The main aim of research was synthesis and spectroscopic characterization of new conjugates in which stigmasterol was linked via carbonate or succinyl linker with 1,3- and 1,2-acylglycerols of palmitic and oleic acid. Acylglycerols containing stigmasterol residue at internal position have been synthesized from 2-benzyloxypropane-1,3-diol or dihydroxyacetone. Their asymmetric counterparts containing stigmasterol residue attached to sn-3 position have been obtained from (S)-solketal. Eight synthesized conjugates were used to create the liposomes as nanocarriers of phytosterols to increase their stability and protect them from degradation during thermal-oxidative treatments. Fluorimetric and ATR-FTIR methods were used to determine the impact of synthesized conjugates on the physicochemical properties of the lipid bilayer. The results indicate that conjugates with palmitic acid are better candidates for use as the potential stigmasterol nanocarriers compared to those with oleic acid because they increase the stiffness of the lipid bilayer and temperature of the main phase transition. The obtained results are the first step in designing of stigmasterol-enriched liposomal carriers with higher thermo-oxidative stability for their potential use in the food industry.

Exocrine meibomian glands (MGs) play a central role in the ocular physiology and biochemistry by producing in situ and, mostly, de novo a secretion (meibum), which is composed of a complex mixture of homologous lipids of various classes, in a metabolic pathway termed meibogenesis. Recent in vivo experiments with a number of mouse models demonstrated that inactivation of any of the major genes of meibogenesis led to alterations in the lipid composition of meibum and severe ocular and MG abnormalities that replicated various human ocular pathologies. However, the role of dietary lipids in meibogenesis, and in the onset and/or alleviation of these diseases, remains controversial. To uncover the role of dietary lipids, the metabolic transformations of a dietary lipid tracer-stable isotope-labeled glyceryl tri(oleate-1,2,3,7,8-13C5) (13C15-TO)-were investigated using liquid chromatography-high-resolution mass spectrometry. We demonstrated that major metabolic transformations of the tracer occurred in the stomach and small intestines where 13C15-TO underwent immediate and extensive transesterification into 13C5- and 13C10-substituted triacylglycerols of various lengths, giving a mixture of 13C-labeled compounds that remain virtually unchanged in the mouse plasma, liver, and white adipose tissue but were almost undetectable in the feces. Importantly, the tracer and its metabolites were virtually undetectable in MGs, even after 4 weeks of daily supplementation. Notably, unbiased principal component analysis of the data revealed no measurable changes in the overall chemical composition of meibum after the treatment, which implies no direct effect of dietary triacylglycerols on meibogenesis, and left their systemic effects as the most likely mechanism.

The effect of acylglycerols on the thermal inactivation of lactic acid bacteria used in the production of fermented products was studied. The starting point was the observation of an increase in thermal sensitivity in the presence of an emulsifier based on mono- and diacylglycerols in the culture medium. Analysis of the emulsifier showed that monoacylglycerols were the compounds responsible for this effect, with monopalmitin being the main contributor. Monostearin, on the other hand, showed significantly less potentiating effect. Interestingly, monoacylglycerols showed a greater bactericidal effect when used individually than when used in combination. On the other hand, the rate of thermal inactivation observed in reconstituted skim milk emulsions was lower than in peptone water emulsions, showing that the presence of proteins and colloidal particles increased the resistance of bacteria to heat treatment. With respect to pH values, a reduction in pH from 6.6 to 5.5 promoted an increase in the rate of thermal death. However, at pH = 5.5, the enhancing bactericidal effect was only detectable when the heat treatment was performed at low temperatures but not at high temperatures. This finding is of interest, since it will allow the design of moderate heat treatments, combining the use of temperature with the addition of acylglycerols, to prolong the shelf life of products fermented with lactic acid bacteria, and minimizing the destruction of desirable compounds that were obtained by the fermentation process.

Plant sterols are known for their health-promoting effects, lowering blood cholesterol levels and alleviating cardiovascular disease. In this work, we continue our research on the asymmetric acylglycerols in which fatty acid residues are replaced by two stigmasterol residues in sn-1 and sn-2 or sn-2 and sn-3 positions as new thermostable carriers of phytosterols for their potential application in foods or as components of new liposomes in the pharmaceutical industry. The aim of this manuscript was to compare and analyze the effects of four distigmasterol-modified acylglycerols (dStigMAs) on the fluidity and the main phase transition temperature of the model phospholipid membrane. Their properties were determined using differential scanning calorimetry (DSC), steady-state fluorimetry and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). The determination of the effect of the tested compounds on the mentioned physicochemical parameters of the model membranes will allow for the determination of their properties and stability, which is essential for their practical application. The results indicated that all compounds effect on the physicochemical properties of the model membrane. The degree of these changes depends on the structure of the compound, especially the type of linker by which stigmasterol is attached to the glycerol backbone, as well as on the type of hydrocarbon chain.

New carriers of phytosterols; acylglycerols containing natural myristic acid at sn-1 and sn-3 positions and stigmasterol residue linked to sn-2 position by carbonate and succinate linker have been designed and synthesized in three-step synthesis from dihydroxyacetone (DHA). The synthetic pathway involved Steglich esterification of DHA with myristic acid; reduction of carbonyl group of 1,3-dimyristoylpropanone and esterification of 1,3-dimyristoylglicerol with stigmasterol chloroformate or stigmasterol hemisuccinate. The structure of the obtained hybrids was established by the spectroscopic methods (NMR; IR; HRMS). Obtained hybrid molecules were used to form new liposomes in the mixture with model phospholipid and their effect on their physicochemical properties was determined, including the polarity, fluidity, and main phase transition of liposomes using differential scanning calorimetry and fluorimetric methods. The results confirm the significant effect of both stigmasterol-containing acylglycerols on the hydrophilic and hydrophobic region of liposome membranes. They significantly increase the order in the polar heads of the lipid bilayer and increase the rigidity in the hydrophobic region. Moreover, the presence of both acylglycerols in the membranes shifts the temperature of the main phase transition towards higher temperatures. Our results indicate stabilization of the bilayer over a wide temperature range (above and below the phase transition temperature), which in addition to the beneficial effects of phytosterols on human health makes them more attractive components of novel lipid nanocarriers compared to cholesterol.

The study investigated the thermo-oxidative stability of distigmasterol-modified acylglycerols as a new structured acylglycerols. Samples were heated at 60 and 180 °C for 8 h. Their percentage degradation and products formed during heating were compared with free stigmasterol and stigmasteryl esters. The remaining of stigmasterol and fatty acid parts, the formation of stigmasterol oxidation products and the composition of polar and non-polar fractions were analysed using chromatographic methods. The cytotoxicity and genotoxicity were determined with the use of an MTT test and a comet assay, respectively. The highest stability during heating was observed for 2,3-distigmasterylsuccinoyl-1-oleoyl-sn-glycerol (dStigS-OA) and the lowest for 2,3-distigmasterylcarbonoyl-1-oleoyl-sn-glycerol (dStigC-OA). Data showed that the formation of thermo-oxidative degradation products is affected by the temperature and chemical structure of lipids present in the molecule. The dStigMAs bonded by a succinate linker and products formed during their thermo-oxidation showed no cytotoxic or genotoxic activity to normal human cells.

Plant sterols, also referred as phytosterols, have been known as bioactive compounds which have cholesterol-lowering properties in human blood. It has been established that a diet rich in plant sterols or their esters alleviates cardiovascular diseases (CVD), and also may inhibit breast, colon and lung carcinogenesis. Phytosterols, in their free and esterified forms, are prone to thermo-oxidative degradation, where time and temperature affect the level of degradation. Looking for new derivatives of phytosterols with high thermo-oxidative stability for application in foods, our idea was to obtain novel structured acylglycerols in which two fatty acid parts are replaced by stigmasterol residues. In this work, asymmetric (1,2- and 2,3-) distigmasterol-modified acylglycerols (dStigMAs) were synthesized by the covalent attachment of stigmasterol residues to sn-1 and sn-2 or sn-2 and sn-3 positions of 3-palmitoyl-sn-glycerol or 1-oleoyl-sn-glycerol, respectively, using a succinate or carbonate linker. The chemical structures of the synthesized compounds were identified by NMR, HR-MS, and IR data. Moreover, the cytotoxicity of the obtained compounds was determined. The dStigMAs possessing a carbonate linker showed potent cytotoxicity to cells isolated from the small intestine and colon epithelium and liver, whereas the opposite results were obtained for compounds containing a succinate linker.

Lipid characterization in art and archeology, together with the study of lipid degradation processes, is an important research area in heritage science. Lipid-based materials have been used as food since ancient times, but also employed as illuminants and as ingredients in cosmetic, ritual, and pharmaceutical preparations. Both animal and plant lipids have also been processed to produce materials used in art and crafts, such as paint binders, varnishes, waterproofing agents, and coatings. Identifying the origin of the lipid materials is challenging when they are found in association with artistic historical objects. This is due to the inherent complex composition of lipids, their widespread occurrence, and the chemical alterations induced by ageing. The most common approach for lipid characterization in heritage objects entails profiling fatty acids by gas chromatography/mass spectrometry after saponification or transesterification. New developments in high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS) for the characterization of acylglycerols, together with more efficient sample treatments, have fostered the introduction of liquid chromatography for characterizing the lipid profile in heritage objects. This review reports the latest developments and applications of HPLC-MS for the characterization of lipid materials in the field of heritage science. We describe the various approaches for sample pretreatment and highlight the advantages and limitations of HPLC-MS in the analysis of paint and archeological samples. © 2020 John Wiley & Sons Ltd.

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.
CONCLUSIONS: 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.

This work proposes a novel method for the direct flow injection profiling of acylglycerols in edible oils and fats without preliminary extraction and consequent reconstitution in the injection solvent. The work exploits the outstanding performance of high-resolution mass spectrometry to target unique elemental compositions even in the most complex matrices. The performance of isopropanol as the unique solvent for both the solubilization and analysis of acylglycerols was investigated in comparison with other classical methods involving preliminary extractions, sample recovery, and analysis. The calibrations of two triglyceride standards (triolein and trilinolenin) were successfully performed in presence and absence of oil matrix. As final application, the effects on the acylglycerol fraction of a heat treatment on three different fat samples (extra virgin olive oil, lard oil, and fat from dry cured ham-speck) were monitored. The proposed method is therefore suitable for a rapid evaluation of acylglycerol fractions in food lipid samples.