Regiospecific analysis of fractions of bovine milk fat triacylglycerols with the same partition number (original) (raw)
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Journal of Dairy Science, 2014
Fatty acids (FA) are nonrandomly distributed within milk fat triacylglycerols (TAG). Moreover, the structure of milk fat TAG differs with feeding regimens. So far, nothing is known about the variation of milk fat TAG structure among individual cows. A deep understanding of the normal variation of TAG structures and the relationships between milk fat FA profile and its TAG structure could help to better control functional and compositional differences between milk fats from various sources and to increase the knowledge on milk fat synthesis. The focus of the present study was to determine the regiospecific TAG structure of individual samples of winter milk fat from Dutch Holstein-Friesian cows with a wide variation of FA profiles and with 2 diacylglycerol acyltransferase 1 (DGAT1) genotypes: DGAT1 K232A genotype AA and DGAT1 K232A genotype KK. From an initial set of 1,918 individual milk fat samples, 24 were selected. The selected samples had a wide range of FA composition and had either DGAT1 K232A genotype AA or KK. The structure analysis was done with a regiospecific approach. This analysis is based on the acyl degradation of TAG by a Grignard reagent and further isolation of sn-2 monoacylglycerols by thinlayer chromatography. An intra-and interpositional approach was used to study the structural variation. With the intrapositional approach, the amount of an FA at the secondary (sn-2) and primary (sn-1,3) positions was related to its total amount in the TAG. With the interpositional approach, the proportion of C8:0, C10:0, C14:1 cis-9, C16:1 cis-9, and C18:1 cis-9 at sn-2 was positively correlated with the amount of C16:0 in the triacylglycerol; in contrast, saturated C14:0, C16:0, and long-chain saturated FA (C14:0-C18:0) were negatively correlated. These observations suggest that the amount of long-chain saturated FA in TAG influences the positioning of other FA in the TAG. With an interpositional approach, the DGAT1 polymorphism had a significant effect on the proportional positioning of C16:0 at sn-2. These results provide a new direction to controlling functional and compositional differences between milk fats.
Journal of the American Oil Chemists’ Society, 1993
The positional distribution of acetic and butyric acids in bovine milk fat triacylglycerols was determined by chiralphase high-performance liquid chromatography (HPLC) of the derived diacylglycerols. Enriched fractions of acetic and butyric acid-containing triacylglycerols were isolated by normal-phase thin-layer chromatography (TLC) from a molecular distillate of butter oil, and they were fully hydrogenated. Mixed sn-1,2(2,3b and X-1,3-diacylglycerols of short-and long~chainlength, which were generated by partial Grignard degradation of the hydrogenated triacylglycerols, were isolated by borate-TLC. The enantiomeric sn-1,2-and sn-2,3-diacylglycerols and the X-1,3-diacylglycerols as their 3,5~lim'trophenylurethanes were resolved by HPLC on chiral columns. Both acetic and butyric acids were exclusively associated with the sn-2,3-and X-1,3-diacylglycerols of short and long chainlength. These results establish the presence of acetic and butyric acids in the sn-3position of bovine milk fat triacylglycerols. Other shortand medium-chalnlength acids were found in progressively increasing proportions also in the sn-1-and sn-2-positions.
Journal of Chromatography A, 1988
The fourth most volatile 2.5% molecular distillate of butteroil obtained by redistillation of the most volatile 10% cut was examined by gas chromatography on a polar capillary column (RSL-300) with electron impact and chemical ionization mass spectrometry. For this purpose the distillate was first freed from the acetyldiacylglycerols by thin-layer chromatography on plain silica gel and the remainder resolved into long and short chain length saturates, cisand trans-monoenes, dienes and trienes by thin-layer chromatography on silver nitrate-silica gel. The order of gas chromatographic elution was established for more than 100 major and minor species making up the bulk of the molecular distillate. The results were used to derive the quantitative composition of the triacylglycerol species making up the various peaks obtained by polar capillary column gas chromatography of the total molecular distillate, which closely resembles the lower half of the molecular mass distribution of whole bovine milk fat.
Specific distribution of short-chain fatty acids in molecular distillates of bovine milk fat
Journal of Lipid Research, 1968
Triglycerides with a total of 34-44 acyl carbon atoms have previously been shown to account for nearly 50y0 of bovine milk fat. About SOY0 of this material was isolated by molecular distillation and a representative fraction of these glycerides was subjected to a stereospecific analysis. Of the 29 moles % of C4-c~ fatty acids present in the analyzed fraction, at least 95% were specifically attached to the glycerol molecule in the position corresponding to carbon 3 of snglycerol 3-(dihydrogen phosphate) (L-a-glycerophosphate). The distribution of the other fatty acids (C~O or greater) did not show such marked specificity for either the 1or the 2-position. The data support the hypothesis that the short-chain fatty acids are esterified with long-chain diglycerides, or are substituted in glycerophosphatide intermediates, during the final step in the biosynthesis of milk fat triglycerides. KEY WORDS bovine milk. triglycerides molecular distillate. short-chain acids specific distribution e stereospecific analysis. gasliquid chromatography A N O N R A N D O M DISTRIBUTION OF FATTY ACIDS in bovine milk fat triglycerides was first claimed by Kumar, Pynadath, and Lalka (2) and McCarthy, Patton, and Evans (3), who used pancreatic lipase hydrolysis to distinguish between the acids a t the 1and 3-positions and those a t the 2-position of the glycerol molecule (sn nomenclature used throughout [1967 J. Lipid Res. 8: This work was presented at the 10th Annual Meeting of the Canadian Federation of Biological Societies held in Montreal, Quebec, July 1967. An abstract has appeared (1). Abbreviations: GLC, gas-liquid chromatography; TLC, thinlayer chromatography. Ca-Cls designates fatty acids with 4 to 18 carbon atoms; Czr-C,, triglycerides with a total number of fatty acid carbon atoms of 24-54; fatty acids are designated by chain length: no. of double bonds.
Separation of milk fat triacylglycerols by argentation thin-layer chromatography
Journal of the American Oil Chemists' Society, 1998
Argentation thin-layer chromatography was investigated as a method of obtaining detailed compositional information about milk fat. A modified argentation thin-layer chromatography procedure, developed to optimize the separation of the complex mixture of total milk fat triacylglycerols, provided nine different groups of triacylglycerols, based on both the degree of unsaturation and the total length of fatty acid groups. Fatty acid methyl ester (FAME) analysis was performed to determine the composition of each band. Separation on the basis of chainlength was most pronounced among the fully saturated triacylglycerol groups, as evidenced by the high level of C 4:0 and C 6:0 in bands 7 and 8, respectively. For the cismonoenoic triacylglycerols, the separation of C 4:0 and C 6:0 was less distinct. The cis,cis dienes and other dienoic, trienoic, or tetraenoic species were principally observed in two bands of retention factor <0.08 on the chromatography plate. Minimal cross-contamination of bands was observed, with the exception of the lowest of the trisaturate bands, band 7, in which transmonoenes were found to be present. Three samples from different points of the New Zealand dairy season were separated by argentation thin-layer chromatography, and their FAME distributions were measured. In addition to differences in the masses of band extracts from these samples, levels of C 10:0 and C 12:0 in all bands, and levels of monounsaturates in the dienoic and trienoic bands, were found to differ. These changes were generally consistent with a pattern of decreasing fat hardness over the November to March period of a typical dairy season.
Complete stereospecific determination of conjugated linoleic acids in triacylglycerol of milk-fat
Reproduction Nutrition Development, 2004
We analyzed two kinds of dairy fat differing in their contents of cis9,trans11-conjugated linoleic acid (cis9,trans11-CLA or rumenic acid), and determined the positional distribution of this CLA-isomer within the three sn-positions of the triacylglycerol. In the high rumenic acid fat (HR), the CLA-isomers amounted to 2.1% of total fatty acids, and 0.8% in the low rumenic acid fat (LR). Over 90% of the total CLA-isomers were in the form of rumenic acid, with an identical isomeric CLA distribution in both fats. The two fats differed mainly with regards to their contents in palmitic acid, α-linolenic acid, and isomers of trans-C18:1. Conversely, our stereospecific determination indicates that the positional distribution of rumenic acid is preserved among both types of fat, and is more specific for the sn-3 position of the triacylglycerol (54 to 64% of the total rumenic acid). Such a positional distribution is believed to be nutritionally relevant. conjugated linoleic acid / milk-fat / positional distribution
Specific distribution of fatty acids in the milk fat triglycerides of goat and sheep
Lipids, 1969
The triglycerides of the fat globules of sheep and goat milk were isolated and separated into short and long chain lengths by silicic acid column chromatography. The short chain lengths comprised major triglycerides with 34-44 acyl carbon atoms and accounted for nearly 50% of the total milk fat. The long chain lengths contained major triglycerides with 40-54 acyl carbons. Stereospecific analyses of the short chain triglyceride fraction showed that of the 20-23 moles per cent of C4-C8 fatty acids present, at least 95% were specifically attached to the glycerol molecule in the position corresponding to carbon 3 of sn-glycerol. The distribution of the other fatty acids (C10 or greater) did not show such marked specificity for either the 1 or the 2 position. Although individual triglycerides were not identified, the specific placement of the fatty acids could best be accounted for by assuming a common pool of long chain 1,2-diglycerides which served as precursors of the bulk of both short and long chain triglycerides during milk fat synthesis.
Structure of bovine milk fat triglycerides: II. Long chain lengths
Lipids, 1969
The long chain triglycerides of bovine milk fat were isolated by thin layer chromatography, and their chemical structure determined by combined thin layer and gas liquid chromatography, and a stereospecific analysis of a molecular distillate of butteroil of comparable composition. The milk fat fraction (39% of total) contained Cs-C20 fatty acids which were distributed among the glycerides of 40-56 acyl carbon atoms in a manner not unlike that found for the same acids in the short chain trig!ycerides. Although individual triglycerides were not identified, the specific distribution of the fatty acids could best be accounted for by assuming a common pool of long chain 1,2-diglyceride precursors from which the bulk of both short and long chain triglycerides are synthesized by a stereospecific introduction of C4-Cls fatty acids in position 3 of sn-glycerol. This hypothesis is compatible with the results of stereospeeific analyses of the short and long chain fractions and of the total butteroil. It is supported by the nonrandom distributions demonstrated for the molecular weights of the milk fat triglycerides of different degrees of saturation.
Stereospecific analysis of triacylglycerols in camel ( Camelus dromedarius) milk fat
International Dairy Journal, 2010
In the lipid fraction of camel (Camelus dromedarius) milk the percentage of saturated fatty acids (SFAs) was 62.8% with a content of palmitic acid of 28.5%. The unsaturated fatty acid (UFA) fraction was dominated by oleic and palmitoleic acids. Enzyme digestion and chemical degradation methods were used to determine the intramolecular fatty acid (FA) composition and then the intermolecular FA distribution in the three sn-positions of the triacylglycerols of the camel milk. FAs showed a specific preference for a particular position: in all samples studied, SFAs were prevalently esterified in the sn-2 position, while UFAs occupied mainly the sn-1 and sn-3 position. As the carbon chain lengthened from 8 to 16 the percentages of SFAs decreased in the sn-2 position and increased in the outer positions. Such data indicated that the length of the carbon chain could be a discriminating factor in the acylation process of SFAs.