Beeswax, structure

A.P. Tulloch, Beeswax structure of the esters and their component hydroxy acids and diols, Chemistry and Physics of Lipids, 6, 235 265 (1971). 

In the present chapter, we first provide some general information concerning the chemistry of waxes and lipids currently encountered in various items from our cultural heritage and we detail the main protocols based on direct mass spectrometry that have been developed so far. We then discuss the mass spectra obtained by EI-MS on a range of reference substances and materials sampled from museum and archaeological artefacts. We then focus on the recent possibilities supplied by electrospray ionisation for the elucidation of the structure of biomarkers of beeswax and animal fats. 

To summarise, a fractionation step allows the isolation of the compounds of interest from the other molecular constituents, particularly from the fatty acids that are well-ionised. To compensate for the low ionisation yield of some compounds, such as TAGs, the solutions may be doped with a cation. Samples are then directly infused into the ion electrospray source of the mass spectrometer. A first spectrum provides an overview of the main molecular compounds present in the solution based on the peaks related to molecular cations. The MS/MS experiment is then performed to elucidate the structure of each high molecular compound. Table 4.2 shows the different methods of sample preparation and analysis of nonvolatile compounds as esters and TAGs from reference beeswax, animal fats and archaeological samples. 

Although El MS is an efficient way to provide structural information on several molecular constituents of various lipid substances it only provides partial information and it is particularly not suitable for the study of the low volatile components. High molecular weight and nonvolatile compounds are particularly difficult to analyse in this way and it may therefore be interesting to explore the possibilities of other ionisation modes such as electrospray for an accurate structural study of high molecular constituents such as monoester and diester species of beeswax (Gamier et al., 2002) and TAGs of animal fats... 

Other waxes have not been studied to the same extent as beeswax. They derive from a variety of plant, animal and also mineral sources, as described in Chapter 1, where more detailed information on their chemical composition is reported. HTGC/MS analysis after solvent extraction has been successfully used to identify spermaceti, candellila and Japan waxes which have been used in the manufacture of works of art [37]. In particular, in the case of spermaceti wax it has been possible to understand the structure of the various isomers of even-numbered esters ranging from C26 to C34, as well as odd-numbered esters detected in low amounts. The mass spectra obtained demonstrated for the first time that spermaceti esters are mainly composed of hexade-canol and octadecanol moieties associated with a range of FAs containing 10 20 carbon atoms. 

Diols have been rarely observed in insect cuticular lipids (Buckner, 1993). Odd-carbon-number diols (C23-C29) were the major lipid class (55%) of the larval cuticular lipids from the flour beetle, Tenebrio molitor (Bursell and Clements, 1967). The major diol constituent was 8, 9-pentacosanediol. For the cuticular lipids of M. sexta larvae, very small amounts (<1%) of 7,8- and 8,9-C27 diols and 8,9- and 9,10-C29 diols were identified (Espelie and Bernays, 1989). Hydroxy n-alkanols are diols with a hydroxyl functional group on the C, position (terminal) of the alkyl chain, but are technically not alcohol derivatives of hydrocarbons. There are a few reports of the occurrence of insect hydroxy -alkanols (Buckner, 1993 Nelson and Blomquist, 1995 Buckner et al., 1996). In a structure analysis study of beeswax, the major alcohol moieties of the diester fraction were identified as 1,23-tetracosanediol (42.2%), 1,27-octacosanediol (26.0%) and 1,25-hexacosanediol (20.2%) (Tulloch, 1971). The hydroxy n-alkanols comprised 16% of the cuticular lipids of FI. zea pupae and were identified as C30-C36 even-chain n-alcohols with hydroxyl groups on carbon numbers 11, 12, 13, 14, or 15 (Buckner et al., 1996). Mass spectral analysis indicated the presence of unsaturation in the alkyl chain of the major diol components. 

Beeswax is the compound made by bees to form their structural nests. Many species of bees produce wax, but most commercially produced beeswax is made by Apis mellifera, the common honeybee. Ghedda is a general term for wax produced by other types of bees, particularly those from Asia. 

Waxes are mixtures of esters of long-chain carboxylic acids with long-chain alcohols. The carboxylic acid usually has an even number of carbons from 16 through 36, while the alcohol has an even number of carbons from 24 through 36. One of the major components of beeswax, for instance, is tria-conty hexadecanoate, the ester of the C30 alcohol triacontanol and the Cib acid hexadecanoic acid. The waxy protective coatings on most fruits, berries, leaves, and animal furs have similar structures. 

Honeybees make lipids that they use to form the honeycomb structure of their hive. The walls of the honeycomb are made of a mixture of lipids known as beeswax. ... 

Hambleton et al. (2009a) showed that incorporation of 3% of -hexanal in alginate matrices induced a more homogeneous structure as observed by an environmental scanning electron microscope (ESEM). To the contrary, n-hexanal provoked a more heterogeneous distribution of the emulsified fat (beeswax + acetylated monoglycerides) in the film cross section. This was attributed to the competition between the emulsifier (glycerol monostearate) and -hexanal. 

Waxes represent a second group of simple lipids that, like fats and oils, are esters of fatty acids. However, the alcohol portion of waxes is derived from long-chain alcohols (12-32 carbons) rather than glycerol. Beeswax, for example, contains a wax with the following structure ... 

Uses Emulsifier, stabilizer, thickener in cosmetics SE base for o/w emulsions in cosmetics and pharmaceuticals excipient for dermal/transdermal pharmaceuticals Features Structural base Trade Name Synonyms Apifil [Gattefosse http //www.gattefosse.com-, Gattefosse SA http //www.gattefosse.com]-, Estol 3752 [Uniqema] Estol E04BW 3752 [Uniqema] PEG-12 beeswax... 

Gas chromatography (GG-FID and GC-MS) can be used for both qualitative and quantitative analyses. Complete identification can be effected if GC retention data and mass spectral data are together taken into consideration. GC-FID identification is based on the comparison of retention times of analytes and authentic standards determined under identical GC conditions or by their co-chromatography. Unfortunately, standards of cuticular wax constituents are rarely commercially available. Some standards may be produced in the laboratory from pure components or natural extracts. For example, the carbon number in the analyses of wax esters can be assigned by comparison of their retention times with that of a synthetic wax ester of known structure (Evershed, 1992a). Beeswax is well-characterized so it can be used as a standard mixture. In beeswax wax esters, the predominant fatty acid moiety is hexadecanoic acid and the chain lengths of the alcohol moieties range from C26 to C36. 

The wax is a complex mixture of esters, fatty acids, and hydrocarbons. We will not review its structure. Its function in producing nest cells is well known, and beeswax is used by humans. Apidae thus use a different set of glands to create homeostatic conditions for their developing young than do those bees that line cells with Dufour s gland secretions. Wax is well-adapted for the construction... 

Waxes are esters formed from long-chain carboxylic acids and long-chain alcohols. For example, beeswax, the structural material of beehives, has a 26-carbon carboxylic acid component and a 30-carbon alcohol component. The word wax comes from the Old English weax, meaning material of the honeycomb. Carnauba wax is a particularly hard wax because of its relatively high molecular weight it has a 32-carbon carboxylic acid component and a 34-carbon alcohol component. Carnauba wax is widely used as a car wax and in floor polishes. 

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