Development of an analytic method for organosulfur compounds in Welsh onion and its use for nutritional quality analysis of five typical varieties in China.

A reliable, simple, and sensitive method capable of quantifying six organosulfur compounds (OSCs) was established. The samples were extracted by water containing 3 % formic acid with a simple vortex, ultrasound, and centrifugation step, and the solutions were analyzed by ultra-high-performance liquid chromatography separation system coupled with a triple-quadrupole mass spectrometry (UHPLC - MS/MS). Then the method was applied for the analysis of six OSCs in five varieties of two types Welsh onions in China, and the moisture content, reducing sugar, total polyphenols, and 21 free amino acids were also analyzed to study the characters of these Welsh onions intensively. Multivariate statistical analysis was used to investigate the differences in OSCs and free amino acids profiles among the samples. This study showed that enzymatic inhibition method combined with UHPLC - MS/MS is an effective technique to analyze OSCs in Welsh onion, and could be valuable for the routine quantitation of OSCs in other foods.

Distinct Quality Changes of Asparagus during Growth by Widely Targeted Metabolomics Analysis.

Asparagus is a popular vegetable and traditional medicine consumed worldwide due to its health benefits. The quality of asparagus, mainly attributed to small components like flavonoids and steroid, is quite differential as a result of different environments and maturities. However, the accumulation pattern and regulatory mechanism of metabolites in asparagus remain unclear so far. Herein, widely targeted metabolomics analysis was employed to study the quality and chemical composition variances of four asparagus, including three green asparagus of different maturities and one white asparagus. A total of 1045 metabolites were annotated in asparagus in which flavonoids and phenolic acids accounted for 37.51% of the total. Green asparagus was found to be rich in flavonoids, while white asparagus contained more steroids. Additionally, 461 biomarkers were screened between matured green and white asparagus, which is much more than that filtered among three green asparagus at different growth stages. These results indicated that sunlight has a stronger effect on the metabolism of asparagus compared to the general development of asparagus. Linoleic acid metabolism and alpha-linolenic acid metabolism were active during green asparagus growth, while flavone and flavonol biosynthesis and flavonoid biosynthesis resulted as two of the most important pathways when asparagus was exposed to sunlight.

Metabolic Changes in Different Tissues of Garlic Plant during Growth.

The accumulation, distribution, and transportation of nutrients in different tissues of garlic during growth are unclear. Thereby, five tissues (leaf, pseudostem, bulb wrapper, clove skin, and clove) collected at 7 weeks were subjected to metabolomics analysis. A total of 84 biomarkers were identified during garlic plant growth. Most organosulfur compounds, amino acids, and dipeptides were upregulated in the clove, while a reversed trend was observed in other tissues. In addition, nucleotides and alkaloids increased because of senescence in the last 2 weeks except for the clove. The results also indicated that the garlic plant at an early stage is an ideal vegetable that is rich in nutrients. When the leaves began to wither, most nutrients were transported from other tissues to cloves, and the content of 7 total flavor precursors and 20 total amino acids in the clove increased by 113% and 65% after week 5, respectively. Therefore, delayed harvest may improve the nutritional quality of garlic bulbs.

Distinct Quality Changes of Garlic Bulb during Growth by Metabolomics Analysis.

Garlic-specialized metabolites contribute to both spicy flavor and healthy function of garlic. Their accumulation pattern and regulatory mechanism vary greatly at different environments and maturities. Herein, metabolomics models were built to evaluate and predict the quality and chemical composition variances of four garlic varieties in two regions at six growth stages. A total of 91 metabolites were identified, and their accumulation pattern during growth in three varieties of garlic in Shandong was similar but obviously distinct from that planted in Heilongjiang. Active metabolism for organosulfur compounds and amino acids was observed, and most metabolites with the "γ-glutamyl-" group were the storage compounds of nitrogen and sulfur in garlic because they increased remarkably during growth. The levels of functional components in garlic varied among different stages, and reliable prediction models for these compounds were provided, which may give a new idea for the estimation of garlic quality and confirmation of the best harvest time.

Profiling of organosulfur compounds and amino acids in garlic from different regions of China.

The quality of garlic is mainly attributed to organosulfur compounds that are the secondary metabolites of certain amino acids. Herein, a sensitive and rapid method for the simultaneous determination of 7 organosulfur compounds and 21 amino acids using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) was developed. Then the levels of these 28 compounds and allicin in garlic among 242 samples from 6 provinces in China were profiled with multivariate data analysis. The results showed that garlic was rich in organosulfur compounds and could be a good supplement for amino acids. Contents of 29 compounds varied greatly among the provinces. The multivariate data analysis demonstrated two major groups for all samples, indicating that the location has a significant influence on the metabolism of garlic. Besides, the compositional differences of garlic from 6 provinces and correlations for growing conditions and contents of components were also analyzed.

Development and validation of an ultra performance liquid chromatography Q-Exactive Orbitrap mass spectrometry for the determination of fipronil and its metabolites in tea and chrysanthemum.

A fast, sensitive and reliable method for the determination of fipronil and its metabolites in tea and chrysanthemum was developed using a modified QuEChERS technique and an ultra performance liquid chromatography Q-Exactive Orbitrap mass spectrometry. The mixture of adsorbents containing primary secondary amine (PSA), octadecylsilane (C18) and carbon nanotubes (CNTs), was used as QuEChERS adsorbents. The use of mass resolution at 70000 full width at half maximum (FWHM) and narrow mass windows at 5 ppm achieved high selectivity and repeatability. Satisfactory linearity with correlative coefficient (R2) higher than 0.996 was achieved for all compounds. Recoveries at three levels (2, 10 and 50 µg kg-1) ranged from 86% to 112%, while the intra- and inter-day accuracies were less than 15%. Limits of quantification for fipronil and its metabolites were 2 µg kg-1, which fulfils the requirement of maximum residue limits formulated by European Union and Japan.

Residue pattern of polycyclic aromatic hydrocarbons during green tea manufacturing and their transfer rates during tea brewing.

Residues of polycyclic aromatic hydrocarbons (PAHs) in green tea and tea infusion were determined using gas chromatography-tandem mass spectrometry to study their dissipation pattern during green tea processing and infusion. Concentration and evaporation of PAHs during tea processing were the key factors affecting PAH residue content in product intermediates and in green tea. PAH residues in tea leaves increased by 2.4-3.1 times during the manufacture of green tea using the electric heating model. After correction to dry weight, PAH residue concentrations decreased by 33.5-48.4% during green tea processing because of PAH evaporation. Moreover, spreading and drying reduced PAH concentrations. The transfer rates of PAH residues from green tea to infusion varied from 4.6% to 7.2%, and PAH leaching was higher in the first infusion than in the second infusion. These results are useful for assessing exposure to PAHs from green tea and in formulating controls for the maximum residue level of PAHs in green tea.

Occurrence and Residue Pattern of Phthalate Esters in Fresh Tea Leaves and during Tea Manufacturing and Brewing.

The residues of 16 phthalate esters (PAEs) in fresh tea leaves and made tea were determined via gas chromatography-tandem mass spectrometry to study their distribution and degradation characteristics during tea planting and processing. Five PAEs were detected in all fresh tea leaves, and higher concentrations were detected in mature leaves. The distribution of PAEs in fresh tea leaves ranged from 69.7 to 2244.0 µg/kg. The degradative percentages of ∑5PAEs during green tea manufacturing ranged from 61 to 63% and were significantly influenced by the drying process. The transfer rates of PAEs-D4 ranged from 5.2 to 100.6%. PAEs with a high water solubility showed the highest transfer coefficient in the range of 91.8-100.6%, whereas PAEs with a high log Kow showed a low leaching efficiency below 11.9%. These results benefit the risk evaluation and establishment of a maximum residue limit for PAEs in tea.