原位电离质谱技术在食品质量安全检测中的应用

原位电离质谱技术能够在常压环境下直接分析各种食品样品,无需或仅需极少的食品制备,大大提高了分析效率,已经成为一种重要的食品快速分析方法。本文对原位电离质谱的离子化技术和工作流程进行了介绍,从食品污染物检测、非法添加物筛查、食品真伪鉴别和品质评价等方面出发,综述了该技术在食品质量安全检测中的应用。讨论了其应用于食品分析领域时面临的挑战和未来发展趋势。     

Isotopic Traceability (13C and 18O) of Greek Olive Oil

In recent years, isotopic analysis has been proven a valuable tool for the determination of the origin of various materials. In this article, we studied the ¹⁸O and ¹³C isotopic values of 210 olive oil samples that were originated from different regions in Greece in order to verify how these values are affected by the climate regime. We observed that the δ¹⁸O isotopic values range from 19.2 ‰ to 25.2 ‰ and the δ¹³C values range from −32.7 ‰ to −28.3 ‰. These differences between the olive oils’ isotopic values depended on the regional temperature, the meteoric water, and the distance from the sea. Furthermore, we studied the ¹³C isotopic values of biophenolic extracts, and we observed that they have same capability to differentiate the geographic origin. Finally, we compared the isotopic values of Greek olive oils with samples from Italy, and we concluded that there is a great dependence of oxygen isotopes on the climatic characteristics of the different geographical areas.     

Newly Generated Atractylon Derivatives in Processed Rhizomes of Atractylodes macrocephala Koidz

Thermally processed rhizomes of Atractylodes macrocephala (RAM) have a long history of use in traditional Chinese medicine (TCM) for treating various disorders, and have been an integral part of various traditional drugs and healthcare products. In TCM, herbal medicines are, in most cases, uniquely processed. Although it is thought that processing can alter the properties of herbal medicines so as to achieve desired functions, increase potency, and/or reduce side effects, the underlying chemical changes remain unclear for most thermally processed Chinese herbal medicines. In an attempt to shed some light on the scientific rationale behind the processes involved in traditional medicine, the RAM processed by stir-frying with wheat bran was investigated for the change of chemical composition. As a result, for the first time, five new chemical entities, along with ten known compounds, were isolated. Their chemical structures were determined by spectroscopic and spectrometric analyses. The possible synthetic pathway for the generation of such thermally-induced chemical entities was also proposed. Furthermore, biological activity evaluation showed that none of the compounds possessed cytotoxic effects against the tested mammalian cancer and noncancer cell lines. In addition, all compounds were ineffective at inhibiting the growth of the pathogenic microorganisms.     

Toward the origin of life over feldspar surfaces: Adsorption of amino acids and catalysis of conformational interconversions

Feldspars are a group of tectosilicate minerals terminated with a full layer of hydroxyl groups and have been regarded as “hotbed” for birth of life. In this study, periodic density functional theory calculations are conducted to address two associated issues, as adsorption of amino acids and conformational interconversions over feldspar surfaces. Distribution of glycine isomers depends strongly on the number of interacted surface silanols (n), and canonical isomers exist exclusively for n ≤ 2 while zwitterions predominate for n = 3. Adsorption of amino acids is significantly affected by sidechains, especially those forming H-bonds with surfaces; however, sidechain contacts with feldspar surfaces disfavor zwitterion stabilization, and zwitterions become preferred without sidechain contacts. For all amino acids, conformational interconversions undergo four elementary steps, and proton transfer between two carboxylic-O atoms (step 2) is always rate-decisive. Step 2 is greatly accelerated with catalysis of surface silanols and activation barriers depend significantly on sidechains. All amino acids have moderate activation barriers and conformational interconversions (in both forward and reverse directions) proceed favorably at ambient conditions. Sidechains of amino acids exhibit influences through sidechain contacts with surfaces rather than as substituent effect.     

Expression profile analysis and stability evaluation of 18 small RNAs in the Chinese Han population

In recent years, differentially expressed small RNAs have been widely used to identify the compositions of forensically relevant biological samples, and a vast number of such RNA candidates have been proposed. Nevertheless, when assessing the expression levels of target small RNAs using relative quantitative analysis methods, credible internal controls are usually required for reliable data normalization. Therefore, the identification of optimal reference genes is an important task. In this study, the expression profile of 18 small RNA reference genes was characterized in the Chinese Han population using TaqMan real-time quantitative PCR. Systematic evaluations of these candidate genes were performed based on their expression levels and stability in several common types of body fluids (i.e., venous blood, menstrual blood, saliva, semen, and vaginal secretions). Analysis results from the ΔCq method, BestKeeper, NormFinder, and geNorm were integrated by RefFinder for ranking and comparing the candidates in each type of body fluid. Among all the candidates, miR-191 was identified as the most suitable reference gene because it had a favorable ranking value in all tested samples. In addition, miR-423, miR-93, miR-484, and let-7i were also shown to be applicable reference genes. Overall, this study provides detailed assessment results of these candidate genes in different body fluids; thus, it could be used as a guide for the selection of reference genes according to their performance in the sample of choice.     

Comparative study of characteristic compounds of three species of truffle

The Panxi area in Sichuan Province is the main area for the production of truffles in China, and several species of truffle are known to exist in this region. Nevertheless, it is unclear what the differences in chemical composition between the truffles are. Using an ultra-high-performance liquid chromatography quadrupole/orbitrap high-resolution mass spectrometry coupled with Compound Discoverer 3.0, we identified chemical components in three mainly known truffles from the Panxi region. Further analysis of chemical composition differences was conducted using principal component analysis, and orthogonal partial least squares discriminant analysis. Note that, 78.9% of the variance was uncovered by the principal component analysis model. As a result of the orthogonal partial least squares discriminant analysis model, the three species of truffles (Tuber pesudohimalayense, Tuber indicum, and Tuber sinense) from Panxi were better discriminated, with R²X, R²Y, and Q² being 0.821, 0.993, and 0.947, respectively. In this study, 87 components were identified. T. pesudohimalayense contained significantly higher levels of nine different compounds than the other two species. Hence, it was possible to identify similarities and differences between three species of truffles from Panxi in terms of chemical composition. This can be used as a basis for quality control.     

High-resolution melt analysis for the detection of skin/sweat via DNA methylation

The determination of tissue type is important when reconstructing a crime scene as skin cells may indicate innocent contact, whereas other types of cells, such as blood and semen, may indicate foul play. Up to now, there has been no specific DNA methylation-based marker to distinguish skin cell DNA from other body fluids. The goal of this study is to develop a DNA methylation-based assay to detect and identify skin cells collected at forensic crime scenes for use in DNA typing. For this reason, we have utilized a DNA methylation chip array-based genome-wide association study to identify skin-specific DNA methylation markers. DNA obtained from skin along with other body fluids, such as semen, saliva, blood, and vaginal epithelia, were tested using five genes that were identified as sites for potential new epigenetic skin markers. Samples were collected, bisulfite converted, and subjected to real-time polymerase chain reaction (PCR) with high-resolution melt analysis. In our studies, when using WDR11, PON2, and NHSL1 assays with bisulfite-modified PCR, skin/sweat amplicons melted at lower temperatures compared to blood, saliva, semen, and vaginal epithelia. One-way analysis of variance demonstrates that these three skin/sweat markers are significantly different when compared with other body fluids (p < 0.05). These results demonstrate that high-resolution melt analysis is a promising technology to detect and identify skin/sweat DNA from other body fluids.     

A NEW SPIROPLASMA FROM THE SURFACE OF PLANT FLOWER IN CHINA

The strain CCH, isolated from the surface of the plant flower in China, is a wall- less,helical prokaryote which passes through a microfilter 0. 22 μm in diameter. Cholesterol isrequired for its growth. The strain CCH could metabolize glucose, fructose, maltose, treha-lose and arginine, but not urea. Its electrophoresis pattern of cell proteins is distinct fromthat of other spiroplasmas. The guanine-plus-cyrosine content of its DNA determined bymelting temperature is 29. 15 mol%. No relation with any known spiroplasmas was found inenzyme-linked immunosorbent assay and deformation tests. According to these results, thestrain CCH is referred to a new species in the genus of Spiroplasma or the representative ofa new spiroplasma group.     

南海软珊瑚Sarcophyton molle化学成分的研究

从中国南海软肉芝软珊瑚(Sarcophyton molle)中分离到七个化合物, 经紫外光谱(UV), 红外光谱(IR), 质谱(MS)和核磁共振光谱(1H NMR, 13C NMR)分析, 确定了其化学结构。它们是: 异新西松烯(1), (E, E, E)-7, 8-环氧-1-异丙基-4, 8, 12-三甲基-十四环-1,3, 11-三烯(2), 正十八烷酸(3), 鲨肝醇(4), 神经酰胺(5), 胸腺嘧啶(6), 胸腺嘧啶脱氧核苷(7)。其中化合物(2)为新化合物。本文是第一次报道软珊瑚Sarcophyton molle的化学成分。     

Use of DSC and TG for identification and quantification of the dosage form

Thermal analysis techniques, DSC and TG can advantageously be used in quality control of drug products.The methods are commonly used in preformulation for the study of polymorphism and for the study of the interactions drug substance-excipients, since these physical interactions can be the basis of the dosage form performance.For routine control of the drug products, DSC and TG methods which are quick, which require only few mg of the samples and which are automated, are very attractive for routine analysis of drug products. A single scan can give several qualitative and quantitative informations.DSC offer analytical possibilities only if the drug substance and the excipients do not have physical interactions or limited interactions (e.g. eutectic behaviour). About twenty marketed products have been analyzed by DSC and TG. In most of them identification of drug substance is easy. Several excipients could be identified in a tablet. Quantitations are demonstrated for some drug substances and excipients. DSC purity calculations have been applied to acetyl salicylic acid, paracetamol, cimetidine, pindolol, ibuprofen.