Sterols and the phytosterol content in oilseed rape - Journal of Cell ...

78 M. Kemal Gül and Samija Amar
oil, second highest phytosterol proportion in oil. The
mean content in oil of five rapeseed varieties was 6900
mg/kg, in which the free phytosterol fraction equals
65 % and the steryl ester fraction equals 35 %, of the
total phytosterol content. They have published that
their phytosterol content in oil can vary to a great
extent from 6540 mg/kg to 8550 mg/kg of oil.
Nevertheless, the average total sterol content of
6900mg/kg classifies rapeseed oil, into oils with the
highest content i.e. higher than 4000 mg/kg of oil. On
the other hand Appelqvist et al. (1981) ascertained the
content of free phytosterols in the total amount of
rapeseed oil would be then 0.3 % and esterified
phytosterols 0.6 %. Piironen et al. (2000) have
published collected results of phytosterol content in
crude corn, cottonseed, rapeseed, olive, soybean and
sunflower oil (Table. 2), in which they have showed
the majority of crude vegetable oils contain, at least
1 g/kg to 5 g/kg of oil. However, they have found that
the most significant exceptions are corn (up to 16 g/kg
of oil) and rapeseed oil (up to 10 g/kg of oil).
According to Abidi et al. (1999) the total
phytosterol content is affected by genetic
modifications. They have compared 10 experimental
transgenic and non-transgenic canola genotypes
differing in fatty acid composition and concluded that
the phytosterol content was influenced by the genetic
modification of the fatty acid composition. A
significant decrease in amount of three major
phytosterols: sitosterol, campesterol and
brassicasterol, was observed in non-transgenic canola
varieties grown for low-linolenic and high oleic acid.
In addition, the amount of brassicasterol varied widely
based on genotype and growing conditions.
Brassicasterol content ranged from 85 to 189 mg/100 g
of modified oil; campesterol content ranged from 205
to 264 mg/100 g; sitosterol from 457 to 509 mg/100 g
and finally variation of the total phytosterol contents
was from 766 to 961 mg/100 g of modified oil. On the
other hand, there wasn’t any systematic trend of
phytosterol content in transgenic canola lines. In his
paper Miettinen (2001) discussed on what plant
breeders should focus when trying to developing new
nutritionally interesting plant with an ideal phytosterol
content, which could be later on used for cholesterollowering
functional food production. He suggested
that ideal phytosterol composition should contain
mainly sitosterol esters with low campesterol ester
content, because apparently campesterol esters result
in similar changes, when reduction of serum
cholesterol level is concerned, but at the same time, in
contrast to sitosterol esters, they increase their own
absorption. His second suggestion for oil, which
would be preferable for preparation of functional food,
was that it should be rich with stanols, especially
sitostanol, esterified with polyunsaturated fatty acids.
Since phytostanols are less abundant in plants than
phytosterols, in order to produce esterified
phytostanols, the final food price will increase.
Result
Plant sterols, also called phytosterols, occur as organic
compounds and essential constituents of cell
membranes in all plant oils. Recently increased
interest in phytosterols lies in their potential to reduce
plasma low-density lipoprotein cholesterol level,
decreasing coronary mortality and therefore acting as
naturally preventive dietary product. High
expectations have already been put forward regarding
phytosterol analysis and traditional plant-breeding
applications in developing improved cultivars with
desirable phytosterol composition and increased
content.
Phytosterols occur in relatively high concentration
in the seeds of oilseed rape (Brassica napus L.).
However, little is known about genetic variation of
phytosterols and almost no data are available of the
impact of geographic location and agricultural
practices on the content and composition of
phytosterols in rapeseed. To improve the phtosterol
composition must be a major breeding aim for a high
quality vegatable oil production.
References
Abidi SL, List GR and Rennick KA. Effect of genetic
modification on the distribution of minor constituents in
canola oil. Journal of American Oil Chemists’ Society,
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Appelqvist LAD, Kornfeldt, AK and Wennerholm JE.
Sterols and steryl esters in some brassica and Sinapis
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Becker HC, Löptien H and Röbbelen G. Breeding: An
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Dutta CP and Normen L. Capillary column gas-liquid