Chemical and physical analyses of wax ester properties

Abstract

Wax esters are major constituents of the surface lipids in many terrestrial arthropods, but their study is complicated by their diversity. We developed a procedure for quantifying isomers in mixtures of straight-chain saturated and unsaturated wax esters having the same molecular weights, using single-ion monitoring of the total ion current data from gas chromatography-mass spectrometry. We examined the biological consequences of structural differences by measuring the melting temperatures, Tm, of >60 synthetic wax esters, containing 26–48 carbon atoms. Compounds containing saturated alcohol and acid moieties melted at 38–73°C. The main factor affecting Tm was the total chain length of the wax ester, but the placement of the ester bond also affected Tm. Insertion of a double bond into either the alcohol or acid moiety decreased Tm by ∼30°C. Simple mixtures of wax esters with n-alkanes melted several °C lower than predicted from the melting points of the component lipids. Our results indicate that the wax esters of primary alcohols that are most typically found on the cuticle of terrestrial arthropods occur in a solid state under physiological conditions, thereby conferring greater waterproofing. Wax esters of secondary alcohols, which occur on melanopline grasshoppers, melted >60°C below primary esters of the same molecular weight and reduced Tm of the total surface lipids to environmental values.

Lubricating and Waxy Esters. VI. Effect of Symmetry about Ester on Crystallization of Linear Monoester Isomers

“…These peaks were superimposed to a wide and large halo, indicating that the β'-crystals were very small and dispersed in a very large liquid phase. At −13 C, a temperature matching the onset temperature of crystallization of JLE-28 1 , several very sharp extra peaks appeared in the WAXD (Figure 2a). At least nine reflections associated with a triclinic subcell (β-phase) were unambiguously indexed ( Table 2).…”

“…They possess unique properties suitable for a wide variety of applications ranging from lubricants to cosmetics, medical formulations, and foods [1]. Monoesters, such as those found in jojoba oil, are known to be very functional as lubricants and performance waxes [2,3].…”

“…We have recently reported on the synthesis, crystallization and melting behavior, solid content evolution and rheology of three pure jojoba-like esters (JLE) incorporating either 1-decenoic acid and/or 1-decenol and oleic acid and/or oleoyl alcohol, namely octadec-9-enyl dec-9-enoate (JLE-28 1 ), dec-9-enyl oleate (JLE-28 2 ) and dec-9-enyl dec-9-enoate (JLE-20) [6]. 1-decenoic acid or 1-decenol is a fatty acid/fatty alcohol whose unique terminal double bond structure has not before been investigated in monoester formulations.…”

“…Their thermal and flow behavior was well correlated to the structural complexity of the molecule (position of the central cis-double bond relative to the C-O-C bond of the ester group and rotations hindrance). In the present work, the phase trajectories and polymorphism of JLE-28 1 and JLE-28 2 were investigated on a conventional X-ray diffractometer by temperature-time resolved XRD during stepped isothermal crystallization, and during cooling from the melt at a constant rate.…”

Body-Surface Compounds in Buckfast and Caucasian Honey Bee Workers (Apis Mellifera)

“…Our studies showed that this percentage was lower in bees, ranging from 52% to 58% in Buckfast bees and from 46% to 55% in Caucasian bees in the total of this fraction. Honeybees and dragonflies contain up to 58% of cuticular wax esters and phenols, having a total of 36-50 carbon atoms (Jacob and Hanssen, 1979;Patel et al, 2001). In our studies, Caucasian and Buckfast bees had respectively 45 Body-surface compounds in honey bee Body-surface compounds in honey bee -54% and 42 -48% of C12 -C32 esters on their cuticles.…”