Plant lipids sterols

A mechanism Is proposed by which water-insoluble plant lipids (sterols etc.) may act as allelochemicals via micelle formation with long-chain fatty acids. By this process plant lipid solubility and transport In the aqueous medium are enhanced. This might suggest a reevaluation of water-insoluble plant constituents such as sterols as potential allelopathic agents. 

Possible Mechanism of Allelopathlc Action of Water-Insoluble Plant Lipids. Many non-polar natural products with germination and growth regulation activities In laboratory tests are In pure form not sufficiently water soluble to account for their allelopathlc activities observed In the field. For this reason the notion exists that sterols and other non-polar plant constituents are not likely to play a role In allelopathlc actions, and It Is generally concluded that the bioactivity data observed In the laboratory are therefore coincidental. 

We have recently observed in our laboratory that water washes of undamaged leaves in a number of plants contained sterols and other lipids in sufficiently high concentration comparable with concentrations used in typical laboratory bioassays. These aqueous lipid solutions are frequently accompanied by long-chain (C-12 to C-18) fatty acids. We therefore suggest that micelle formation between the lipids and fatty acids may occur. By this mechanism the lipid solubility in the aqueous medium is significantly enhanced, thus allowing the release of otherwise water-insoluble plant constituents into the environment. Presently, experiments are in progress in our laboratory to provide further evidence for the "micelle-mechanism" of allelopathlc lipids. 

Schrick, K., Nguyen, D., Karlowski, W. M., and Mayer, K. F. 2004. START lipid/sterol-binding domains are amplified in plants and are predominantly associated with homeodomain transcription factors. Genome Biol., 5(6) R41. 

Sterols are seldom detected in archaeological residues due to their low concentration and the tendency to undergo chemical degradation. In any case, the presence of sterols or of their oxidation products in a sample can help distinguish between animal and plant lipid materials cholesterol is the most abundant animal sterol, while campesterol and sitosterol are the two major plant ones. 

The example of a total extract composition of a tropical soil from the Amazon, Brazil, shows mycose as the major compound, numerous other monosaccharides, lipid components such as fatty acids and fatty alcohols, and natural product biomarkers (Fig. 9a). The mycose and elevated levels of the other saccharides reflect the efficient fungal/microbial degradation of plant detritus in the tropics. This can be compared to the saccharides in the soil from an almond orchard in California, where glucose and mycose are the main sugars with lipids, sterols and triterpenoids (Fig. 9b, ). 

Nes, D.W. Biosynthesis and requirement for sterols in die growth and reproduction of Oomycetes. In Ecology and Metabolism of Plant Lipids. Fuller, G, Nes, W.D. ed., American Chemical Society, Washington, DC. 1987 pp. 304-328. 

Plant waxes are concentrated on leaves and leaf sheaths and on fruit skins, or in some exceptional cases in the seeds of plants. Most vegetable waxes contain predominantly wax esters plus a variety of other lipid materials, which affect the degree of saturation and other properties of the wax derived from different sources. Most use has been made of plant waxes in the cosmetic sector, but there is increasing interest in the use of plant-derived sterols as dietary supplements to reduce cholesterol formation. 

The major dietary lipids for humans are animal and plant triacylglycerols, sterols, and membrane phospholipids. The process of lipid metabolism fashions and degrades the lipid stores and produces the structural and functional lipids characteristic of individual tissues. For example, the evolution of a highly organized nervous system has depended on the natural selection of specific enzymes to synthesize and degrade (turn over) the lipids of the brain and central nervous system. 

Unesterified sterols modulate the function of eukaryotic membranes. In human cells, sterol is esterified to a storage form by acyl-co-enz)me A (CoA) cholesterol acyltransferase (SGTase). In plants, free sterols are associated mainly with microsomal membranes, whereas the steryl esters are stored in lipid granules. The esterification process may, thus, allow regulation of the... 

Moisture, impurities, and unsaponifiables (MIU) A summation of the non-acylglycerol materials in the product. Moisture is undesirable because it will support microbial growth and facihtate hpid hydrolysis. Unsaponifiables are any materials that will not saponify (form soap) when incubated with sodium hydroxide. These include sterols, pigments, and hydrocarbons. These are natural components of both animal and plant lipids, but excessive amounts can indicate a sample that will not perform comparably with a sample richer in acylglycerols, and they can indicate adulteration or contamination by petroleum products. 

Once non-lipid contaminants have been removed, then it is necessary to purify the phospholipids from other lipids such as neutral lipids, glycolipids and sterols. Cold acetone precipitation is very useful, although it is not completely efficient for mixtures containing high concentrations of neutral lipids and only small amounts of phosphatides (Kates, 1972). Certain plant lipids such as diacyldigalactosyl-glycerol and diacylsulphoquinovosylglycerol may also be precipitated by acetone to some extent. 

Other common food lipids are the sterols and to-copherols. Sterols are generally present in natural oils as both the free sterol and sterol fatty esters. Animal fats exhibit solely cholesterol while plant lipids contain a range of phytosterols. Tocopherols are found in vegetable oils as a mixture of four iso-mers a-tocopherol (true vitamin E) and 3-, y-, and d-tocopherol. Four unsaturated analogs, tocotrienols, exist with the same numbering terminology and are particularly abundant in palm oil. 

The r61e of nutrients in inducing feeding is indicated by the presence of sugar and amino acid receptors. Receptor cells for lipids (sterols, phospholipids) have not yet been identified despite their rdle in nutrition (Beck and Schoonhoven, 1980 House, 1974) and host plant selection (Stddler and Hanson, 1976,1978). This is probably the result of the methodology (see Section 1.3) and not a general lack of sensitivity of contact chemoreceptors. 

Nes W D, Heupel R C, Le P H 1974 A comparison of sterol biosynthesis in fungi and tracheophytes and its phylogenetic and functional implications. In Siegenthaler P A, Eichenberger W (eds) Structure, function, and metabolism of plant lipids. Elsevier Amsterdam, 207-216... 

In addition to -sterols, A -sterols occur in plant lipids for example ... 

Plant lipids contain 0.15-0.9% sterols, with sitosterol as the main component (Table 3.52). In order to identify blends of fats (oils), the data on the predominant steroids are usually expressed as a quotient. For example, the ratio of stigmas-terol/campesterol is determined in order to detect adulteration of cocoa butter. As seen from Table 3.53, this ratio is significantly lower in a number of cocoa butter substitutes than in pure cocoa butter. The phytosterol fraction (e. g. sito- and campesterol) has to be determined in order to detect the presence of plant fats in animal fats. 

Patterson, G.W. 1971. The distribution of sterols in algae. Lipids 6 120-127. Patterson, G.W. 1987. Sterol synthesis and distribution and algal phylogeny. In The Metabolism, Structure and Function of Plant Lipids (Stumpf, P.K., Mudd, J.B. Nes, W.D., eds.), 631-636. Plenum Press, New York. 

The analysis of plant steryl esters has typically proceeded by isolation of the steryl ester fraction from a plant lipid extract followed by saponification to yield the sterol and fatty acid moieties. These are then identified and quantified by GC analysis, usually after preparation of the fatty acid methyl esters. However, this method of analysis has the disadvantage that the integrities of the steryl esters are lost. With the often multicomponent mixtures of sterols and fatty acid methyl esters resulting from a typical plant steryl ester mixture... 

A. Rahier, M. Taton, P. Bouvier-Nave, P. Schmitt, P. Benveniste, F. Schuber, A.S. Narula, L. Cattel, C. Anding and P. Place, Design of high energy intermediate analogues to study sterol biosynthesis in higher plants. Lipids 21 52 (1986). 

A number of people who were attending the Symposium for the first time commented on the open and friendly atmosphere. There is a family feeling since the community of people who work on plant lipids is still fairly small. At this Symposium however, there were several friends of the family, people accustomed to reporting their research in other areas who have much to contribute to the field of plant lipids. We think in particular of the contribution of Leo Parks on the function of sterols in yeast, the presentation of Joe Kuc on the importance of lipids in host-pathogen interactions, and the paper of Rudy Demel on the dynamics of glycerolipid, sphingolipid and sterol interaction in membranes. 

Bach TJ, Lichtenthaler HK. Plant growth regulation by mevinolin and otherr sterol biosynthesis inhibitors. In Fuller G, Nes WD, editors. Ecology and Metabolism of Plant Lipids, Am Chem Soc Symposium Series 325, American Chemical Society, Washington, 1987 109-139. 

Vanhanen, H. X, Blomqvist, S., Ehnholm, C., et al., 1993. Sernm cholesterol, cholesterol precursors, and plant sterols in hypercholesterolemic subjects widi different apoE phenotypes during dietary sitostanol ester treatment. Journal of Lipid Research 34 1535-1544. 

Irrespective of the physical form of the carotenoid in the plant tissue it needs to be dissolved directly into the bulk lipid phase (emulsion) and then into the mixed micelles formed from the emulsion droplets by the action of lipases and bile. Alternatively it can dissolve directly into the mixed micelles. The micelles then diffuse through the unstirred water layer covering the brush border of the enterocytes and dissociate, and the components are then absorbed. Although lipid absorption at this point is essentially complete, bile salts and sterols (cholesterol) may not be fully absorbed and are not wholly recovered more distally, some being lost into the large intestine. It is not known whether carotenoids incorporated into mixed micelles are fully or only partially absorbed. 

Lipid responses to plant-sterol-enriched reduced-fat spreads incorporated into a national cholesterol education program step I diet , American Journal of Nutrition, 74, 33-43. 

Lipid-soluble food grade copper chlorophyll is manufactured similarly by extraction of adequate plant material, followed by replacement of magnesium by copper, and purihcation steps to remove carotenoids, waxes, sterols, oils, and other minor components that are co-extracted. Commercial copper chlorophylls may vary physically, ranging from viscous resins to fluid dilutions in edible oils as well as granulated forms and emulsions standardized with edible vegetable oil. Colors may vary... 

Weete JD (1989) Structure and function of sterols in fungi. Adv Lipid Res 23 115 Morrissey JP, Osbourn AE (1999) Fungal resistance to plant antibiotics as a mechanism of pathogenesis. Microbiol Mol Biol Rev 63 708... 

Lipid Metabolism. Next we explored changes in lipid metabolism in leaves exposed to ozone. Sterols and sterol derivatives were particularly interesting to us because they have been associated with membrane-containing fractions of leaves ( ). Changes produced in these compounds may be early events in the toxicity of ozone to plant cells. 

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