Cuticular waxes from Ivy leaves (Hedera helix L.): analysis of high‐molecular‐weight esters

AbstractSoluble 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. Copyright © 2006 John Wiley & Sons, Ltd.