Brassica sterol

The plasma membrane-enriched fractions of the T, deformans reference cells contained membrane-bound vesicles typical of such fractions (Weete et al., 1985b). The major fatty acids of these membranes were those expected for this fungus (Sancholle, 1984 Weete et al., 1983), i.e. palmitic, stearic, oleic, linoleic and linolenic acids (Table 1). The A/mole was relatively low at 0.84 which indicated that the lipids of these membranes had a relatively high amount of saturated fatty acids. Brassica-sterol and an unidentified C28 diene were detected as previously reported for this species at 84.5% and 15.5%, respectively (Weete et al., 1985a). 

The above shows that rapeseed oil can easily be detected, or eliminated, as a contaminant by sterol analysis. It is also, at least in Europe, the oil most likely to be used to dilute another oil. Although low levels (as a percentage of the total sterols) have been reported in some other oils (Desbordes etal., 1993), the presence of brassicasterol in an oil is good evidence of contamination in any oil from a non-Brassica species. It is likely that the traces reported as present in some other oils arise from contamination of the sample with rapeseed oil, or from some other Brassica species, or from traces of some similarly behaving non-sterol not fully separated from the sterol fraction during the work-up of the sample (Desbordes et al., 1983). 

Acid composition Sum of the trans-oleic isomers Sum of the trans-linoleic and trans-linolenic isomers (%) Chole- sterol (%) Brassica- Campesterol sterol Stigma- sterol (%) p- sitosterol apparent (%) 8-7- Stigma- stenol (%) Total sterols (mg/kg) Erytro- diol + uvaol (%)... 

Appelqvist, L.A., Kornfeldt, A. and Wennerholm, J. (1981) Sterols and sterol esters in some Brassica and Sinapis seeds. Phytochem., 20, 207-210. 

Sterols or phytosterols are present in flax oils at a level lower than those in many vegetable oils, 2.3 mg/g in flaxseed oil versus 4.1 to 6.9 mg/g in other oils (Table 2). The composition of sterols was similar to other oils, where p-sitosterol was the main component followed by campesterol and A -avenasterol. Brassicasterol was found in trace amounts in flax oil. This phytosterol is characteristic to plants from the Brassica family and often is used as a marker for oil adulteration (Table 2). 

Plant sterols identified in this oil consist mainly of p-sitosterol and campesterol (Table 4). About 4% brassicasterol was detected in the oU, which is typical for Brassica family plants (51). The total content of sterols in oil is comparable with other commercial oils (Tables 2 and 4). The presence of cholesterol in camelina oil makes it unique among vegetable oils, where only a trace has been detected in some tropical oils (51). 

Italian and Spanish ohve oil from the 1991-1992 crop year contained a very high level of 9,19-cyclolanosterol (>400 mg/kg), which was not found with the standard method for sterol analysis. Two isomers of this sterol were identified by GC/MS of the unsaponifiable fraction, and their levels were found to be inversely proportional to the levels of p-sitosterol in the oils. GC/MS of the unsaponifiable fraction with high-resolution GC capillary columns provides a relatively rapid means of checking product purity and the identity of individual components. Thus, triterpene diols were identifiable at m/z 203, ot-tocopherol at m/z 165, squalene at m/z 69, cholesterol at m/z 386, and brassicasterol, characteristic of canola oil and other Brassica oils, at m/z 398. 

Preparative HPLC was used to separate sterols and triterpene alcohols from the unsaponifiable matter in plant oils from Camellia weiningensis L., Brassica juncea L., and Microula sikkimensis. The isolated compounds were acetylated and further purified by AgN03-impregnated silica gel preparative thin layer chromatography (TLC). The identification was done by IR and MS. 

The composition of major sterols in common vegetable oils is presented in Table 4.8. Brassicasterol is a major sterol in rapeseed and canola oils and as it is unique to brassica oils it is often used to detect adulteration of other oils with rapeseed/canola oils (Strocchi 1987 Ackman 1990). Sterols are affected by processing and about 40% of these components can be removed from the oil during deodorization. Refining also causes changes in the chemical structure of sterols (Kochar 1983 Marchio el al. 1987). 

HEAR and LEAR oils contain brassicasterol, a C28 sterol (Fig. 3) characteristic of Brassica oils. It does not occur in other common edible vegetable oils (Table XII) except for mustard oil. Brassicasterol is, thus, a key factor in identifying Brassica oils either by themselves or after blending with other edible oils, since fatty acid compositions cover a range for each oil due to cultivar, climate, or maturity, and overlaps in physical properties are common (Spencer et al., 1976). Among recent authors examining this question... 

Content of Free Sterols, Esterified Sterols and Steryl Esters in Oils from Brassica campestris and B, napus Seeds ... 

The Free Sterols and Esterified Sterols of Some Seeds of Brassica and Sinapis Species"... 

As many will appreciate, the detection of small amounts of rapeseed oil in soybean oil can be easily accomplished by determination of sterol composition. Table 8.4 shows sterol compositions of nine oils, including rapeseed and soybean oil rapeseed oil contains quite significant quantities of brassicas-terol, whereas the level in soybean oil is almost zero. Table 8.4 also shows that rapeseed oil contains a small amount of cholesterol. In some countries it may be claimed that vegetable oils are free from cholesterol. Although this may be permitted under the local law, it is not, of course, scientifically correct. 

Brassicastarol, ergosta-S,22-dien-3p-ol a plant sterol (see Sterols), M, 398.69, [a]o -64°, m.p. 148 °C, first isolated form rapeseed (Brassica campes-tris) oil. 

A > -sterol (brassicasterol) with little or no 22-dihydro derivative present. The monoenic 24-methylcholesterols, therefore, are composed almost entirely of the 24a-eplmer (campesterol). However, in the mature leaf brassicasterol has all but disappeared and the 24-methylsterols have become the usual main line mixture of campesterol with smaller amounts of 22-dihydrobrassicasterol. It appears from this that in the synthesis of Brassica seed sterols a A22-dehydrogenase is present which declines during ontogeny suggesting functionality for the sterols used and/or produced. 

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