Extraction, chromatographic and mass spectrometric methods for lipid analysis

Standardization of lipid sample preparation for monitoring phospholipase activity

Phospholipase enzymes, such as A1, A2, B, and D, are found in the venom of venomous animals, including brown spiders. Phospholipase D (PLD) isoforms from brown spider venom can cause dermonecrosis, hemolysis, and nephrotoxicity. New methods to monitor PLD activity are essential for understanding its mechanisms and molecular characteristics. One effective approach is using 31P nuclear magnetic resonance (31P NMR) spectroscopy to track PLD enzymatic activity by identifying the 31P signals of phosphorylated substrates and products. However, sample preparation for 31P NMR is challenging, as the lipid substrates' carbon chain length and unsaturation degree can affect solubilization, oxidation, and enzyme interaction, impacting the reaction kinetics. This study standardizes a phospholipid sample preparation method with fatty acids of different chain lengths for monitoring PLD activity. The addition of CHAPS detergent is essential for solubilizing lipids with long-chain fatty acids, but its concentration needs optimization, as higher amounts can inhibit PLD activity. Storing lipids in ethanol, forming lipid films, and injecting nitrogen into stock solutions improved lipid quantification and assay reproducibility. These standardized conditions can be adapted to other experimental approaches for monitoring phospholipase activity.

Lipidomic profiling reveals the protective mechanism of nitrogen-controlled atmosphere on brown rice quality during storage

Rice, a globally important staple, requires effective preservation methods to maintain its quality during extended storage. This study explored the efficacy of nitrogen-controlled atmosphere (NCA) storage in preserving the quality of brown rice during a one-year period using UHPLC-MS/MS based lipidomic profiling. A total of 1013 lipids were identified and categorized into five main groups. Specific lipids including triglycerides (TG), diglycerides (DG), phosphatidylethanolamines (PE), cardiolipins (CL), and ceramides (Cer), were highlighted as potential biomarkers for assessing rice rancidity. NCA storage significantly suppressed lipase and lipoxygenase activities, reducing lipid hydrolysis and oxidation to effectively delayed rice quality deterioration. Furthermore, NCA regulated glycerolipid and glycerophospholipid metabolisms, promoting lipid remodeling while reducing the degradation of TGs and phospholipids. This regulation preserved cellular membrane integrity, limited fatty acid release, and mitigate rancidity and quality loss during storage. These findings elucidate the mechanism by which NCA storage delays deterioration and extends the stored rice shelf-life.

Evaluation of tissue-specific extraction protocols for comprehensive lipid profiling

BACKGROUND

Robust tissue pre-treatment and lipid extraction workflows are crucial to metabolic phenotyping studies and accurate interpretation of lipid profiles. Numerous methods for lipid extraction from tissues have been developed, and the choice of technique influences analysis. This study provides a comprehensive evaluation of six liquid-liquid extraction methods (three biphasic and three monophasic) used for lipidomic tissue analysis by liquid chromatography-mass spectrometry. Extraction methods were assessed for their suitability for comprehensive lipid profiling across diverse tissue types: adipose, liver, and heart. These techniques were compared using lyophilised and fresh frozen samples.

RESULTS

The study revealed significant differences in the coverage and reliability of lipid species extracted using each technique, dependent on the tissue type. The optimal extraction method for adipose tissue was butanol:methanol (BUME) (3:1) which achieved the highest lipid coverage, yield and reproducibility (886 lipids with a coefficient of variation (CV) < 30 %); methyl tert-butyl ether (MTBE) with ammonium acetate was most effective for liver tissue (707 lipids CV < 30 %) and BUME (1:1) for heart tissue (311 lipids CV < 30 %). These findings showed that the most effective lipid extraction methods are highly tissue-specific, underscoring the critical need for bespoke protocols tailored to each tissue type. The optimised tissue-specific methods were validated using an intervention study in C57BL/6 mice to investigate diet-induced metabolic changes. The results demonstrated distinct discriminating lipid profiles unique to each tissue type, with 374 lipid species from 13 subclasses significantly different between high-fat diet (HFD) and normal diet (ND) in adipose tissue, while 485 lipid species from 17 subclasses were significantly different between HFD and ND in liver tissue.

SIGNIFICANCE AND NOVELTY

This study presents a new approach to studying lipid profiles derived from diverse tissues that substantially improve comprehensive lipid species' detection sensitivity and reliability. Our systematic evaluation provides evidence that tailored tissue-specific extraction protocols are highly valuable in comprehensive lipidomics studies, offering robust tools for reliably identifying lipid changes and facilitates a deeper understanding of tissue-specific metabolic processes in diverse research and clinical applications.

Evaluation of Green and Biobased Solvent Systems for the Extraction of β-Carotene and Lipids from Rhodosporidium toruloides

Oleaginous microorganisms are promising for the biotechnological production of valuable hydrophobic bioactive components. For an environmentally friendly extraction, we evaluated a two-step process for β-carotene and lipid isolation from wet Rhodosporidium toruloides biomass using biphasic green and biobased solvent systems: 2-methyl tetrahydrofuran (2-MeTHF) or cyclopentyl-methyl-ether (CPME) with ethanol or 1-butanol and water. Initially, components were extracted with a single-phase solvent mixture, followed by separating hydrophobic target components from polar impurities via phase separation. We employed the Conductor-like Screening Model for Real Solvents (COSMO-RS) to predict the solubility of β-carotene and select compositions with higher solubility. Our study highlights the potential of these solvent systems for extracting hydrophobic components and the importance of understanding the system's liquid-liquid equilibria for effective process design. We present a framework for evaluating new solvent systems for extracting hydrophobic bioactive compounds by demonstrating the impact of solvent composition selection on extraction yields and solvent consumption.

Alahmari A, A. Alqabbani A, Aldayel AM. Exploring the landscape of Lipid Nanoparticles (LNPs): A comprehensive review of LNPs types and biological sources of lipids

Lipid nanoparticles (LNPs) have emerged as promising carriers for delivering therapeutic agents, including mRNA-based immunotherapies, in various biomedical applications. The use of LNPs allows for efficient delivery of drugs, resulting in enhanced targeted delivery to specific tissues or cells. These LNPs can be categorized into several types, including liposomes, solid lipid nanoparticles, nanostructured lipid carriers, and lipid-polymer hybrid nanoparticles. The preparation of LNPs involves the manipulation of their structural, dimensional, compositional, and physical characteristics via the use of different methods in the industry. Lipids used to construct LNPs can also be derived from various biological sources, such as natural lipids extracted from plants, animals, or microorganisms. This review dives into the different types of LNPs and their preparation methods. More importantly, it discusses all possible biological sources that are known to supply lipids for the creation of LNPs. Natural lipid reservoirs have surfaced as promising sources for generating LNPs. The use of LNPs in drug delivery is expected to increase significantly in the coming years. Herein, we suggest some environmentally friendly and biocompatible sources that can produce lipids for future LNPs production.

Are Lean Body Mass and Fat-Free Mass the Same or Different Body Components? A Critical Perspective

The 2-component molecular-level model dividing body mass into fat and fat-free mass (FFM) is a cornerstone of contemporary body composition research across multiple disciplines. Confusion prevails, however, as the term lean body mass (LBM) is frequently used interchangeably with FFM in scientific discourse. Are LBM and FFM the same or different body components? Captain Albert R. Behnke originated the LBM concept in 1942 and he argued that his "physiological" LBM component included "essential" fat or structural lipids whereas FFM is a chemical entity "free" of fat. Classical experimental animal and human studies conducted during Behnke's era laid the foundation for the widely used body density and total body water 2-component molecular-level body composition models. Refined body composition models, organization of lipids into structural and functional groupings, and lipid extraction methods all have advanced since Behnke's era. Our review provides an in-depth analysis of these developments with the aim of clarifying distinctions between the chemical composition of LBM and FFM. Our retrospective analysis reveals that FFM, derived experimentally as the difference between body weight and extracted neutral or nonpolar lipids (mainly triglycerides), includes polar or structural lipids (that is, Behnke's "essential" fat). Accordingly, LBM as originally proposed by Behnke has the same chemical composition as FFM, thus answering a longstanding ambiguity in the body composition literature. Bringing body composition science into the modern era mandates the use of the chemically correct term FFM with the elimination of the duplicative term LBM that today has value primarily in a historical context. Avoiding the use of the term LBM additionally limits confusion surrounding similar widely used body composition terms such as lean mass, lean soft tissue mass, and lean muscle mass.

Lipid fingerprinting and geographical origin identification of large yellow croaker (Larimichthys crocea) using UHPLC-QTOF-MS

The Large Yellow Croaker (LYC) with rich lipids offers numerous health benefits, yet its lipid profile remains underexplored. Therefore, the lipids of LYC were comprehensively profiled and compared based lipidomics. Higher nutritional value of LYC was identified based on lipid and fatty acid assessment, particularly ovary and brain. A total of 963 lipid species belonging to 47 lipid subclasses were identified, exhibiting higher levels of glycerophospholipids (GPs) and sphingolipids (SPs) in the brain, as well as high levels of glycolipids (GLs) in the muscle. Furthermore, unique lipid subclasses were detected in the brain (Acylcarnitine (CAR), Alpha-hydroxy-N-stearoyl phytosphingosine (Cer-AP)) and ovary (N-arachidonoyl glycine (NAGly)). Notably, 8 lipid subclasses were selected as potential contributors for four tissues differentiation. Additionally, identification of LYC from various origins was achieved through lipidomics for the first time. LYC from Zhejiang and Fujian provinces could be distinguished by 100 lipid biomarkers. Most different lipids significantly negatively correlated with seawater pH and dissolved oxygen, but positively correlated with netting density, depth, environmental temperature and salinity. This comprehensive analysis provided valuable insights into LYC's nutritional values and origin identified.

Human Cerebrospinal Fluid Sample Preparation and Annotation for Integrated Lipidomics and Metabolomics Profiling Studies

Cerebrospinal fluid (CSF) is a metabolically diverse biofluid and a key specimen for exploring biochemical changes in neurodegenerative diseases. Detecting lipid species in CSF using mass spectrometry (MS)-based techniques remains challenging because lipids are highly complex in structure, and their concentrations span over a broad dynamic range. This work aimed to develop a robust lipidomics and metabolomics method based on commonly used two-phase extraction systems from human CSF samples. Prioritizing lipid detection, biphasic extraction methods, Folch, Bligh and Dyer (B&D), Matyash, and acidified Folch and B&D (aFolch and aB&D) were compared using 150 μL of human CSF samples for the simultaneous extraction of lipids and metabolites with a wide range of polarity. Multiple chromatographical separation approaches, including reversed-phase liquid chromatography (RPLC), hydrophilic interaction liquid chromatography (HILIC), and gas chromatography (GC), were utilized to characterize human CSF metabolome. The aB&D method was found as the most reproducible technique (RSD < 15%) for lipid extraction. The aB&D and B&D yielded the highest peak intensities for targeted lipid internal standards and displayed superior extracting power for major endogenous lipid classes. A total of 674 unique metabolites with a wide polarity range were annotated in CSF using, combining RPLC-MS/MS lipidomics (n = 219), HILIC-MS/MS (n = 304), and GC-quadrupole time of flight (QTOF) MS (n = 151). Overall, our findings show that the aB&D extraction method provided suitable lipid coverage, reproducibility, and extraction efficiency for global lipidomics profiling of human CSF samples. In combination with RPLC-MS/MS lipidomics, complementary screening approaches enabled a comprehensive metabolite signature that can be employed in an array of clinical studies.

Comprehensive analysis of phospholipid in milk and their biological roles as nutrients and biomarkers

Phospholipids (PL) have garnered significant attention due to their physiological activities. Milk and other dairy products are important dietary sources for humans and have been extensively used to analyze the presence of PL by various analytical techniques. In this paper, the analysis techniques of PL were reviewed with the eight trigrams of phospholipidomics and a comprehensive fingerprint of 1295 PLs covering 8 subclasses in milk and other dairy products, especially. Technology is the primary productive force. Based on phospholipidomics technology, we further review the relationship between the composition of PL and factors that may be involved in processing and experimental operation, and emphasized the significance of the biological role played by PL in dietary supplements and biomarkers (production, processing and clinical research), and providing the future research directions.

Microwave-Assisted Extraction/UHPLC-Q-Orbitrap-MS-Based Lipidomic Workflow for Comprehensive Study of Lipids in Soft Cheese

In this work, Microwave-Assisted Extraction (MAE) was proposed as an alternative and environmentally friendly technique in lipidomics to study the lipid fingerprint of soft cheeses, such as mozzarella. For method development, a first step concerning an evaluation of extraction solvents was carried out via testing three different mixtures, including methanol/ethyl acetate, isopropanol/ethyl acetate, and ethanol/ethyl acetate, at a 1:2 v/v ratio. The latter was chosen as a solvent mixture for subsequent method optimization. MAE conditions, in terms of solvent volume, time, and temperature, were explored to define their effects on extraction capability through a full factorial experimental design. The best compromise to extract more lipids at the same time was obtained with 24 mL g-1 for solvent-to-solid ratio, 65 °C for temperature, and 18 min for time. Lipid analyses were conducted by UHPLC-Q-Orbitrap-MS associated with multivariate statistics. The developed lipidomic workflow allowed for the extraction of over 400 lipids grouped into 18 different subclasses. The results confirmed that MAE is a suitable technique for lipid extraction in the omics approach with high efficiency, even using low-cost and less toxic solvents. Moreover, a comprehensive structure characterization of extracted lipids, in terms of fatty acid composition and regiochemistry, was carried out.

Exploring the plant lipidome: techniques, challenges, and prospects

Plant lipids are a diverse group of biomolecules that play essential roles in plant architecture, physiology, and signaling. To advance our understanding of plant biology and facilitate innovations in plant-based product development, we must have precise methods for the comprehensive analysis of plant lipids. Here, we present a comprehensive overview of current research investigating plant lipids, including their structures, metabolism, and functions. We explore major lipid classes, i.e. fatty acids, glyceroglycolipids, glycerophospholipids, sphingolipids, and phytosterols, and discuss their subcellular distributions. Furthermore, we emphasize the significance of lipidomics research techniques, particularly chromatography-mass spectrometry, for accurate lipid analysis. Special attention is given to lipids as crucial signal receptors and signaling molecules that influence plant growth and responses to environmental challenges. We address research challenges in lipidomics, such as in identifying and quantifying lipids, separating isomers, and avoiding batch effects and ion suppression. Finally, we delve into the practical applications of lipidomics, including its integration with other omics methodologies, lipid visualization, and innovative analytical approaches. This review thus provides valuable insights into the field of plant lipidomics and its potential contributions to plant biology.

Recent Analytical Methodologies in Lipid Analysis

Lipids represent a large group of biomolecules that are responsible for various functions in organisms. Diseases such as diabetes, chronic inflammation, neurological disorders, or neurodegenerative and cardiovascular diseases can be caused by lipid imbalance. Due to the different stereochemical properties and composition of fatty acyl groups of molecules in most lipid classes, quantification of lipids and development of lipidomic analytical techniques are problematic. Identification of different lipid species from complex matrices is difficult, and therefore individual analytical steps, which include extraction, separation, and detection of lipids, must be chosen properly. This review critically documents recent strategies for lipid analysis from sample pretreatment to instrumental analysis and data interpretation published in the last five years (2019 to 2023). The advantages and disadvantages of various extraction methods are covered. The instrumental analysis step comprises methods for lipid identification and quantification. Mass spectrometry (MS) is the most used technique in lipid analysis, which can be performed by direct infusion MS approach or in combination with suitable separation techniques such as liquid chromatography or gas chromatography. Special attention is also given to the correct evaluation and interpretation of the data obtained from the lipid analyses. Only accurate, precise, robust and reliable analytical strategies are able to bring complex and useful lipidomic information, which may contribute to clarification of some diseases at the molecular level, and may be used as putative biomarkers and/or therapeutic targets.

Flaxseed oil fraction reverses cardiac remodeling at a molecular level: improves cardiac function, decreases apoptosis, and suppresses miRNA-29b and miRNA 1 gene expression

Flaxseed is an ancient commercial oil that historically has been used as a functional food to lower cholesterol levels. However, despite its longstanding treatment, there is currently a lack of scientific evidence to support its role in the management of cardiac remodeling. This study aimed to address this gap in knowledge by examining the molecular mechanism of standardized flaxseed oil in restoring cardiac remodeling in the heart toxicity vivo model. The oil fraction was purified, and the major components were standardized by qualitative and quantitative analysis. In vivo experimental design was conducted using isoproterenol ISO (85 mg/kg) twice subcutaneously within 24 h between each dose. The rats were treated with flaxseed oil fraction (100 mg/kg orally) and the same dose was used for omega 3 supplement as a positive control group. The GC-MS analysis revealed that α-linolenic acid (24.6%), oleic acid (10.5%), glycerol oleate (9.0%) and 2,3-dihydroxypropyl elaidate (7%) are the major components of oil fraction. Physicochemical analysis indicated that the acidity percentage, saponification, peroxide, and iodine values were 0.43, 188.57, 1.22, and 122.34 respectively. As compared with healthy control, ISO group-induced changes in functional cardiac parameters. After 28-day pretreatment with flaxseed oil, the results indicated an improvement in cardiac function, a decrease in apoptosis, and simultaneous prevention of myocardial fibrosis. The plasma levels of BNP, NT-pro-BNP, endothelin-1, Lp-PLA2, and MMP2, and cTnI and cTn were significantly diminished, while a higher plasma level of Topo 2B was observed. Additionally, miRNA - 1 and 29b were significantly downregulated. These findings provide novel insight into the mechanism of flaxseed oil in restoring cardiac remodeling and support its future application as a cardioprotective against heart diseases.

Research-based Analytical Procedures to Evaluate Diabetic Biomarkers and Related Parameters: In Vitro and In Vivo Methods

BACKGROUND

The degenerative tendency of diabetes leads to micro- and macrovascular complications due to abnormal levels of biochemicals, particularly in patients with poor diabetic control. Diabetes is supposed to be treated by reducing blood glucose levels, scavenging free radicals, and maintaining other relevant parameters close to normal ranges. In preclinical studies, numerous in vivo trials on animals as well as in vitro tests are used to assess the antidiabetic and antioxidant effects of the test substances. Since a substance that performs poorly in vitro won't perform better in vivo, the outcomes of in vitro studies can be utilized as a direct indicator of in vivo activities.

OBJECTIVE

The objective of the present study is to provide research scholars with a comprehensive overview of laboratory methods and procedures for a few selected diabetic biomarkers and related parameters.

METHOD

The search was conducted on scientific database portals such as ScienceDirect, PubMed, Google Scholar, BASE, DOAJ, etc. Conclusion: The development of new biomarkers is greatly facilitated by modern technology such as cell culture research, lipidomics study, microRNA biomarkers, machine learning techniques, and improved electron microscopies. These biomarkers do, however, have some usage restrictions. There is a critical need to find more accurate and sensitive biomarkers. With a few modifications, these biomarkers can be used with or even replace conventional markers of diabetes.

Lipidomics insight on differences in lipid profiles and phytosterol compositions of coconut oils extracted by classical and green solvents

Searching for green and ecofriendly solvents to replace classical solvents for industrial scale extraction of coconut oil is of great interest. To explore these possibilities, this study performed comprehensive comparative analyses of lipid profiles and phytosterol compositions in coconut oils obtained by extraction with n-hexane, absolute ethyl alcohol, deep eutectic solvent/n-hexane, dimethyl carbonate (DME) and cyclopentyl methyl ether (CPME) using a foodomics approach. Results indicated that CPME (64.23 g/100 g dry matter) and DME (65.64 g/100 g dry matter) showed comparable capacity for total lipid extraction of total lipids to classical solvents (63.5-65.66 g/100 g dry matter). Considering the phytosterol yield, CPME (644.26 mg/kg) exhibited higher selectivity than other solvents (535.64-622.13 mg/kg). No significant difference was observed in the fatty acid composition of coconut oil by the different solvents assayed. Additionally, total 468 lipid molecules were identified in the samples. For glycerolipid and sphingolipid, the five solvents showed comparable extraction capabilities. However, CPME exhibited higher extraction efficiency of polar lipids (glycerophospholipid and saccharolipid) than other solvents. Overall, these results may be a useful guide for the application of green solvents in industrial production of coconut oil.

Set up and validation of a sensitive method to quantify prostaglandins, prostaglandin-glycerol esters and prostaglandin-ethanolamides, as well as their respective precursors

Arachidonic acid-derived prostaglandins are widely studied for their role in inflammation. However, besides arachidonic acid, other arachidonic moiety-containing lipids can be metabolized by COX-2. Indeed, the endocannabinoids 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (anandamide, AEA) can follow the same biochemical pathways than arachidonic acid leading to the formation of prostaglandin-glycerol esters (PG-G) and prostaglandin-ethanolamides (or prostamides, PG-EA), respectively. The data reported so far support the interest of these bioactive lipids in inflammatory conditions. However, there is only a handful of methods described for their quantification in biological matrices. Moreover, given the shared biochemical pathways for arachidonic acid, 2-AG and AEA, a method allowing for the quantification of these precursors and the corresponding prostaglandin derivatives appears as largely needed. Thus, we report here the development and validation of a single run UPLC-MS/MS quantification method allowing the quantification of these endocannabinoids-derived mediators together with the classical prostaglandin. Moreover, we applied the method to the quantification of these lipids in vitro (using lipopolysaccharides-activated J774 macrophage cells) and in vivo in several tissues from DSS-induced colitis mice. This femtomole-range method should improve the understanding of the interaction between these lipid mediators and inflammation.

Sphingolipidoses in Morocco: Chemical profiling for an affordable and rapid diagnosis strategy

Sphingolipidoses are a group of metabolic diseases in which lysosomal hydrolases dysfunction disrupt normal sphingolipids' metabolism, leading to excess accumulation in cellular compartments and excretion in urine. These pathologies represent a significant burden among Moroccan population, for which an easy access to enzymatic assays and genetic tests is not guaranteed. Parallel analytical methods thus have to be developed for preliminary screening. In this study, 107 patients were addressed to the metabolic platform of the Marrakesh Faculty of Medicine for diagnosis confirmation. Thin-Layer Chromatography was used as a first step to perform chemical profiling of the patients' urinary lipids, allowing 36% of the patients to be efficiently oriented towards the adequate enzymatic assay. UPLC-MS/MS analyses of urinary sulfatides excreted in urines patient had been used to control the reliability of TLC analysis and to obtain more accurate information related to the sulfatides isoforms. This analytical process combining TLC with UPLC-MS/MS has enabled rapid and appropriate patient management in a reduced time and with reduced resources.

Microwave-assisted extraction in closed vessel in food analysis

Microwave-assisted extraction (MAE) is an important technique in analytical chemistry. It offers several advantages over traditional extraction methods, such as improved extraction efficiency, shorter extraction times, reduced solvent consumption, and enhanced analyte recovery. Using microwaves, heat is directly applied to the sample, leading to rapid and efficient extraction of target compounds by enhancing the solubility and diffusion of the target compounds, thus requiring lower solvent volume. Therefore, MAE can be considered a more environmentally friendly and cost-effective option facilitating the transition toward greener and more sustainable analytical chemistry workflows. This contribution systematically reviews the application of MAE to a selection of target compounds/compounds classes of relevance for food quality and safety assessment. As inclusion criteria, MAE active temperature control and molecularly-resolved characterization of the extracts were considered. Contents include a brief introduction of the principles of operation, available systems characteristics, and key parameters influencing extraction efficiency and selectivity. The application section covers functional food components (e.g., phenols, diterpenes, and carotenoids), lipids, contaminants (e.g., polycyclic aromatic hydrocarbons and mineral oil hydrocarbons), pesticides, veterinary drug residues, and a selection of process contaminants and xenobiotics of relevance for food safety.

Lipidomic Profiles of Lipid Biosynthesis in Oil Palm during Fruit Development

The fruit of the oil palm (Elaeis guineensis Jacq.) has fleshy mesocarpic tissue rich in lipids. This edible vegetable oil is economically and nutritionally significant across the world. The core concepts of oil biosynthesis in oil palms remain to be researched as the knowledge of oil biosynthesis in plants improves. In this study, we utilized a metabolite approach and mass spectral analysis to characterize metabolite changes and identify the sequences of protein accumulation during the physiological processes that regulate oil synthesis during oil palm fruit ripening. Here, we performed a comprehensive lipidomic data analysis in order to understand the role of lipid metabolism in oil biosynthesis mechanisms. The experimental materials were collected from the mesocarp of oil palm (Tenera) at 95 days (early accumulation of fatty acid, first stage), 125 days (rapid growth of fatty acid accumulation, second stage), and 185 days (stable period of fatty acid accumulation, third stage) after pollination. To gain a clear understanding of the lipid changes that occurred during the growth of the oil palm, the metabolome data were found using principal component analysis (PCA). Furthermore, the accumulations of diacylglycerols, ceramides, phosphatidylethanolamine, and phosphatidic acid varied between the developmental stages. Differentially expressed lipids were successfully identified and functionally classified using KEGG analysis. Proteins related to the metabolic pathway, glycerolipid metabolism, and glycerphospholipid metabolism were the most significantly changed proteins during fruit development. In this study, LC-MS analysis and evaluation of the lipid profile in different stages of oil palm were performed to gain insight into the regulatory mechanisms that enhance fruit quality and govern differences in lipid composition and biosynthesis.

Fatty Acid 2-Hydroxylase and 2-Hydroxylated Sphingolipids: Metabolism and Function in Health and Diseases

Sphingolipids containing acyl residues that are hydroxylated at C-2 are found in most, if not all, eukaryotes and certain bacteria. 2-hydroxylated sphingolipids are present in many organs and cell types, though they are especially abundant in myelin and skin. The enzyme fatty acid 2-hydroxylase (FA2H) is involved in the synthesis of many but not all 2-hydroxylated sphingolipids. Deficiency in FA2H causes a neurodegenerative disease known as hereditary spastic paraplegia 35 (HSP35/SPG35) or fatty acid hydroxylase-associated neurodegeneration (FAHN). FA2H likely also plays a role in other diseases. A low expression level of FA2H correlates with a poor prognosis in many cancers. This review presents an updated overview of the metabolism and function of 2-hydroxylated sphingolipids and the FA2H enzyme under physiological conditions and in diseases.

Expanding the Molecular Disturbances of Lipoproteins in Cardiometabolic Diseases: Lessons from Lipidomics

The increasing global burden of cardiometabolic diseases highlights the urgent clinical need for better personalized prediction and intervention strategies. Early diagnosis and prevention could greatly reduce the enormous socio-economic burden posed by these states. Plasma lipids including total cholesterol, triglycerides, HDL-C, and LDL-C have been at the center stage of the prediction and prevention strategies for cardiovascular disease; however, the bulk of cardiovascular disease events cannot be explained sufficiently by these lipid parameters. The shift from traditional serum lipid measurements that are poorly descriptive of the total serum lipidomic profile to comprehensive lipid profiling is an urgent need, since a wealth of metabolic information is currently underutilized in the clinical setting. The tremendous advances in the field of lipidomics in the last two decades has facilitated the research efforts to unravel the lipid dysregulation in cardiometabolic diseases, enabling the understanding of the underlying pathophysiological mechanisms and identification of predictive biomarkers beyond traditional lipids. This review presents an overview of the application of lipidomics in the study of serum lipoproteins in cardiometabolic diseases. Integrating the emerging multiomics with lipidomics holds great potential in moving toward this goal.

Combined Use of MALDI-TOF Mass Spectrometry and 31P NMR Spectroscopy for the Analysis of (Phospho)Lipids

Lipids are important and abundant constituents of all biological tissues and body fluids. In particular, phospholipids (PLs) constitute a major part of the cellular membrane and play a role in signal transduction, and some selected PLs are increasingly considered as potential disease markers. Unfortunately, methods of lipid analysis are less established in comparison to techniques of protein analysis. Mass spectrometry (MS) is an increasingly used technique to analyze lipids, especially in combination with electrospray ionization MS, which is the most commonly used ionization technique in lipidomics. Matrix-assisted laser desorption/ionization coupled to time-of-flight MS (MALDI-TOF MS) has itself proven to represent a useful tool in the field of lipid analysis. ³¹P nuclear magnetic resonance (NMR) spectroscopy, another powerful method for PL analysis, represents a direct quantitative method and does not suffer from suppression effects.This paper gives an overview of methodological aspects of MALDI-TOF MS and ³¹P NMR in lipid research and summarizes the specific advantages and drawbacks of both methods. In particular, suppression effects in MS will be highlighted, and possible ways to overcome this problem, e.g., the use of different matrices and separation of the relevant lipid mixture prior to analysis, will be discussed.

Whole blood analysis for medical diagnostics by GC-MS with Cold EI

This study covers a new method and related instrumentation for whole blood analysis for medical diagnostics. Two-μL whole blood samples were collected using "minimal invasive" diabetes lancet and placed on a thin glass rod mounted on a newly designed BloodProbe. The BloodProbe with the whole blood sample was inserted directly into a ChromatoProbe mounted on the GC inlet, and thus, no sample preparation was involved. The analysis was performed within 10 min using a GC-MS with Cold EI that is based on interfacing GC and MS with supersonic molecular beams (SMB) along with electron ionization of vibrationally cold sample compounds in the SMB (hence the name Cold EI). Our blood analysis revealed several observations: (1) Detailed mass chromatograms were generated with full range of all the nonpolar lipids in blood including fatty acids, cholesterol, cholesteryl esters, vitamin E, monoglycerides, diglycerides, and triglycerides. (2) The analysis of whole blood was found to be as informative as the conventional clinical analysis of blood serum. (3) Cholesteryl esters were more sensitive than free cholesterol alone to the effect of diet of obese people. (4) Major enhancement of several fatty acid methyl esters was found in the blood of a cancer patient with liver dysfunction. (5) Vitamin E as both α- and β-tocopherol was found with person-dependent ratio of these two compounds. (6) Elemental sulfur S₈ was identified in blood. (7) Several drugs and other compounds were found and need further study of their correlation to medical issues.

Optimizing accelerated solvent extraction combined with liquid chromatography-Orbitrap mass spectrometry for efficient lipid profile characterization of mozzarella cheese

In this study, a novel Accelerated Solvent Extraction (ASE) procedure combined with UHPLC-Q-Orbitrap-MS was developed for detailed untargeted lipid profile of mozzarella cheese. Response Surface Methodology and Pareto front, using a Central Composite Design (CCD), were employed to define the optimised combination of extraction temperature, number of extraction cycles and mix of solvents. LipidSearch™ software was used for a reliable and accurate lipid identification. A total of 13 subclasses, including ceramides, diacylglycerols, triacylglycerols, lysophosphatidylcholines, lysophosphatidylethanolamines, phosphatidylcholines, phosphatidylethanolamines, phosphatidylinositols, sphingomyelins, bismethyl phosphatidic acids, cholesterol ester, zymosterol ester, hexosyl ceramides were measured. The elaboration of the CCD showed that the solvents ratio was the main factor affecting the extraction efficiency. The optimised ASE method, together with the Folch extraction, synergistically contributed to a complete characterization of lipid profile of mozzarella cheese, confirming ASE technique, associated with high resolution mass spectrometry detection, as an efficient tool for Lipidomics in food science.

A simple and rapid method for extraction and measurement of circulating sphingolipids using LC-MS/MS: a targeted lipidomic analysis

Sphingolipids are a class of lipids with high structural diversity and biological pleiotropy. Mounting evidence supports a role for sphingolipids in regulating pathophysiology of cardiometabolic diseases, and they have been proposed as potential cardiometabolic biomarkers. Current methods for quantifying sphingolipids require laborious pretreatment and relatively large sample volumes, and cover limited species, hindering their application in epidemiological studies. Herein, we applied a time-, labor-, and sample-saving protocol simply using methanol for plasma sphingolipid extraction. It was compared with classical liquid-liquid extraction methods and showed significant advantages in terms of simplicity, sphingolipid coverage, and sample volume. By coupling the protocol with liquid chromatography using a wide-span mobile phase polarity parameter and tandem mass spectrometry operated in dynamic multiple reaction monitoring mode, 37 sphingolipids from 8 classes (sphingoid base, sphingoid base phosphate, ceramide-1-phosphate, lactosylceramide, hexosylceramide, sphingomyelin, ceramide, and dihydroceramide) were quantified within 16 min, using only 10 μL of human plasma. The current method showed good performance in terms of linearity (R² > 0.99), intra- and interbatch accuracy (70-123%) and precision (RSD < 12%), matrix effect (91-121%), recovery (96-101%), analyte chemical stability (deviation < 19%), and carryover (< 16%). We successfully applied this method to quantify 33 detectable sphingolipids from 579 plasma samples of an epidemiological study within 10 days. The quantified sphingolipid concentrations were comparable with previous studies. Positive associations of ceramide C22:0/C24:0 and their precursors with homeostasis model assessment of insulin resistance suggested that the synthesis of the ceramides might be involved in insulin resistance. This novel method constitutes a simple and rapid approach to quantify circulating sphingolipids for epidemiological studies using targeted lipidomic analysis, which will help elucidate the sphingolipid-regulated pathways underlying cardiometabolic diseases.

New approach in determination of urinary diagnostic markers for prostate cancer by MALDI-TOF/MS

In our study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) is proposed as a novel tool, which can be applied to analyze lipids in urine samples. For this reason, the main aim of the study was to develop and optimize the preparation protocol for urine samples in lipidomics, using urine samples obtained from patients with diagnosed cancer and non-cancer controls. Several conditions like extraction method and types of matrices were evaluated. For this purpose, two methods for the extraction of lipids, namely modified Folch and Bligh & Dyer were employed. Furthermore, two types of matrices (α-cyano-4-hydroxycinnamic acid (HCCA) and 2,5-dihydroxybenzoic acid (DHB)) for the separation of lipids into individual components was tested. The results of this study can serve as an essential source for the selection of appropriate extraction methods and the appropriate choice of a matrix for the purification and identification of a particular class of lipid in human biological fluids. Based on it, Bligh & Dyer method associated with the usage of HCCA matrix was found to be the most effective for lipidomics using MALDI-TOF/MS. The optimized method was applied to compare the lipid profile of 139 urine samples collected from both healthy individuals and patients with prostate cancer. The tandem spectroscopic analysis allowed to identify lysophosphatidylcholine, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and triacylglycerols in urine samples. Finally, MALDI-TOF/MS analysis enabled to discriminate between the two tested groups (healthy individuals and patients with prostate cancer). A preliminary statistical model suggested that classification accuracy ranging from 83.3 to100.0% may be achieved by using pre-selected MS signals.

Advances in Lipid Extraction Methods-A Review

Extraction of lipids from biological tissues is a crucial step in lipid analysis. The selection of appropriate solvent is the most critical factor in the efficient extraction of lipids. A mixture of polar (to disrupt the protein-lipid complexes) and nonpolar (to dissolve the neutral lipids) solvents are precisely selected to extract lipids efficiently. In addition, the disintegration of complex and rigid cell-wall of plants, fungi, and microalgal cells by various mechanical, chemical, and enzymatic treatments facilitate the solvent penetration and extraction of lipids. This review discusses the chloroform/methanol-based classical lipid extraction methods and modern modifications of these methods in terms of using healthy and environmentally safe solvents and rapid single-step extraction. At the same time, some adaptations were made to recover the specific lipids. In addition, the high throughput lipid extraction methodologies used for liquid chromatography-mass spectrometry (LC-MS)-based plant and animal lipidomics were discussed. The advantages and disadvantages of various pretreatments and extraction methods were also illustrated. Moreover, the emerging green solvents-based lipid extraction method, including supercritical CO2 extraction (SCE), is also discussed.

Metal Organic Framework Nanomaterial-Based Extraction and Proteome Analysis of Membrane and Membrane-Associated Proteins

Membrane proteins (MPs) play a key role in various biological processes, while difficulties still exist in the extraction because of their inherent low abundance and poor solubility caused by high hydrophobicity. Metal organic framework (MOF) materials with good hydrophobic properties have the ability to absorb MPs, especially zeolitic imidazolate framework (ZIF) materials. Here, two MOF materials (ZIF-8 and ZIF-67) were compared for MP extraction, and our results revealed that higher yield was obtained with ZIF-67. After method development, the optimal enrichment effect was obtained when the mass ratio of proteins and ZIF-67 reached 1:20 with 100 mM NaCl in 20% ethanol at 4 °C and pH 9.0. When compared with a commercial kit, the extraction yield increased by 88.11% and the average number of identified MPs elevated by 29.17% with the developed ZIF method. Normal lung cell MRC5 was employed to verify the effectiveness of the ZIF method. Results showed 45.13% increase in yield and 22.88% increase in average number of identified MPs by the ZIF method. Our method was further applied to the enrichment of MPs for high-metastatic (95D) and low-metastatic (95C) human lung cancer cells. A total of 1732 (95D) and 1711 (95C) MPs were identified, among which 710 MPs were dysregulated significantly; 441 upregulated MPs in 95D cells were found to be closely related to the growth, proliferation, and migration of lung cancer cells. Our results collectively demonstrated that ZIF-67 was an ideal material for MP extraction, which might be helpful for analysis of cancer proteomics and discovery of cancer migration associated MPs.

Analytical approaches to assess metabolic changes in psoriasis

Psoriasis is one of the most common human skin diseases, although its development is not limited to one tissue, but is associated with autoimmune reactions throughout the body. Overproduction of pro-inflammatory cytokines and growth factors systemically stimulates the proliferation of skin cells, which manifests as excessive exfoliation of the epidermis, and/or arthritis, as well as other comorbidities such as insulin resistance, metabolic syndrome, hypertension, and depression. Thus, there is a great need for a thorough analysis of the pathophysiology of psoriatic patients, including classical methods, such as spectrophotometry, chromatography, or Western blot, and also novel omics approaches such as lipidomics and proteomics. Moreover, the extensive pathophysiology forces increased research examining biological changes in both skin cells, and systemically. A wide range of techniques involved in lipidomic research based on a combination of mass spectrometry and different types of chromatography (RP-LC-QTOF-MS/MS, HILIC-QTOF-MS/MS or RP-LC-QTRAP-MS/MS), have allowed comprehensive assessment of lipid modification in psoriatic skin and provided new insight into the role of lipids and their mechanism of action in psoriasis. Moreover, proteomic analysis using gel-nanoLC-OrbiTrap-MS/MS, as well as MALDI-TOF/TOF techniques facilitates the description of panels of enzymes involved in lipidome modifications, and the response of the endocannabinoid system to metabolic changes. Psoriasis is known to alter the expression of proteins that are involved in the inflammatory and antioxidant response, as well as protein biosynthesis, degradation, as well as cell proliferation and apoptosis. Knowledge of changes in the lipidomic and proteomic profile will not only allow the understanding of psoriasis pathophysiology, but also facilitate proper and early diagnosis and effective pharmacotherapy.

Recommendations for good practice in MS-based lipidomics

In the last 2 decades, lipidomics has become one of the fastest expanding scientific disciplines in biomedical research. With an increasing number of new research groups to the field, it is even more important to design guidelines for assuring high standards of data quality. The Lipidomics Standards Initiative is a community-based endeavor for the coordination of development of these best practice guidelines in lipidomics and is embedded within the International Lipidomics Society. It is the intention of this review to highlight the most quality-relevant aspects of the lipidomics workflow, including preanalytics, sample preparation, MS, and lipid species identification and quantitation. Furthermore, this review just does not only highlights examples of best practice but also sheds light on strengths, drawbacks, and pitfalls in the lipidomic analysis workflow. While this review is neither designed to be a step-by-step protocol by itself nor dedicated to a specific application of lipidomics, it should nevertheless provide the interested reader with links and original publications to obtain a comprehensive overview concerning the state-of-the-art practices in the field.

Analytical methods in fatty acid analysis for microbial applications: the recent trends

Fatty acids are among the most important components of many biological systems and have been highlighted in many research fields in recent decades. In the food industry, it is important to check the amount and types of fatty acids in edible oils, beverages and other foods products, and checking the fatty acids parameters are among the quality control parameters for those products. In medical applications, investigation of fatty acids in biological samples and comparing imbalances in them can help to diagnose some diseases. On the other hand, the development of cell factories for the production of biofuels and other valuable chemicals requires the accurate analysis of fatty acids, which serve as precursors in development of those products. As a result, given all these different applications of fatty acids, rapid and accurate methods for characterization and quantification of fatty acids are essential. In recent years, various methods for the analysis of fatty acids have been proposed, which according to the specific purpose of the analysis, some of them can be used with consideration of speed, accuracy and cost. In this article, the available methods for the analysis of fatty acids are reviewed with a special emphasis on the analysis of microbial samples to pave the way for more widespread metabolic engineering research.

Bioactive Sugarcane Lipids in a Circular Economy Context

Most of the global sugar and ethanol supply trade comes from the harvesting of Saccharum officinarum (i.e., sugarcane). Its industrial processing results in numerous by-products and waste streams, such as tops, straw, filter cake, molasses and bagasse. The recovery of lipids (i.e., octacosanol, phytosterols, long-chain aldehydes and triterpenoids) from these residues is an excellent starting point for the development of new products for various application fields, such as health and well-being, representing an important feature of the circular economy. By selecting green scalable extraction procedures, industry can reduce its environmental impact. Refluxed ethanol extraction methods have been demonstrated to meet these characteristics. On the other hand, effective non-solvent methodologies such as molecular distillation and supercritical CO2 extraction can fractionate lipids based on high temperature and pressure application with similar yields. Sugarcane lipophilic extracts are usually analyzed through gas chromatography (GC) and liquid chromatography (LC) techniques. In many cases, the identification of such compounds involves the development of high-temperature GC-MS/FID techniques. On the other hand, for the identification and quantification of thermolabile lipids, LC-MS techniques are suitable for the separation and identification of major lipid classes. Generically, its composition includes terpenes, phytosterols, tocopherol, free fatty acids, fatty alcohols, wax esters, triglycerides, diglycerides and monoglycerides. These compounds are already known for their interesting application in various fields such as pharma and cosmetics due to their anti-hypercholesterolemic, anti-hyperglycemic, antioxidant and anti-inflammatory properties.

High Confidence Shotgun Lipidomics Using Structurally Selective Ion Mobility-Mass Spectrometry

Ion mobility (IM) is a gas phase separation strategy that can either supplement or serve as a high-throughput alternative to liquid chromatography (LC) in shotgun lipidomics. Incorporating the IM dimension in untargeted lipidomics workflows can help resolve isomeric lipids, and the collision cross section (CCS) values obtained from the IM measurements can provide an additional molecular descriptor to increase lipid identification confidence. This chapter provides a broad overview of an untargeted ion mobility-mass spectrometry (IM-MS) workflow using a commercial drift tube ion mobility-quadrupole-time-of-flight mass spectrometer (IM-QTOF) for high confidence lipidomics.

Structure determination of conjugated linoleic and linolenic acids

Conjugated linoleic and linolenic acids (CLA and CLnA) can be found in dairy, ruminant meat and oilseeds, these types of unsaturated fatty acids consist of various positional and geometrical isomers, and have demonstrated health-promoting potential for human beings. Extensive reviews have reported the physiological effects of CLA, CLnA, while little is known regarding their isomer-specific effects. However, the isomers are difficult to identify, owing to (i) the similar retention time in common chromatographic methods; and (ii) the isomers are highly sensitive to high temperature, pH changes, and oxidation. The uncertainties in molecular structure have hindered investigations on the physiological effects of CLA and CLnA. Therefore, this review presents a summary of the currently available technologies for the structural determination of CLA and CLnA, including the presence confirmation, double bond position determination, and the potential stereo-isomer determination. Special focus has been projected to the novel techniques for structure determination of CLA and CLnA. Some possible future directions are also proposed.

Mass spectrometry-based lipidomics in food science and nutritional health: A comprehensive review

With the advance in science and technology as well as the improvement of living standards, the function of food is no longer just to meet the needs of survival. Food science and its associated nutritional health issues have been increasingly debated. Lipids, as complex metabolites, play a key role both in food and human health. Taking advantages of mass spectrometry (MS) by combining its high sensitivity and accuracy with extensive selective determination of all lipid classes, MS-based lipidomics has been employed to resolve the conundrum of addressing both qualitative and quantitative aspects of high-abundance and low-abundance lipids in complex food matrices. In this review, we systematically summarize current applications of MS-based lipidomics in food field. First, common MS-based lipidomics procedures are described. Second, the applications of MS-based lipidomics in food science, including lipid composition characterization, adulteration, traceability, and other issues, are discussed. Third, the application of MS-based lipidomics for nutritional health covering the influence of food on health and disease is introduced. Finally, future research trends and challenges are proposed. MS-based lipidomics plays an important role in the field of food science, promoting continuous development of food science and integration of food knowledge with other disciplines. New methods of MS-based lipidomics have been developed to improve accuracy and sensitivity of lipid analysis in food samples. These developments offer the possibility to fully characterize lipids in food samples, identify novel functional lipids, and better understand the role of food in promoting healt.

Lipid metabolism of leukocytes in the unstimulated and activated states

Lipidomics has emerged as a powerful technique to study cellular lipid metabolism. As the lipidome contains numerous isomeric and isobaric species resulting in a significant overlap between different lipid classes, cutting-edge analytical technology is necessary for a comprehensive analysis of lipid metabolism. Just recently, differential mobility spectrometry (DMS) has evolved as such a technology, helping to overcome several analytical challenges. We here set out to apply DMS and the Lipidyzer™ platform to obtain a comprehensive overview of leukocyte-related lipid metabolism in the resting and activated states. First, we tested the linearity and repeatability of the platform by using HL60 cells. We obtained good linearities for most of the thirteen analyzed lipid classes (correlation coefficient > 0.95), and good repeatability (%CV < 15). By comparing the lipidome of neutrophils (PMNs), monocytes (CD14+), and lymphocytes (CD4+), we shed light on leukocyte-specific lipid patterns as well as lipidomic changes occurring through differential stimulation. For example, at the resting state, PMNs proved to contain higher amounts of triacylglycerides compared to CD4+ and CD14+ cells. On the other hand, CD4+ and CD14+ cells contained higher levels of phospholipids and ceramides. Upon stimulation, diacylglycerides, hexosylceramides, phosphatidylcholines, phosphoethanolamines, and lysophosphoethanolamines were upregulated in CD4+ cells and PMNs, whereas CD14+ cells did not show significant changes. By exploring the fatty acid content of the significantly upregulated lipid classes, we mainly found increased concentrations of very long and polyunsaturated fatty acids. Our results indicate the usefulness of the Lipidyzer™ platform for studying cellular lipid metabolism. Its application allowed us to explore the lipidome of leukocytes.

Simultaneous Quantification of DPPG, DEPC and Cholesterol in Propofol Liposome by HPLC-ELSD Using Alkaline Hydrolysis

A high-performance liquid chromatography method with evaporative light-scattering detection (ELSD) was performed for simultaneous determination of dipalmitoyl phosphatidylglycerol (DPPG), dierucoyl phosphatidylcholine (DEPC) and cholesterol in propofol liposome by the pretreatment of alkaline hydrolysis (temperature, concentration of KOH anhydrous ethanol solution and reaction time were 90°C, 1 mol · L-1 and 10 min, respectively). The analysis was carried out on an Agilent TC-C18 column (4.6 mm × 250 mm, 5 μm) with isocratic elution of methanol and 0.1% acetic acid aqueous solution (95:5, v/v) at a flow rate of 1.0 mL · min-1. The column temperature was 30°C. The drift tube temperature of the ELSD system was set at 30°C, and the pressure of carrier gas was 350 KPa. The regression equation revealed a good linear relationship (r = 0.9990-0.9993) during the test ranges. The RSD of stability and repeatability (n = 6) was found to be less than 1.96 and 1.46%, respectively. The average recoveries ranged from 97.90 to 101.00%. The proposed method was validated and showed good precision, stability, repeatability and recovery, which indicated that the method could be readily utilized as a quality evaluation method for the determination of DPPG, DEPC and cholesterol in propofol liposome.

Comparative evaluation of the extraction and analysis of urinary phospholipids and lysophospholipids using MALDI-TOF/MS

Lipids, particularly phospholipids (PLs) and lysophospholipids (LPLs), are attracting increasing scientific interest for their biological functions in cells and their potential as disease biomarkers for Alzheimer's disease and several types of cancer. Urinary PLs and LPLs could be ideal clinical biomarkers, because urine can be collected easily and noninvasively. However, due to their very low concentrations in urine compared with the relatively large quantity of contaminants in this matrix, efficient extraction and sensitive detection are required for analyzing urinary PLs and LPLs. In this study, various methods for analyzing PLs and LPLs in urine were compared and optimized from a clinical perspective. An optimized lipid extraction method and a matrix for matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) were established using two external ionization standards and an internal standard mix containing 13 human urinary lipids. 9-Aminoacridine (9-AA) was a useful and effective matrix for the MALDI-TOF/MS analysis of all the internal standard lipids in both positive and negative ion modes. However, it was necessary to determine the proportional lipid concentrations from the balance between the extracted lipid and the matrix. The extraction efficiency and reproducibility of the acidified Bligh and Dyer method were excellent for both positively and negatively charged lipids. Analysis of small volumes of urine was the most efficient with the 9-AA MALDI matrix at concentrations of or below 5 mM. The combined analytical procedures allowed rapid and comprehensive screening of low concentrations of PLs and LPLs in clinical samples.

Tissue-Specific Sample Dilution: An Important Parameter to Optimise Prior to Untargeted LC-MS Metabolomics

When developing a sample preparation protocol for LC–MS untargeted metabolomics of a new sample matrix unfamiliar to the laboratory, selection of a suitable injection concentration is rarely described. Here we developed a simple workflow to address this issue prior to untargeted LC–MS metabolomics using pig adipose tissue and liver tissue. Bi-phasic extraction was performed to enable simultaneous optimisation of parameters for analysis of both lipids and polar extracts. A series of diluted pooled samples were analysed by LC–MS and used to evaluate signal linearity. Suitable injected concentrations were determined based on both the number of reproducible features and linear features. With our laboratory settings, the optimum concentrations of tissue mass to reconstitution solvent of liver and adipose tissue lipid fractions were found to be 125 mg/mL and 7.81 mg/mL respectively, producing 2811 (ESI+) and 4326 (ESI−) linear features from liver, 698 (ESI+) and 498 (ESI−) linear features from adipose tissue. For analysis of the polar fraction of both tissues, 250 mg/mL was suitable, producing 403 (ESI+) and 235 (ESI−) linear features from liver, 114 (ESI+) and 108 (ESI−) linear features from adipose tissue. Incorrect reconstitution volumes resulted in either severe overloading or poor linearity in our lipid data, while too dilute polar fractions resulted in a low number of reproducible features (<50) compared to hundreds of reproducible features from the optimum concentration used. Our study highlights on multiple matrices and multiple extract and chromatography types, the critical importance of determining a suitable injected concentration prior to untargeted LC–MS metabolomics, with the described workflow applicable to any matrix and LC–MS system.

In-depth lipidomic analysis of tri-, di-, and mono-acylglycerols released from milk fat after in vitro digestion

Milk fat is arguably one of the most complex fats found in nature and varies widely between animal species. Analysis of its digestion products is tremendously challenging, due to the complexity, diversity, and large range of concentrations of triacylglycerols (TAGs) and their digestion products (i.e. diacylglycerols (DAGs), monoacylglycerols (MAGs), and free fatty acids (FFAs)). Therefore, a method combined the solid phase extraction (SPE), high-performance liquid chromatography (HPLC) and multi-dimension mass spectrometry (MDMS) was developed to identify and semi-quantify the TAGs, DAGs and MAGs in milk fat after in vitro digestion. Up to 105, 64, 14 and 30 species of TAGs, DAGs, MAGs, and FFAs were determined with their concentrations of 0.01-22.3, 0.01-39.2, 0.01-47.8, and 0.04-191.0 mg/g fat, respectively, during the in vitro digestion of cow and sheep milk. The validation of the method shows that this method was precise and reliable.

Quantitative analysis of 10 classes of phospholipids by ultrahigh-performance liquid chromatography tandem triple-quadrupole mass spectrometry

We have developed fast and sensitive label-free quantitation with normalization of acyl chain length to quantify 10 classes of phospholipids by UHPLC-MS.

Microbial Lipid Alternatives to Plant Lipids

Lipids are in high demand in food production, nutritional supplements, detergents, lubricants, and biofuels. Different oil seeds produced from plants are conventionally extracted to yield lipids. With increasing population and reduced availability of cultivable land, conventional methods of producing lipids alone will not satisfy increasing demand. Lipids produced using different microbial sources are considered as sustainable alternative to plant derived lipids. Various microorganisms belonging to the genera of algae, bacteria, yeast, fungi, or marine-derived microorganisms such as thraustochytrids possess the ability to accumulate lipids in their cells. A variety of microbial production technologies are being used to cultivate these organisms under specific conditions using agricultural residues as carbon source to be cost competitive with plant derived lipids. Microbial oils, also known as single cell oils, have many advantages when compared with plant derived lipids, such as shorter life cycle, less labor required, season and climate independence, no use of arable land and ease of scale-up. In this chapter we compare the lipids derived from plants and different microorganisms. We also highlight various analytical techniques that are being used to characterize the lipids produced in oleaginous organisms and their applications in various processes.

Extraction techniques and potential health benefits of bioactive compounds from marine molluscs: a review

Marine molluscs and their bioactive compounds are of particular relevance to the growing pool of nutraceutical resources under global investigation.