10
saccharina Walker. Morris et al. 2000 described 1-octacosanal
C28-aldehyde as the major component of wheat epicuticular wax that stimulates oviposition of the Hessian fly, Mayetiola destructor.
Comparison of the activity of five straight-chain primary aldehydes with chain lengths from C22 to C30 revealed a relationship between chain length
and the number of eggs laid by female Hessian flies, with 1-hexacosanal and 1-heptacosanal the most active of the aldehydes tested.
Wax is valuable source for many industries such as cosmetic, food ingredient, lubricant, printing and many other applications. Wax esters,
oxo esters of long-chain fatty acids esterified with long-chain alcohols, can be used as high pressure lubricants, as replacements for hydraulic oil, and in
the pharmaceuticals, leather, and food industries, as well as in candles and polishes. Long chain alkanals are known as favorable cosurfactants of
liquids containing charged micelles Meziani et al. 1997. Lately, long chain aliphatic alcohols of sugarcane wax have been used as
cholesterol-lowering products Taylor et al. 2000; Castano et al. 2003.
D. Wax Compositional Analysis
Wax content and composition, including long chain alcohols and aldehydes, can be analyzed with many techniques and instruments. The
determination of wax composition often requires extensive sample extraction and preparation prior to instrumental analysis. Cuticular wax from potato
leaf was extracted by dipping and shaking the leaves in dichloromethane Szafranek Synak 2006, as same as with cyclohexane in beeswax,
11
spermaceti, carnauba, candellila and Japan waxes Regert et al. 2005. Sorghum wax was extracted from grain sorghum using hot hexane and
precipitating it in a -18°C Hwang et al. 2002; Adhikari et al. 2006. Similar extraction concept was applied by Kanya et al. 2007, where
sunflower seed wax was purified from oil refineries through extraction using solvents and precipitation with chilled acetone. Liquid-liquid extractions
were successfully applied in beeswax, sugarcane and wheat Irmak Dunford 2005; Irmak et al. 2006.
Recently, non conventional methods for wax extraction have been developed with many techniques. Super critical carbon dioxide extractions
were reported to have higher waxes yields than solvent extractions, i.e. cuticular wax from flax processing waste Morrison et al. 2006, beeswax
Jackson Eller 2006, and sugarcane crude wax Lucas et al. 2007. Solvent-free extraction with high-intensity ultrasound treatment was studied
in rice bran wax. Under sonochemical conditions bran wax could also be hydrolyzed yielding long chain alcohols Cravotto et al. 2004. Molecular
distillation was used to increase the purity of octacosanol C28-alcohol extracts from transesterified rice bran wax Chen et al. 2005, 2007.
Compositional analysis of wax can be conducted with some instruments, whether qualitative or quantitative analysis. Thin layer
chromatography was widely used to separate wax components Hwang et al. 2002; Adhikari et al. 2006. Analytical methods of wax quantification
were applied with high performance liquid chromatography Hwang et al. 2002; 2005. Wax compounds were identified and confirmed by gas
chromatography-mass spectrometry Nuissier et al. 2002; Jiménez et al.
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2003; Kanya et al. 2007 and liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization Rezanka Sigler 2006.
Main components of plant waxes were composed of fatty aldehydes, fatty alcohols, fatty acids, hydrocarbons, wax esters, sterol esters and
triacylglycerols Hwang et al. 2002; Adhikari et al. 2006, based on HPLC data. Recently, mixture of long chain aliphatic primary alcohols,
policosanols, has been well investigated with gas chromatography technique Cravotto et al. 2004; Irmak Dunford 2005; Irmak et al. 2006; Wang et al.
2007. The mixture contains mainly docosanol C22, tetracosanol C24, hexacosanol C26, octacosanol C28, and triacontanol C30, listed in
Table 3.
Table 3 Mixture composition of aliphatic alcohols policosanols
No Structure
Nomenclatur Molecular
Weight Carbon number
1 CH
3
CH
2 20
CH
2
Docosanol OH
326.67 C22-alcohol
2 CH
3
CH
2 22
CH
2
Tetracosanol OH
354.40 C24-alcohol
3 CH
3
CH
2 24
CH
2
Hexacosanol OH
382.40 C26-alcohol
4 CH
3
CH
2 25
CH
2
Heptacosanol OH
396.40 C27-alcohol
5 CH
3
CH
2 26
CH
2
Octacosanol OH
410.74 C28-alcohol
6 CH
3
CH
2 27
CH
2
Nonacosanol OH
424.74 C29-alcohol
7 CH
3
CH
2 28
CH
2
Triacontanol OH
438.80 C30-alcohol
Sugarcane is the major source for the production of commercial policosanol products. Irmak et al. 2006 reported that sugarcane peel
contained the highest amount of total policosanols, about 270 mgkg. The total policosanol contents of sugarcane leaves 181 mgkg were quite
similar to that of the wheat straw 164 mgkg. Although, policosanol
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compositions of sugarcane plant parts varied significantly, C28 about 81 was the main component in all the sugarcane samples Table 4.
Policosanols in the perilla seeds were composed of 67–68 octacosanol, 16–17 hexacosanol, and 6–9 triacontanol. The analysis of
commercially milled wheat grain fractions, germ, bran, shorts, and flour showed that policosanols where concentrated in the bran. Wheat germ
contained a significant amount of policosanols 10.1 mgkg. These results were expected since policosanols are associated with lipids and wax in plant
tissues. About 36 of the total policosanols in the wheat bran fraction was constituted of tetracosanol.
Table 4 Content and composition of policosanols in some materials
No Material
Policosanol content mgkg C24
C26 C28
C30
1 Whole sugarcane
1.68 ± 0.08
a
0.9 ± 0.2 10 ± 0.2
1.0 ± 0.2 2
Sugarcane peel 7.7 ± 0.2
a
2.3 ± 2 219 ± 3
16 ± 2 3
Sugarcane leaves 29.4 ± 0.5
a
22.4 ± 0.8 84 ± 4
26.6 ± 0.6 4
Beeswax brown 2.6 ± 0.1
a
1.7 ± 0.1 2.0 ± 0.1
5.7 ± 0.5 5
Beeswax yellow 1.11 ± 0.06
a
0.86 ± 0.07 0.90 ± 0.03
2.3 ± 0.4 6
Perilla Seed Korea 1.6 ± 0.13
b
17.6 ± 0.01 68.4 ± 1.44
6.8 ± 1.42 7
Perilla Seed China 1.5 ± 0.06
b
16.6 ± 0.43 67.4 ± 0.07
9.1 ± 0.17 8
Wheat germ 1.4 ± 0.2
c
n.d. 2.9 ± 0.3
2.5 ± 0.3 9
Wheat bran 10.68 ± 0.01
c
4.87 ± 0.03 4.39 ± 0.02
n.d. 10
Wheat shorts 0.82 ± 0.01
c
0.45 ± 0.03 0.39 ± 0.01
0.22 ± 0.03
Note: n.d. = not detected
a
Irmak et al. 2006
b
Adhikari et al. 2006
c
Irmak Dunford 2005
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E. Policosanol in Human Health
