Thin layer chromatography in the study of natural waxes and their constituents

Differences of wax-based emulsion gel in 3D printing performance: Crystal distribution and droplet stability

Six kinds of natural waxes were used for emulsion gels preparation. The differences in printing performance were explored based on the crystal distribution and droplet stability. Firstly, the effect of crystal distribution was investigated through microstructures and rheological properties. It was found that the dense crystal network/interfacial crystallization could stabilize the droplet and provide modulus to ensure the self-supporting behavior after printing, whereas excessive crystal could lead to droplet rupture and coalescence. Furthermore, all emulsion gels could recrystallize by heating, which could enhance the performance of 3D printing. Then, the droplet stability was investigated after storing/freeze-thawing. It was found that emulsion gels with dense crystal networks/interfacial crystallization had more stable droplets, which ensure the continuous extrusion during printing. Finally, printing performance was investigated comprehensively. Three emulsion gels with denser crystal networks/interfacial crystallization had higher recovery rates (16.17-21.15%) and more stable droplets, which perform better in 3D printing correspondingly.

Comparative study of natural wax-based W/O emulsion gels: Microstructure and macroscopic properties

In this paper, six kinds of natural wax, including sunflower wax (SFX), rice bran wax (RBX), carnauba Brazilian wax (CBX), beeswax (BWX), candelilla wax (CDX), and sugarcane wax (SGX) were used to prepare water-in-oil (W/O) emulsion gels. Microstructures and rheological properties of all emulsion gels were investigated by microscopy, confocal laser scanning microscope (CLSM), scanning electron microscopy (SEM), and rheometer, respectively. By comparing polarized light images of wax-based emulsion gels and corresponding wax-based oleogels, it could be found that dispersed water droplets greatly affected the crystal distribution and hindered crystal growth. Polarized light microscopy and CLSM images proved that natural wax could perform a dual-stabilization mechanism by interfacial crystallization and crystal networks. SEM images illustrated all waxes except SGX were platelets and formed networks by stacking on top of each other, while flocs-like SGX was easier to adsorb on the interface and formed a "crystalline shell". The surface area and pore formed by different wax varied wildly, which accounted for their differences in the gelation ability, oil binding capacity, and strength of the crystal network. The rheological study showed that all wax had solid-like properties and wax-based oleogels with denser crystal networks correspond to emulsion gels with higher modules. The dense crystal network and interfacial crystallization could improve the stability of W/O emulsion gels proved by recovery rates and critical strain. All the above proved that natural wax-based emulsion gels can be used as stable, low-fat, and thermal-sensitive fat mimics.

Separation and determination of closely related triterpenic acids by high performance thin-layer chromatography after iodine derivatization

A method based on high performance thin-layer chromatography combined with densitometry for the simultaneous determination of oleanolic and ursolic acids is described. Because of the similarity of chemical structure the prechromatographic derivatization was necessary to separate these triterpenic acids. The samples were treated by 1% iodine solution in chloroform directly on the chromatographic plate and developed with the mobile phase consisting of A (petroleum ether), B (ethyl acetate) and C (acetone) (8.2:1.8:0.1, v/v/v). After drying, the plates were sprayed with 10% (v/v) ethanol solution of sulfuric acid(VI) and heated to 120 degrees C for 3 min. Quantification was performed in absorbance/transmittance mode at a wavelength of 530 nm by using a computer-controlled densitometer Desaga CD 60. The presented method was validated for linearity, precision and accuracy. Correlation coefficient (r(2)>0.99), R.S.D. values (1.4-3.5%), detection limits as well as recovery values (98.4-103.1%) were found to be satisfactory. The method has been successfully applied in the analysis of both triterpenic acids in plant extract.

Gas and liquid chromatography of hydrocarbons in edible vegetable oils

Hydrocarbons, an important part of the minor constituents belonging to vegetable oils are reviewed. Their importance, origin, characterization and detection in edible vegetable oils are considered. The determination of some of them as a means of establishing oil quality and genuineness is also highlighted. The official methodologies, as well as the most commonly procedures used for isolation and analysis are reviewed. Furthermore, novel procedures applying new techniques for determining those compounds are also presented.

Comparison of Kernel Wax from Corn Genotypes Resistant or Susceptible to Aspergillus flavus

ABSTRACT Russin, J. S., Guo, B. Z., Tubajika, K. M., Brown, R. L., Cleveland, T. E., and Widstrom, N. W. 1997. Comparison of kernel wax from corn genotypes resistant or susceptible to Aspergillus flavus. Phytopathology 87: 529-533.Kernels of corn genotype GT-MAS: gk are resistant to Aspergillus flavus. Earlier studies showed that this resistance is due in part to kernel pericarp wax. Experiments were conducted to compare wax from GTMAS: gk kernels with that from kernels of several susceptible commercial hybrids. GT-MAS: gk had more pericarp wax than did the susceptible hybrids. Scanning electron microscopy revealed that GT-MAS: gk kernels appeared rough and showed abundant wax deposits on kernel surfaces. Susceptible kernels appeared much more smooth and lacked the abundant surface deposits observed in GT-MAS: gk. In vitro bioassays showed that kernel wax from GT-MAS: gk reduced A. flavus colony diameter by 35%. Colony diameters on a medium amended with wax from susceptible kernels did not differ from those of controls. Thin-layer chromatography and analyses of chromatograms using NIH Image software showed a distinctive composition for GT-MAS: gk kernel wax. Chromatograms of wax from GT-MAS: gk contained a peak unique to this genotype, but also lacked a peak common to all susceptible hybrids. This is the first report of specific kernel factors involved in resistance to A. flavus in corn.

Aliphatic components of the epicuticular wax of developing saskatoon (Amelanchier alnifolia) fruit

The epicuticular wax of saskatoon fruit (Amelanchier alnifolia Nutt. cv. Smoky) was analyzed at four stages of maturity. Total wax per unit surface area varied during fruit development, with a net decline from the youngest to the most ripe stage. Surface wax ultrastructure, as revealed by scanning electron microscopy, consisted of pinhead-like crystals that decreased with maturity and platelike crystals that increased with maturity. The major aliphatic compounds were alkanes (C23 to C29), long chain esters (C36 to C42), primary alcohols (C20 to C30), and a secondary alcohol (C29). The esters were composed of primary alcohols (C20 to C28) and saturated fatty acids (C16 to C24). The most abundant wax components at all stages were nonacosan-10-ol and nonacosane. Keywords: serviceberry, saskatoon fruit, epicuticular wax, aliphatic chemistry, ultrastructure.

Analysis of ear sebum of the Syrian hamster (Mesocricetus auratus) reveals pronounced sexual dimorphism

External ear of male and female Syrian hamsters (Mesocricetus auratus) were extracted with hexane and separated by class on thin-layer chromatography (TLC). Separated lipid classes were eluted and saponified, and non-saponifiable lipids further characterized by TLC, gas-liquid chromatography (GLC), UV and IR spectroscopy and functional group analyses. Many sex differences were observed, most notably the presence of sex-specific sterols of males and females. Mature animals were found to have greater quantities of ear sebum, but the characteristic qualitative lipid profiles of each sex were apparent in immature animals.

Ultrastructure and chemistry of soluble and polymeric lipids in cell walls from seed coats and fibres of Gossypium species

Electron-microscopic examination in conjunction with extraction procedures and chemical analysis have confirmed that a suberin-like lipid biopolymer is located within the concentric polylamellate layers found in the secondary cell walls of green cotton fibres (Gossypium hirsutum cv. green lint). A polymer of similar ultrastructure and chemical constitution also occurs mainly in the secondary seed-coat walls of the outer epidermis of both green and white varieties of G. hirsutum. The suberins composed of predominantly C22 compounds are, however, markedly different from those present in the periderms of the same plants; these comprise mainly C16 and C18 compounds. Long-chain 1-alkanols (C26-C36) and alkanoic acids (C16-C36) are the principal components of the wax from white fibres but these lipid classes comprise a much smaller proportion of that from green fibres. unidentified highmolecular-weight compounds were the major constituents of the green-fibre was extract which also contains a number of yellow-green pigments, probably flavonoid in nature. These pigments are thought to be associated with the ultrahistochemical reaction with silver proteinate that was observed only in the green-fibre cell walls. A total of 16 wild and cultivated cotton species were examined with the electron microscope for the presence of suberin. The outer seed-coat epidermis of all the examined species but only the fibres of the wild ones were found to be suberized. Among the analysed mutants of fibre colour in G. hirsutum only the gene Lg (green lint) seemed to be associated with suberin.

Composition and molecular structure of chromoplast globules of Viola tricolor

Plastoglobules have been isolated in pure form from petals of the pansy, Viola tricolor L. Their chemical composition has been determined up to a recovery of 96% dry weight. Triacyl glycerols (57%) as well as carotenoids and their esters (23%) are the main constituents. Polar lipids, proteins, alkanes, phytyl esters, plastid quinones, and steryl esters have been detected in smaller amounts (cf. Table 1). The mean diameter of chromoplast globules is 280±70 nm (corresponding to a volume of 11.7×10(6) nm(3)), their buoyant density 0.93 g cm(-3). The plastoglobules are devoid of a surrounding unit membrane. However, electron microscopical evidence and analytical data are consistent with a structural model envisaging the globules to consist mainly of an apolar core, covered by a 'half unit membrane' of polar constituents.

The chromatographic analysis of spermaceti

The alkyl esters of spermaceti can be analysed directly by high temperature gas chromatography on a 10% Silicone Elastomer E301 column following the injection of the whole wax. The validity of the technique was established by initial chromatographic work on the isolated alkyl ester fraction and its saponification products. In three commercial wax samples, four homologues C28 (hexadecyl dodecanoate), C30 (hexadecyl tetradecanoate), C32 (hexadecyl hexadecanoate) and C34 (hexadecyl octadecanoate), accounted for 86–89% of the total alkyl esters. Variation in the ester homologue content is produced only by variations in the fatty acid homologue content.

Leaf epicuticular waxes

The external surface of the higher plants comprises a cuticular layer covered by a waxy deposit. This deposit is believed to play a major part in such phenomena as the water balance of plants and the behavior of agricultural sprays. The wax contains a wide range of organic compounds. These complex mixtures are amenable to modern microchromatographic and microspectrometric analytical procedures. The few surveys which have been made of the species distribution of certain classes of constituents indicate that such distribution may be of limited taxonomic value; however, the wax composition of a species may differ for different parts of the same plant and may vary with season, locale, and the age of the plant. This fascinating subject, in which the disciplines of botany, biochemistry, chemistry, and physics overlap and interact, is still in a very active state. Much remains to be learned about the composition and fine structure of the wax deposits, and, for this, experimental study of wax crystallization and permeation through artificial membranes will be required. Enzymic studies, radiolabeling, and electron microscopy will be needed to reveal the mode of biogenesis of the wax constituents and their site of formation and subsequent pathway through the cuticle to the leaf surface.