Lipids substances

Excretion is the process by which a substance leaves the body. The most common ways are via the kidneys and via the gut. Renal excretion is favored by water-soluble compounds that can be filtered (passively by the glomeruli) or secreted (actively by the tubuli) and that are collected into urine. Fecal excretion is followed by more lipid substances that are excreted from the liver into the bile, which is collected in the gut and passed out by the feces. Other routes of excretion are available through the skin and the lungs. 

Because wax and lipid substances may contain high molecular constituents, a first run is usually performed with a scan range from m/z 50 to 900 or 1000. In a second step, if the mass spectrum excludes the presence of high molecular weight compounds, and if enough matter is available for analysis, another run is performed over a narrower scan range, often between m/z 50 and 500 (Colombini et al., 2005b). 

Figure 4.1 Analytical strategy in which direct mass spectrometry analyses using either elec tron ionisation or electrospray are used for detecting and identifying lipid substances in archaeological and museum samples...

These results show that, depending on the lipid substances present in a sample, direct mass spectrometry may allow the identification of all the lipid substances present in a material, in particular when their mass spectral fingerprints do not overlap, or to determine the main molecular constituents still preserved in the sample. 

Although El MS is an efficient way to provide structural information on several molecular constituents of various lipid substances it only provides partial information and it is particularly not suitable for the study of the low volatile components. High molecular weight and nonvolatile compounds are particularly difficult to analyse in this way and it may therefore be interesting to explore the possibilities of other ionisation modes such as electrospray for an accurate structural study of high molecular constituents such as monoester and diester species of beeswax (Gamier et al., 2002) and TAGs of animal fats... 

Although most of the analytical studies focused on lipid substances encountered in archaeological objects and museum works of art are carried out using separation techniques, direct mass spectrometry represents an alternative or a complementary analytical way for identifying such complex materials. 

This method gives a bright fluorescence of callose but also a side effect due to the presence of chlorophyll. Chlorophyll dispersed in the specimen yields a red fluorescence all around the tissue, especially a red layer on the surface of the organs due to chlorophyll deposition in any lipid substances, such as a cuticle. 

The procedures for irradiation, collection, and analysis of the volatile compounds have all been described (1, 2, 3, 5, 7, 9, 11). A cryogenically programmed gas chromatograph coupled to a rapid scanning mass spectrometer provided for the analysis of the volatile components isolated from several irradiated meats and lipid substances (6). These studies have now been extended to include other component substances in order to acquire still further understanding of the source of the irradiation-induced volatile compounds from among the various meat constituents. 

Table I summarizes the various meats, meat constituents, and other related substances which have been analyzed, including substances reported on previously (6) as well as those for which new data are given. The substances chosen are intended to provide a cross-section of the type of inherently related material from which volatile irradiation odor and flavor compounds might be expected to form. Thus, in addition to several whole meats, the volatile irradiation products from a number of protein and lipid substances have been analyzed. Among the lipid substances included are typical whole fats and separate moieties such as triglycerides, fatty acid esters, and cholesterol, as an example of a steroid. Among the proteinaceous substances included are a protein, a polypeptide, and some individual amino acids. Finally, beef itself has been separated into a protein, a lipid, and a lipoprotein fraction, and these have been separated, irradiated, and analyzed.

Our present efforts are being devoted to studying pea lipides in situ, in the hope of determining whether hormone activation by lipide substances is a natural method of growth regulation. Gas chromatography has already confirmed that our original active pea extract is a mixture of conventional fatty acid esters. 

Figure 6. Characteristic plaque debris retrieved by a filtration device. ALS amorphous lipid substance, FC foam cell, T thrombus. Arrows point to cholesterol crystals (by permission from Skyschally111 ).

Fats, oils, and lipids are common components of meats, nuts, and dairy products and manufactured goods, such as potato chips, cookies, and chocolate. They are soluble in nonpolar solvents, such as hexane and methylene chloride. The analyte, of course, should also be soluble in the extraction solvent. Typically normal-phase SPE would be used to retain a compound from this extraction solvent. A solid fat may be homogenized in a blender with hexane, filtered or centrifuged, then the solvent would be passed through a normal-phase column for retention of the solute. Another approach is the use of matrix solid-phase dispersion, where the solid would be ground into the silica and C-18 directly, then the analyte eluted directly from the ground mixture with either hexane or methylene chloride. The hexane or methylene chloride extract could then be applied directly to a normal-phase sorbent for separation. Liquid oils may be directly diluted with hexane or methylene chloride and applied to the normal-phase sorbent. Other lipid substances may be handled either as solids or liquids depending on their form. 

The development of methods for separating lipid substances from natural sources has opened up new aspects in this field, (a) The use of chromatography has led to rapid and exact separation of compounds on a preparative scale, as well as in micro quantities, (b) It was found that, in tissues other than the central-nervous material (of mammals), there exists a group of glycosphingolipids having a sulfate group. 

The classic profile of the stroke victim is one with high blood pressure, evidence of arterial hardening, and high levels of cholesterol and other lipid substances in the blood. Diabetes or gout are frequently present as is a long history of smoking. All of these factors have been found to compound the risk of morbidity and mortality greatly. 

As summarized in the review by Clifford (1985b), the terms crude and total lipid refer to substances extracted by a non-polar solvent and may include non-lipid substances such as caffeine. The yield is a function of the extraction method as much as of the composition of the beans. The crude lipid includes the wax coating the coffee bean (0,2-0.3 %), the main constituents of which are the C2o and C22 amides of 5-hydroxytryptamine [l//-indol-5-ol, 3-(2-aminoethyl-), serotonine]. These amides have their importance. As they are possible antioxidants, it has been suggested that premature dewaxing leads to a fall in the bean quality during storage. The major part of the crude lipid is a typical seed oil, with triglycerides of fatty acids, some other esters and unsaponifiable matter. 

The stringent structural characteristics that cannabinoid compounds must possess in order to exert their psychotropic effects, and the key observation that cannabinoids inhibit adenylate cyclase, supported the presence of a specific, high-affinity binding site for these lipidic substances (Howlett and Fleming, 1984). Shortly afterwards, the first membrane receptor for A -TF1C was identified in rat brain (Devane et al., 1988). Its distribution was consistent with the pharmacological properties of psycotropic cannabinoids, and therefore it was... 

Although they are a chemically diverse assortment of compounds, lipids share a number of properties. The amphipathic nature of lipid molecules encourages the formation of more complex structnres such as micelles, bilayers, and liposomes. These structures, as well as the actual lipid substances themselves, affect all aspects of cell biology, see also Fats and Fatty Acids Lipid Bilayers Membrane Phospholipids. 

Steroids Internal lipid substances Natural/thermally altered... 

Triterpenoid e.sters Internal lipid substances Natural... 

In this section the structures, nomenclature, synthesis and reactions of the tocopherols are discussed. a-Tocopherol, is a lipidic substance (ref.95) and is almost certainly the most important member of the group, generally referred to as vitamin E. The term a-tocopherol is now widely used instead of vitamin E although some consider the term vitamin E should be reserved for all tocol and tocotrienol derivatives qualitatively having the biological activity of a-tocopherol. 

Cholesterol A lipid substance that we both make and take in via our diet. Important component of membranes, lipoproteins, etc. but in excessive levels contributes to atherosclerotic plaques. Precursor of steroid hormones. 

Crude fat Methods based on the extraction of lipid substances by a solvent such as diethyl ether, hence the usual appellation of ether extract . In France, the reference method for most feed materials is AFNOR NFVI8-117 (1997). The use of HCI hydrolysis before extraction is indicated for some products. 

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