PubMed · 14823786
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N D ZELINSKII, L S BONDAR', V N KOST, B V LIFSHITS. [Higher ramified acids].. https://pubmed.ncbi.nlm.nih.gov/14823786/
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Fatty acids play critical roles in biological systems. Imbalances in fatty acids are related to a variety of diseases, which makes the measurement of fatty acids in biological samples important. Many analytical strategies have been developed to investigate fatty acids in various biological samples. Due to the structural diversity of fatty acids, many factors need to be considered when developing analytical methods including extraction methods, derivatization methods, column selections, and internal standard selections. This review focused on gas chromatography-mass spectrometry (GC-MS)-based methods. We reviewed several commonly used fatty acid extraction approaches, including liquid-liquid extraction and solid-phase microextraction. Moreover, both acid and base derivatization methods and other specially designed methods were comprehensively reviewed, and their strengths and limitations were discussed. Having good separation efficiency is essential to building an accurate and reliable GC-MS platform for fatty acid analysis. We reviewed the separation performance of different columns and discussed the application of multidimensional GC for improving separations. The selection of internal standards was also discussed. In the final section, we introduced several biomedical studies that measured fatty acid levels in different sample matrices and provided hints on the relationships between fatty acid imbalances and diseases.
The mixed micellization between the nonionic surfactant decanoyl-N-methylglucamide (MEGA-10) and the common sodium dodecyl sulfate (SDS) in aqueous solutions of 0.1 M NaCl was investigated by the fluorescence probe method. The critical micelle concentrations were determined by the pyrene 1:3 ratio method. The experimental data are discussed in light of two mixing thermodynamic models within the framework of the pseudophase separation model, including the conventional regular solution theory and a recent treatment proposed by Maeda (J. Phys. Chem. B 2004, 108, 6043). This last approach provides a more appropriate description of the mixed system, particularly in two aspects: the nature of the interactions responsible for the stability of the mixed micelle and the behavior of the excess free energy per monomer of the system. By using the static quenching method, the mean micellar aggregation numbers of mixed micelles in the whole range of compositions were obtained. It was found that the micellar aggregation number initially increases with the content of the ionic component, then remains roughly constant, and, finally, decreases slightly for high content of this component. This behavior was analyzed taking into account the effects produced by the presence of the charged headgroups of sodium dodecyl sulfate, as this component increases its participation in the mixed micelle. The micropolarity of the mixed micelles was studied by the pyrene 1:3 ratio index. It was observed that the increasing participation of the ionic component induces the formation of micelles with a more dehydrated structure. Data of micellar microviscosity were obtained by using different methods, including fluorescence intensity measurements of Auramine O and steady-state fluorescence anisotropy of rhodamine B and diphenylbutadiene. The results obtained from these experiments are in good agreement and suggest the formation of mixed micelles with a less ordered structure as the content of SDS increases.
Total and individual fatty acid contents were determined in raw tubers of four genotypes from each of the two species Solanum phureja and S. tuberosum. The four S. phureja genotypes contained statistically significantly higher concentrations of total fatty acids, with their average value being 37% greater than that for the mean of the four S. tuberosum cultivars. In both species, a total of 17 fatty acids were detected in quantifiable amounts, and in all genotypes the predominant fatty acid was linoleic followed by alpha-linolenic and palmitic acids. Unusually, 15-methyl hexadecanoate was present as a minor acid in both species. Although a number of statistically significant differences in the fatty acid percentage compositions were found between and within the two species, these were generally small. Averaged over all species and genotypes, tuber storage resulted in an initial small but statistically significant increase in total fatty acid content, but prolonged storage resulted in a fall to the initial values detected close to harvest. The same trend was evident for S. phureja alone (for mean values of all genotypes), but for S. tuberosum the total fatty acid content remained constant over the whole storage period. For both species, the contents (both as absolute levels and as percent compositions) of linoleic acid decreased and alpha-linolenic acid increased in tubers over the whole storage period, and possible mechanisms are discussed. Also, the absolute levels of these two acids were greater in S. phureja than in S. tuberosum, and this is discussed in relation to the development of flavor-related compounds during cooking. The polar lipids of one representative of S. tuberosum and of S. phureja were qualitatively similar. There were only minor differences in the polar lipid percentage compositions and in the corresponding fatty acid compositions of the individual polar lipids between the two species, although the absolute levels of the total, and of some individual, polar lipids were higher in S. phureja.