Validation of a HILIC UHPLC-MS/MS Method for Amino Acid Profiling in Triticum Species Wheat Flours

Measurement of atmospheric amines and aminoamides by column adsorption/extraction and hydrophilic liquid chromatography-electrospray-tandem mass spectrometry

Sampling and chromatography-mass spectrometry methods were investigated to measure atmospheric amines and aminoamides. Amines and their amide derivatives play significant roles in new particle formation (NPF) in the atmosphere, especially diamines and aminoamides have higher NPF potentials compared to monoamines. For amine sampling, silica gel tube collection and formic acid extraction gave good overall recoveries (>93 ± 8%) for mono-, di-, tri-, tetramines, and aminoamides. Two chromatography methods were subjected to analyze the extracted amines. One involved direct analysis using hydrophilic interaction liquid chromatography with carboxyl or diol group functioned separation column (carboxyl-HILIC or diol-HILIC), and the other utilized derivatization with 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F) and subsequent reversed-phase chromatography (HPLC). Separated amines were detected by electrospray ionization and tandem mass spectrometry in both cases. DBD-F-HPLC method provided good sensitivity for mono- and all polyamines (limit of detection (LOD) < 4.6 nM, relative standard deviation (RSD) for 100 nM < 9.2%). However, aminoamides could not be detected by DBD-F-HPLC. Carboxyl-HILIC provided good sensitivities for mono- and diamines and aminoamides (LOD < 1.6 nM, RSD < 4.8%). Forest air measurement was performed and data obtained by carboxyl-HILIC and DBD-F-HPLC showed good agreement for 1,3-diaminopropane, 1,4-diaminobutane (putrescine) and 1,5-diaminopentane (cadaverine) (R2 = 0.9215-0.9739, n = 7-14). Carboxyl-HILIC method was the best for the amine analysis, and combination with silica gel tube sampling provides atmospheric monitoring available. The developed method can be used not only to study atmospheric chemistry of diamines and aminoamides but also to analyze flavor/odor of foods, flowers and wastes.

Development and Validation of a Method for Hydrolysis and Analysis of Amino Acids in Ruminant Feeds, Tissue, and Milk Using Isotope Dilution Z-HILIC Coupled with Electrospray Ionization Triple Quadrupole LC-MS/MS

Current analytical methods for amino acid (AA) analysis in ruminant nutrition are time-consuming and expensive. This study aimed to develop a method for AA analysis that is faster, more efficient, rugged, and accessible. Four representative matrixes were selected for method development and validation: milk, tissue, feed, and soy flour standard reference material from National Institute of Standards and Technology. Acid and alkaline hydrolysis were used to analyze 18 AA. Separation of AA was performed using a Z-HILIC column in an 18-min run coupled to a triple quadrupole LC/MS system in positive and negative electrospray ionization for identification and quantitation. The method was evaluated for recovery, precision, calibration curve linearity, and limits of detection (LODs) and limits of quantitation (LOQs) and applied to other feed samples. Good quantitation results were achieved for all AA, with coefficients of determination (R2) over 0.995; LODs at 0.2-28.2 and LOQs at 0.7-94.1 ng/mL; intraday and interday precision <14.9% relative standard deviation; blank recovery between 75.6 and 116.2%; and sample recovery between 75.6 and 118.0%. Overall, AA concentrations were similar to literature values, and there was a tendency for higher N recovery as AA. In conclusion, an efficient and robust method was validated to routinely analyze AA for appropriate characterization in diet formulation for dairy cattle.

Quantitative 1H NMR with global spectral deconvolution approach for quality assessment of natural and cultured Cordyceps sinensis

Cordyceps sinensis is a precious medicinal food which has been successfully cultivated indoors. It remains to be investigated for a simultaneous comparison on aqueous components of natural and cultivated samples. Herein, an approach of quantitative nuclear magnetic resonance (qNMR) analysis combined with global spectral deconvolution (GSD) was established for simultaneous quantification of 26 aqueous components in C. sinensis. Processed by GSD, the distorted baselines of 1H NMR spectra were greatly improved, and overlapped signals were also well separated so as to achieve accurate identification and quantitation of components in C. sinensis. Method validation by UHPLC-QTOF-MS and TOF-SIMS analysis revealed that qNMR combined with GSD is a reliable approach for simultaneous quantification of multiple components including characteristic markers of glutamine, GABA and trehalose in authentic and fake C. sinensis. The well-established qNMR approach can be used for quality assessment of natural and cultivated C. sinensis as well as differentiation from fake ones.

Integrated Metabolome and Transcriptome Analyses Reveal Amino Acid Biosynthesis Mechanisms during the Physiological Maturity of Grains in Yunnan Hulled Wheat (Triticum aestivum ssp. yunnanense King)

Yunnan hulled wheat (YHW) possesses excellent nutritional characteristics; however, the precise amino acid (AA) composition, contents, and molecular mechanisms underlying AA biosynthesis in YHW grains remain unclear. In this study, we aimed to perform metabolomic and transcriptomic profiling to identify the composition and genetic factors regulating AA biosynthesis during the physiological maturation of grains of two YHW genotypes, Yunmai and Dikemail, with high and low grain protein contents, respectively. A total of 40 and 14 differentially accumulated amino acids (AAs) or AA derivatives were identified between the waxy grain (WG) and mature grain (MG) phenological stages of Yunmai and Dikemail, respectively. The AA composition differed between WG and MG, and the abundance of AAs-especially that of essential AAs-was significantly higher in WG than in MG (only 38.74-58.26% of WG). Transcriptome analysis revealed differential regulation of structural genes associated with the relatively higher accumulation of AAs in WG. Weighted gene co-expression network analysis and correlation analyses of WG and MG indicated differences in the expression of clusters of genes encoding both upstream elements of AA biosynthesis and enzymes that are directly involved in AA synthesis. The expression of these genes directly impacted the synthesis of various AAs. Together, these results contribute to our understanding of the mechanism of AA biosynthesis during the different developmental stages of grains and provide a foundation for further research to improve the nutritional value of wheat products.

Amino acids profiling and transcriptomic data integration demonstrates the dynamic regulation of amino acids synthesis in the leaves of Cyclocarya paliurus

Background

Cyclocarya paliurus is a tree well known for its edible and medicinal leaves. Amino acids are essential nutritional components that are present in foods and closely related to the flavor and quality of tea. However, the abundance of amino acids and the regulation of amino acid biosynthesis in the leaves of C. paliurus have not been investigated across different developmental stages.

Methods

A combined metabolomic and transcriptomic analysis was employed to investigate the changes in the amino acid profile over several developmental stages (S1, the smallest fully expanded leaf; S3, full leaf enlargement and full leaf thickness; and S2, an intermediate developmental stage between S1 and S3) and the molecular mechanism was elucidated.

Results

The results showed that leaves at the S1 stage had the highest content, while those at the S3 stage had the lowest content of amino acids; fourteen differentially expressed genes were involved in the glycolysis pathway, the tricarboxylic acid cycle and the pentose phosphate pathway, which indicated that the reduced abundance of amino acids in the leaves of C. paliurus (mature leaves) may be attributable to reduced gene expression related to carbohydrate metabolism. Four basic leucine zipper transcription factors might play important roles in the regulation of the biosynthesis of amino acids in the leaves of C. paliurus.

Conclusions

Leaves at the S1 stage are recommended for high quality tea production because of their high content of amino acids, while leaves at the S2 stage are recommended for generous tea production because of their high levels of sweet flavor amino acids (alanine) and essential amino acids (methionine, phenylalanine, threonine, and tryptophan).

Maltose-functionalized HILIC stationary phase silica gel based on self-assembled oligopeptides and its application for the separation of polar compounds

In this study, carbonyldiimidazole was used to bond maltose-modified oligopeptides (Ala-Glu-Ala-Glu-Ala-Lys-Ala-Lys) to the surface of silica spheres for hydrophilic interaction liquid chromatography (HILIC). Attenuated total reflectance-Fourier transform infrared spectroscopy, elemental analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis, BET technique, and water contact angle measurement results confirmed the successful immobilization of the obtained material. Compared with the conventional method for preparing carbohydrate stationary phases, this method involves simpler steps and less time-consuming processes. The experimental results proved that the retention mechanism of the maltose-based HILIC column matched the typical HILIC retention mechanism. The column showed high separation efficiency and stability toward the separation of polar compounds such as amino acids, bases, nucleosides, water-soluble vitamins, and salicylic acid and its analogs. The column achieved high selectivity toward oligosaccharide separation. In addition, this efficient analysis demonstrates the applicability of the as-prepared material in the field of food inspection.

Performance of ion pairing chromatography and hydrophilic interaction liquid chromatography coupled to charged aerosol detection for the analysis of underivatized amino acids

The charged aerosol detector (CAD) is frequently employed in liquid chromatography for the analysis of small polar and ionizable compounds such as amino acids and amino sugars, which provide a weak chromophore only. Separation of these compounds is achieved by means of ion pair chromatography (IPC), and, more recently, hydrophilic interaction chromatography (HILIC) techniques. However, as the CAD's response is highly dependent on the mobile phase composition, the substantial differences in the mobile phase composition of IPC and HILIC have a distinct impact on the detector's performance. This study was aimed at systematically comparing the performance of IPC and HILIC when coupled to the CAD. Therefore, the separation techniques characterized by their specific mobile phase compositions were evaluated for their influence on the CAD response and the signal-to-noise ratio (S/N) of the amino acids L-alanine, L-leucine, and L-phenylalanine applying the response surface methodology (RSM). The RSM results derived from flow injection analysis (FIA) indicated that the CAD response and thus the obtainable S/N are significantly higher in HILIC compared to IPC where the S/N decreased with the chain length of the applied ion-pairing reagent. In addition, an IPC and a HILIC method, respectively, were developed for the impurity profiling of the branched-chain amino acids (BCAAs) L-leucine, L-isoleucine, and L-valine. The beneficial effects of the HILIC conditions on the S/N observed under FIA conditions were partly offset by moderate column bleed effects when using an amide functionalized column, which facilitates the separation in the HILIC method. Satisfactory LOQs (3-10 ng on column) were obtained with both methods; however, the HILIC method was found to be slightly superior in terms of sensitivity and separation efficiency.

Acetonitrile adduct analysis of underivatised amino acids offers improved sensitivity for hydrophilic interaction liquid chromatography tandem mass-spectrometry

LC-MS/MS method development for native amino acid detection can be problematic due to low ionisation efficiencies, in source fragmentation, potential for cluster ion formation and incorrect application of chromatography techniques. This has led to the majority of the scientific community derivatising amino acids for more sensitive analysis. Derivatisation has several benefits including reduced signal-to-noise ratios, more efficient ionisation, and a change in polarity, allowing the use of reverse phase chromatography. However, derivatisation of amino acids can be expensive, requires additional sample preparation steps, is more time consuming and increases sample instability, due to the most derivatised amino acids only be stable for finite amount of time. While showing initial promise, development of reliable hydrophilic interaction liquid chromatography (HILIC) separation methods has presented difficulties for the analyst including irreproducible separation and poor sensitivity. This study aimed to find a means to improve the detection sensitivity of the 20 protein amino acids by HILIC-MS/MS. We describe the use of previously undescribed amino acid-acetonitrile (ACN) adducts to improve detection of 16 out of the 20 amino acids. While all amino acids examined did form an ACN adduct, 4 had low intensity adduct formation compared to their protonated state, 3 of which are classified as basic amino acids. For 15 of the 20 amino acids tested, we used the ACN adduct for both quantification and qualification ions and demonstrated a significant enhancement in signal-to-noise ratio, ranging from 23 to 1762% improvement. Lower LODs, LOQs and lower ranges of linearity were also achieved for these amino acids. The optimised method was applied to a human neuroblastoma cell line (SH-SY5Y) with the potential to be applied to other complex sample types. The improved sensitivity this method offers simplifies sample preparation and reduces the costs of amino acid analysis compared to those methods that rely on derivatisation for sensitivity.

Recent Techniques in Nutrient Analysis for Food Composition Database

Food composition database (FCD) provides the nutritional composition of foods. Reliable and up-to date FCD is important in many aspects of nutrition, dietetics, health, food science, biodiversity, plant breeding, food industry, trade and food regulation. FCD has been used extensively in nutrition labelling, nutritional analysis, research, regulation, national food and nutrition policy. The choice of method for the analysis of samples for FCD often depends on detection capability, along with ease of use, speed of analysis and low cost. Sample preparation is the most critical stage in analytical method development. Samples can be prepared using numerous techniques; however it should be applicable for a wide range of analytes and sample matrices. There are quite a number of significant improvements on sample preparation techniques in various food matrices for specific analytes highlighted in the literatures. Improvements on the technology used for the analysis of samples by specific instrumentation could provide an alternative to the analyst to choose for their laboratory requirement. This review provides the reader with an overview of recent techniques that can be used for sample preparation and instrumentation for food analysis which can provide wide options to the analysts in providing data to their FCD.

Application of Analytical Chemistry to Foods and Food Technology

Foods are a mixture of substances capable of supplying the human body with nutrients, which, once metabolized, are used mainly for the production of energy, heat, replenishment, and growth material for organs and tissues, ensuring the normal performance of vital functions necessary for growth of the human body. Therefore, the study of the chemical composition of foods and the properties of their constituents helps to define their nutritional and commodity values. Furthermore, it allows for evaluation of the chemical modifications that the constituents of the food undergo following the treatments (Food Technology) to which they are subjected. Analytical chemistry is the branch of chemistry based on the qualitative and quantitative determination of compounds present in a sample under examination. Therefore, through its application, it is possible to determine the quality of a product and/or its nutritional value, reveal adulterations, identify the presence of xenobiotic substances potentially harmful to human health (heavy metals, IPA, pharmaceuticals, etc.). Furthermore, some foods, in particular those of plant origin, contain numerous substances, secondary metabolites, with huge beneficial effects for human health. These functional components can be taken both through a correct diet, but also obtained from different food matrices by technological or biotechnological processes for the formulation of both functional foods and/or nutraceutical products. This Special Issue brings together 10 original studies and two comprehensive reviews on the above topics, in particular: (i) processes of extraction, identification, and characterization of biologically active compounds from different food matrices, (ii) overview of the main techniques applied for the determination of food colors, (iii) newer and greener solid-liquid extraction techniques.

Amino Acid Composition of Novel Plant Drinks from Oat, Lentil and Pea

Plant-based drinks (PBDs) as alternatives to milk is a fast-growing market in much of the western world, with the demand increasing every year. However, most PBDs from a single plant ingredient do not have an amino acid profile that matches human needs. Therefore, this study set out to combine plant ingredients to achieve a more balanced amino acid profile of novel plant drinks, by combining a high content of oat with the pulses pea (Pisum sativum) and lentil (Lens culinaris) in a solution. After removal of the sediment, the resulting plant drinks were composed of what could be kept in suspension. The amino acid and protein composition of the plant drinks were investigated with capillary electrophoresis, to identify the amino acids, and SDS-PAGE to assess the proteins present. The amino acid profile was compared against recommended daily intake (RDI). It was determined that the plant drinks with only oat and lentil did not have a strong amino acid profile, likely due to the higher pH of the lentil concentrate affecting which proteins could be kept in solution. Plant drinks with a combination of both lentil and pea, or only pea, added to the oat drink had an improved concentration of the amino acids that were otherwise in the low end compared to RDI. This includes a high content of phenylalanine, leucine and threonine, as well as a moderate amount of isoleucine, valine and methionine, and a contribution of histidine and lysine. An assessment of stability and sensory parameters was also conducted, concluding there was an advantage of combining oat with a legume, especially pea.