Cuticular waxes from ivy leaves (Hedera helix L.): analysis of high-molecular-weight esters.
Soluble waxes were extracted from the cuticle of ivy (Hedera helix L.) leaves with dichloromethane in a yield of ca. 13%. The cuticular waxes were directly analysed by GC-MS, high-temperature GC-MS and ESI-MS/MS. The GC-MS analysis showed mostly n-alkanols (45.3%), monoacids (18.8%), triterpenes (9.7%), n-aldehydes (8.7%) and n-alkanes (7.7%). The high-temperature GC-MS and the ESI-MS/MS analyses showed the presence of ester waxes, namely alkyl alkanoates and alkyl coumarates. Alkyl alkanoates comprised esters of the hexadecanoic acid with n-alkanols ranging from C16 to C34. Alkyl coumarates included esters of coumaric acid with n-alkanols ranging from C16 to C32. The cuticular waxes were hydrolysed and the resulting organic and aqueous phases analysed by GC-MS. The hydrolysate showed a major increase in the quantities of n-alkanols, hexadecanoic acid and coumaric acid derived from the alkyl and acyl moieties from the ester waxes. A content of ester waxes of 38% was estimated based on the results from the GC-MS analysis of the non-hydrolysed and hydrolysed cuticular waxes. Alkyl alkanoates were analysed by ESI-MS/MS as [M + Li]+ adduct ions and the alkyl coumarates as [M - H]- deprotonated ions. The ESI-MS/MS analysis allowed the detection of a wider range of ester waxes than high-temperature GC-MS, and was shown to be a useful technique for the qualitative analysis of ester waxes from plant cuticles.
Santos
Sara
S
Departamento de Engenharia Florestal, Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Tapada da Ajuda, 1349-017, Lisboa, Portugal.
Schreiber
Lukas
L
Graça
José
J
D002851:Chromatography, High Pressure Liquid; D004952:Esters / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry; D035981:Hedera / Q000737:chemistry*; D006868:Hydrolysis; D008970:Molecular Weight; D018515:Plant Leaves / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D014885:Waxes / Q000032:analysis*
D004952:Esters; D014885:Waxes