Application of UHPLC for the determination of free amino acids in different cheese varieties

Pubertal origin of growth retardation in inborn errors of protein metabolism: A longitudinal cohort study

OBJECTIVES

Inherited amino-acid metabolism disorders (IAAMDs) require lifelong protein-restricted diet. We aimed to investigate: 1/ whether IAAMDs was associated with growth, pubertal, bone mineral apparent density (BMAD) or body composition impairments; 2/ associations linking height, amino-acid mixture (AAM), plasma amino-acids and IGF1 concentrations.

DESIGN

Retrospective longitudinal study of 213 patients with neonatal-onset urea cycle disorders (UCD,n = 77), organic aciduria (OA,n = 89), maple syrup urine disease (MSUD,n = 34), or tyrosinaemia type 1 (n = 13).

METHODS

We collected growth parameters, pubertal status, BMAD, body composition, protein-intake, and IGF1 throughout growth.

RESULTS

Overall final height (n = 69) was below target height (TH): -0.9(1.4) vs. -0.1(0.9) SD, p < 0.001. Final height was ≤ TH-2SD in 12 (21%) patients. Height ≤ - 2SD was more frequent during puberty than during early-infancy and pre-puberty: 23.5% vs. 6.9%, p = 0.002; and vs. 10.7%, p < 0.001. Pubertal delay was frequent (26.7%). Height (SD) was positively associated with isoleucine concentration: β, 0.008; 95%CI, 0.003 to 0.012; p = 0.001. In the pubertal subgroup, height (SD) was lower in patients with vs. without AAM supplementation: -1.22 (1.40) vs. -0.63 (1.46) (p = 0.02). In OA, height and median (IQR) isoleucine and valine concentrations(μmol/L) during puberty were lower in patients with vs. without AAM supplementation: -1.75 (1.30) vs. -0.33 (1.55) SD, p < 0.001; and 40 (23) vs. 60 (25) (p = 0.02) and 138 (92) vs. 191 (63) (p = 0.01), respectively. No correlation was found with IGF1. Lean-mass index was lower than fat-mass index: -2.03 (1.15) vs. -0.44 (0.89), p < 0.001.

CONCLUSIONS

In IAAMDs, growth retardation worsened during puberty which was delayed in all disease subgroups. Height seems linked to the disease, AAM composition and lower isoleucine concentration, independently of the GH-IGF1 pathway. We recommend close monitoring of diet during puberty.

Positive + negative is not equal to zero: Use of negative ionisation as analyte identity confirmation tool in LC-ESI-MS analysis

In this study the use of negative electrospray ionisation mode as a confirmation tool for identifying derivatized amino acids using LC-ESI-MS, was evaluated. The derivatization reagent was based on azobenzene N-hydroxysuccinimide carbamate. The results indicate that even though negative ionisation mode produced less intense peaks, the ratio of peak area of quantifier ion (obtained in positive mode) to the qualifier (or identifier) ion measured in negative mode meets the requirements established by two prominent validation guidelines: SANTE/11312/2021 and 2002/657/EC. Therefore, the use of product ions obtained via negative transitions as qualifier ions, while using product ions from positive transitions as quantifier ions is a fruitful approach that widens the choice of transitions to choose from for obtaining suitable qualifier ions. This methodology was applied to the LC-ESI-MS/MS determination of amino acids in different beverages (tomato juice, watermelon juice, kvass).

Comparison of the ionisation mode in the determination of free amino acids in beers by Liquid Chromatography tandem mass spectrometry

A comparison of positive and negative ionization modes in LC-ESI-MS/MS was carried out for the analysis of derivatized amino acids in 15 different beer samples. 22 free amino acids were derivatized using Diethyl ethoxymethylenemalonate (DEEMM) and their content was determined. When using the DEEMM as derivatization reagent the negative ionization mode provided analytical performance equal to or in some cases even superior to the positive ionization mode. For 6 amino acids (Thr, β-Ala, α-Ala, Met, Val and Orn) the negative mode led to lower LoQ values, while the positive mode offered lower LoQ values for 5 amino acids (Arg, Asp, Glu, GABA, and Pro). The remaining 11 amino acids showed similar LoQ values in both modes. Because of this, negative ionization mode allowed to detect and quantify amino acids such as: β-Alanine, threonine, and ornithine whose concentrations were low in most of the analysed samples. The relative standard deviation (RSD) for the results in both modes were similar. The method's linearity was determined to be in the range of 1 to 130 ppb with r² > 0.99. Recoveries ranged from 93 to 112%. Negative mode was less affected by matrix effects the main effect was signal enhancement. In contrast, the positive ionization mode suffered from signal enhancement as well as signal suppression.

Development and Validation of a Simple, Selective, and Accurate Reversed-Phase Liquid Chromatographic Method with Diode Array Detection (RP-HPLC/DAD) for the Simultaneous Analysis of 18 Free Amino Acids in Topical Formulations

Even though there are reported methods for the quantification of free amino acids (FAAs) in biological products, no work has been done on the analysis of these substances in formulations. Moreover, further research is required as the reported methods do not fulfill analytical method requirements. The objective of this study was, therefore, to develop and validate a rapid, reliable, and appropriate RP-HPLC/DAD method for the simultaneous determination of 18 FAAs (l-Ala, l-Arg, l-Asn, l-Asp, l-Gln, l-Glu, l-Gly, l-His, l-Ile, l-Lue, l-Lys, l-Met, l-Orn, l-Phe, l-Pro, l-Ser, l-Thr, and l-Val) in topical formulations. After appropriate method development, the technique was validated for selectivity, linearity and range, limit of detection, limit of quantification, precision, and accuracy. The samples were derivatized with 9-fluorenylmethyl chloroformate (Fmoc-Cl). Chromatographic separation was performed on InfinityLab Poroshell 120 E.C 18 (3 × 50) mm, 2.7 μm column at 25 °C. The mobile phase consisting of water and acetonitrile adjusted to appropriate pH was pumped in gradient mode at a flow rate of 0.7 mL/min. Ten microliters were injected and analyte detection was conducted using a DAD. The results indicate that the method was selective for these FAAs. It was linear over the concentration range of 5–80 µM with a correlation coefficient greater than 0.995. Moreover, it was sensitive, precise, accurate, and robust. All the reported drawbacks of RP-HPLC-based analysis of FAAs were resolved, and hence, this new method can be considered appropriate for the analysis of these FAAs in topical formulations.

Comparative Study on Volatile Compounds and Taste Components of Different Durian Cultivars Based on GC-MS, UHPLC, HPAEC-PAD, E-Tongue and E-Nose

In order to comprehensively evaluate the aroma-active substances and taste components of durian, solid-phase microextraction combined with gas chromatography mass spectrometry (SPME/GC-MS), high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and ultra-high-performance liquid chromatography (UHPLC) were used to test the key components of three popular durian cultivars. A total of 27 volatile compounds, 5 sugars, 27 organic acids and 19 free amino acids were detected in Black Thorn (BT) durian. A total of 38 volatile compounds, 4 sugars, 27 organic acids and 19 free amino acids were detected in Monthong (MT) durian. A total of 36 volatile compounds, 4 sugars, 27 organic acids and 20 free amino acids were detected in Musang King (MK) durian. Finally, the flavor differences of the three durians were evaluated using electronic nose (e-nose) and electronic tongue (e-tongue), and different cultivars were classified through principal component analysis (PCA).

Enhanced carboxypeptidase efficacies and differentiation of peptide epimers

Carboxypeptidases enzymatically cleaves the peptide bond of C-terminal amino acids within peptides. In humans, it is involved in enzymatic synthesis and maturation of proteins and peptides. Carboxypeptidases A and Y have difficulty hydrolyzing the peptide bond of dipeptides and some other amino acid sequences. Early investigations into different N-blocking groups concluded that larger moieties increased substrate susceptibility to peptide bond hydrolysis with carboxypeptidase. This study conclusively demonstrates that 6-aminoquinoline-N-hydroxysuccimidyl carbamate (AQC) as an N-blocking group greatly enhances substrate hydrolysis with carboxypeptidase. AQC addition to the N-terminus of amino acids and peptides also improves chromatographic peak shape and sensitivities via mass spectrometry detection. These enzymes have been used for amino acid sequence determination prior to the advent of modern proteomics. However, most modern proteomic methods assume that all peptides are comprised of l-amino acids and therefore cannot distinguish L-from d-amino acids within the peptide sequence. The majority of existing methods that allow for chiral differentiation either require synthetic standards or incur racemization in the process. This study highlights the resistance of d-amino acids within peptides to enzymatic hydrolysis by Carboxypeptidase Y. This stereoselectivity may be advantageous when screening low abundance peptide epimers.

Optimizing the acceleration of Cheddar cheese ripening using response surface methodology by microbial protease without altering its quality features

Cheddar cheese proteolysis were accelerated employing Penicillium candidum PCA1/TT031 protease into cheese curd. In the present study, several of the significant factors such as protease purification factor (PF), protease concentration and ripening time were optimized via the response surface methodology (RSM). The ideal accelerated Cheddar cheese environment consisted of 3.12 PF, 0.01% (v/v) protease concentration and 0.6/3 months ripening time at 10 °C. The RSM models was verified to be the most proper methodology for the maintain of chosen Cheddar cheese. Under this experimental environment, the pH, acid degree value (ADV), moisture, water activity (a_w), soluble nitrogen (SN)%, fat and overall acceptability were found to be 5.4, 6.6, 35%, 0.9348, 18.8%, 34% and 13.6, respectively of ideal Cheddar cheese. Furthermore, the predicted and experimental results were in significant agreement, which confirmed the validity and reliability of the suggested method. In spite of the difference between the ideal and commercial Cheddar cheese in the concentration of some of amino acids and free fatty acids, the sensory evaluation did not show any significant difference in aroma profile between them.

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

Amino acids are essential nutritional components as they occur in foods either in free form or as protein constituents. An ultra-high-performance (UHPLC) hydrophilic liquid chromatography (HILIC)-tandem Mass Spectrometry (MS) method has been developed and validated for the quantification of 17 amino acids (AA) in wheat flour samples after acid hydrolysis with 6 M HCl in the presence of 4% (v/v) thioglycolic acid as a reducing agent. The developed method proved to be a fast and reliable tool for acquiring information on the AA profile of cereal flours. The method has been applied and tested in 10 flour samples of spelt, emmer, and common wheat flours of organic or conventional cultivation and with different extraction rates (70%, 90%, and 100%). All the aforementioned allowed us to study and evaluate the variation of the AA profile among the studied flours, in relation to other quality characteristics, such as protein content, wet gluten, and gluten index. Significant differences were observed in the AA profiles of the studied flours. Moreover, AA profiles exhibited significant interactions with quality characteristics that proved to be affected based mainly on the type of grain. A statistical and multivariate analysis of the AA profiles and quality characteristics has been performed, as to identify potential interactions between protein content, amino acids, and quality characteristics.

A hydrophilic interaction chromatography-tandem mass spectrometry method for amino acid profiling in mussels

A UHPLC-HILIC-tandem MS method has been developed and validated for the quantification of 21 amino acids (20 protein amino acids and cystine) in their free form (FAA) and as protein constituents (total amino acids, TAA) in a rich protein food matrix such as lyophilized mussels (Mytilus galloprovincialis) samples. FAA were analyzed after suspending the samples in the presence of trichloroacetic acid in order to prevent dissolving the proteins, while TAA were determined after acid hydrolysis with 6M HCl in the presence of 4% v/v thioglycolic acid as a reducing agent. In hydrolysed samples 17 amino acids could be determined since tryptophan, cysteine, cystine and asparagine were degraded during acid hydrolysis. Linear regression coefficients (R²) were above 0.99 for all amino acids. Accuracy and precision, expressed as recovery (%) and relative standard deviation (RSD, %) were in acceptable levels, ranging from 78.2 to 123.3% and below 15%, respectively for both FAA and TAA. Uncertainty was also below 12% for FAA and below 22% for TAA. Sensitivity of the method was high with LOD values ranging from 0.003 to 0.034g/100g for FAA and 0.001 to 0.004g/100g for TAA, while LOQ ranged from 0.009 to 0.104g/100g for FAA and 0.002 to 0.011g/100g for TAA. The method proved to be a fast and reliable tool for acquiring information on free and total amino acids profile in high protein content foodstuffs such as mussels.

Investigation of free amino acid, total phenolics, antioxidant activity and purine alkaloids to assess the health properties of non-Camellia tea

To find novel functional beverages from folk teas, 33 species of frequently used non-Camellia tea (plants other than Camellia) were collected and compared with Camellia tea (green tea, pu-erh tea and black tea) for the first time. Data are reported here on the quantities of 20 free amino acids (FAAs) and three purine alkaloids (measured by UHPLC), total polyphenols (measured by Folin-Ciocalteu assay), and antioxidant activity (DPPH). The total amounts of FAAs in non-Camellia tea (0.62–18.99 mg/g) are generally less than that of Camellia tea (16.55–24.99 mg/g). However, for certain FAAs, the quantities were much higher in some non-Camellia teas, such as γ-aminobutyric acid in teas from Ampelopsis grossedentata, Isodon serra and Hibiscus sabdariffa. Interestingly, theanine was detected in tea from Potentilla fruticosa (1.16±0.81 mg/g). Furthermore, the content of polyphenols in teas from A. grossedentata, Acer tataricum subsp. ginnala are significantly higher than those from Camellia tea; teas from I. serra, Pistacia chinensis and A. tataricum subsp. ginnala have remarkable antioxidant activities similar to the activities from green tea (44.23 μg/mL). Purine alkaloids (caffeine, theobromine and theophylline) were not detected in non-Camellia teas. The investigation suggest some non-Camellia teas may be great functional natural products with potential for prevention of chronic diseases and aging, by providing with abundant polyphenols, antioxidants and specific FAAs.

Effect of fermentation and subsequent pasteurization processes on amino acids composition of orange juice

The fermentation of fruit produces significant changes in their nutritional composition. An orange beverage has been obtained from the controlled alcoholic fermentation and thermal pasteurization of orange juice. A study was performed to determine the influence of both processes on its amino acid profile. UHPLC-QqQ-MS/MS was used for the first time for analysis of orange juice samples. Out of 29 amino acids and derivatives identified, eight (ethanolamine, ornithine, phosphoethanolamine, α-amino-n-butyric acid, hydroxyproline, methylhistidine, citrulline, and cystathionine) have not previously been detected in orange juice. The amino acid profile of the orange juice was not modified by its processing, but total amino acid content of the juice (8194 mg/L) was significantly increased at 9 days of fermentation (13,324 mg/L). Although the pasteurization process produced partial amino acid degradation, the total amino acid content was higher in the final product (9265 mg/L) than in the original juice, enhancing its nutritional value.