Fatty acids and triacylglycerols

The fatty acid composition of olive oil ranges from 7.5-20% palmitic acid, 0.5-5% stearic acid, 0.3-3.5% palmitoleic acid, 55-85% oleic acid, 7.5-20% linoleic acid, and 0.0-1.5% linolenic acid. Myristic, heptadecanoic and eicosanoic acids are found only in trace amounts (Table 9.1). Recently, Scano and co-workers (1999), using 13C nuclear magnetic resonance spectroscopy, detected and quantified c/.v-vaccenic (11-18 1) and eicosenoic acids. 

Fatty acid composition may differ from sample to sample, depending on the place of production, the latitude, the climate, the variety, and the stage of maturity of the fruit. Greek, Italian, and Spanish olive oils are low in linoleic and palmitic acids and have a high percentage of oleic acid. Tunisian olive oils are higher in linoleic and palmitic acids and lower in oleic acid. Table 9.2 presents values of fatty acid composition for Greek olive oils from a study of the State Chemical Labaratory in Athens. 

Triacylglycerols found in significant proportions in olive oil are OOO (40-59%), POO (12-20%), OOL (12.5-20%), POL (5.5-7%) and SOO (3-7%) (Boskou 1996). Smaller amounts of POP, POS, OLnL, LOL, OLnO, PLL, PLnO and LLL are also encountered (Regulation 282/98, Official Journal of European Communities, L 28.5/4-2-1998). These three letter symbols represent all the isomeric triacylglycerols containing the three acyl groups indicated where P = palmitic, O = oleic, S = stearic, L = linoleic and Ln = linolenic acid. 

According to Santinelli and co-workers (1992), the 1-random, 2-random, 3-random distribution theory is not always applicable to olive oil. Like other vegetable oils, olive oil has a high concentration of oleic acid and a low concentration of palmitic and stearic acids in position 2 of the triacylglycerol molecules. 

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PTLC was also used for the separation of lipid components in pathogenic bacteria. Mycobacterium avium has a requirement for fatty acids, which can be fulfilled by palmitic or oleic acid, and these fatty acids are then incorporated into triagylglycerols [80]. PTLC was used for the separation of fatty acids and triacylglycerols in the extracts of these bacterial cells to study the lipid classes in the bacterial cells cultured under different growth conditions. 

Aveldano, M. I. and Bazan, N. G. Differential lipid deacylation during brain ischemia in a homeotherm and a poikilo-therm. Content and composition of free fatty acids and triacylglycerol. Brain Res. 100 99-110,1975. 

Glucose transport into the adipocyte and its subsequent metabolism are depressed owing to low levels of circulating insulin. This leads to a decrease in fatty acid and triacylglycerol synthesis. 

Summary of Chapter 16 Fatty Acid and Triacylglycerol Metabolism... 

UNIT III Lipid Metabolism Chapter 15 Metabolism of Dietary Lipids 171 Chapter 16 Fatty Acid and Triacylglycerol Metabolism 179 Chapter 17 Complex Lipid Metabolism 199 Chapter 18 Cholesterol and Steroid Metabolism 217... 

The advent of relatively inexpensive computers has enabled the accumulation and rapid analysis of large sets of data. By this means patterns and trends not always apparent from visual inspection of chromatograms or tables of data can be discriminated by being sorted into recognizable patterns. This approach is essential for some techniques such as pyrolysis where the quantity of data produced would otherwise be overwhelming. Several statistical approaches to exploit the information content of fatty acid and triacylglycerol patterns for the detection and quantification of CBEs in cocoa butter have been reported (Lipp et al., 2001 Simoneau et al., 1999). 

The fractions obtained by supercritical CO2 extraction are different from those by dry fractionation. There are differences in the fatty acid and triacylglycerol compositions and melting profiles (Table 8.1). As the characteristics of the fractions depend on the conditions of the processes and the number of fractions obtained, any comparison between fractions should take into account not only the type of processes employed but also the specific process conditions. 

TABLE 8. Fatty Acids and triacylglycerols of Kokum and Madhua Fats. 

Finally, genes required for particular aspects of fatty acid and triacylglycerol biosynthesis can be identified in appropriate sources, cloned, and transferred to other plants. Rapeseed has proved to be particularly flexible in this respect, and its fatty acid composition has been modified in several ways, some of which have now reached or are very close to commercial application (Section 9.4). Genetic modification procedures are also applied to soybean and other oilseed crops. 

TABLE 10. Fatty Acid and Triacylglycerol Composition (%) of Reguiar Sunfiower Oii and of High-Oieic Sunfiower Oii [based on (25)]. 

Silver ion TLC offers an effective means of fractionation of Upid mixtures into distinct fractions differing in the number of double bonds. It is often used to simplify the further examination with gas chromatography, GC-mass spectrometry, Fourier transform infrared, and so forth. Ag TLC serves also as an enrichment procedure for minor components and allows for more accurate estimation of their content and identity. Quantitative procedures have been developed for the determination of fatty acids and triacylglycerols by using Ag TLC and densitometry. 

Reversed-phase (RP) TLC is less popular and has been applied so far only for the resolution of fatty acids and triacylglycerols. It is based on the distribution of lipid molecules between a nonpolar stationary phase and a relatively polar mobile phase. Lipids are, therefore, separated according to their overall polarity, expressed by the partition number (PN). PN relates the migration of a component to the total number of carbon atoms, CN (in the acyl residues only), and the total number of double bonds, n, so that PN = CN - In. The higher the PN, the stronger is the component retained in the nonpolar layer (the lower the Rf value). 

Figure 6-6. Synthesis of fatty acids and triacylglycerols from glucose. G-6-P = glucose 6-phosphate F-6-P = fructose 6-phosphate F-1.6-P = fructose 1,6-bisphosphate DHAP = dihydroxyacetone phosphate AcCoA = acetyl CoA VLDL = very-low-density lipoprotein.

In the liver, in the fed state, amino acid carbons are converted to fatty acids and triacylglycerol. During fasting, amino add carbons are converted to glucose or to ketone bodies. 

Acetyl-CoA is oxidized in the TCA cycle and is used in liver and adipose tissue for biosynthesis of fatty acids and triacylglycerol. 

Alcoholism affects about 10% of the drinking population and alcohol (ethanol) abuse has been implicated in at least 20% of admissions to general hospitals. This chronic disease exhibits high mortality due to a wide variety of factors. Ethanol produces effects in virtually every organ system. The biochemical effects of ethanol are due to increased production of NADH that decreases the [NAD ]/[NADH] ratio in the cytoplasm of liver cells at least tenfold from the normal value of about 1000. Increased production of lactate and inhibition of gluconeo-genesis (Chapter 15) result. The hyperuricemia associated with ethanol consumption has been attributed to accelerated turnover of adenine nucleotides and their catabolism to uric acid (Chapter 27). Alcohol increases hepatic fatty acid and triacylglycerol synthesis and mobilization of fat from adipose tissue, which can lead to fatty liver, hepatitis, and cirrhosis. These effects are complicated by a deficiency of B vitamins and protein. 

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