Lipase‐mediated hydrolysis of flax seed oil for selective enrichment of α‐linolenic acid

Polyunsaturated fatty acids (PUFA) are important ingredients of human diet because of their prominent role in the function of human brain, eye and kidney. α‐Linolenic acid (ALA), a C18, n‐3 PUFA is a precursor of long chain PUFA in humans. Commercial lipases of Candida rugosa, Pseudomonas cepacea, Pseudomonas fluorescens, and Rhizomucor miehei were used for hydrolysis of flax seed oil. Reversed phase high performance liquid chromatography followed by gas chromatography showed that the purified oil contained 12 triacylglycerols (TAGs) with differences in fatty acid compositions. Flax seed oil TAGs contained α‐linolenic acid (50%) as a major fatty acid while palmitic, oleic, linoleic made up rest of the portion. Among the four commercial lipases C. rugosa has preference for ALA, and that ALA was enriched in free fatty acids. C. rugosa lipase mediated hydrolysis of the TAGs resulted in a fatty acid mixture that was enriched in α‐linolenic to about 72% yield that could be further enriched to 80% yield by selective removal of saturated fatty acids by urea complexation. Such purified ALA can be used for preparation of ALA‐enriched glycerides. Practical applications : This methodology allows purifying ALA from fatty acid mixture obtained from flax seed oil by urea complexation.     

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.     

Ecological and simultaneous seed oil extraction/saponification/γ‐linolenic acid concentration

The essential fatty acid γ‐linolenic (GLA, C18:3n‐6), which has several pharmaceutical properties, has been concentrated from the seed oil of three plant species, Borago officinalis, Anchusa azurea and Echium fastuosum. The process was effected through one single and ecological step: simultaneous seed oil extraction/saponification/GLA concentration. Finally, the mother liquor containing the GLA concentrate was stored at low temperature to crystallize saturated fatty acids and further increase GLA purity. Two variables affecting the process were found: water content in the saponification mixture and filtration temperature. Best results were obtained from B. officinalis (GLA purity 68%, GLA yield 64%), although closely followed by the concentrates from the other species.     

Dietary trans α‐linolenic acid does not inhibit Δ5‐ and Δ6‐desaturation of linoleic acid in man

Dietary trans monoenes have been associated with an increased risk of heart disease in some studies and this has caused much concern. Trans polyenes are also present in the diet, for example, trans α‐linolenic acid is formed during the deodorisation of α‐linolenic acid‐rich oils such as rapeseed oil. One would expect the intake of trans α‐linolenic acid to be on the increase since the consumption of rapeseed oil in the western diet is increasing. There are no data on trans α‐linolenic acid consumption and its effects. We therefore carried out a comprehensive study to examine whether trans isomers of this polyunsaturated fatty acid increased the risk of coronary heart disease. Since inhibition of Δ6‐desaturase had also been linked to heart disease, the effect of trans α‐linolenic acid on the conversion of [U‐¹³C]‐labelled linoleic acid to dihomo‐γ‐linolenic and arachidonic acid was studied in 7 healthy men recruited from the staff and students of the University of Edinburgh. Thirty percent of the habitual fat was replaced using a trans ‘free’‐ or ‘high’ trans α‐linolenic acid fat. After at least 6 weeks on the experimental diets, the men received 3‐oleyl, 1,2‐[U‐¹³C]‐linoleyl glycerol (15 mg twice daily for ten days). The fatty acid composition of plasma phospholipids and the incorporation of ¹³C‐label into n‐6 fatty acids were determined at day 8, 9 and 10 and after a 6‐week washout period by gas chromatography‐combustion‐isotope ratio mass spectrometry. Trans α‐linolenic acid of plasma phospholipids increased from 0.04 ? 0.01 to 0.17 ? 0.02 and cis ? ‐linolenic acid decreased from 0.42 ? 0.07 to 0.29 ? 0.08 g/100 g of fatty acids on the high trans diet. The composition of the other plasma phospholipid fatty acids did not change. The enrichment of phosphatidyl ¹³C‐linoleic acid reached a plateau at day 10 and the average of the last 3 days did not differ between the low and high trans period. Both dihomo‐γ‐linolenic and arachidonic acid in phospholipids were enriched in ¹³C, both in absolute and relative terms (with respect to ¹³C‐linoleic acid). The enrichment was slightly and significantly higher during the high trans period (P<0.05). Our data suggest that a diet rich in trans α‐linolenic acid (0.6% of energy) does not inhibit the conversion of linoleic acid to dihomo‐γ‐linolenic and arachidonic acid in healthy middle‐aged men consuming a diet rich in linoleic acid.     

Gamma‐linolenic and stearidonic acids from Moroccan Boraginaceae

Seeds from 20 species belonging to Boraginaceae, subfamilies Boraginoideae and Heliotropioideae, were surveyed in a search for new sources of γ‐linolenic acid (GLA) and stearidonic acid (SDA). Seed oil content ranged from 7.5% in Echium humile ssp. pycnanthum to 28.8% in Anchusa undulata. GLA ranged from 0.2% of total fatty acids in Heliotropium undulatum to 20.2% in Lithodora maroccana. This last species may be considered as new source of GLA. GLA content was also tested in other Lithodora species from the south east of Spain, to compare GLA percentages among related taxa. GLA amounts in all Echium species reached approximately 12%, in good agreement with previous findings in other European Echium species. SDA ranged from an absence in several Cynoglossum species to 16.2% in Echium humile ssp. pycnanthum, which may be considered as a new source of this fatty acid.     

Protective effect of dietary perilla oil on allergic inflammation in asthmatic mice

Perilla oil (PER) is rich in α‐linolenic acid (n‐3 fatty acid). To unravel the effects of dietary PER on allergic asthmatic inflammation, three kinds of dietary oil, including PER, corn oil (COR), and perilla compound oil (50% PER and 50% COR), were used for replacing the oil in an AIN76 feed consumed by ovalbumin (OVA)‐sensitized and challenged mice continuously for 5 wk. T‐helper type 1 lymphocyte (Th1)/T‐helper type 2 lymphocyte (Th2) and pro‐/anti‐inflammatory cytokines secreted by the cells from the airway, the lungs, and the spleen of experimental mice were determined by ELISA. The results showed that dietary PER inhibited interleukin (IL)‐1β and tumor necrosis factor (TNF)‐α secretions by lipopolysaccharide (LPS)‐stimulated lung cells, as well as interferon (IFN)‐γ and IL‐6 secretions by LPS‐stimulated splenocytes. Perilla compound oil increased the secretion ratio of IFN‐γ/IL‐5 (Th1/Th2 cytokines) in LPS‐stimulated bronchoalveolar lavage fluid cells, but decreased the ratio of IL‐6/IL‐10 (pro‐/anti‐inflammatory cytokines) in LPS‐stimulated splenocytes. The present study demonstrated that dietary PER and its compound oil protected the airways, the lungs, and the spleen from allergic inflammation in OVA‐challenged asthmatic mice, suggesting that an appropriate n‐6/n‐3 fatty acid ratio at a ratio of 1:1 or less in dietary oil may be beneficial to improve the Th2‐skewed allergic asthmatic inflammation. Practical applications: The present study demonstrated that dietary PER and its compound oil protected the airways, the lungs, and the spleen from allergic inflammation in OVA‐challenged asthmatic mice, suggesting that an appropriate n‐6/n‐3 fatty acid ratio at a ratio of 1:1 or less in dietary oil may be beneficial to improve the Th2‐skewed allergic asthmatic inflammation.     

Mass Spectrometric Confirmation of γ-Linolenic Acid Ester-Linked Ceramide 1 in the Epidermis of Borage Oil Fed Guinea Pigs

Ceramide 1 (Cer1), a Cer species with eicosasphingenine (d20:1) amide‐linked to two different ω‐hydroxy fatty acids (C30wh:0:C32wh:1), which are, in turn, ester‐linked to linoleic acid (LNA; 18:2n‐6), plays a critical role in maintaining the structural integrity of the epidermal barrier. Prompted by the recovery of a disrupted epidermal barrier with dietary borage oil [BO: 36.5 % LNA and 23.5 % γ‐linolenic acid (GLA; 18:3n‐6)], in essential fatty acid (EFA)‐deficient guinea pigs, we further investigated the effects of BO on the substitution of ester‐linked GLA for LNA in these two epidermal Cer1 species by LC–MS in positive and negative modes. Dietary supplementation of BO for 2 weeks in EFA‐deficient guinea pigs increased LNA ester‐linked to C32wh:1/d20:1 and C30wh:0/d20:1 of Cer1. Moreover, GLA ester‐linked to C32wh:1/d20:1, but not to C30wh:0/d20:1, of Cer1 was detected, which was further confirmed by the product ions of m/z 277.2 for ester‐linked GLA and m/z 802.3 for the deprotonated C32wh:1/d20:1. C20‐Metabolized fatty acids of LNA or GLA were not ester‐linked to these Cer1 species. Dietary BO induced GLA ester‐linked to C32wh:1/d20:1 of epidermal Cer1.     

Serum n-3 Tetracosapentaenoic Acid and Tetracosahexaenoic Acid Increase Following Higher Dietary α-Linolenic Acid but not Docosahexaenoic Acid

n‐3 Tetracosapentaenoic acid (24:5n‐3, TPAn‐3) and tetracosahexaenoic acid (24:6n‐3, THA) are believed to be important intermediates to docosahexaenoic acid (DHA, 22:6n‐3) synthesis. The purpose of this study is to report for the first time serum concentrations of TPAn‐3 and THA and their response to changing dietary α‐linolenic acid (18:3n‐3, ALA) and DHA. The responses will then be used in an attempt to predict the location of these fatty acids in relation to DHA in the biosynthetic pathway. Male Long Evans rats (n = 6 per group) were fed either a low (0.1% of total fatty acids), medium (3%) or high (10%) ALA diet with no added DHA, or a low (0%), medium (0.2%) or high (2%) DHA diet with a background of 2% ALA for 8 weeks post‐weaning. Serum n‐3 and n‐6 polyunsaturated fatty acid (PUFA) concentrations (nmol/mL ± SEM) were determined by gas chromatography–mass spectrometry. Serum THA increases from low (0.3 ± 0.1) to medium (5.8 ± 0.7) but not from medium to high (4.6 ± 0.9) dietary ALA, while serum TPAn‐3 increases with increasing dietary ALA from 0.09 ± 0.04 to 0.70 ± 0.09 to 1.23 ± 0.14 nmol/mL. Following DHA feeding, neither TPAn‐3 or THA change across all dietary DHA intake levels. Serum TPAn‐3 demonstrates a similar response to dietary DHA. In conclusion, this is the first study to demonstrate that increases in dietary ALA but not DHA increase serum TPAn‐3 and THA in rats, suggesting that both fatty acids are precursors to DHA in the biosynthetic pathway.     

Lipid components of flax,perilla, and chia seeds

Composition of fatty acids, tocopherols, sterols, and TAGs in the lipids of flax, perilla, and chia seeds were investigated where lipid content was at 45, 40, and 35%, respectively. α‐Linolenic acid (ALA) dominated among fatty acids in all oils and accounted for 58.2, 60.9, and 59.8% in flax, perilla, and chia, correspondingly in these three oils trilinolenin was the main TAG found at 19.7, 22.6, and 21.3%. Triunsaturated TAGs accounted for 77.9, 77.5, and 74.5% of the total amounts in flax, perilla, and chia oils. Contents of tocopherol were at 747 in flax, 734 in perilla, and 446 mg/kg in chia seed lipids. γ‐Tocopherol was the dominating isomer contributing 72.7% in flax, 94.3% in perilla, and 94.4% in chia to the total amount of tocopherols. Flaxseed lipids contained 25.6% of plastochromanol‐8, derivative of γ‐tocotrienol with longer side chain; perilla and chia oils contained only 1.4% of it. Phytosterols were present at 4072, 4606, and 4132 mg/kg in those seeds, respectively. Among sterols, β‐sitosterol dominated and was found at 35.6, 73.3, and 49.8% of the total amounts of sterols in flax, perilla, and chia seed lipids. All of the investigated oilseeds have an excellent nutritional quality and can be a potential source of nutraceutical fats which can enrich diet in linolenic acid and other functional components.     

Properties and biotechnological methods to produce lipids containing conjugated linoleic acid

In this review, the occurrence, properties, nutritional importance and especially biotechnological methods for the production of conjugated linoleic acids (CLA) and CLA‐rich lipids are summarized. Beside information from medical and nutritional studies on the biological activity of CLA, the focus is on the enzymatic synthesis of structured lipids containing CLA and the microbial synthesis of CLA.     

Thermostability of genetically modified sunflower oils differing in fatty acid and tocopherol compositions

The objective of the study was to investigate the performance at frying temperature of a new sunflower oil with high content of oleic and palmitic acid (HOHPSO) and containing γ‐tocopherol as the most abundant natural antioxidant. HOHPSO either containing α‐ or γ‐tocopherol (HOHPSO‐α and HOHPSO‐γ, respectively) were obtained from genetically modified sunflower seeds and refined under identical conditions. The oil stability against oxidation, as measured by Rancimat at 120 °C, was much higher for the oil containing γ‐tocopherol, suggesting the higher effectiveness of γ‐tocopherol as compared to α‐tocopherol to delay oxidation. Experiments at high temperature (180 °C) simulating the conditions applied in the frying process clearly demonstrated that, for the same periods of heating, the oil degradation and the loss of natural tocopherol were significantly lower for the oil containing γ‐tocopherol. Comparison of different genetically modified sunflower oils with different fatty acid compositions confirmed that oil degradation depended on the fatty acid composition, being higher at a higher degree of unsaturation. However, the loss of tocopherol for a similar level of oil degradation was higher as the degree of unsaturation decreased. Overall, the results showed that HOHPSO‐γ had a very high stability at frying temperatures and that mixtures of HOHPSO‐α and HOHPSO‐γ would be an excellent alternative to fulfill the frying performance required by the processors and the vitamin E content claimed by the consumers.     

Novel Poly(linolenic acid) Graft Copolymers: Synthesis,Characterization and Electrical Properties

A poly(linolenic acid)‐g‐poly(tert‐butyl acrylate) graft copolymer was synthesized from polymeric linolenic acid peroxide possessing peroxide groups in the main chain by free radical polymerization of tert‐butyl acrylate. Graft copolymers having structures of poly(linolenic acid)‐g‐poly(caprolactone)‐g‐poly(tert‐butyl acrylate) were synthesized from polymeric linolenic acid, possessing peroxide groups on the main chain by the combination of free radical polymerization of tert‐butyl acrylate and ring‐opening polymerization of ε‐caprolactone in one‐pot. The obtained graft copolymers were characterized by proton nuclear magnetic resonance, gel permeation chromatography, thermal gravimetric analysis, differential scanning calorimetry, and scanning electron microscopy techniques. Furthermore, Au/n‐Si diodes were fabricated with and without poly(linolenic acid)‐g‐poly(caprolactone)‐g‐poly(tert‐butyl acrylate)‐4 to form a new interfacial polymeric layer for the purpose of investigating this polymer's conformity in electronic applications. Some main electrical characteristics of these diodes were investigated using experimental current–voltage measurements in the dark and at room temperature.     

Chemical Synthesis of Rare Natural Bile Acids: 11α‐Hydroxy Derivatives of Lithocholic and Chenodeoxycholic Acids

A method for the preparation of 11α‐hydroxy derivatives of lithocholic and chenodeoxycholic acids, recently discovered to be natural bile acids, is described. The principal reactions involved were (1) elimination of the 12α‐mesyloxy group of the methyl esters of 3α‐acetate‐12α‐mesylate and 3α,7α‐diacetate‐12α‐mesylate derivatives of deoxycholic acid and cholic acid with potassium acetate/hexamethylphosphoramide; (2) simultaneous reduction/hydrolysis of the resulting △¹¹‐3α‐acetoxy and △¹¹‐3α,7α‐diacetoxy methyl esters with lithium aluminum hydride; (3) stereoselective 11α‐hydroxylation of the △¹¹‐3α,24‐diol and △¹¹‐3α,7α,24‐triol intermediates with B₂H₆/tetrahydrofuran (THF); and (4) selective oxidation at C‐24 of the resulting 3α,11α,24‐triol and 3α,7α,11α,24‐tetrol to the corresponding C‐24 carboxylic acids with NaClO₂ catalyzed by 2,2,6,6‐tetramethylpiperidine 1‐oxyl free radical (TEMPO) and NaClO. In summary, 3α,11α‐dihydroxy‐5β‐cholan‐24‐oic acid and 3α,7α,11α‐trihydroxy‐5β‐cholan‐24‐oic acid have been synthesized and their nuclear magnetic resonance (NMR) spectra characterized. These compounds are now available as reference standards to be used in biliary bile acid analysis.