Development of a Simple, Underivatized Method for Rapid Determination of Free Amino Acids in Honey Using Dilute-and-Shoot Strategy and Liquid Chromatography-Tandem Mass Spectrometry

Development of a LC-QTOF-MS based dilute-and-shoot approach for the botanical discrimination of honeys

Honeys of particular botanical origins can be associated with premium market prices, a trait which also makes them susceptible to fraud. Currently available authenticity testing methods for botanical classification of honeys are either time-consuming or only target a few "known" types of markers. Simple and effective methods are therefore needed to monitor and guarantee the authenticity of honey. In this study, a 'dilute-and-shoot' approach using liquid chromatography (LC) coupled to quadrupole time-of-flight-mass spectrometry (QTOF-MS) was applied to the non-targeted fingerprinting of honeys of different floral origin (buckwheat, clover and blueberry). This work investigated for the first time the impact of different instrumental conditions such as the column type, the mobile phase composition, the chromatographic gradient, and the MS fragmentor voltage (in-source collision-induced dissociation) on the botanical classification of honeys as well as the data quality. Results indicated that the data sets obtained for the various LC-QTOF-MS conditions tested were all suitable to discriminate the three honeys of different floral origin regardless of the mathematical model applied (random forest, partial least squares-discriminant analysis, soft independent modelling by class analogy and linear discriminant analysis). The present study investigated different LC-QTOF-MS conditions in a "dilute and shoot" method for honey analysis, in order to establish a relatively fast, simple and reliable analytical method to record the chemical fingerprints of honey. This approach is suitable for marker discovery and will be used for the future development of advanced predictive models for honey botanical origin.

Impact of Whey Protein Corona Formation around TiO2 Nanoparticles on Their Physiochemical Properties and Gastrointestinal Fate

Previously, we found that whey proteins form biomolecular coronas around titanium dioxide (TiO2) nanoparticles. Here, the gastrointestinal fate of whey protein-coated TiO2 nanoparticles and their interactions with gut microbiota were investigated. The antioxidant activity of protein-coated nanoparticles was enhanced after simulated digestion. The structure of the whey proteins was changed after they adsorbed to the surfaces of the TiO2 nanoparticles, which reduced their hydrolysis under simulated gastrointestinal conditions. The presence of protein coronas also regulated the impact of the TiO2 nanoparticles on colonic fermentation, including promoting the production of short-chain fatty acids. Bare TiO2 nanoparticles significantly increased the proportion of harmful bacteria and decreased the proportion of beneficial bacteria, but the presence of protein coronas alleviated this effect. In particular, the proportion of beneficial bacteria, such as Bacteroides and Bifidobacterium, was enhanced for the coated nanoparticles. Our results suggest that the formation of a whey protein corona around TiO2 nanoparticles may have beneficial effects on their behavior within the colon. This study provides valuable new insights into the potential impact of protein coronas on the gastrointestinal fate of inorganic nanoparticles.

Carnosol ameliorated cancer cachexia-associated myotube atrophy by targeting P5CS and its downstream pathways

Introduction: Carnosol exhibited ameliorating effects on muscle atrophy of mice developed cancer cachexia in our previous research. Method: Here, the ameliorating effects of carnosol on the C2C12 myotube atrophy result from simulated cancer cachexia injury, the conditioned medium of the C26 tumor cells or the LLC tumor cells, were observed. To clarify the mechanisms of carnosol, the possible direct target proteins of carnosol were searched using DARTS (drug affinity responsive target stability) assay and then confirmed using CETSA (cellular thermal shift assay). Furthermore, proteomic analysis was used to search its possible indirect target proteins by comparing the protein expression profiles of C2C12 myotubes under treatment of C26 medium, with or without the presence of carnosol. The signal network between the direct and indirect target proteins of carnosol was then constructed. Results: Our results showed that, Delta-1-pyrroline-5-carboxylate synthase (P5CS) might be the direct target protein of carnosol in myotubes. The influence of carnosol on amino acid metabolism downstream of P5CS was confirmed. Carnosol could upregulate the expression of proteins related to glutathione metabolism, anti-oxidant system, and heat shock response. Knockdown of P5CS could also ameliorate myotube atrophy and further enhance the ameliorating effects of carnosol. Discussion: These results suggested that carnosol might ameliorate cancer cachexia-associated myotube atrophy by targeting P5CS and its downstream pathways.

Rapid and sensitive dilute-and-shoot analysis using LC-MS-MS for identification of multi-class psychoactive substances in human urine

The emergence of new psychoactive substances currently exceeding a thousand is rapidly changing substance prevalence patterns and straining the methods used for detection, most of which are suitable only for a single class of substances. This study presents a rapid and facile dilute-and-shoot system operated in conjunction with an optimized liquid chromatographic separation system for the high-sensitivity detection of substances across a range of substance classes with 3 isotopes used only. The proposed method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) is able to identify 68 substance and their metabolites in urine samples as small as 50 μL. Optimal chromatographic conditions including 95% water/methanol ratio with 0.1% added formic acid and a prolonged LC gradient run-time (15 min) improved the peak shape of polar compounds and enhanced signal strength by 5%. Under 4-fold dilution, all analytes were within 80-120% of tolerance response levels, indicating that the matrix effect was insignificant. In experiments, the limit of detection (LOD) ranged from 0.05 to 0.5 ng mL^-1, while the coefficient of determination (R²) was > 0.9950. The retention time shift of each peak remained at < 2% with an inter-day relative standard deviation (RSD) of 0.9-14.9% and intra-day RSD of 1.1%- 13.8%. The rapid dilute-and-shoot presents a high-sensitivity, significant stability, robustness and reproducibility without serious interference. To demonstrate the effectiveness of the system, 532 urine samples were collected from suspected drug abusers, and the proposed method was used for rapid analysis. Of these samples, 79.5% contained between one and twelve analytes, and 12.4% tested positive for new psychoactive substances, mostly derivatives of amphetamine and synthetic cathinones. The study presents a high-sensitivity analytic system that is capable of detecting substances from multiple classes and can be used for effective monitoring of substance prevalence in urine.

Chlorantraniliprole in foods: Determination, dissipation and decontamination

Chlorantraniliprole (CAP) is the first commercially available anthranilic diamide insecticide that targets ryanodine receptors. However, excessive use of CAP can lead to persistent contamination on treated foods and adverse effects on human wellness. The current review focuses on CAP residue analysis in foods by using chromatographic techniques. QuEChERS (quick, easy, cheap, effective, rugged and safe) is the most widely used sample preparation strategy and liquid chromatography tandem mass spectrometry is the predominant analytical method for various food matrices including vegetable, fruit, grain, fish and so on. Moreover, this review summarizes the dissipation pattern of CAP on foods and found it usually dissipates fast on plant in open-field environment. For decontamination, common culinary cleaning methods could effectively remove CAP from vegetables. Finally, some new directions are proposed for better advancement.

Advances in Accurate Quantification Methods in Food Analysis

Food safety is an important topic, and with the perfection of regulations and technologies, food safety is improving [...]

Simple and Effective Derivatization of Amino Acids with 1-Fluoro-2-nitro-4-(trifluoromethyl)benzene in a Microwave Reactor for Determination of Free Amino Acids in Kombucha Beverages

Kombucha is a fermentation product of sweetened tea with a symbiotic culture of acetic acid and yeast bacteria, consumed worldwide for its health-promoting properties. Few reports can be found about free amino acids among the health-promoting compounds found and determined in kombucha. These compounds influence the sensory properties of kombucha, and they are precursors of bioactive compounds, which have a significant role as neurotransmitters and are involved in biological functions. The presented studies proposed a convenient, simple, and "more green" procedure of the synthesis of amino acid derivatives, assisted by microwave energy, followed by chromatographic determination. The structure of 1-Fluoro-2-nitro-4-(trifluoromethyl)benzene was used as a suitable reagent for the derivatization of free amino acids in fermented kombucha beverages prepared from selected dry fruit such as Crataegus L., Morus alba L., Sorbus aucuparia L., Berberis vulgaris L., Rosa canina L., and black tea. The obtained results were discussed regarding the tested beverages' application as a source of amino acids in one's daily diet. The obtained results point out that the proposed microwave-assisted derivatization procedure prior to HPLC analyses allows for a significant time reduction and the limitation of using organic reagents.

Analysis of 18 Free Amino Acids in Honeybee and Bumblebee Honey from Eastern and Northern Europe and Central Asia Using HPLC-ESI-TQ-MS/MS Approach Bypassing Derivatization Step

The profile of amino acids and mono- and disaccharides in conventional polyfloral honey originated from Latvia and Tajikistan and less found in nature bumblebee honey from Russia was investigated. The analysis of free amino acids (FAAs) accomplished by multiple reaction monitoring (MRM) using triple quadrupole mass selective detection (HPLC-ESI-TQ-MS/MS) revealed the presence of 17 FAAs. The concentration of FAAs varied in the range of 0.02–44.41 mg 100 g−1 FW. Proline was the main representative of FAAs, contributing to the total amount of FAAs from 41.7% to 80.52%. The highest concentration of proline was found in bumblebee and buckwheat honey, corresponding to 44.41 and 41.02 mg 100 g−1, respectively. The concentration of essential amino acids (AAs), i.e., leucine, and isoleucine was found to be the highest in buckwheat honey contributing up to 12.5% to the total amount of FAAs. While, the concentration of branched-chain AAs fluctuated within the range of 1.08–31.13 mg 100 g−1 FW, with buckwheat honey having the highest content and polyfloral honey the lowest, respectively. The results of this study confirmed the abundance of FAAs both in honeybee and bumblebee honey. However, the concentration of individual FAAs, such as proline, aspartic acid, leucine, and isoleucine in bumblebee honey was many folds higher than observed in honeybee polyfloral honey.

Underivatized Amino Acid Chromatographic Separation: Optimized Conditions for HPLC-UV Simultaneous Quantification of Isoleucine, Leucine, Lysine, Threonine, Histidine, Valine, Methionine, Phenylalanine, Tryptophan, and Tyrosine in Dietary Supplements

Amino acids (AAs) are considered as the building blocks of life. Unlike nonessential AAs, the human body cannot synthesize essential AAs and should be supplied in food or dietary supplements. The aim of the work is simultaneous HPLC-UV determination of 10 structurally related AAs without pre- or postderivatization in powdered dietary supplements (PDSs). This was challenging, especially because PDS has no standardized procedures for its quality control. HPLC-UV chromatograms of the 10 AAs were recorded using a gradient elution of the mobile phase on a CLC-C18 column at 225 nm. The elution started with 100% of phosphate buffer (pH 7.4, 10 mM) for 10 min; then, the concentration of acetonitrile increased linearly to reach 50% for another 15 min at room temperature. Good separation was achieved within a 25 min run time without pre- or postderivatization. The method was carefully validated according to the ICH guidelines over the linearity range of 100-200, 50-200, 20-150, 50-400, 20-250, 75-175, 50-250, 50-250, 50-300, and 5-100 μg/mL for l-lysine, l-threonine, l-histidine, l-valine, l-methionine, l-isoleucine, l-leucine, l-tyrosine, l-phenylalanine, and l-tryptophan, respectively, with mean recoveries ranges between 98.91 and 100.77. The method was found to be precise, and the relative standard deviation (RSD) was found to be between 0.28 and 1.92 with recoveries between 97.91 and 101.11. The method was found to be robust that resists deliberate changes in pH, flow rate, and mobile-phase percentages. It was successfully applied for the analysis of PDSs. The proposed method could be very useful for the quality control of the 10 structurally related AAs during their synthesis and for testing raw materials and pharmaceutical preparations.

Impurity Profiling of Dinotefuran by High Resolution Mass Spectrometry and SIRIUS Tool

Dinotefuran (DNT) is a neonicotinoid insecticide widely used in pest control. Identification of structurally related impurities is indispensable during material purification and pesticide registration and certified reference material development, and therefore needs to be carefully characterized. In this study, a combined strategy with liquid chromatography high-resolution mass spectrometry and SIRIUS has been developed to elucidate impurities from DNT material. MS and MS/MS spectra were used to score the impurity candidates by isotope score and fragment tree in the computer assisted tool, SIRIUS. DNT, the main component, worked as an anchor for formula identification and impurity structure elucidation. With this strategy, two by-product impurities and one stereoisomer were identified. Their fragmentation pathways were concluded, and the mechanism for impurity formation was also proposed. This result showed a successful application for combined human intelligence and machine learning, in the identification of pesticide impurities.