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

Journal of Cell and Molecular Biology 5: 71-79, 2006.

Haliç University, Printed in Turkey.

Sterols and the phytosterol content in oilseed rape (Brassica napus L.)

Muhammet Kemal Gül *1 and Samija Amar 2

1 Çanakkale Onsekiz Mart University Department of Field Crops, 17020 Çanakkale, Turkey

2 Goettingen Georg-August University Department für Nutzpflanzenwisschenschaften, A b t e i l u n g

Pflanzenzüchtung Von-Siebold Str. 8 37075 Goettingen/, Germany (*author for correspondence)

Received 23 February 2006; Accepted 12 July 2006

Abstract

Sterols are natural, organic compounds with a molecular nucleus of 17 carbon atoms and a characteristic threedimensional

arrangement of four rings. From the chemical point of view sterols are steroid alcohols and their name

is derived from Greek stereos, which mean solid with ending –ol, which is the suffix for alcohols. As essential

constituents of cell membranes, they are widely distributed in all eukaryotic organisms. Playing a structural role in

cellular membranes, they present a significant part of the organism membrane biomass, while their functional role is

evident through the participation in the control of membrane-associated metabolic processes, such as: regulations of

membrane permeability and fluidity, signal transduction events and the activity of membrane-bound enzymes.

Sterols are the precursors of steroid hormones and bile acids in humans, brassinosteroids - phytohormones in plants

and, as the recent identifications of sterol mutants have shown, they are involved in important growth and

developmental processes in living organisms. In recent years 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. In the last decades, more than 40 different sterols were well identified in

different cultivars. These sterols are called phytosterols and they are predominantly present in oilseed plants. The

phytosterol content range between 1.41-15.57 gr/ kg oil and this depends to plant species. Oilseed rape is one of the

most important oil seed crop in the world. phytosterol content in new oilseed rape varieties rang between 5.13 and

9.79 gr/kg oil.

Key Words: Sterol, phytosterol oilseed rape, plant, human

Kolza bitkisinde (Brassica napus L.) sterol ve fitosterol içeri¤i

Özet

Steroller organik bileflikler olup 17 karbon atomundan ve 3 boyutlu dört halka dizisinden oluflmufllard›r. Kimyasal

aç›da bak›ld›¤›nda steroller steroid alkolü olup, sterol ad› Yunanca’da stereos, dayan›kl› yada bozulmayan anlam›na

gelmektedir. Sterolün sonuna eklenen –ol tak›s› ise alkolden gelmektedir. Hücre membranlar›n›n özel yap›s›ndan

dolay› steroller tüm okaryotik canlilarda bulunurlar. Hücre membran›nda yap›sal bir rol oynad›klar›ndan steroller

organizmalar›n membranlar›n›n önemli bir k›sm›n› teflkil ederken, hücre membran› geçirgenli¤inde önemli görevler

alarak bu sistem içinde görev alan enzimlerin aktif hale getirmektirler. Son olarak sterollerin insanlarda öncü steroid

hormanlar› ile safra asitlerini, bitkilerde brassinosteroidler ile fitohormonlar› etkiledi¤ini, son yap›lan çal›flmalarda

da sterollerin canl› organizmalar›n önemli büyüme ve geliflme evrelerinde rol ald›klar› saptanm›flt›r. Son y›llarda

fitosterollerin LDL kolesterol düzenleyicisi özellikleri, kroner ölümleri azalt›c› etkileri bak›m›ndan do¤al önleme

ürünü olmalar› sebebiyle önemleri artm›flt›r. Bitkilerde çok iyi tespit edilip belirlenen 40’dan fazla farkl› sterol

bulunmufltur. Bu steroller ço¤unlukla ya¤ bitkilerinde saptanarak fitosterol olarak adland›r›lm›fllard›r. Yap›lan

çal›flmalarda kültür bitkisine göre elde edilen 1 kg ya¤da bulunabilecek fitosterol iktar› 1,41-15,57 gr/kg arala¤›nda

oldu¤u saptanm›flt›r. Kolza dünyada üretilen en önemli ya¤ bitkilerinden biridir. Kolzada fitosteroller miktar› 5,13 ile

9,79 gr/kg ya¤ aras›nda de¤iflim göstermektedir.

Anahtar Sözcükler: Sterol, fitosterol, kolza, bitki, insan

71

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72 M. Kemal Gül and Samija Amar

Introduction

Sterols are natural, organic compounds and they are

widely distributed in all eukaryotic organisms. They

present a significant part of the organism membrane

biomass, while their functional role is evident through

the participation in the control of membraneassociated

metabolic processes, such as: regulations of

membrane permeability and fluidity, signal

transduction events and the activity of membranebound

enzymes (Piironen et al., 2000). Sterols are the

precursors of steroid hormones and bile acids in

humans, brassinosteroids - phytohormones in plants

and, as the recent identifications of sterol mutants have

shown (Lindsey et al., 2003), they are involved in

important growth and developmental processes in

living organisms (Hartmann, 1998). Plants have a

variety of more than 40 well-identified and studied

sterols (Law, 2000), which are termed phytosterols and

are predominantly present in oilseed plants. Cereals

are recognised as a significant source of phytosterols

as well, whereas phytosterol content in vegetables and

nuts is considerably lower (Piironen et al., 2000;

Piironen et al., 2003; Normen et al., 1999). The most

abundant phytosterols are: sitosterol, campesterol and

stigmasterol. Other phytosterols like avenasterol and

cycloartenol are synthesised earlier in the biosynthetic

pathway and as sterol precursors they usually occur in

relatively smaller amounts (Määttä et al., 1999).

Phytosterols are, with respect to their physiological

function and their chemical structure, similar to the

major and only animal produced sterol – cholesterol.

Increased scientific interest and economic

importance, in the past few decades, in the most

important oil crop in Europe – rapeseed, has been

largely due to its improved quality of oil seeds, which

can yield between 40 and 47 percentages of oil

(Becker et al., 1999). Brassica napus L., known as

rapeseed, rape, or in some cultivars, low in erucic acid

and glucosinolate content, as canola, belongs to the

genus B r a s s i c a , which is a member of the

Brassicaceae (Cruciferae) f a m i l y. This family, of

about 375 genera and 3200 species, includes crops,

condiments and ornamentals but only genus Brassica

is well known for their admirable phenotypical

diversity: cabbage, cauliflower, broccoli, Brussels

sprouts, kohl-rabi, turnip, black and white mustards,

garden cress and so forth (Gomez-Campo, 1999). Like

other vegetable oils, the rapeseed oil is the richest

natural source of phytosterols. Apart from phytosterols

rapeseed oil is predominantly composed of fatty acids,

such as oleic acid, linoleic and linolenic acid (vitamin

F complex), of phospho- and glycolipids and of

tocopherols (vitamin E) and carotenoids - pro-vitamin

A (Rehm and Espig, 1991). Therefore, it became

reasonable to increase the rapeseed oil production.

According to “Food Outlook” (FAO, 2004) from Food

and Agriculture Organisation of the United Nations,

global production of rapeseed crop rose more than

10 % from 1998 to 2002, with the estimation for 2004

that it will reach second place after soybean.

Encouraged with the development of improved rape

cultivars with high quality edible oils and most recent

utilisation of rapeseed oil for bio-diesel (biogenic fuel)

production (UFOP, 2004), the EU farmers expanded

rapeseed planting, exceeding those of soybean,

sunflower, groundnut and cottonseed (Kimber and

McGregor, 1995).

Literature review

Phytosterols have been isolated from a large number

of species and according to numerous publications

(Grunwald, 1980; Gordon and Miller, 1997; Dutta and

Normen, 1998; Piironen et al., 2000) they probably

exist in all angiosperm and gymnosperm species.

Although, there are more than 40 diff e r e n t

phytosterols found in higher plants, sitosterol,

campesterol and stigmasterol often predominate,

while other phytosterols are usually typical only for

certain plant family or even species. Brassicasterol is

for example typical only for Brassicaceae family, and

therefore it could be used for identification

(Benveniste, 2002).

Chemical structure and properties

Sterols belong to a large group of hydrocarbons,

o rganic chemical compounds known as

polyisoprenoids with carbon skeletons structurally

based and derived from multiple isoprene, five carbon

unit -CH 2=C(CH 3)CH=CH 2. Sterols are, together with

tocopherols, carotenoids and chlorophylls, formed by

polymerisation of isoprene unit (Grunwald, 1980).

The structural feature, which virtually all sterols

have in common, is that they are derivatives of a

tetracyclic perhydro-cyclopentano-phenanthrene ring

system with a flexible side chain at the C-17 atom

(Figure 1) and 3β-monohydroxy compounds and

(Hartmann, 1998).

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Animal cells contain only one major sterol, i.e.

c h o l e s t e ro l (Figure 2a). Cholesterol also occurs,

though only in a few percentage of the whole sterol

content, in plants (Gordon and Miller, 1997).

Chemically, it is an analogue to the phytosterols,

differing only in the side chain. Fungal cells, together

with some unicellular algae and lichens synthesise

ergosterol - provitamin D2 (Grunwald, 1980; Rehm

and Espig, 1991). Namely, ergocalciferol (vitamin D2)

is produced by ultraviolet irradiation of provitamin D2

( e rgosterol), which occurs in yeast and fungi (Figure 2b).

In contrast to animal cells and fungi, plant cells

synthesize complex array of phytosterol mixtures with

the sterol profiles varying between species.

The scientific names of phytosterols are given to

them according to the number of C atoms in the C-17

side chain, the number and the position of the double

Sterols and phytosterols in oilseed rape 73

Figure 1. Chemical structure of 5 α cholestan 3β-ol (adapted from Piironen et al., 2000)

a. b.

bond in the ring system and the side chain. Their

scientific names are usually very complex, so the most

common phytosterols are referred to by their trivial

names. The trivial and the scientific names of the most

important phytosterols are given in Table 1.

According to the IUPAC recommendations from

1989, sterol molecules consist of four rings marked as

A, B, C and D with standard carbon numbering

(Figure 1). Three rings, A, B and C, have 6 carbons

atom nonlinear structure and they are fused to one 5

carbons atom ring (D). The various phytosterols found

in plants differ in number of C atom in the side chain

at the C-17 atom and the position and the number of

the double bonds in the ring system. T h e

predominating phytosterols in plants are: campesterol

sometimes referred to as 24-methylcholesterol (Figure

3a), sitosterol (Figure 3c) and stigmasterol (Figure 3d).

Figure 2. Chemical structure of a. cholesterol and b. ergosterol (taken from Kyoto Encyclopedia of Genes and Genomes, 2004)

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74 M. Kemal Gül and Samija Amar

The phytosterol composition of family Brassicaceae

to which rapeseed belongs, differ from most plant

species for an additional brassicasterol (Figure 3e)

while avenasterol (Figure 3b) is considered as one of

the main phytosterol in cereals but, as it has been

discussed (Dutta and Normen, 1998; Piironen et al.,

2002), avenasterol also occurs in Brassica napus seed.

In addition to their vast structural variations,

arising from different substitution in the side chain and

number and the position of double bonds in the

tetracyclic skeleton, different phytosterols play

various roles in higher plants. Yet, it still remains

unknown why do plants require a mixture of

phytosterols instead of only one like animals and fungi

and does each phytosterol play a specific function in

plant metabolism? Further on, for the phytosterol

classification, it is important whether the different side

chains, or functional groups of rings system, are in α,

i.e. under the plain of the cyclic system, or above the

plain - in a β position (IUPAC, 1989). For example,

the side chain and the two methyl groups at C-18 and

C-19 are angular to the ring structure and above the

plane, thus having β-stereochemistry, with additional

3-hydroxyl group also having β- s t e r e o c h e m i s t r y

(Figure 1). Another characteristic specific only to

phytosterols is the alkylation of a C atom at 24 th

position (Figure 3). Sitosterol and stigmasterol have

an ethyl group at C-24 in α-position, whereas

campesterol a methyl group at α- and brassicasterol a

methyl group at β-position (Table 1). According to

their structural and biosynthetical basis, phytosterols

can be divided into three groups: 4-desmethyl, 4monomethyl

and 4,4-dimethyl phytosterols (Table. 1).

Most abundant are three 4-desmethyl sterols:

sitosterol, campesterol and stigmasterol. Other

phytosterols like 4-mono- and 4,4-dimethyl sterols are

synthesised earlier in biosynthetic pathway, so they are

mainly sterol precursors and usually occur in

relatively smaller amounts (Määttä et al., 1999). The

last two are mostly precursors of the sterol

biosynthetical pathway and exist in lower level. The 4desmethyl

sterols can also be distinguished according

to their saturation and position of double bond on the

C-5 and C-7 atoms in the B ring (Figure 1). The

unsaturated sterols are marked with Δ 5 and Δ 7 ,

r e s p e c t i v e l y. Most phytosterols (e.g. stigmasterol,

sitosterol, campesterol, brassicasterol and avenasterol)

belong to the group of Δ 5 unsaturated phytosterols.

Phytosterols with ethyl group at the 24 th C-atom - 24-

ethylsterols (sitosterol, stigmasterol and avenasterol),

mainly have only one type of configuration: 24α.

According to Salo et al. (2003) and Hartmann (1998),

24-methylsterols can consist of a mixture of two

epimers. That is to say, 24-methylsterol is a mixture of

2 4α-methylsterol and 24β-methylsterol know as

campesterol or 22,23 dihydrobrassicasterol (Figure 3a).

Phytosterols are largely hydrophobic having one

polar - hydroxyl group at 3 rd C-atom, making them

amphiphilic. According to one of the sterol

classifications phytosterols with free 3β- hydroxyl

group, are named free phytosterols (Figure 3) and they

are the major end product of biosynthetic pathway of

phytosterols. However, phytosterols also occur as

steryl esters where 3β-hydroxyl group of free

phytosterols is esterified with a long chain of saturated

or unsaturated fatty acids (Figure 4a), mainly linoleic

and oleic, or with phenolic acids (Figure 4d). Steryl

glycosides are formed when the 3β-hydroxyl group is

linked with monosaccharides, usually glucose, at the

first C position (Figure 4c).

When this monosaccharide is at the 6-C position

esterified with fatty acid, than so-called acylated steryl

glycosides are formed (Figure 4b).

Biological functions in plants

Phytosterols have both structural and metabolic

functions. Structural role is obvious through the fact

that they are integral membrane components. Being

incorporated into membranes they are determining the

characteristics of plasma membrane and, additionally,

of endoplasmic reticulum and mitochondria

membranes. Most likely, they also have a certain

function in the membrane adaptation to temperature

variations (Piironen et al., 2000). Participating in the

control of metabolic processes, such as regulation of

membrane permeability, fluidity, signal transduction

events for cell division and even activity of

membrane-bound enzymes, they fulfil their metabolic

role (Hartmann, 1998; Lindsay et al., 2003).

Interacting with their side chain, with the fatty acyl

moiety of membrane phospholipids and proteins

complexes, phytosterols restrict the motion of

membrane bilayers (i.e. the sterol ordering effect),

regulating membrane fluidity (Nes, 1987).

It has been postulated that sitosterol and

campesterol are most efficient in membrane

permeability and fluidity regulation and there are

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a. b.

d. e.

evidence that stigmasterol play an important role in

cell proliferation, but has reduced ordering effect

(Hartmann, 1998). Finally, it appears that they

influence the plant development through the

localisation and functionality of key regulatory

proteins (Lindsey et al., 2003). During the seed

germination, the phytosterol content increases, which

is due to intensive membrane biosynthesis.

Phytosterols that are accumulated in seeds and

meristematic tissue are playing an important role in

cellular proliferation and differentiation. Furthermore,

in youngest plant tissues, the membrane biosynthesis

is more intensive. Consequently, phytosterol synthesis

will appear mostly during the seed formation and

germination and phytosterols themselves will provide

a supply for the growth of new cells and young shoots.

By the time when seeds are already mature or tissues

ages, the intensity of biosynthesis will decline

(Grunwald, 1980). Besides, the high phytosterol

amount could be also largely explained by the

anatomical structure of different plant tissues. For

instance, flower heads of broccoli and cauliflower

(Brassica oleracea L. ) have higher proportion of

membrane-rich meristematic tissue, which results in

Sterols and phytosterols in oilseed rape 75

Figure 3. Examples of the most important phytosterols showing the difference in their chemical structure: a. campesterol,

b. avenasterol, c. sitosterol, d. stigmasterol and e. brassicasterol (taken from Kyoto Encyclopedia of Genes and Genomes, 2004)

c.

higher content of total phytosterols in this species in

comparison with other vegetables, fruits or berries

(Piironen et al., 2003; Normen et al., 1999).

M o r e o v e r, free phytosterols are precursors of

bioactive steroids, growth factors and substrates for

synthesis of numerous secondary plant metabolites

(Willmann, 2000; Piironen et al., 2003). Campesterol

is the precursor of brassinosteroids - phytohormones

found in Brassica pollen (Benveniste, 2002). Plant

steryl esters, intracellularly distributed, represent a

storage form of phytosterols, analogously as

cholesterol esters in mammalian cells (Piironen et al.,

2000).

Biological functions of phytosterols in humans

In contrast to phytosterols, cholesterol can be in

humans, either synthesised de novo in liver, or taken

up from the environment. During the process of

cholesterol absorption, it is being transported from the

lumen of intestine, across the intestinal wall and into

the blood. Low-density lipoprotein (LDL) then

transports cholesterol through the blood system.

Narrowing the channels of the blood vessels, LDL-

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76 M. Kemal Gül and Samija Amar

Figure 4. Examples of steryl conjugated structures: a. oleic acid steryl ester, b. palmitic acid steryl glycosides, c. steryl glycosides

and d. phenolic acid steryl ester (adapted from Piironen et al., 2000)

cholesterol thus constricts the blood flow and those

people with high cholesterol levels eventually become

more susceptible to Cardiovascular Diseases (CVD)

such as: coronary heart disease (CHD), also known as

heart attack, hypertension (high blood pressure),

cerebrovascular (stroke) and peripheral vascular

diseases (Salo et al., 2003). According to the “World

Health Report 2003” of United Nations World Health

Organisation, heart attacks and strokes kill 12 million

people around the world every year, from which,

around 75% of CVD can be attributed to the major

risks: high cholesterol, high blood pressure and low

fruit and vegetable intake. By 2010 estimations are

that CVD will be the leading cause of death in

developing countries. Since the medical care of CVD

is costly and prolonged, there is, consequently, an

evident need for cholesterol suppression.

According to many conducted experiments

phytosterols decreases serum total and LDL

cholesterol levels (Gylling et al., 1997; Miettinen,

2001; Nissinen et al., 2002; Trautwein et al., 2003). It

was suggested that phytosterols compete at the same

time, in the micellar phase of the small intestine, for

the limited space with cholesterol. Micelles are the

essentially small aggregates, which are carrying a

mixture of lipids and bile salts in intestinal lumen.

Sitostanol esters, 5α-saturated sitosterol esters, were

recognised as the most efficient for reducing the serum

cholesterol concentration and the intestinal cholesterol

absorption (Nissinen et al., 2002). As it seems they

could be easily produced by sterol hydrogenation and

trans-esterification with polyunsaturated fatty acids

(Piironen et al., 2000). Sitostanol esters apparently

result similar in prevention of cholesterol absorption

but, in contrast to phytosterol esters, they do not

increase their own absorption. In addition to this fact,

it has been confirmed (Miettinen, 2001) that relatively

high campesterol content, in some phytosterol

complexes like soy phytosterols for example, can

increase the campesterol proportion in serum, what

w a s n ’t acknowledged for plant stanols, including

campestanol (5α-saturated campesterol). Phytosterol-

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ich diets may thus, result in symptoms analogue to

phytosterolemia, hereditary metabolic disorder

characterised by elevated phytosterol level in blood

and tissue. Additional esterification of phytosterols

and stanols with long chain of mono- or

polyunsaturated fatty acids will increase their lipid

solubility, facilitating their incorporation into the food,

at the same time.

A new rapeseed margarine Benecol, obtained from

rapeseed oil by phytostanols trans-esterification

(Miettinen, 2001) and enriched with sitostanol-esters

was first launched in ’95 in Finland (Miettinen et al.,

1995) and by the end of ’99 already introduced in

several other European countries and worldwide (Law,

2000). Functional spreadable oils and fats, with

corresponding products like: margarine, milk and

yoghurt, first appeared in Germany in July 2002,

under the product name “Becel pro-activ”. It was

found that 3 g/day of phytostanol ester margarine, like

Benecol, could actually reduce the LDL cholesterol

level up to 14-22 %, decreasing the amount of

Sterols and phytosterols in oilseed rape 77

Table 1. Trivial and scientific names of selected sterols from the sterol biosynthetic pathway (adapted from Grunwald, 1980)

Trivial Name Scientific Name Sterol Class

Cycloartenol 9beta,19-cyclo-24-lanosten-3beta-ol 4,4-dimethyl

24-Methylene Lophenol 4-alpha-Methyl-5-alpha-ergosta-7,24-dien-3-beta-ol 4-methyl

Avenasterol 24-ethylcholesta-5,24(28)Z-dien-3‚-ol 4-desmethyl

Cholesterol cholest-5-en-3‚-ol 4-desmethyl

Campesterol 24·-methyl-5-cholestern-3‚-ol 4-desmethyl

Brassicasterol 5,22-cholestadien-24‚-methyl-3‚-ol 4-desmethyl

Sitosterol 24·-ethylcholest-5-en-3‚-ol 4-desmethyl

Stigmasterol 5,22-cholestadien-24·-ethyl-3‚-ol 4-desmethyl

Table 2. Variation of phytosterol content in six different vegetable oils (g/kg of oil) (adapted from Piironen et al., 2000)

Oil Type Brassicasterol Campesterol Stigmasterol Sitosterol Avenasterol Total Phytosterols

Corn * 2.59 0.98 9.89 0.36 8.09-15.57

Rapeseed 0.55-0.73 1.59-2.48 0.02-0.04 2.84-3.59 0.13-0.19 5.13-9.79

Sunflower - 0.69 0.75 4.65 0.28 3.74-7.25

Cottonseed * 0.26 * 4.00 0.05 4.31-5.39

Soybean - 0.62-0.76 0.45-076 1.22-2.31 - 2.29-4.59

Olive (Extra Virgin) - 0.05 0.01 1.18-1.21 0.17-0.18 1.41-1.50

*found in traces

-not available

absorbed cholesterol up to 65 % (Law 2000; Miettinen

et al., 1995; Miettinen, 2001; Jones et al., 1999). The

reduction of LDL cholesterol level up to 20 % was,

according to Gylling et al. (1997), achieved with the

rapeseed margarine (5 %) and with the sitostanol

esters (15 %) present in that margarine. In this study, it

has been also proven that consumption of roughly 2 g

a day of phytosterol-enriched margarines can decrease

the coronary mortality, by about 25 %. Furthermore,

latest experimental studies have shown that dietary

phytosterols may be used also as prevention for

several types of cancer e.g. stomach and colon cancer

(Normen et al., 2001).

Genetic variation and modification

Gordon and Miller (1997) have published results of a

steryl ester composition in 10 different oil types: corn,

rapeseed, groundnut, olive, soybean, safflower, oleic

sunflower, linoleic sunflower, cottonseed and palm oil.

They have discovered that rapeseed had, after the corn

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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

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