Fatty acid detection

In addition to these numerous results, two other points are discussed by the authors fatty acid speciation and oil identification. These two aspects are developed in another publication written by the same authors [Keune et al. 2005]. The fatty acid speciation is based on the positive ion ToF-SIMS analysis and aims to prove if the fatty acids detected exist as free fatty acids, ester bound fatty acids or metal soaps. On account of the study of different standards, it is shown that when free fatty acids are present, the protonated molecular ion and its acylium ([M-OH]+) ion are detected. In cases of ester-bound fatty acid only the... 

The composition of the free fatty acids is also unique. In both human and pig stratum cornea, the free fatty acid fraction consists mainly of long and saturated hydrocarbon chains [44,45], Oleic and linoleic acid are the only unsaturated free fatty acids detected in the stratum corneum. There are various sterols present in human stratum corneum, of which cholesterol predominates. Cholesterol is the only major lipid class that is present in both plasma membranes and the intercellular lipid lamellae. Cholesterol is synthesized in the epidermis and this synthesis is independent of the hepatic one. A minor fraction is sulfated to... 

Rose, Rosa canina L., also known as dogberry or hop fruit, is in the Rosaceae family. The fruit of this particular species of rose is generally used to prepare a stew. The seeds from Rosa canina L. were investigated for their chemical composition and nutritional values for medicinal purposes. Seed oils were prepared from fruits grown at three locations in Turkey and evaluated for their fatty acid composition (31). Linoleic acid was the primary fatty acid detected, which ranged from 48.6-54.4% of total fatty acids, followed by a-linolenic acid (16.4-18.4%) and oleic acid (14.7-18.4%) (Table 4). The seed oil contained approximately 85% total unsaturated fatty acids, indicating that Rosa canina L. seed oil may be an excellent source for unsaturated and essential fatty acids. 

Seong-Sil-Kang et al. (36) studied wastes from squid processing factories because they contain high levels of EPA and DHA. Extractions were performed with and without 3% ethanol as entrainer in a semi continuous flow extractor with pressures in the range of 83-138 bar and temperatures of 25-50°C to improve the extraction efficiency. The extracts they obtained contained high levels of DHA, EPA and other PUPA. Highest extraction yield was achieved at 124 bar and 40°C with or without ethanol. Major fatty acids detected in the extracts (in addition to DHA and EPA) were myristic acid, palmitic acid, palmitoleic acid, oleic acid and arachidic acid. 

Fatty acids are also characteristic natural products of species of thrips in a diversity of genera. A total extract of Hoplothrips japonicus was dominated by (E)-3-dodecenoic acid which is considered to be an alarm-aggregation pheromone (Z)-5-dodecenoic acid is a minor concomitant ( ) 2-Methylbutyric acid, a defensive allomone of swallowtail larvae ( ), is the only free fatty acid detected in the previously described anal exudate of Varshneyia pasanii (20). It is believed that the anal discharge of this species, thoroughly dominated by alkanes, acetates, and oxygenated monoterpenes, exhibits an increased repellent punch because of the presence of the C5 acid. 

There was a direct association between the amount of c9,fl 1-CLA in plasma PC and in PBMC, which su ests that plasma PC is an important source of c9,tl 1-CLA for uptake into PBMC, although this was not significant for rlO,cl2-CLA. The concentrations of the other 26 fatty acids detected in PBMC lipids did not change with increasing consumption of the supplements. Overall, the relatively low incorporations into PBMC lipids in this and in other studies may explain, at least in part, the disappointing and variable effects of supplementation with CLA on biological outcomes in humans (34). 

Akoto, L. SteUaard, F. hth, H. Vreuls, R.J.J. Pel, R. Improved fatty acid detection in micro-algae and aquatic meiofauna species using a direct thermal desorption interface combined with comprehensive gas chromatography-time-of-flight mass spectrometry. J. Chromatogr. A, 2008, 1186, 254-261. 

Although the number of fatty acids detected in plant tissues approaches 300, most of them only occur in a few plant species (Hitchcock and Nichols, 1971). The major fatty acids are all saturated or unsaturated monocarboxylic acids with an unbranched even-numbered carbon chain. The saturated fatty acids, lauric (dodecanoic), myristic (tetradecanoic), palmitic (hexadeca-noic), and stearic (octadecanoic), and the unsaturated fatty acids, oleic (cis-9-octadecenoic), linoleic (c/5 -9,cw-12-octadecadienoic), and linolenic (all-cij-9,12,15-octadecatrienoic (Table I), together account for almost all of the fatty acid content of higher plants. For example, about 94% of the total fatty acids of commercial oils and 89-97% of leaf fatty acids consist of these seven structures alone. It will be noted that the unsaturated acids all contain a cis-9 double bond and that the polyunsaturated acids contain a methylene-interrupted structure. The four saturated fatty acids differ from each other by two carbons. These structural relationships are due to the principal pathways of fatty acid biosynthesis in plants (see Stumpf, this volume. Chapter 7). 

Table 1. Fatty acids detected by radio-HPLC upon embryo feeding with " C-labeled fatty acids. Percentage of total peak area and standard errors of the means of 3 or more replicates (in parentheses) are shown.

As might be anticipated from fbese condusions, there was considerable variation in the proportion of polyunsaturated fatty acids present in the spore oils studied, even between species within a genus. Thus, spores of four Puccinia spp. of cereal rusts included only 2-11% 18 3, while the spore oils of four other Pucdnia spp. from Compositae had 22-34% 18 3. Some rust spore oils yielded 40-55% 18 3, but the polyenoic content of rust spore oils showed little qualitative variety, 18 3 (presmnably a-Iinolenic add), 18 2, and occasionally 16 2 being the only polyimsaturated fatty acid detected. 

Eatty acids from commercial fats and oils, such as peanut oil, are extracted with methanolic NaOH and made volatile by derivatizing with a solution of methanol/BE3. Separations are carried out using a capillary 5% phenylmethyl silicone column with MS detection. By searching the associated spectral library students are able to identify the fatty acids present in their sample. Quantitative analysis is by external standards. 

Measurement of Unsaturation. The presence of double bonds in a fatty acid side chain can be detected chemically or through use of instmmentation. Iodine value (IV) (74) is a measure of extent of the reaction of iodine with double bonds the higher the IV, the more unsaturated the oil. IV may also be calculated from fatty acid composition. The cis—trans configuration of double bonds may be deterrnined by infrared (59) or nmr spectroscopy. Naturally occurring oils have methylene-intermpted double bonds that do not absorb in the uv however, conjugated dienes maybe deterrnined in an appropriate solvent at 233 nm. 

In crystallizing fatty acids, solvent polarity does not influence crystal form as much as temperature and concentration (9). Infrared (9,10) and wide-line nmr spectra (11) as well as x-ray methods (12,13) can be used to detect the various crystalline forms. 

Acids can also be converted to fluorescent dansyl derivatives The reaction of Cg to C24 fatty acids with dansyl semipiperazide or semicadavende provides an excellent example (Fig 34) [87] Odd-numbered and unsaturated fatty acids [88] and propionic, sorbic and benzoic acid [89] can be detected in the same manner... 

Dicarboxylic acids react more sensitively than do monocarboxylic acids. Fatty acids and amino acids cannot be detected. 

In situ quantitation The fluorimetric analysis was carried out in long-wavelength UV light (A c = 365 nm An > 560 nm). The detection limit for fatty acids was ca. 100 ng per chromatogram zone. 

It is evident that, in order to obtain accurate results, the method of working must be clearly and minutely adhered to, especially so in view of the fact that the determination of ester by the method of steam distillation is a very valuable indication as to the purity of an oil, serving to detect the fraudulent addition to oils of such esters as diethyl succinate, triethyl citrate, and diethyl oxalate, the free acids of which are nonvolatile in steam. It will not detect glyceryl acetate, terpinyl acetate, nor the esters of coconut oil fatty acids. 

Fatty acids may readily be detected by the increase in acid value. 

Hydrazinocarbonylpropyl)-6,7-dimethoxy-l-methyl-2(177)-quinoxalinone (126) undergoes acylation by fatty acids (EtN=C=NCH2CH2CH2NMe2, H2O, pyridine, 20°C) to afford highly fluorescent derivatives that are useful for the detection and estimation of such fatty acids. ... 

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