Acyl Migration Kinetics of 2-Monoacylglycerols from Soybean Oil via 1H NMR

Distribution and Level of Bioactive Monoacylglycerols in 12 Marine Microalgal Species

Microalgae are currently considered an attractive source of highly valuable metabolites potentially exploitable as anticancer agents, nutraceuticals and cosmeceuticals and for bioenergy purposes. Their ease of culturing and their high growth rates further promote their use as raw material for the production of specialty products. In the present paper, we focused our attention on specific glycerol-based lipid compounds, monoacylglycerols (MAGs), which displayed in our previous studies a selective cytotoxic activity against the haematological U-937 and the colon HCT-116 cancer cell lines. Here, we performed a quali/quantitative analysis of MAGs and total fatty acids (FAs) along with a profiling of the main lipid classes in a panel of 12 microalgal species, including diatoms and dinoflagellates. Our results highlight an inter- and intraspecific variability of MAG profile in the selected strains. Among them, Skeletonema marinoi (strain FE7) has emerged as the most promising source for possible biotechnological production of MAGs.

Chiral high-performance liquid chromatography analysis of mono-, di-, and triacylglycerols with amylose- and cellulose-phenylcarbamate-based stationary phases

The ever-increasing technological advancement in the (ultra)high-performance liquid chromatography tandem (high-resolution) mass spectrometry platforms have largely contributed to steeply intensify the interest towards lipidomics research. However, mass spectrometers alone are unable to distinguish between enantiomers. This obstacle is especially evident in the case of glycerolipids analysis due the prochiral nature of glycerol. Until a couple of decades ago, the stereoselective analysis of triacylglycerols (TAGs) was performed on the end products generated either from their enzymatic or chemical hydrolysis, namely on mono- or diacyl-sn-glycerols (MAGs and DAGs, respectively). These were then mostly analyzed with Pirkle-type chiral stationary phases (CSPs) after dedicated multi-step derivatization procedures. One of the most significant drawbacks of these traditional methods for enantioselective TAGs analysis (actually of the produced MAGs and DAGs, often investigated as target species per se) was the difficulty to totally abolish the migration of fatty acyls between glycerol positions. This made difficult to control and keep unaltered the stereochemistry of the original molecules. Over the last two decades, it has been widely demonstrated that the enantioselective analysis of intact TAGs as well as of non-derivatized MAGs and DAGs can be efficiently obtained using polysaccharide-based CSPs incorporating either amylose- or cellulose-phenylcarbamate derivatives chiral selectors. In this paper, the enantioselective methods developed with these CSPs for the enantioselective direct LC analysis of MAGs, DAGs and TAGs embedding different types of fatty acid residues are comprehensively reviewed.

Preparation of 2-Arachidonoylglycerol by Enzymatic Alcoholysis: Effects of Solvent and Water Activity on Acyl Migration

Enzymatic alcoholysis was performed in an organic medium to synthesize 2-monoacylglycerol (2-MAG) rich in arachidonic acid. The results showed that solvent type and water activity (a_w) significantly affected the 2-MAG yield. Under the optimum conditions, 33.58% 2-MAG was produced in the crude product in t-butanol system. Highly pure 2-MAG was obtained after two-stage extraction using 85% ethanol aqueous solution and hexane at first stage and dichloromethane and water at second stage. Isolated 2-MAG was used as substrate to investigate the effect of solvent type and a_w on 2-MAG acyl migration in a lipase-inactivated system. The results indicated that non-polar solvents accelerated the acyl migration of 2-MAG, whereas isomerization was inhibited in polar solvent systems. The a_w exhibited the strongest inhibition effect on 2-MAG isomerization at 0.97, but also affected the hydrolysis of glycerides and lipase selectivity.

2-Arachidonoylglycerol Synthesis: Facile and Handy Enzymatic Method That Allows to Avoid Isomerization

A simple and practical synthesis of 2-arachidonoyl glycerol (2-AG), an endogenous agonist for cannabinoid receptors, based on a two-step enzymatic process and a chemical coupling, was achieved with a good yield and negligible amount of the isomerization product 1-AG. Commercial preparation of immobilized lipase from Mucor miehei (MML) was selected as the most suitable enzyme to catalyze the efficient protection of glycerol using vinyl benzoate as an acyl transfer reagent in tetrahydrofuran. The same enzyme was used to remove the protective groups in positions 1 and 3. Owing to the mild neutral conditions and easy suitability of the method, 2-AG was obtained without any isomerization to the more stable 1-AG and air oxidation of acid chain. The synthetic method proposed here allows us to easily obtain 2-AG from the protected precursor in a one-step reaction without purification requirement.

Progress in enrichment of n-3 polyunsaturated fatty acid: a review

n-3 Polyunsaturated fatty acids (n-3 PUFA) has been widely used in foods, and pharmaceutical products due to its beneficial effects. The content of n-3 PUFA in natural oils is usually low, which decreases its added value. Thus, there is an increasing demand on the market for n-3 PUFA concentrates. This review firstly introduces the differences in bioavailability and oxidative stability between different types of PUFA concentrate (free fatty acid, ethyl ester and acylglycerol), and then provides a comprehensive discussion of different methods for enrichment of lipids with n-3 PUFA including physical-chemical methods and enzymatic methods. Lipases used for catalyzing esterification, transesterification and hydrolysis reactions play an important role in the production of highly enriched various types of n-3 PUFA concentrates. Lipase-catalyzed alcoholysis or hydrolysis reactions are the mostly employed method to prepare high-quality n-3 PUFA of structural acylglycerols. Although many important advantages offered by lipases in enrichment of n-3 PUFA, the high cost of enzyme limits its industrial-scale production. Further research should focus on looking for biological enzymes with extraordinary catalytic ability and clear selectivity. Other novel technologies such as protein engineering and immobilization may be needed to modify lipases to improve its selectivity, catalytic ability and reuse.

Kinetic modeling of lipase-catalysed hydrolysis of triacylglycerol in a reverse micelle system for the determination of integral stereoselectivity

A kinetic model for lipase-catalysed stepwise hydrolysis of triacylglycerol was developed for quantification of integral stereoselectivity.

Influence of different dietary oil consumption on nutrient malabsorption: An animal trial using Sprague Dawley rats

In the present study, the influences of five typical dietary oils (i.e., palm oil, PO; leaf lard oil, LO; rapeseed oil, RO; sunflower oil, SO; and linseed oil, LN) consumption on the nutrients malabsorption were studied using adult male Sprague Dawley rats. Results suggested that the C16:0 (24.534 ± 2.26% to 54.269 ± 1.28%) and C18:0 (18.433 ± 4.421% to 36.455 ± 3.316%) were the dominant fatty acids in fecal samples in different groups. After 6-week intervention by different dietary oils, the fecal moisture and water soluble protein content in PO group, the reducing sugar content in PO, LO, and RO groups were significantly increased compared with those in the control group (p < .05). Moreover, the Na, K, and Fe contents in LO group were all the highest among the all groups. These effects were probably due to the different fatty acids composition as illustrated in the correlation analysis results. The different effects were probably due to their distinct fatty acids composition as illustrated in the correlation analysis results. Results further indicated that the different dietary oils treatment, especially for the PO (SFAs, 43.17 ± 0.98%) and LO (SFAs, 36.44 ± 0.65%), increased the upstream inflammatory cytokine expression level in the Toll-like receptor signal pathway (i.e., TLR4 and MyD88), enhancing the gut permeability. This resulted in significant increase of serum lipopolysaccharide (LPS) levels (p < .05), which was closely connected with different metabolic diseases. The present study may provide basic understandings about different dietary oil enteral nutrition and their effects on gut health. PRACTICAL APPLICATIONS: The PO, LO, RO, SO, and LN are the five of the most typical dietary lipids in Asia countries, especially in China. They are the natural edible oils which are rich in C16:0, C18:0, C18:1, C18:2ω6, and C18:3ω3, respectively. The present study indicated that the different dietary lipid consumption may result in different dietary nutrients malabsorption, which are related with the dietary lipid fatty acid composition.

Effect of Solvent on Acyl Migration of 2-Monoacylglycerols in Enzymatic Ethanolysis

Acyl migration occurs in many reactions and is the main obstacle for structured lipid synthesis. In this study, 2-monoacylglycerol (2-MAG) was prepared by enzymatic ethanolysis in three different media to evaluate the effect of environment on product composition. The contents of 2-MAG obtained in ethanol, hexane + ethanol, and t-butanol + ethanol systems were 30.6, 15.7, and 32.4%, respectively, after 3 h reaction. Afterward, the acyl migration kinetics of 2-MAG were studied in solvent and solventless systems without the use of lipase. Results indicate that 2-MAG in the solventless system had the highest acyl migration rate. The isomerization was efficiently prevented by the use of polar solvents, especially t-butanol. The rate constants were shown to be the highest and activation energy values were the lowest in solventless systems. The novel finding in this study was that solvent had inhibitory effect on 2-MAG isomerization, but the nonpolar hexane had the lowest inhibition of acyl migration compared to other solvents.

Solvent-based strategy improves the direct determination of key parameters in edible fats and oils by 1 H NMR

BACKGROUND

Edible fats and oils are very important in nutrition and as a main source of energy and are also essential nutrients. There are several methods for the analysis of edible fats and oils, but nowadays nuclear magnetic resonance (NMR) is emerging as a powerful tool (albeit complex and high-tech demanding) to identify, quantify, and differentiate many types of food, including fats and oils. In this sense, the challenges of this technique are the simplification of methodology and taking advantage of a 400 MHz NMR instrument.

RESULTS

Through an adequate mixture of solvents, we have developed a methodology to quantify essential parameters in edible fats and oils, including 1,2-diacylglycerol, 1,3-diacylglycerol, and 1-monoacylglycerol, by using a single experiment and without the need for matrix derivatization.

CONCLUSION

This methodology has been successfully applied to the analysis of olive, sunflower, corn, sesame, and peanut oils, as well as butter, walnut, salmon, and spicy pork sausage. Moreover, the evolution of thermal oxidation and lipolysis of virgin olive oil and sunflower has been analyzed. © 2020 Society of Chemical Industry.

Rapid Raman spectroscopic determination of 1-feruloyl-sn-glycerol and 1,3-diferuloyl-sn-glycerol

Ferulic acid and its derivatives are important natural products found throughout the plant kingdom and are of special interest due to their health benefits. 1-Feruloyl-sn-glycerol (FG) and 1,3-diferuloyl-sn-glycerol (F₂G) are two common bioproducts of ferulic acid that co-occur in nature and during the biocatalytic production of feruloylated lipids. In this paper, we report a comprehensive characterization of FG and F₂G using Raman and UV spectroscopies and theoretical density functional theory calculations at the B3LYP/6-311+G** level. UV spectroscopy produced spectra for FG and F₂G with similar peak shape, but difference intensities. The vibrational frequency calculations aided in the assignment of the Raman bands. The Raman analysis demonstrates that Raman spectroscopy is a rapid label free method to clearly distinguish between FG and F₂G.

Enzymatic Synthesis and Flash Chromatography Separation of 1,3-Diferuloyl-sn-Glycerol and 1-Feruloyl-sn-Glycerol

Ethyl ferulate was transesterified with Enova Oil (a soy-based vegetable oil containing 80-85% diacylglycerol) using Novozym 435 at 60 °C. The resultant feruloylated vegetable oil reaction product produced a precipitate (96.4 g, 4.02 wt%) after 7 d of standing at room temperature. Preliminary characterization of the precipitate identified the natural phenylpropenoids 1,3-diferuloyl-sn-glycerol (F2G) and 1-feruloyl-sn-glycerol (FG) as the major components. A flash chromatography method was developed and optimized (e.g., mass of sample load, flow rate, binary solvent gradient slope, and separation run length) using a binary gradient of hexane and acetone mobile phase and silica gel stationary phase to separate and isolate F2G and FG. The optimized parameters afforded F2G (1.188 ± 0.052 g, 39.6 ± 1.7%) and FG (0.313 ± 0.038 g, 10.4 ± 1.3%) from 3.0 g of the transesterification precipitate, n = 10 trials. Overall, all flash chromatography separations combined, F2G (39.1 g, 40.6%) and FG (9.4 g, 9.8%) were isolated in a combined yield of 48.5 g (51.4%), relative to the 96.4 g of transesterification precipitate collected. The optimized flash chromatography method was a necessary improvement over previously reported preparative HPLC and column chromatography methods used to purify milligram to low gram quantities of F2G and FG to be able to process ~100 g of material in a timely, efficient manner.

Monoacylglycerides from the Diatom Skeletonema marinoi Induce Selective Cell Death in Cancer Cells

Microalgae are an excellent source of valuable compounds for nutraceutical and cosmeceutical applications. These photosynthesizing microorganisms are amenable for large-scale production, thus overcoming the bottleneck of biomass supply for chemical and activity characterization of bioactive compounds. This characteristic has recently also prompted the screening of microalgae for potential pharmaceutical applications. Here, we show that monoacylglycerides (MAGs) purified from the marine diatom Skeletonema marinoi have selective cytotoxic activity against the haematological cancer cell line U-937 and colon cancer cell line HCT-116 compared to normal MePR-2B cells. LC-MS analysis of the raw extract revealed that in their natural form, MAGs occur as 2-monoacyl derivatives and include mainly C16 and C20 analogues, but they are converted into the corresponding 1-isomers during purification processes. Pure compounds along with the synthetic 1-monoarachidonoylglycerol tested on HCT-116 and U-937 tumor cell lines induced cell death via apoptosis. The mechanism of action was investigated, and we show that it involves the induction of apoptosis through caspase 3/7 activation. These findings pave the way for the possible use of these molecules as potential anticancer agents or as precursors for the generation of new and more potent and selective compounds against tumor cells.

Catalytic characteristics of a sn-1(3) regioselective lipase from Cordyceps militaris

A total of 39 agricultural products were screened for natural sources of lipases with distinctive positional specificity. Based on this, Cordyceps militaris lipase (CML) was selected and subsequently purified by sequential chromatography involving anion-exchange, hydrophobic-interaction, and gel-permeation columns. As a result of the overall purification procedure, a remarkable increase in the specific activity of the CML (4.733 U/mg protein) was achieved, with a yield of 2.47% (purification fold of 94.54). The purified CML has a monomeric structure with a molecular mass of approximately 62 kDa. It was further identified as a putative extracellular lipase from C. militaris by the partial sequence analysis using ESI-Q-TOF MS. In a kinetic study of the CML-catalyzed hydrolysis, the values of V_max , K_m , and k_cat were determined to be 4.86 μmol·min^-1 ·mg^-1 , 0.07 mM, and 0.29 min^-1 , respectively. In particular, the relatively low K_m value indicated that CML has a high affinity for its substrate. With regard to positional specificity, CML selectively cleaved triolein at the sn-1 or 3 positions of glycerol backbone, releasing 1,2(2,3)-diolein as the major products. Therefore, CML can be considered a distinctive biocatalyst with sn-1(3) regioselectivity. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2744, 2019.

A Novel Modified Lipid: Enzymatic Esterification of 2-Monoacylglycerol with N-acetyl-l-leucine

The objective of this research was to synthesize and characterize a novel modified lipid which is composed of mainly oleic acid at sn-2 position and a hydrophobic essential amino acid derivative (N-acetyl-l-leucine) at sn-1(3) or sn-1, 3 positions. LC-MS-MS analysis indicated that the target modified lipid structure was obtained at the end of the developed reaction. Response surface methodology was applied to enhance a reliable empirical model for prediction and to optimize reaction conditions: reaction time (8 to 24 hr), reaction temperature (40 to 55 °C), and enzyme load (15 to 30 wt%). The percentage of total reaction products was found to be 28.5 at the optimum conditions of 54 °C, 8 hr and 15% (by mass) enzyme load. This result is closely correlated to the predicted highest total reaction product (29.3%) obtained by response surface methodology. The physical and thermal characteristics of the modified lipid and refined olive pomace oil were compared and found to be similar. Caloric value of modified lipid was decreased by 18.65% compared to that of refined olive pomace oil. A novel modified lipid which may have potential uses in healthy food industries was successfully produced with the incorporation of N-acetyl-l-leucine to 2-monoacylglycerol.

PRACTICAL APPLICATION

A novel modified lipid was synthesized by enzymatic incorporation of a "hydrophobic and essential amino acid derivative" into 2-monoacylglycerol. This modified lipid contains mainly oleic acid at sn-2 position and N-acetyl-l-leucine at sn-1,3 positions. The product behaved as an oil above 10 °C. Caloric value of the novel oil-like product was reduced by 18.65%. The modified lipid may have the potential for replacement with the oil in food products such as margarine, shortenings, salad dressing, and mayonnaise.

Purification process for MUFA- and PUFA-based monoacylglycerols from edible oils

Important health benefits have been attributed to monoacylglycerols (MAGs) due to their various physiological functions, owing to which they become candidates for use as functional foods in order to prevent the onset of certain diseases such as colon cancer. In this work, six edible oils, namely: olive, linseed, sunflower, evening primrose, DHASCO^® and ARASCO^® have been processed to obtain different MUFA- and PUFA- based MAGs. First, the oils were hydrolyzed by means of an enzymatic process using porcine pancreatic lipase and then the reaction products were fractionated by using a liquid chromatography column containing silica gel as stationary phase in order to purify the MAGs-enriched fraction. A second chromatography process was performed using silver nitrate coated silica gel as stationary phase, in order to obtain the different MUFA- and PUFA-based MAGs from the corresponding oils. Overall, MAGs based on oleic, linoleic, α-linolenic, γ-linolenic, arachidonic and docosahexaenoic acids have been isolated in high yields and purities (92.6, 97.4, 95.3, 90.9, 100 and 95.3% purity, respectively). Positional distribution was determined by means of ¹H NMR, which revealed a mix of 1(3) and 2-MAGs in variable proportions in the different MAGs.

Highly Branched Bio-Based Unsaturated Polyesters by Enzymatic Polymerization

A one-pot, enzyme-catalyzed bulk polymerization method for direct production of highly branched polyesters has been developed as an alternative to currently used industrial procedures. Bio-based feed components in the form of glycerol, pentaerythritol, azelaic acid, and tall oil fatty acid (TOFA) were polymerized using an immobilized Candida antarctica lipase B (CALB) and the potential for an enzymatic synthesis of alkyds was investigated. The developed method enables the use of both glycerol and also pentaerythritol (for the first time) as the alcohol source and was found to be very robust. This allows simple variations in the molar mass and structure of the polyester without premature gelation, thus enabling easy tailoring of the branched polyester structure. The postpolymerization crosslinking of the polyesters illustrates their potential as binders in alkyds. The formed films had good UV stability, very high water contact angles of up to 141° and a glass transition temperature that could be controlled through the feed composition.

A novel method for the synthesis of symmetrical triacylglycerols by enzymatic transesterification

A novel two-step enzymatic method is described in this study to synthesize symmetrical triacylglycerols (TAGs) with arachidonic acid (ARA) at the sn-2 position. The processes included the synthesis of 2-monoacylglycerols (2-MAGs) rich in 2-arachidonoylglycerol (2-AG) by enzymatic ethanolysis and the synthesis of symmetrical TAGs by enzymatic transesterification between 2-MAGs and vinyl palmitate. Under the optimal conditions, desired symmetrical TAGs were obtained at 89% yield. In this study, vinyl palmitate rather than palmitic acid was used as a novel acyl donor to react with 2-MAGs. It was the first study reporting the synthesis of symmetrical TAGs by enzymatic transesterification. The reaction using fatty acid vinyl ester as acyl donor is irreversible and temperature is low. Low-temperature reaction greatly suppressed the acyl migration of 2-MAGs and the irreversible reaction is much more effective compared to reversible reactions using free fatty acid and fatty acid ester as acyl donors.

Synthesis of enantiopure reversed structured ether lipids of the 1-O-alkyl-sn-2,3-diacylglycerol type

This report describes the synthesis of reversed structured 1-O-alkyl-2,3-diacyl-sn-glycerols (DAGEs) possessing a pure saturated even number fatty acid (C6:0-C16:0) at the sn-2 position along with a pure EPA or DHA located at the terminal sn-3 position of the glycerol backbone of chimyl, batyl and selachyl alcohols. These adducts were synthesized by a highly efficient two-step chemoenzymatic process involving an immobilized Candida antarctica lipase to introduce pure EPA and DHA activated as oxime esters exclusively to the sn-3 terminal position of enantiopure chimyl, batyl and selachyl alcohols in excellent yields. The saturated fatty acids were subsequently incorporated to the remaining sn-2 position of the resulting 3-monoacylglyceryl ethers (3-MAGEs) using EDAC coupling agent in the presence of DMAP in very high to excellent yields (85%-98%). No losses of enantiomeric composition were observed during these processes. The multiple utilities of the resulting focused library of reversed structured DAGEs are discussed including how such compounds may possibly be utilized within the pharmaceutical area.

Kinetics of transesterification of olive oil with methanol catalyzed by immobilized lipase derived from an isolated Burkholderia sp. strain

This work was carried out to investigate the acyl migration phenomena which has been considered as the factor having significant impact on kinetics of transesterification of oils catalyzed by a Burkholderia lipase with 1,3-regioselectivity. Transesterification of olive oil with methanol catalyzed by the immobilized lipase produces various intermediates, including 1-monoglyceride, 2-monoglyceride, 1,2-diglyceride, and 1,3-diglyceride. Migration kinetics of fatty acid groups from sn-2 of 2-monoglyceride and 1,2-diglyceride to 1-monoglyceride and 1,3-diglyceride were investigated for the temperature range of 25-65°C. The kinetics of transesterification of olive oil with methanol involving acyl migration in the presence of water was also systematically studied at 25, 40, and 65°C. Increasing temperature could increase the acyl migration rate. The overall biodiesel conversion was improved from 73.4% (at 25°C) to 90.0% and 92.4% when conducting at 40 and 65°C, respectively. Thermodynamics aspects of equilibrium state of the immobilized lipase-catalyzed transesterification were also discussed.

Continuous lipase-catalyzed production of esters from crude high-oleic sunflower oil

The objective of this work was to develop an economically relevant enzymatic process of butyl ester production using crude high-oleic sunflower oil. Novozym 435, a non-regiospecific biocatalyst, provided the best compromise between activity and butyl-ester yield. The inhibition caused by the presence of phopholipids in crude oil was eliminated by using tert-butanol. It demonstrates the key role of the medium polarity in order to insure the stability of a process. Initial substrate concentrations and their molar ratio were optimized in a continuous packed-bed reactor to maximize product yield and productivity. The best compromise was obtained for an initial oil concentration of 500 mM and a molar ratio of 5. It enabled a high productivity of 13.8 tons year(-1)kg Novozym 435(-1) with a butyl-ester purity of 96.5% to be obtained. Experiments with the continuous reactor were performed over 50 days without any loss of enzyme activity.

A methodology for radiolabeling of the endocannabinoid 2-arachidonoylglycerol (2-AG)

The metabolic intermediate and endocannabinoid signaling lipid 2-arachidonoylglycerol (2-AG) has not been readily labeled, primarily because of its instability toward rearrangement. We now detail a synthetic method that easily gives tritiated 2-AG from [5,6,8,9,11,12,14,15-(3)H(N)]arachidonic acid in two steps. We utilized a short chain 1,3-diacylglycerol and proceeded through the "structured lipid" [5'',6'',8'',9'',11'',12'',14'',15''-(3)H(N)]2-arachidonoyl-1,3-dibutyrylglycerol, a triacylglycerol that was conveniently deprotected in ethanol with acrylic beads containing Candida antarctica lipase B to give [5'',6'',8'',9'',11'',12'',14'',15''-(3)H(N)]2-arachidonoylglycerol ([(3)H]2-AG). The flash chromatographic separation necessary to isolate the labeled 2-acylglycerol [(3)H]2-AG resulted in only 4% of the rearrangement byproducts that have been a particular problem with previous methodologies. This reliable "kit" method to prepare the radiolabeled endocannabinoid as needed gave tritiated 2-arachidonoylglycerol [(3)H]2-AG with a specific activity of 200 Ci/mmol for enzyme assays, metabolic studies, and tissue imaging. It has been run on unlabeled materials on over 10 mg scales and should be generally applicable to other 2-acylglycerols.