Sterol composition

It has been suggested [6] that these unusual sterols, especially in those cases where these unusual sterols comprise the entire sterol content of the organisms, likely replace conventional sterols as cell-membrane components. Evidence for this comes from subcellular fractionation and subsequent analysis of two marine sponges [10]. The sterol composition of the membrane isolates was found to be identical to that of the intact sponge. Most common variation of the marine sterol is in the side-chain, situated deep in the lipophylic environment of the phospholipid bilayer. This suggests that unusual fatty acids might accompany the sterols, and indeed this is often the case [8]. 

The sterol composition of marine organisms, including molluscs, has been reviewed by Goad [105] and more recently by Kerr and Baker [106]. A general picture emerges that molluscs do not possess the spectrum of exotic sterols... 

J.S. Mills, R. White, The identification of paint media from the analysis of their sterol composition, Studies in Conservation, 20, 176 182 (1975). 

Marshall JA et al (2001) Soybean sterol composition and utihzation by Phytophthora sojae. Phytochemistry 58 423... 

Bergenstrahle, A., Borga, P, Jonsson, L. (1996). Sterol composition and synthesis in potato tuber discs in relation to glycoalkaloid synthesis. Phytochemistry, 41, 155-161. 

Bitman, J. 1976. Status report on the alteration of fatty acid and sterol composition in lipids in meat, milk, and eggs. In Fat Content and Composition of Animal Products. National Academy of Sciences, Washington, D. C., pp. 200-237. 

T Itoh, T Tamura, T Matsumoto. Sterol composition of 19 vegetable oils. J Amer Oil Chem Soc 50 122-125,1973. 

To determine whether our strategies could be applied to all of the human pathogens we studied, the sterol composition and the rate of sterol biosynthesis in untreated organisms have been estimated (Figure 16). All the organisms synthesize ergosterol up to 90 % or... 

Griffiths, K.M., Bacic, A., Howlett, B.J. Sterol composition of mycelia of die plant pathogenic ascomycete Leptosphaeria maculans. Phytochemistry 2003 62 147-153. 

Schor, L. and Seldes, A. M., Steroids from aquatic organisms — XVII. Sterol composition of the salp Ihlea racovitzai from the Antarctic Ocean, Comp. Biochem. Physiol., 92B, 195, 1989. 

Zlatanov, M. and Ivanov, S.A. (1995) Studies on sterol composition of the seed oil of some representatives of the family Apiaceae. Fett issenschaft Technologie 97(10), 381-383. 

Andriamanantena, R.W., Artuad, J., Caydofn, E.M., latrides, M.C. and Chavalier, J.L. (1983) Fatty acid and sterol composition of Malagasy tamarind kernels. Journal of the American Oil Chemists Society 60(7), 1318-1321. 

Dyas, L., Threlfall, D.R. and Goad, L.J. (1 994) The sterol composition of five plant species grown as cell suspension cultures. Phytochemistry 35(3), 655-660. 

Colombini, M., Vanoni, M.C. and Amelotti, G. (1979) Oil of walnut, hazelnut, almond, avocado sterol composition. Riv. Ital. Sost. Grasse, 56, 392-393. 

Desbordes, S., Morin, O. and Prevot, A. (1983) Study of occurrence of brassicasterol in sunflower oil and variations in sterol composition of French sunflower seeds. Ann. Falsif. Exp. Chim. Toxicol., 76, 151-169. 

Gargano, A. (1981) Fatty acid and sterol composition of oils used in foods. Ind. Aliment., 20, 510-513. 

Sciancalepore, V. and Dorbessan, W. (1982) Sterol composition of avocado oil. Grasas Aceites, 33, 273-275. 

Table 4.9 Sterol composition of evening primrose and cottonseed oils...

Because of the toxic nature of these oxidized components, the authors cautioned regular intake of encapsulated fish oils. The sale of oxidized fish oil products can be considered criminal as they pose potential health risks to the consumer. In addition to ensuring that the consumer is buying the authentic product, it must be fresh, with a clear and realistic shelf-life date indicated. The presence of vegetable oils in a fish oil is best tested for by examination of the sterol composition, as fish oils consist almost entirely of cholesterol and 24-methyl cholesterol (Paganuzzi, 1983). Analysis of the sterol fraction of the oil can often identify the oil, or at least indicate which oils might be present. 

Although many vegetable oils are quite similar in sterol composition, there are some important differences. Detection of brassicasterol can be used to detect adulteration of many oils by rapeseed oil as this sterol is only present in most oils in small amounts but rapeseed oil contains up to 780 mg/kg brassicasterol (see Table 6.1). The detection of adulteration of vegetable oils with animal fats can be achieved by analysis of the cholesterol content, since this sterol is either absent or present at very low concentrations in vegetable oils. 

Homberg,V. (1974) Alteration of sterols by industrial processing of fats and oils, I Influence of refining conditions on the sterol content and sterol composition. Fette Seif. Anstrichm., 76(10), 433 135. 

FENNER, G.P., PATTERSON, G.W., KOINES, P.M., Sterol composition during the life cycle of the soybean and the squash, Lipids, 1986,21,48-51. 

Nabil, S., and Cosson, J. 1996. Seasonal variation in sterol composition of Delesseria sanguinea (Ceramiales, Rhodophyta). Hydrobiologia, 326/327, 511-514. 

Analytical methods for plant sterol analysis are commonly based on procedures used for cholesterol analysis. However, a significant shortcoming of these methods is the fact that cholesterol occurs only as free cholesterol and fatty acid esters. Therefore, the analytical methods optimized for cholesterol analysis are not suitable, or only suitable with some restrictions, for the analysis of conjugates found only in plants (SFs, SGs, and ASGs). Further, the methods described below only give the total amount of plant sterols and no information of the different sterol species found in the samples. However, if detailed information about the sterol composition is not required, and the amount of sterols to be analyzed is sufficiently high for these less sensitive but simpler methods, they provide a less laborious alternative for the analysis. 

All in all, the spectrophotometric methods for the measurement of SFs in various samples are a rapid and simple way to get a value for the total SFs. However, they do not provide any information on the sterol composition (molecular species of different sterols) found in a sample, which may be of biological significance. The spectrophotometric detemination works best on oil samples, where the extraction of SFs and the challenges caused by the selection of an extraction solvent are omitted Extraction . 

When applying acid hydrolysis, one must be aware of the possible isomerization and destmction of some of the less stable sterol species caused by the treatment with acid. The acid treatment is known to cause, for example, the isomerization of A -avenasterol to stigmastadienol (Kamal-Eldin et al., 1998), which will alter the sterol composition of the sample (artifacts). Furthermore, when acid hydrolysis is performed on an extract of sterols (not direct hydrolysis, where solid material is also present), the treatment must be sensitive enough not to destroy the labile sterols (weaker acid concentration, less heating, shorter reaction time). 

Giner J.-L., Li X., and Boyer G. L. (2001) Sterol composition of Aureoumbra lagunensis, the Texas brown tide alga. Phytochemistry 57, 787-789. 

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