Regiospecific distribution of fatty acids in triacylglycerols and phospholipids from broad beans (Vicia faba)

Regiospecific distributions of fatty acids of triacylglycerols (TAG) and phospholipids (PL) separated from broad beans (Vicia faba) of four cultivars (Minpo, Sanuki, Nintoku and Sanren) were investigated. The major lipid components were PL (47.5–50.5 wt‐%) and TAG (47.7–50.1 wt‐%), while steryl esters, hydrocarbons, free fatty acids, diacylglycerols and monoacylglycerols were present in minor proportions (1.6–2.4 wt‐%). The PL components isolated from the four cultivars were phosphatidylcholine (56.4–58.4 wt‐%), phosphatidylethanolamine (20.3–21.7 wt‐%) and phosphatidylinositol (16.6–18.6 wt‐%). Phosphatidylinositol was unique in that it had the highest saturated fatty acid content among these PL. The principal characteristics of the fatty acid distribution in the TAG and PL were evident in the beans: Unsaturated fatty acids were predominantly concentrated in the sn‐2 position while saturated fatty acids primarily occupied the sn‐1 or sn‐3 position in these lipids. The lipid components and fatty acid distributions were almost the same in the four cultivars and were not influenced by genetic variability and planting location. These results could be useful information to both consumers and producers for the manufacture of traditional broad bean foods in Japan.     

Positional distribution of fatty acids in triacylglycerols and phospholipids from adzuki beans (Vigna angularis)

The fatty acid distributions of triacylglycerols (TAG) and major phospholipids (PL) obtained from adzuki beans (Vigna angularis) were investigated. The total lipids extracted from the beans were separated by thin‐layer chromatography (TLC) into eight fractions. The major lipid components were PL (63.5 wt‐%), TAG (21.2 wt‐%), steryl esters (7.5 wt‐%) and hydrocarbons (5.1 wt‐%), while free fatty acids, diacylglycerols (1,3‐DAG and 1,2‐DAG) and monoacylglycerols were also present in minor proportions (0.2–1.1 wt‐%). The major PL components isolated from the beans were phosphatidylcholine (45.3 wt‐%), phosphatidylethanolamine (25.8 wt‐%) and phosphatidylinositol (21.5 wt‐%). Phosphatidylinositol was unique in that it had the highest saturated fatty acid content among the three PL. With a few exceptions, however, the principal characteristics of the fatty acid distribution in the TAG and three PL were evident in the beans: Unsaturated fatty acids were predominantly concentrated in the sn‐2 position while saturated fatty acids primary occupied the sn‐1 or sn‐3 position in the oils of the adzuki beans. In general, these results could be useful to both consumers and producers for the manufacture of traditional adzuki foods in Japan.     

Tocopherol Content and Fatty Acid Distribution of Peas (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

The positional distribution of fatty acids (FA) of triacylglycerols (TAG) and major phospholipids (PL) prepared from four cultivars of peas (Pisum sativum L.) were investigated as well as their tocopherol contents. The lipids extracted from these peas were separated by thin-layer chromatography (TLC) into seven fractions. The major lipid components were PL (52.2–61.3%) and TAG (31.2–40.3%), while the other components were also present in minor proportions (5.6–9.2%). γ-Tocopherol was present in the highest concentration, and α- and δ-tocopherols were very small amounts. The main PL components isolated from the four cultivars were phosphatidylcholine (42.3–49.2%), followed by phosphatidylinositol (23.3–25.2%) and then phosphatidylethanolamine (17.7–20.5%). Small but significant differences (P < 0.05) in FA distribution existed when different pea cultivars were determined. However, the principal characteristics of the FA distribution in the TAG and the three PL were evident among the four cultivars; unsaturated FA were predominantly located in the sn-2 position, and saturated FA primary occupied the sn-1 or sn-3 position in the oils of the peas. These results suggest that the regional distribution of tocopherols and fatty acids in peas is not dependent on the climatic conditions and the soil characteristics of the cultivation areas during the growing season.     

Stereospecific analysis of phospholipid classes in rat muscle

The fatty acid and dimethyl acetal (DMA) compositions of the sn‐1 and the sn‐2 positions from individual phospholipid (PL) classes [phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI)], obtained from the Longissimus dorsi muscle of rat were studied. The profile of fatty acids and DMA in the sn‐1 and sn‐2 positions of all the PL classes showed marked differences. Overall, saturated fatty acids and monounsaturated fatty acids were in a higher proportion in the sn‐1 position than in the sn‐2 one, while polyunsaturated fatty acids were mainly in the sn‐2 position. Significant differences in the DMA and fatty acid compositions between individual PL classes for each position were found. PC contained the highest proportion of palmitic acid (16:0) in the sn‐1 position and of linoleic acid (18:2 n‐6) in the sn‐2 one. The highest values for stearic acid (18:0) and DMA in the sn‐1 position and for docosahexaenoic acid (22:6 n‐3) in the sn‐2 position were found in PE. PS and PI showed the highest proportion of oleic acid (18:1 n‐9) in the sn‐1 position and of arachidonic acid (20:4 n‐6) in the sn‐2 position.     

Characteristic profiles of lipid classes,fatty acids and triacylglycerol molecular species of peas (Pisum sativum L.)

Seed oils from four legume cultivars of Pisum sativum, grown in Japan, were extracted and classified by thin‐layer chromatography (TLC) into seven fractions: hydrocarbons (HC; 0.5–0.9 wt‐%), steryl esters (SE; 0.8–2.4 wt‐%), triacylglycerols (TAG; 31.2–40.3 wt‐%), free fatty acids (FFA; 1.3–2.7 wt‐%), 1,3‐diacylglycerols (1,3‐DAG; 1.0–1.8 wt‐%), 1,2‐diacylglycerols (1,2‐DAG; 1.0–2.2 wt‐%) and phospholipids (PL; 52.2–61.3 wt‐%). All lipid samples had high amounts of total unsaturated fatty acids, representing 75.0–84.3 wt‐% for TAG and PL. Molecular species and fatty acid distributions of TAG, isolated from the total lipids in the peas, were analyzed by a combination of argentation‐TLC and GC. Eighteen different molecular species were detected. With a few exceptions, the main TAG components were SMD (7.5–10.3 wt‐%), M₂D (8.0–8.9 wt‐%), SD₂ (12.0–18.3 wt‐%), SMT (9.8–11.0 wt‐%), MD₂ (12.0–20.3 wt‐%), SDT (9.7–10.8 wt‐%), M₂T (2.5–7.3 wt‐%) and D₃ (14.5–15.2 wt‐%) (where S denotes a saturated fatty acid, M denotes a monoene, D denotes a diene, and T denotes a triene). It seems that the four cultivars were highly related to each other based on the fatty acid composition of the TAG as well as the distribution profiles in the different TAG molecular species. In general, these results suggest that there are no essential differences (p >0.05) in the oil components among the four cultivars.     

Influence of microwave roasting on positional distribution of fatty acids of triacylglycerols and phospholipids in sunflower seeds (Helianthus annuus L.)

Whole sunflower seeds were exposed to microwave roasting for 6, 12, 20 or 30 min at a frequency of 2450 MHz. The kernels were then separated from the sunflower seeds, and the lipid components and the positional distribution of fatty acids in triacylglycerols (TAGs) and phospholipids (PLs) were investigated. Major lipid components were TAGs and PLs, while steryl esters, free fatty acids and diacylglycerols were also present in minor proportions. The greatest PL losses (p < 0.05) were observed in phosphatidyl ethanolamine, followed by phosphatidyl choline or phosphatidyl inositol. Significant differences (p < 0.05) in fatty acid distributions occurred (with few exceptions) when sunflower seeds were microwaved for 20 min or more. Nevertheless, the principal characteristics for the positional distribution of fatty acids still remained after 20 min of microwave roasting; unsaturated fatty acids, especially linoleic, were predominantly concentrated in the sn‐2‐position and saturated fatty acids, especially stearic and palmitic acids, primarily occupied the sn‐1‐ or sn‐3‐position. These results indicate that no significant changes in fatty acid distribution of TAGs and PLs would occur within 12 min of microwave roasting, ensuring that a good‐quality product would be attained.     

Regional distribution of tocopherols and fatty acids within soybean seeds

Seed coat, axis, and sections of cotyledons in three soybean cultivars were analyzed by high-performance liquid chromatography for tocopherols, and by gas-liquid chromatography for acyl lipids. Tocopherols were predominantly detected in axis, followed by cotyledons and seed coat. With a few exceptions, dominant components were γ- and δ-tocopherols, with much smaller amounts of α- and β-tocopherols. However, α-tocopherol was higher (P<0.05) for the Mikawajima cultivar than for Okuhara and Tsurunoko in all tissues. Triacylglycerols (TAG) were the major fraction of total lipids, representing 70% in axis and coat and 94% in cotyledons. A small difference (P<0.05) occurred in fatty acid composition of TAG when comparing seed coat to the axis. The fatty acid composition of phosphatidylinositol (PI) differed (P<0.05) from phosphatidylethanolamine (PE) and phosphatidylcholine (PC) in each tissue. Principally, the percentage of palmitic acid was higher, especially in axis and coat. In PE and PC, linoleic was greater, followed by palmitic, in all samples except for seed coat tissue in Mikawajima. The percentages of palmitic acid in both phospholipids were significant higher in the seed coat tissue from this cultivar than in cotyledon or axis of the other varieties. These results suggest that the differences in soybean cultivars could be appreciable, based on the distribution of tocopherols and fatty acids in each component part within soybean seeds.     

Characteristic distributions of fatty acids in different lipids from Jack beans (Canavalia gladiata DC.)

Extracted lipids obtained from Jack beans (white and red) were fractionated by TLC into nine subfractions. The major components were TAGs (TAG: 43.8–45.7 wt%) and phospholipids (PL: 46.7–47.0 wt%), while other components were also present in minor proportions (0.3–2.7 wt%). The principal fatty acids (FA) are generally palmitic (18.8–28.8%), stearic (0.7–6.8%), oleic (42.0–51.8%), linoleic (16.2–22.8%), and α‐linolenic (3.0–8.2%) acids, the distribution of which differs according to these lipid classes. There were no significant differences (p>0.05) in the positional distribution of FA in the TAG; unsaturated FA (97.5%) were predominantly concentrated in the sn‐2 position while saturated FA (33.3%) primarily occupied the sn‐1 position or sn‐3 position. However, significant differences (p<0.05) in FA distribution existed when the individual PL were compared between the white and red beans. Based on the FA composition of these lipids, it seems that the two cultivars of Jack beans are very similar to each other with a few exceptions. The results could be useful to both producers and consumers for our daily diet to improve value of the Japanese diet. Practical applications : The lipid composition suggests that these beans could be a good source of nutraceuticals with providing heath benefits. The white and red beans may be well incorporated into our daily Japanese diets to improve nutritional value. The data obtained in this study provide valuable information for manufacturing functional drinks such as Jack bean tea in Japan.     

Lipid classes,fatty acid composition and triacylglycerol molecular species of kidney beans (Phaseolus vulgaris L.)

Seed oils from five legume cultivars of Phaseolus vulgaris, grown in Japan, were extracted and classified by thin‐layer chromatography (TLC) into seven fractions: hydrocarbons (HC; 0.7–1.4 wt‐%), steryl esters (SE; 1.7–3.3 wt‐%), triacylglycerols (TAG; 33.8–45.9 wt‐%), free fatty acids (FFA; 0.6–1.5 wt‐%), sn‐1,3‐diacylglycerols (1,3‐DAG; 0.3–1.0 wt‐%), sn‐1,2‐diacylglycerols (1,2‐DAG; 0.4–1.2 wt‐%) and phospholipids (PL; 49.4–58.8 wt‐%). Fatty acids derivatized as methyl esters were analyzed by gas chromatography (GC) and a flame ionization detector. Molecular species and the fatty acid distribution of TAG isolated from the total lipids in the beans were analyzed by a combination of argentation‐TLC and GC. A modified argentation‐TLC procedure, developed to optimize the separation of the complex mixture of total TAG, provided 18 different groups of TAG, based on both the degree of unsaturation and the total length of the three acyl chains of fatty acid groups. SDT (3.2–4.2 wt‐%), M₂T (3.8–5.0 wt‐%), D₃ (4.8–5.9 wt‐%), MDT (8.0–13.9 wt‐%), D₂T (12.5–15.8 wt‐%), MT₂ (19.4–22.7 wt‐%), DT₂ (17.8–23.5 wt‐%) and T₃ (9.2–13.0 wt‐%) were the main TAG components. The dominant fatty acids of TAG were α‐linolenic (48.5–57.8 wt‐%) and linoleic (16.7–25.8 wt‐%) acids, with appreciable amounts of palmitic (8.3–13.2 wt‐%) and oleic (7.8–13.8 wt‐%) acids. The high content of α‐linolenic acid in the cultivars of P. vulgaris could very likely play a beneficial role in reducing the risk of coronary heart disease among the large populations consuming them in Japan.     

Triacylglycerols of Apiaceae seed oils: Composition and regiodistribution of fatty acids

Oils from the seeds of caraway (Carum carvi), carrot (Daucus carota), celery (Apium graveolens) and parsley (Petroselinum crispum), all from the Apiaceae family, were analyzed by gas chromatography for their triacylglycerol (TAG) composition and fatty acid (FA) distribution between the sn‐1(3) and sn‐2 positions of TAG. Twenty‐two TAG species were quantified. Glyceryl tripetroselinate was the major TAG species in seed oils of carrot, celery and parsley, with levels ranging from 38.7 to 55.3%. In caraway seed oil, dipetroselinoyllinoleoylglycerol was the major TAG species at 21.2%, while the glyceryl tripetroselinate content was 11.4%. Other TAG species were linoleoyloleoylpetroselinoylglycerol and dipetroselinoyloleoylglycerol. Predominantly, TAG were triunsaturated (72.2–84.0%) with diunsaturates at 14.4–25.9%, and small amounts of monounsaturated TAG. Results for regiospecific analysis showed a non‐random FA distribution in Apiaceae for palmitic, petroselinic, linoleic and oleic acids. Petroselinic acid was predominantly located at the sn‐1(3) position in carrot, celery and parsley seed oils, while it was mainly at the sn‐2 position in caraway seed oil. The distribution of linoleic acid was opposite to that of petroselinic acid. Oleic acid was mostly located at the sn‐2 position, except for caraway, where it was evenly distributed between the sn‐1(3) and sn‐2 positions. Both the saturated FA, palmitic and stearic acid, were located mainly at the sn‐1(3) position. The presence of a high level of tripetroselinin in parsley seed oil (55.3%) makes it a potential source for the production of petroselinic acid.     

Marine phospholipids as dietary carriers of long‐chain polyunsaturated fatty acids

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are polyunsaturated fatty acids (PUFA) of the n‐3 series. Fish oil is a classical source of n‐3 PUFA, where they occur in the form of triacylglycerols (TAG). However, new sources of n‐3 PUFA esterified in phospholipids (PL) are emerging. We prepared liposomes from a natural marine lipid extract and examined their behaviour under conditions mimicking that of the gastrointestinal tract. This physicochemical approach proved that liposomes could be used as an effective oral PUFA delivery system. In vivo studies in rats were performed to examine the metabolic fate of EPA (20:5 n‐3) and DHA (22:6 n‐3) delivered either in PL from liposomes or in TAG from oil. Liposome ingestion increased PUFA bioavailability in lymph compared with fish oil. The proportion of n‐3 PUFA esterified in the sn‐2 position of chylomicron TAG depended on the dietary lipid source. Complex time‐course profiles were observed for plasma lipids with liposome supplementation over a 2‐week period, suggesting time‐dependent regulations. Taken together, the type of PUFA, EPA or DHA, as well as its intramolecular distribution in chylomicron TAG seemed to influence the metabolic fate of the fatty acids and their physiological activities.     

Preparation of Human Milk Fat Substitutes from Lard by Lipase‐Catalyzed Interesterification Based on Triacylglycerol profiles

Human milk fat substitutes (HMFSs) with triacylglycerol profiles highly similar to those of human milk fat (HMF) were prepared from lard by physical blending followed by enzymatic interesterification. Based on the fatty acid profiles of HMF, different vegetable and single‐cell oils were selected and added to the lard. Blend ratios were calculated based on established physical blending models. The blended oils were then enzymatically interesterified using a 1,3‐regiospecific lipase, Lipozyme RM IM (RML from Rhizomucor miehei immobilized on Duolite ES562; Novozymes A/S, Bagsværd, Denmark), to approximate HMF triacylglycerol (TAG) profiles, particularly with respect to the distribution of palmitic acid in the sn?2 position. The optimized blending ratios were determined to be: lard:sunflower oil:canola oil:palm kernel oil:palm oil:algal oil:microbial oil = 1.00:0.10:0.50:0.13:0.12:0.02:0.02. The optimized reaction conditions were determined to be: enzyme load of 11 wt%, temperature of 60 °C, water content of 3.5 wt%, and reaction time of 3 hours. The resulting product was evaluated for total and sn?2 fatty acids, polyunsaturated fatty acids, and TAG composition. A high degree of similarity was obtained, indicating the great potential of the product as a fat alternative for use in infant formulas.     

Phospholipid fatty acid composition and stereospecific distribution of soybeans with a wide range of fatty acid composition

Phospholipid (PL) fatty acid composition and stereospecific distribution of 25 genetically modified soybean lines with a wide range of compositions were determined by gas chromatography and phospholipase A₂ hydrolysis. Pl contained an average of 55.3% phosphatidylcholine, 26.3% phosphatidylethanolamine, and 18.4% phosphatidylinositol. PL class proportions were affected by changes in overall fatty acid composition. PL fatty acid composition changed with oil fatty acid modification, especially for palmitate, stearate, and linolenate. Stereospecific analysis showed that saturated fatty acids were primarily located at the sn-1 position of all PL, and changes of the saturates in PL were largely reflected on this position. Oleate was distributed relatively equally between the sn-1 and sn-2 positions. Linoleate was much more concentrated on sn-2 than on sn-1 position for all PL. Linolenate was distributed relatively equally at low concentration but preferred sn-2 position at high concentration.     

Hypolipidemic Effects of Phospholipids (PL) Containing n-3 Polyunsaturated Fatty Acids (PUFA) Are Not Dependent on Esterification of n-3 PUFA to PL

Phospholipids (PL) containing n‐3 polyunsaturated fatty acids (PUFA) have beneficial effects of maintaining and promoting health compared with triacylglycerols (TAG) containing n‐3 PUFA or general PL. This study evaluated the effects of dietary PL containing n‐3 PUFA and elucidated the effects of the glycerophosphate structure and n‐3 PUFA on fatty acid (FA) metabolism in rats. Rats were fed a basal diet containing soybean oil alone, TAG containing n‐3 PUFA (1.8 %), soybean PL (2.7 %), PL containing n‐3 PUFA (2.7 %), or TAG containing n‐3 PUFA (1.8 %) + soybean PL (2.7 %). The present n‐3 PUFA‐supplemented diets had similar FA compositions, and the PL diets had similar PL compositions. TAG containing n‐3 PUFA reduced serum TAG contents, but did not affect serum cholesterol contents compared with soybean oil alone. PL diets containing n‐3 PUFA and the combination of TAG containing n‐3 PUFA and soybean PL resulted in decreased serum and liver TAG contents compared with the diet containing soybean oil alone, reflecting enhanced liver FA β‐oxidation. The results of this study show that TAG containing n‐3 PUFA with added soybean PL affects serum and liver TAG and cholesterol contents to a similar degree as PL containing n‐3 PUFA. TAG containing n‐3 PUFA and soybean PL are widely used as functional food ingredients and pharmaceutical constituents and are inexpensive compared with PL containing n‐3 PUFA. Therefore, the combination of TAG containing n‐3 PUFA and soybean PL has potential as a useful and inexpensive component of functional foods.     

Triacylglycerol composition and structure in genetically modified sunflower and soybean oils

Changes in composition were examined in oils extracted from genetically modified sunflower and soybean seeds. Improvements were made to the analytical methods to accomplish these analyses successfully. Triacylglycerols (TAG) were separated on two 300 mm × 3.9 mm 4μ Novapak C18 high-performance liquid chromatography (HPLC) columns and detected with a Varex MKIII evaporative light-scattering detector. Peaks were identified by coelution with known standards or by determining fatty acid composition of eluted TAG by capillary gas chromatography (GC). Stereospecific analysis (fatty acid position) was accomplished by partially hydrolyzing TAG with ethyl magnesium bromide and immediately derivatizing the resulting diacylglycerols (DAG) with (S)-(+)-1-(1-naphthyl)ethyl isocyanate. The derivatized sn-1,2-DAG were completely resolved from the sn-2,3-DAG on two 25 mm × 4.6 mm 3 μ silica HPLC columns. The columns were chilled to −20°C to obtain baseline resolution of collected peaks. The distribution of fatty acids on each position of the glycerol backbone was derived from the fatty acid compositions of the two DAG groups and the unhydrolyzed oil. Results for the sn-2 position were verified by hydrolyzing oils with porcine pancreatic lipase, isolating the resulting sn-2 monoacylglycerols by TLC, and determining the fatty acid compositions by GC. Results demonstrated that alterations in the total fatty acid composition of these seed oils are determined by the concentration of TAG species that contain at least one of the modified acyl groups. As expected, no differences were found in TAG with fatty acid quantities unaffected by the specific mutation. In lieu of direct metabolic or enzymatic assay evidence, the authors’ positional data are nevertheless consistent with TAG biosynthesis in these lines being driven by the mass action of available acyl groups and not by altered specificity of the acyltransferases, the compounds responsible for incorporating fatty acids into TAG.     

Fatty acid profiles in tissues of mice fed conjugated linoleic acid

The incorporation of vaccenic acid (VA, 0.5 and 1.2%), conjugated linoleic acid (CLA, mixture of primarily c9,t11‐ and t10,c12‐CLA, 1.2%), linoleic acid (LA, 1.2%) and oleic acid (OA, 1.2%) into different tissues of mice was examined. The effects on the fatty acid composition of triacylglycerols (TAG) and phospholipids (PL) in kidney, spleen, liver and adipose tissue were investigated. VA and CLA (c9,t11‐ and t10,c12‐CLA) were primarily found in TAG, especially in kidney and adipose tissue, respectively. Conversion of VA to c9,t11‐CLA was indicated by our results, as both fatty acids were incorporated into all the analyzed tissues when a diet containing VA but not c9,t11‐CLA was fed. Most of the observed effects on the fatty acid profiles were seen in the CLA group, whereas only minor effects were observed in the VA groups compared with the OA group. Thus, CLA increased n‐3 polyunsaturated fatty acids (PUFA) in PL from kidney and spleen and lowered the ratio of n‐6/n‐3 PUFA in these tissues. Furthermore, CLA increased C₂₂ PUFA in the PL fraction of kidney, spleen and liver, but reduced the level of arachidonic acid in PL of liver and spleen and lowered the Δ⁹‐desaturation indexes in all analyzed tissue TAG.     

Lipid body formation by <Emphasis Type="Italic">Thraustochytrium aureum</Emphasis> (ATCC 34304) in response to cell age

The heterotrophic marine protist, Thraustochytrium aureum produces substantial amounts of polyunsaturated fatty acids (PUFAs). In the present investigation, changes in the lipid and fatty acid profiles of T. aureum were studied according to the culture age. T. aureum was grown in artificial sea water medium for 10 days at 25 °C in shake culture condition. One to 10 day old cell samples were analyzed for cell biomass production, total lipid content, fatty acid profile and lipid body formation. In all the samples tested, total lipid production was found to be directly proportional to the dry cell weight of T. aureum. In the early phase of cell growth, cell biomass production, lipid content and glucose consumption were found to be higher. Thin layer chromatographic analysis (TLC) of lipids showed the presence of triacylglycerol (TAG; 169 mg/g, 90%), phospholipids (PL; 83 mg/g, 66%) and sterol (ST; 6 mg/g, 5%), which were recorded at maximum levels in the early growth phase of the cells. The composition of PUFAs and saturated fatty acids (SFAs) of the cell biomass and lipid class components (TAG and PL) was identified by gas chromatographic analysis (GC). In the early phase of cell growth, production of PUFAs in the total fatty acids was found to have attained maximum levels (61.3%) in which docosahexaenoic acid alone showed higher content of occurrence (99.0 mg/g in total lipid; 65.2 mg/g in TAG and 41.0 mg/g in PL). In the middle phase of cell growth, palmitic acid production was found to be higher (36.7 mg/g in total lipid; 31.3 mg/g in TAG and 12.6 mg/g in PL). Transmission electron microscopic studies of the cells showed the presence of a membrane around the lipid bodies in the early phase of cell growth. TAG and PL were actively involved in the formation of lipid bodies in the cells of T. aureum. Large-sized lipid bodies accumulated in 3 day old cells which were then fragmented into smaller bodies in the late growth phase.     

Triacylglycerol structure of human colostrum and mature milk

Because triacylglycerol (TAG) structure influences the metabolic fate of its component fatty acids, we have examined human colostrum and mature milk TAG with particular attention to the location of the very long chain polyunsaturated fatty acid on the glycerol backbone. The analysis was based on the formation of various diacylglycerol species from human milk TAG upon chemical (Grignard degradation) or enzymatic degradation. The structure of the TAG was subsequently deduced from data obtained by gas chromatographic analysis of the fatty acid methyl esters in the diacylglycerol subfractions. The highly specific TAG structure observed was identical in mature milk and colostrum. The three major fatty acids (oleic, palmitic and linoleic acids) each showed a specific preference for a particular position within milk TAG: oleic acid for thesn-1 position, palmitic acid for thesn-2 position and linoleic acid for thesn-3 position. Linoleic and α-linolenic acids exhibited the same pattern of distribution and they were both found primarily in thesn-3 (50%) andsn-1 (30%) positions. Their longer chain analogs, arachidonic and docosahexaenoic acids, were located in thesn-2 andsn-3 positions. These results show that polyunsaturated fatty acids are distributed within the TAG molecule of human milk in a highly specific fashion, and that in the first month of lactation the maturation of the mammary gland does not affect the milk TAG structure.     

Distribution of the major fatty acids of human milk betweensn-2 andsn-1,3 positions of triacylglycerols

Human milk triacylgycerols (TAG) were analyzed by tandem mass spectrometry. The SIMPLEX method and a simple linear model were used to interpret the distribution of fatty acids between thesn-2 andsn-1,3 positions in 24 major molecular weight groups of TAG. The number of regio-isomeric pairs of TAG varied between 3 and 18 in each of these groups. Hexadecanoic (16∶0), tetradecanoic (14∶0) and dodecanoic acids (12∶0) typically occupied thesn-2 position in TAG containing less than 54 acyl carbons, whereas long-chain C18 and C20 acids were predominantly located at the primary positions. The positions of the three fatty acids within a TAG molecule were shown to depend on the fatty acid combination. The maximum of 12∶0 in thesn-2 position appeared at acyl carbon number (ACN) 48, the maxima of 14∶0 were at ACN 44 and ACN 50, and for 16∶0 at ACN 46 and 52.