Ki-Teak Lee

Structured lipids: Synthesis and applications

Abstract Structured lipids (SL) are defined as triacylglycerols (TAG) restructured or modified to change the fatty acid composition and/or their positional distribution in glycerol molecules by chemical or enzymatic processes. SL may provide the most effective means of delivering desired fatty acids for nutritive or therapeutic purposes. In this review, the synthesis and applications of structured lipids, nutritional/clinical aspects of fatty acids, immobilization, and characteristics of lipases are discussed.

Immobilized lipase-catalyzed production of structured lipids with eicosapentaenoic acid at specific positions

Structured lipids (SL) were synthesized by the interesterification reaction between medium-chain triacylglycerols and eicosapentaenoic acid (EPA) ethyl ester. The products were partially purified, and the fatty acid at thesn-2 position was determined after pancreatic lipase-catalyzed hydrolysis. The effect of additives (water and glycerol) on the rate of reaction was also investigated. Mol% EPA incorporated into the triacylglycerols was increased by adding water when trilaurin and tricaprylin were the substrates and IM 60 was the biocatalyst. With SP 435, EPA incorporation was always less with additional water than without water. The addition of glycerol (0.005 g or 0.01 g) improved interesterification catalyzed by IM 60 to some degree, but an excess amount (0.02 g) inhibited the reaction. The reaction with glycerol showed no significant difference with SP 435. After scale-up and fractionation by column chromatography, we could recover approximately 0.3–0.4 g of product/g of reaction products. After hydrolysis by pancreatic lipase, we can conclude that IM 60 has a high specificity forsn-1,3 positions. With SP 435 lipase, 34.8–39.3 mol% of EPA was found at thesn-2 position of the recovered SL.

Monoacylglycerol (MAG)-oleic acid has stronger antioxidant, anti-atherosclerotic, and protein glycation inhibitory activities than MAG-palmitic acid.

A functional oil containing diacylglycerol (DAG) and monoacylglycerol (MAG) has been shown to have a strong anti-atherosclerotic effect in a mouse model. Among the lipid components, MAG is responsible for the beneficial effect with an enhanced antioxidant effect in the mouse model. In this report, several MAG-containing fatty acids (MAG-oleic acid [MAG-O], MAG-palmitic acid [MAG-P], and MAG-stearic acid [MAG-S]) were synthesized, and the antioxidant and anti-atherogenic activities were evaluated in vitro and in a cellular model. MAG-O had the strongest radical scavenging and antioxidant activities against copper-mediated low-density lipoprotein (LDL) oxidation and the strongest inhibitory activity against LDL-associated phospholipase A(2) and exhibited potent activation of paraoxonase activity, which contributes to the maintenance of antioxidant activity. All MAG species in this study exhibited inhibitory activity against glycation of apolipoproteins, in contrast to DAG. Oxidized LDL uptake into THP-1 cells was strongly inhibited by MAG-O treatment at a final concentration of 20 microM. MAG-O-treated cell culture medium showed the lowest production of malondialdehyde and lipid hydroperoxide compared to MAG-S and MAG-P. In conclusion, MAG-O had potent antioxidant, antidiabetic, and anti-atherogenic effects in vitro and in a cellular model.

Optimized synthesis of 1,3-dioleoyl-2-palmitoylglycerol-rich triacylglycerol via interesterification catalyzed by a lipase from Thermomyces lanuginosus

1,3-Dioleoyl-2-palmitoylglycerol (OPO)-rich human milk fat substitute (HMFS) was synthesized from tripalmitin-rich fraction and ethyl oleate by a lipase-catalyzed interesterification. Response surface methodology was employed to optimize its OPO content and acyl migration with reaction factors - substrate mole ratio of PPP-rich fraction to ethyl oleate (1:4, 1:5 and 1:6), reaction temperature (50, 55 and 60 degrees C) and time (3, 7.5 and 12 hours). The predictive models for OPO content and acyl migration were adequate and reproducible. The OPO content increased with substrate ratio, and decreased with reaction time and temperature, whereas acyl migration increased with temperature and time. The optimal conditions for HMFS synthesis while maximizing OPO content (31.43% OPO) and minimizing acyl migration (6.07%) were predicted at the reaction combination of 50 degrees C, three hours and 5.5 substrate ratio. HMFS was resynthesized under the same condition, and no significant difference between the observed and predicted values was found. Further, the major fatty acid of HMFS was palmitic acid (80.6%) at sn-2 position, and oleic acid (64.9%) at sn-1,3 position.

Dietary docosahexaenoic acid‐rich diacylglycerols ameliorate hepatic steatosis and alter hepatic gene expressions in C57BL/6J‐Lepob/ob mice

We examined the effect of docosahexaenoic acid (DHA)-enriched structured lipids-diacylglycerol (SL-DG), which were synthesized using soybean oil (SO) and algae oil (AO), on hepatic lipid metabolism and the mRNA expression of genes involved in hepatic steatosis of C57BL/6J-Lep(ob/ob) compared to the SL-triacylglycerol (TG). The animals were fed a high-fat (10% lard and 10% test oils) and high-cholesterol (0.2% cholesterol) diet for 12 weeks. Mice fed SL-DG showed a lower total white adipose tissue weight and plasma triglyceride concentration than the SO group. Reduction of hepatic triglyceride content in the SL-DG group was related with the suppression of hepatic enzyme activities for fatty acid and triglyceride synthesis along with fecal triglyceride excretion compared to the SL-TG. SL-DG also lowered hepatic cholesterol levels by suppressing cholesterol regulating enzyme activity compared to the SO group. Moreover, SL-DG lowered the mRNA expressions of sterol regulatory element binding protein-1 and its target genes than TG-form oils (SO, AO and SL-TG) in the liver. Thus, the current results suggest that DHA-enriched SL-DG oil used in this study is beneficial for ameliorating hepatic steatosis in obese animal model by improving hepatic fatty acid and cholesterol metabolic enzyme activity and their gene expression.

Characterization of Medium-Chain Triacylglycerol (MCT)-Enriched Seed Oil from Cinnamomum camphora (Lauraceae) and Its Oxidative Stability

Medium-chain triacylglycerol (MCT)-enriched oil was extracted by supercritical fluid extraction of carbon dioxide (SFE-CO(2)) from Cinnamomum camphora seeds. The SFE-CO(2) process was optimized using the Box-Behnken design (BBD). The maximum oil yield (42.82%) was obtained under the optimal SFE-CO(2) conditions: extraction pressure, 21.16 MPa; extraction temperature, 45.67 °C; and extraction time, 2.38 h. Subsequently, the physicochemical characteristics, fatty acid composition, triacylglycerol (TAG) composition, tocopherol content, and DSC profile as well as oxidative stabilities of C. camphora seed oil (CCSO) were studied. Results showed that CCSO contained two major medium-chain fatty acids, capric acid (53.27%) and lauric acid (39.93%). The predominant TAG species in CCSO was LaCC/CLaC (ECN 32, 79.29%). Meanwhile, it can be found that CCSO had much higher oxidative stabilities than coconut oil due to the higher content of tocopherols in CCSO (α-tocopherol, 8.67 ± 0.51 mg/100 g; γ-tocopherol, 22.6 ± 1.02 mg/100 g; δ-tocopherol, 8.38 ± 0.47 mg/100 g). Conclusively, CCSO with such a high level of MCTs and high oxidative stabilities could be potentially applied in special food for specific persons such as weak patients and overweight persons because oils enriched in MCTs can be rapidly absorbed into body to provide energy without fat accumulation.

High-yield production of functional human lactoferrin in transgenic cell cultures of siberian ginseng (Acanthopanax senticosus)

Human lactoferrin (hLf) is an iron-binding glycoprotein that has been considered to play many biological roles in the human, including the stimulation of the immune system, antimicrobial and anti-inflammatory effects, and regulation of iron absorption. We generated transgenic Siberian ginseng (Acanthopanax senticosus) cell cultures producing a functional hLf protein using the signal peptide sequence from the endoplasmic reticulum and driven by an oxidative stress-inducibleSWPA2 promoter which is highly expressed in plant cell cultures. The production of hLf increased proportionally to cell growth and showed a maximal level (up to 3.6% of total soluble protein) at the stationary phase in suspension cultures. Full-length hLf protein was identified by immunoblot analysis in transgenic cell cultures of Siberian ginseng. Recombinant hLf (rhLf) was purified from suspension cells of Siberian ginseng by ammonium sulfate precipitation, cation-exchange and gel filtration chromatography. N-terminal sequences of rhLf were identical to native hLf (nhLf). The overall monosaccharide composition of rhLf showed the presence of plant specific xylose while sialic acid is absent. Antibacterial activity of purified rhLf was higher than that of nhLf. Taken together, we anticipate that medicinal Siberian ginseng cultured cells, as demonstrated by this study, will be a biotechnologically useful source for commercial production of functional hLf not requiring further purification.

Nutritional effects of enzymatically modified soybean oil with caprylic acid versus physical mixture analogue in obese Zucker rats.

Enzymatically modified soybean oil with caprylic acid (SL), a physical mixture of tricaprylin and soybean oil (PHY), and soybean oil as control were fed (20% of diet weight) to female obese Zucker rats. Both lipids (SL and PHY) have similar total fatty acid composition containing 23.4 mol % caprylic acid (C8:0) but have different lipid structures. After 21 days of feeding, the body weight gain was 36.4% in the SL-fed group and 35.2% in the PHY-fed group, respectively; whereas the body weight of the control group increased 41.6%. Significant differences in the respiratory exchange ratio were observed between the SL and PHY groups. However, the contents of glucose, total and high density lipoprotein (HDL) cholesterol, and very low density and low density lipoprotein (VLDL + LDL) cholesterol in serum were not significantly different between the SL- and PHY-fed groups or among the three dietary groups (control, SL, and PHY) (p < 0.05). On the other hand, plasma total cholesterol and plasma triacylglycerol (TAG) were significantly higher in SL- and PHY-fed groups than in the control group. In the liver and inguinal adipocyte TAG, C8:0 was found in the SL-fed group, whereas it was not observed in the liver and inguinal adipocyte TAG of the PHY-fed group, which suggests that positional distribution of C8:0 of the TAG molecule is an important consideration in the metabolism of lipids. This study showed that different positional distribution in TAG molecules lead to different metabolic fates, resulting in the change of fatty acid composition in liver and inguinal adipose TAG in female Zucker rats.

Comparison of Nutritional Compounds in Premature Green and Mature Yellow Whole Wheat in Korea

ABSTRACT Until now few comparisons of nutritional compounds in premature green and mature yellow wheat have been reported. In this study, the contents of amino acids, vitamins, mineral compounds, phytosterols, and fatty acids as well as the proximate composition of premature green and mature yellow wheat were investigated. Premature green wheat had lower protein content (12.0 g/100 g db) and higher dietary fiber content (19.3 g/100 g db) than mature yellow wheat (13.6 and 14.3 g/100 g db for protein and dietary fiber, respectively). Despite a small difference in total amino acids, protein in premature wheat had a significantly greater proportion of essential amino acids: 16.1, 39.9, and 32.7 mg/g of protein for methionine, lysine, and threonine, respectively. Furthermore, the protein digestibility-corrected amino acid scores of whole grain premature green and mature yellow wheat were 62.8 and 46.4, respectively, showing significant difference (P < 0.05). Total fatty acids content was 2.66 g/100 g db for p...

Optimisation of tripalmitin-rich fractionation from palm stearin by response surface methodology.

BACKGROUND Solvent fractionation is effective in improving separation at low temperature, resulting in higher yield and purity of the final product. Tripalmitin (PPP) is an important substrate for the synthesis of human milk fat substitute (HMFS). In this study a fraction rich in PPP was separated from palm stearin by solvent fractionation. RESULTS The PPP-rich fraction was concentrated from palm stearin by acetone fractionation. Response surface methodology (RSM) was employed to optimise PPP purity (Y(1), %) and PPP content (Y(2), g kg(-1) palm stearin) with the independent variables fractionation temperature (X(1), 25, 30 and 35 degrees C) and weight ratio of palm stearin to acetone (X(2), 1:3, 1:6 and 1:9). The predictive models for PPP purity and PPP content of the solid fraction were adequate and reproducible, with no significant lack of fit and satisfactory levels of R(2). PPP purity showed a positive correlation with temperature and acetone ratio, whereas PPP content exhibited a negative correlation. The optimised fractionation condition for a targeted PPP-rich fraction with > 92% PPP purity and > 225 g kg(-1) PPP content from palm stearin was predicted. CONCLUSION The RSM model for optimising PPP purity and PPP content in the PPP-rich fraction from palm stearin by acetone fractionation was valid. The scaled-up PPP-rich fraction obtained can be used as a substrate for the synthesis of 1,3-dioleoyl-2-palmitoylglycerol, which is a main component of HMFS in infant formulas.