Seed triacylglycerols

Octanoic Caprylic 12.7 Minor compound of most animal and plant fats, major component of milk and some seed triacylglycerols. 

Decanoic Capric 29.6 Minor compound in many tissues. Major acid in milk and some seed triacylglycerols. 

Docosanoic Behenic 80.0 Minor component in some seed triacylglycerols and plant waxes. 

Seed triacylglycerols often contain unusual fatty acids. 110... 

Taylor, D.C., D.L. Barton, E.M. Giblin, S.L. MacKenzie, C.GJ. Van Den Berg, and P.B.E. McVetty. 1995. Microsomal lyso-phosphatidic acid acyltransferase from a Brassica oleracea cultivar incorporates erucic acid into the sn-2 position of seed triacylglycerols. Plant Physiology 109 409 20. 

Elongation of fatty acids is important in two commercial oil seeds, rape and jojoba. Most varieties of rape accumulate large quantities of d5-13-docosenoic (erucic) acid in their seed triacylglycerols. This is formed by elongation of oleic acid and the reactions have been studied in rape and the closely related Crambe abyssinica (Appleby etaL, 1974). Elongation in jojoba (which accumulates lipid as wax esters) uses a system with oleoyl-CoA and malonyl-CoA as substrates. The enzymes involved have been studied in jojoba and other plants where very-long-chain fatty acids are synthesized (Pollard and Stumpf, 1980). 

Where rare acids are found, they are almost always confined to the seed triacylglycerol fraction rather than to the phospholipids (Vijayalkshmi and... 

These hypotheses were examined by characterizing the selectivity of CPT and DAGAT in microsomal preparations from developing cotyledons of a series of oilseed plants towards different DAG species. Four different plants were used as model systems safflower (Carthamus tinctorius), a plant producing no unusual fatty acids rapeseed (Brassica napus), which stores erucic acid (22 1) in its TAG species Cuphea, a plant accumulating medium chain fatty acids (C8 - C12) in its seed triacylglycerols and castor bean (Ricinus communis) which stores up to 90% ricinoleic acid (18 1-OH) in its seed oils. 

Figure 29 shows the separation of triacylglycerols from sunflower seed oil. In the analysis of linoleic acid-rich seed oils, well-shaped peaks are obtained, and excellent resolution of all the main fractions is achieved, with species containing linoleic acid being predominant. 

Fig. 29 Separation of triacylglycerols from sunflower seed oil by HPLC with a silver ion column and mass detection. For conditions see text. S = saturated fatty acid M = monounsaturated fatty acid D = di-unsaturated fatty acid.

Fig. 30 Silver ion high-performance liquid chromatography (Ag-HPLC-FID) with flame ionization detector (FID) analysis of the triacylglycerols of chromatographed Crepis alpina seed oil. Ag-HPLC-FID conditions 0.5-mg sample 5-micron Chromspher Lipids column (Chrompack International, Middelburg, The Netherlands) (4.6 X 250 mm) mobile phase 0.5% acetonitrile in hexane (v/v) flow rate 1.0 ml/min FID. Chromatogram peak triacylglycerol fatty acid abbreviations S, saturated (palmitic and stearic) O, oleic L, linoleic and Cr, crepenynoic fatty acids.

Oleosins are hydrophobic plant proteins found only in association with small storage oil drops. These oil bodies are discrete spherical organelles, mainly composed of triacylglycerols and are surrounded by a phospholipids/oleosin annulus. Several oleosins were lately described, confirming that all of them comprise three distinct domains a conserved hydrophobic domain of about 70 amino acid residues being particularly rich in aliphatic amino acids flanked by an N- and a C-terminal domain, which are more hydrophilic with less conserved amino acid sequences. Allergenic oleosins were identified in sesame (Ses i 4 and Ses i 5), nuts (peanut and hazelnut oleosins), legumes, and seeds (Capuano et al. 2007, Leduc et al. 2006). 

Seeds contain 7.5% total lipids, of which neutral lipids constituted 84.1%, glycolip-ids 5.4% and phospholipids 10.5%. Neutral lipids consisted mostly of triacylglycerols (86%), diacylglycerols (6.3%) and small... 

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