High-performance liquid chromatography with evaporative light-scattering detection for the determination of phospholipid classes in human milk, infant formulas and phospholipid sources of long-chain polyunsaturated fatty acids

Progress of Mass Spectrometry-Based Lipidomics in the Dairy Field

Lipids play important biological roles, such as providing essential fatty acids and signaling. The wide variety and structural diversity of lipids, and the limited technical means to study them, have seriously hampered the resolution of the mechanisms of action of lipids. With advances in mass spectrometry (MS) and bioinformatic technologies, large amounts of lipids have been detected and analyzed quickly using MS-based lipidomic techniques. Milk lipids, as complex structural metabolites, play a crucial role in human health. In this review, the lipidomic techniques and their applications to dairy products, including compositional analysis, quality identification, authenticity identification, and origin identification, are discussed, with the aim of providing technical support for the development of dairy products.

Quantification of phospholipids and glycerides in human milk using ultra-performance liquid chromatography with quadrupole-time-of-flight mass spectrometry

Human milk lipids, which are an important source of energy and affect growth and development of infants, require a comprehensive method for its qualitative and quantitative analysis. This work describes a method for the analysis of phospholipids, glycerides, free fatty acids and gangliosides in human milk by ultra-performance liquid chromatography using a C18 column with quadrupole-time-of-flight mass spectrometry (Q-TOF-MS). The lipids were extracted by liquid-liquid extraction and phospholipids were separated by solid phase extraction (SPE). The chromatographic columns with two different specifications (4.6 mm × 150 mm, and 3 mm × 50 mm) were used to detect phospholipids and glycerides in human milk, respectively. The sphingolipids and glycerides were analyzed in positive ion mode, and the glycerophospholipids and free fatty acids were analyzed in negative ion mode. Both internal and external standards were used for absolute quantification in this experiment. 483 species of lipids, including phospholipids, glycerides, free fatty acids and gangliosides, in human milk were analyzed using UPLC-Q-TOF-MS with high sensitivity and good linearity, with coefficient of correlation above 0.99, the relative standard deviation of accuracy and precision less than 10%. The results in a large number of human milk samples showed that this method was suitable for qualitative and quantitative analysis of lipids in human milk, even for other mammalian milk and infant formulae.

Development and Application of Feature-Based Molecular Networking for Phospholipidomics Analysis

Phospholipids are small but critical lipids in milk. Conventional lipidomics is a powerful method for the analysis of lipids in milk. Although the number of lipidomics software has drastically increased over the past five years, reducing false positives and obtaining structurally accurate annotations of phospholipids remain a significant challenge. In this study, we developed a rapid and accurate method for measuring a wide spectrum of phospholipids in milk. The developed approach that employed information-dependent acquisition (IDA) mode and feature-based molecular networking has exhibited better performance on data processing and lipid annotation when compared with sequential window acquisition of all theoretical mass spectra (SWATH) and MS-DIAL. This validated method was further evaluated using three kinds of sheep milk. A total of 150 phospholipids were identified, including rarely reported phospholipids containing ethers or vinyl ethers. The result indicated that phospholipids could be used as potential markers to distinguish sheep milk from different varieties and origins. The experimental and computational methods provide a rapid and reliable method for the investigation of phospholipids in milk.

Determination of three Unsaturated Fatty Acids in Pressure Ulcer Rats Using A UPLC-MS/MS Method

Background:

The serum levels of Docosahexaenoic Acid (DHA), Eicosapentaenoic Acid (EPA) and Arachidonic Acid (AA) under the state of Pressure Ulcers (PUs) are still unclear.

Introduction:

In order to investigate serum levels of DHA, EPA, and AA in PUs rats, an ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/ MS) method was developed and validated.

Methods:

Chromatographic separation of DHA, EPA, AA was carried out on a BEH C18 column and gradient elute consisted of 5 mM ammonium acetate-0.1% formic acid and acetonitrile. Subsequently, fifty rats were divided into five groups (n=10), four PU groups (A-D) underwent various pressure and release time protocols, with group E as the control. The concentrations of DHA, EPA, AA from five groups were determined by using a validated method.

Results:

The results showed there was good linearity for DHA (327.3/283.4), EPA (301.2/257.0), and AA (303.1/258.9) within 0.05-6.4 μg/mL. In control group, the levels of DHA, AA and EPA were 1.16±0.68, 0.59±0.19 and 0.78±0.21 μg/mL. At the end of modeling, concentrations of DHA, EPA and AA were increased after long and persistent pressure (>8 h). Especially, the level of DHA was significantly higher (P<0.01) than that of control group.

Conclusion:

A stable, rA stable, reliable and accurate UPLC-MS/MS for determination of DHA, EPA, AA in blood was developed. Serum concentrations of DHA, EPA and AA were altered differently after long and persistent pressure (>8 h), and DHA is a remarkable one.eliable and accurate UPLC-MS/MS for determination of DHA, EPA, AA in blood was developed. Serum concentrations of DHA, EPA and AA were altered differently after long and persistent pressure (>8 h), and DHA is a remarkable one.

A Reliable HPLC-ELSD Method for Determination of Cholesterol, Phosphatidylcholine, Lysophosphatidylcholine Content and the Stability of a Liposomal Formulation

Background:

Liposomes continue to play an important role in drug delivery research due to their ability to improve transport and targeting of a wide range of active molecules. Analysis of liposomal components is a key point in the characterization and evaluation of formulation stability. The aim of this work was to develop and validate an HPLC-ELSD method for the characterization and quality control of liposomes.

Methods:

HPLC-ELSD method was validated by assessing selectivity, linearity, precision, accuracy, limit of detection and quantitation. The mobile phase consisted of a 0.1% (v/v) of trifluoroacetic acid (TFA) and methanol in gradient elution. Initial rate was 20:80 (0.1% TFA: methanol), with a ramp reaching 100% methanol. HPLC-MS/MS was used to confirm the presence of the fatty acid mixture in the analyzed lipids, as well as sub-products generated under pre-determined conditions in the stability study.

Results:

A HPLC-ELSD method has been developed to detect and measure cholesterol, phosphatidylcholine and lysophosphatidylcholine. High specificity, sensitivity and linearity within the predetermined range for all the compounds analyzed (R2>0.99) were obtained. Accuracy and precision results for all the compounds were within the acceptance limit of ≤5% and 90-110%, respectively. Mass spectrometry results showed complementary information about the phospholipid composition to evaluate the degree of degradation of liposomes over different storage conditions.

Conclusion:

The method was successfully applied as a quality control tool for the analysis of a wide range of lipids, present in liposomal formulations. HPLC-MS/MS was used to ensure complete elucidation of the lipid components and the detected lyso-forms.

Lipidomics of Brain Tissues in Rats Fed Human Milk from Chinese Mothers or Commercial Infant Formula

Holistic benefits of human milk to infants, particularly brain development and cognitive behavior, have stipulated that infant formula be tailored in composition like human milk. However, the composition of human milk, especially lipids, and their effects on brain development is complex and not fully elucidated. We evaluated brain lipidome profiles in weanling rats fed human milk or infant formula using non-targeted UHPLC-MS techniques. We also compared the lipid composition of human milk and infant formula using conventional GC-FID and HPLC-ELSD techniques. The sphingomyelin class of lipids was significantly higher in brains of rats fed human milk. Lipid species mainly comprising saturated or mono-unsaturated C18 fatty acids contributed significantly higher percentages to their respective classes in human milk compared to infant formula fed samples. In contrast, PUFAs contributed significantly higher percentages in brains of formula fed samples. Differences between human milk and formula lipids included minor fatty acids such as C8:0 and C12:0, which were higher in formula, and C16:1 and C18:1 n11, which were higher in human milk. Formula also contained higher levels of low- to medium-carbon triacylglycerols, whereas human milk had higher levels of high-carbon triacylglycerols. All phospholipid classes, and ceramides, were higher in formula. We show that brain lipid composition differs in weanling rats fed human milk or infant formula, but dietary lipid compositions do not necessarily manifest in the brain lipidome.

31P NMR-Based Phospholipid Fingerprinting of Powdered Infant Formula

Infant formula (IF), regarded as the optimal substitute for human breast milk, is very important for infant growth and development. Phospholipids (PLs) are ubiquitous components of infant formula as they have good emulsifier properties in addition to their nutritional and biological functions. In this study, the PL contents in four different commercial IF brands (indicated as A, M, O, and W) were characterized and quantified using optimized ³¹P NMR spectroscopy. PLs (nine) were identified and quantified, and among these, phosphatidylethanolamine and sphingomyelin occurred at lower concentrations (5.72 and 8.89 mg/100 g, respectively) in IFs from brand O, whereas phosphatidic acid was higher (2.83 mg/100 g) in IFs from brand W. In summary, ³¹P NMR spectroscopy, combined with the multivariate data analysis, proved to be an effective analytical toolbox for evaluating the PL contents in IF and the comparative differences between IF brands.

Quantification of Lipids: Model, Reality, and Compromise

Lipids are key molecules in various biological processes, thus their quantification is a crucial point in a lot of studies and should be taken into account in lipidomics development. This family is complex and presents a very large diversity of structures, so analyzing and quantifying all this diversity is a real challenge. In this review, the different techniques to analyze lipids will be presented: from nuclear magnetic resonance (NMR) to mass spectrometry (with and without chromatography) including universal detectors. First of all, the state of the art of quantification, with the definitions of terms and protocol standardization, will be presented with quantitative lipidomics in mind, and then technical considerations and limitations of analytical chemistry's tools, such as NMR, mass spectrometry and universal detectors, will be discussed, particularly in terms of absolute quantification.

Quantification of glycerophospholipids and sphingomyelin in human milk and infant formula by high performance liquid chromatography coupled with mass spectrometer detector

Phospholipids and sphingomyelin have a central role in infant nutrition, phospholipid acting as a nutrient carrier of long chain polyunsaturated fatty acids and sphingomyelin having an important role in cognitive function. However, analytical methods to precisely characterize and quantify these compounds in maternal milk are needed. Phospholipids and sphingomyelin were extracted using chloroform and methanol and separated on Polaris 3 Si column 250×2.0mm from Varian and analyzed by high performance liquid chromatography (HPLC) coupled with mass spectrometer detector (MS). The analytical method was validated and repeatability, intermediate reproducibility, and recovery values were calculated. The relative standard deviation of repeatability (CV(r)) and intermediate reproducibility (CV(iR)) values ranged between 2.3 and 7.2% and 9.5 and 17.8%, respectively and the recovery values between 96 and 109%. Finally, the validated method was tested on human milk samples and on infant formula which were analysed also by HPLC coupled with evaporative light scattering detector (ELSD). In human milk, sphingomyelin (9.28mg100mL^-1) was the most abundant compound, followed by phosphatidylcholine (5.39mg100mL^-1), phosphatidylethanolamine (2.85mg100mL^-1) and phosphatidylinositol (1.82mg100mL^-1).

Phospholipids in Human Milk and Infant Formulas: Benefits and Needs for Correct Infant Nutrition

The composition of human milk has served as a basis for the development of infant formulas, which are used when breastfeeding is not possible. Among the human milk nutrients, 50% of the total energetic value corresponds to fat, with a high level of fatty acids and 0.2-2.0% present in the form of phospholipids (PLs). The PL contents and fatty acid distribution in PL species have been investigated as bioactive elements for the production of infant formulas, since they offer potential benefits for the optimum growth and health of the newborn infant. The differences in the amount of PLs and in fatty acid distribution in PL species between human milk and infant formulas can imply biologically significant differences for newborn infants fed with infant formulas versus human milk-mainly due to the greater proportion of sphingomyelin with respect to phosphatidylcholine in infant formulas. The limited information referred to the characterization of fatty acid distribution in PL species in infant formulas or in ingredients used to enrich them merits further research in order to obtain products with benefits similar to those of human milk in terms of infant growth, visual acuity, and neurological development. The present review establishes the scientific basis for helping to adjust formulations to the requirements of infant nutrition.

Detection of related substances in polyene phosphatidyl choline extracted from soybean and in its commercial capsule by comprehensive supercritical fluid chromatography with mass spectrometry compared with HPLC with evaporative light scattering detection

Supercritical fluid chromatography with tandem mass spectrometry was used to comprehensively profile polyene phosphatidyl choline (PPC) extracted from soybean. We achieved an efficient chromatographic analysis using a BEH-2EP column (3 × 100 mm(2) , 1.7 μm) with a mobile phase consisting of CO2 and a cosolvent in gradient combination at a flow rate of 1.0 mL/min. The cosolvent consisted of methanol, acetonitrile, and water (containing 10 mM ammonium acetate and 0.2% formic acid). The total single-run time was 7 min. We used this method to accurately detect ten different phospholipids (PLs) during extraction. The limits of quantification for phosphatidyl choline, lyso-phosphatidylcholine (LPC), phosphatidic acid (PA), sphingomyelin, phosphatidyl glycerol, phosphatidyl inositol (PI), cholesterol, cardiolipin, phosphatidyl serine, and phosphatidyl ethanolamine (PE) were 20.6, 19.52, 1.21, 2.38, 0.50, 2.28, 54.3, 0.60, 0.65, and 4.85 ng/mL, respectively. However, adopting the high-performance liquid chromatography with evaporative light scattering detection method issued by the China Food and Drug Administration, only PA, LPC, PE, PI, and PPC could be analyzed accurately, and the limits of quantification were 33.89, 60.5, 30.3, 10.9, and 61.79 μg/mL, respectively. The total single-run time was at the least 20 min. Consequently, the supercritical fluid chromatography with tandem mass spectrometry method was more suitable for the analysis of related PLs.

Quantification of phospholipids classes in human milk

Phospholipids are integral constituents of the milk fat globule membranes and they play a central role in infants’ immune and inflammatory responses. A methodology employing liquid chromatography coupled with evaporative light scattering detector has been optimized and validated to quantify the major phospholipids classes in human milk. Phospholipids were extracted using chloroform and methanol and separated on C18 column. Repeatability, intermediate reproducibility, and recovery values were calculated and a large sample set of human milk analyzed. In human milk, phospholipid classes were quantified at concentrations of 0.6 mg/100 g for phosphatidylinositol; 4.2 mg/100 g for phosphatidylethanolamine, 0.4 mg/100 g for phosphatidylserine, 2.8 mg/100 g for phosphatidylcholine, and 4.6 mg/100 g for sphingomyelin. Their relative standard deviation of repeatability and intermediate reproducibility values ranging between 0.8 and 13.4 % and between 2.4 and 25.7 %, respectively. The recovery values ranged between 67 and 112 %. Finally, the validated method was used to quantify phospholipid classes in human milk collected from 50 volunteers 4 weeks postpartum providing absolute content of these lipids in a relatively large cohort. The average content of total phospholipids was 23.8 mg/100 g that corresponds to an estimated mean intake of 140 mg phospholipids/day in a 4-week old infant when exclusively breast-fed.

Analysis of phospholipids in infant formulas using high performance liquid chromatography-tandem mass spectrometry

Phospholipids have been used widely in the food industry as emulsifiers, but it is their biological and nutritional function that has been the focus over recent years. The recognition of the importance of phospholipids and sphingomyelin for infant development has led to an increase in the number of infant formulas claiming to contain these complex lipid components. Therefore, the ability to measure these lipids in infant formulas and dairy-derived complex lipid ingredients for fortification purposes is important. A high-performance liquid chromatography-tandem mass spectrometry method that quantifies phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and sphingomyelin found in infant formulas and dairy-derived complex lipid ingredients is described. The method uses external standards of similar fatty acid profile for calibration. The recovery of phospholipids ranged from 92% to 102% with a method repeatability coefficient of variation of 6-10%. In addition to the specificity and selectivity of the method, details of the molecular species in the individual phospholipid classes are available using this method.

Simple chromatographic method for simultaneous analyses of phosphatidylcholine, lysophosphatidylcholine, and free fatty acids

This study describes a simple chromatographic method for the simultaneous analyses of phosphatidylcholine (PC) and its hydrolytic degradation products: lysophosphatidylcholine (LPC) and free fatty acids (FFA). Quantitative determination of PC, LPC, and FFA is essential in order to assure safety and to accurately assess the shelf life of phospholipid-containing products. A single-run normal-phase high-performance liquid chromatography (HPLC) with evaporative light scattering detector has been developed. The method utilizes an Allsphere silica analytical column and a gradient elution with mobile phases consisting of chloroform: chloroform-methanol (70:30%, v/v) and chloroform-methanol-water-ammonia (45:45:9.5:0.5%, v/v/v/v). The method adequately resolves PC, LPC, and FFA within a run time of 25 min. The quantitative analysis of PC and LPC has been achieved with external standard method. The free fatty acids were analyzed as a group using linoleic acid as representative standard. Linear calibration curves were obtained for PC (1.64-16.3 μg, r(2) = 0.9991) and LPC (0.6-5.0 μg, r(2) = 0.9966), while a logarithmic calibration curve was obtained for linoleic acid (1.1-5.8 μg, r(2) = 0.9967). The detection and quantification limits of LPC and FFA were 0.04 and 0.1 μg, respectively. As a means of validating the applicability of the assay to pharmaceutical products, PC liposome was subjected to alkaline hydrolytic degradation. Quantitative HPLC analysis showed that 97% of the total mass balance for PC could be accounted for in liposome formulation. The overall results show that the HPLC method could be a useful tool for chromatographic analysis, stability studies, and formulation characterization of phospholipid-based pharmaceuticals.

Quantification of phosphatidylserine, phosphatidic acid and free fatty acids in an ultrasound contrast agent by normal-phase high-performance liquid chromatography with evaporative light scattering detection

Sonazoid is a new contrast agent for ultrasound imaging. The product is an aqueous suspension of perfluorobutane microbubbles coated with phospholipids obtained from hydrogenated egg phosphatidylserine (H-EPS). A normal-phase high-performance liquid chromatographic (HPLC) method with evaporative light scattering detection was developed for quantification of free fatty acids, phosphatidylserine and phosphatidic acid in H-EPS and Sonazoid. Separation of the lipids was carried out on an HPLC diol column and a gradient of chloroform and methanol with 0.2% formic acid titrated to pH 7.5 with ammonia. The calibration standards contained stearic acid, distearoyl-phosphatidic acid (DSPA) and distearoyl-phosphatidylserine (DSPS) in the concentration range of 0.016-1.0mg/ml (0.4-25microg injected). The method was validated with a limit of quantification of the three lipids set to 0.4microg (approximately 20-60microM). The best fit of the three calibration curves were obtained when the logarithmic transformed theoretical lipid concentration was plotted against the logarithmic transformed area under the peak and fitted to a second order polynomial equation. Stearic acid, DSPA and DSPS were analysed with an intermediate precision ranging from 4.4% to 5.3% R.S.D. and they were extracted from an aqueous suspension with a recovery ranging from 103.3% to 113.3%. The sum of total phospholipid concentration determined in H-EPS ranged from 96.4% to 103.2% of the theoretical values. The lipids in the ultrasound product were quantitated with a repeatability ranging from 6.2% to 11.7% R.S.D.

Comparison of the phospholipid classes in human milk in Japanese mothers of term and preterm infants

BACKGROUND

Phospholipids (PLs) play an essential role in the growth and brain development of infants.

AIM

To investigate PL composition in human milk (HM), including lysophosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylcholine (PC) and sphingomyelin (SM), from healthy Japanese mothers. Analyses were performed on colostrum, transitional milk and mature milk from mothers of preterm and term infants.

METHODS

HM samples were collected from mothers of 15 term infants (term group) and of 19 preterm infants (preterm group). PL composition was determined by two-dimensional thin-layer chromatography in conjunction with phosphorus analysis.

RESULTS

In both groups, the PL content (% of total lipid) of mature milk was significantly lower than in colostrum. SM and PC were the main PLs in HM, but in the preterm group, the percentage of SM in mature milk was significantly higher and PC in mature milk was significantly lower than in the term group.

CONCLUSION

The transition from colostrum to mature milk leads to an increase in SM and a decrease in PC in the HM of preterm infants, along with a decrease in PL content. This is the first report to demonstrate the differences in PL composition in HM between mothers of preterm and term infants.

Lipid composition in human breast milk from Granada (Spain): changes during lactation

OBJECTIVE

To determine possible differences of composition in the course of lactation, phospholipid (PL) classes (phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylcholine, and sphingomyelin) and fatty acid composition of PL and triacylglycerol (TGs) fractions of milk fat were analyzed in 66 samples from mothers from Granada (Spain) who gave birth to full-term infants. Analyses included colostrum, transitional milk, and mature milk.

METHODS

After milk fat extraction, PLs and TGs were separated by thin-layer chromatography and fatty acids of each fraction were converted into their methyl esters, which were analyzed by gas chromatography. PL classes were determined by high-performance liquid chromatography using an evaporative light-scattering detector.

RESULTS

Mature human milk showed a lower content (P = 0.020) of PLs than did the other milks. Percentage of sphingomyelin was constant for all stages of lactation, whereas the percentage of phosphatidylcholine in mature milk was significantly lower (P < 0.05) than in colostrum and transitional milk. TGs in mature human milk contained lower percentages (P < 0.001) of arachidonic acid, docosahexaenoic acid, and nervonic acid. Docosahexaenoic acid and nervonic acid also showed a significant decrease (P < 0.001) in total PLs from colostrum and mature milk.

CONCLUSIONS

The composition of PL classes and fatty acids in PLs and TGs in milk of mothers in Granada (Southern Europe) is different from that in milk from mothers in other parts of the world. In addition, the ratio of long-chain polyunsaturated fatty acids delivered in the form of PLs to long-chain polyunsaturated fatty acids delivered in the form of triacylglycerols diminishes as lactation proceeds.

Phospholipid hydrolysis in a pharmaceutical emulsion assessed by physicochemical parameters and a new analytical method

The aim of this work was to develop a simple high-performance liquid chromatography (HPLC) technique with evaporative light scattering detection (ELSD) for the separation and quantification of the major phospholipid (PL) and lysophospholipid (LPL) classes contained in a pharmaceutical phospholipid-based emulsion. In the established method, phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyeline (SM), lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE) were separated with a PVA-Sil stationary phase and a binary gradient from pure chloroform to methanol:water (94:6 v/v) at 3.4%/min. The ELSD detection was enhanced using 0.1% triethylamine and formic acid in each gradient mobile phases. Factors such as stationary phase and ELSD drift tube temperature were optimized, concluding in optimal temperatures of 25 degrees C for separation and 50 degrees C for evaporation. This HPLC-ELSD method was then applied to a PL-emulsion exposed to autoclaving and accelerated thermal conditions at 50 degrees C. Hydrolysis of PC and PE followed first-order kinetics, representing only 45% of the total lipid mass after 3 months. The chemical stability was correlated to commonly measured formulation physical and physico-chemical parameters such as droplet size, emulsion pH and zeta-potential.

Light-scattering detection of phospholipids resolved by HPLC

An improved method for the analysis of phospholipids by normal-phase HPLC is described. Addition of methanol and acetonitrile to a gradient based on 2-propanol/hexane/water promoted a rapid separation of major classes of bovine surfactant phospholipids (PL) by using a conventional silica column. The use of an ELSD permitted an accurate analysis of a mixture of PL. Calibration curves were linear within the range of 5-40 microg with detection limits below 1 microg for PE and PC, and CV ranged from 0.6 to 9.6%. PL present in surfactant homogenates were separated by a solid-phase extraction (SPE) procedure before HPLC analysis. This methodology gave a recovery of 95% and combined SPE-HPLC and quantification of biological PL within a 30-min run. The use of ELSD detection of the eluted compounds was precise, linear, and sensitive.