutin suggests a macromolecular assembly based on glycerol linked to lipid oligomeric chains with moderate cross-linking.

The Chemical Landscape of Leaf Surfaces and Its Interaction with the Atmosphere

“…C 16 acids are typically present in large amounts in every plant species, while the specific substitution pattern and relative contribution of C 18 acids varies. In some plants, cutin contains small amounts of glycerol. ,, Overall, the amount of cutin ranges from a few μg cm –2 to up to 1 mg cm –2 , corresponding to 40–80% of the total cuticle’s mass. , …”

“…In some plants, cutin contains small amounts of glycerol. 66,69,70 Overall, the amount of cutin ranges from a few μg cm −2 to up to 1 mg cm −2 , 36 corresponding to 40−80% of the total cuticle's mass. 32,36 Waxes are the second most abundant components of leaf cuticles by mass and are mixtures of compounds including longchain fatty acids, n-alcohols, n-alkanes, n-aldehydes, alkyl esters, and triterpenoids.…”

The chemical landscape of leaf surfaces and its interaction with the atmosphere

“…License: CC BY-NC-ND 4.0 of glycerol. 66,69,70 Overall, the amount of cutin ranges from a few µg cm -2 to up to 1 mg cm -2 , 36 corresponding to 40 -80% of the total cuticle's mass. 32,36 Waxes are the second most abundant components of leaf cuticles by mass and are mixtures of compounds including long-chain fatty acids, n-alcohols, n-alkanes, n-aldehydes, alkyl esters, and triterpenoids.…”

The chemical landscape of leaf surfaces and its interaction with the atmosphere

“…In some plants, cutin contains small amounts 208 of glycerol. 64,67,68 Overall, the amount of cutin ranges from a few µg cm -2 to up to 1 mg cm -2 , 34 corresponding to 40 -80% of the total cuticle's mass. 30,34 Waxes are the second most abundant components of leaf cuticles by mass and are mixtures of compounds including long-chain fatty acids, n-alcohols, n-alkanes, n-aldehydes, alkyl esters, and triterpenoids.…”