Isoguanine and 5‐Methyl‐Isocytosine Bases,In Vitro and In Vivo

The synthesis, base‐pairing properties and in vitro and in vivo characteristics of 5‐methyl‐isocytosine (isoC^Me) and isoguanine (isoG) nucleosides, incorporated in an HNA(h) (hexitol nucleic acid)–DNA(d) mosaic backbone, are described. The required h‐isoG phosphoramidite was prepared by a selective deamination as a key step. As demonstrated by T_m measurements the hexitol sugar showed slightly better mismatch discrimination against dT. The d‐isoG base mispairing follows the order T>G>C while the h‐isoG base mispairing follows the order G>C>T. The h‐ and d‐isoC^Me bases mainly mispair with G. Enzymatic incorporation experiments show that the hexitol backbone has a variable effect on selectivity. In the enzymatic assays, isoG misincorporates mainly with T, and isoC^Me misincorporates mainly with A. Further analysis in vivo confirmed the patterns of base‐pair interpretation for the deoxyribose and hexitol isoC^Me/isoG bases in a cellular context, through incorporation of the bases into plasmidic DNA. Results in vivo demonstrated that mispairing and misincorporation was dependent on the backbone scaffold of the base, which indicates rational advances towards orthogonality.     

Development of an automatic multiple dynamic hollow fibre liquid-phase microextraction procedure for specific migration analysis of new active food packagings containing essential oils

A two-phase based hollow fibre liquid-phase microextraction (HFLPME) with a high automatization degree and able to process up to six samples simultaneously by means of a multiple channel syringe pump has been successfully developed. The experimental set-up allows to carry out dynamic extractions with a considerable reduction of sample handling. The system has been applied for the first time to the determination in aqueous food simulant of migrants from prototypes of active packagings to assess their safety before marketing, showing detection limits in the ng g(-1) range, relative standard deviations below 13% and concentration factors ranging from 83 to 338.     

Determination of the antioxidant capacity of active food packagings by in situ gas-phase hydroxyl radical generation and high-performance liquid chromatography-fluorescence detection

An experimental laboratory-made assembly to determine for the first time the antioxidant capacity with respect to hydroxyl (OH*) radicals of several new active packagings directly in the materials has been developed. Gas-phase OH* radicals are generated by UV-light irradiation of an aqueous H(2)O(2) aerosol. After on-line reaction with up to eight parallel test samples, remaining OH* is quantitatively trapped by a salicylic acid solution, and antioxidant capacity is indirectly assessed by HPLC-fluorescence determination of the high sensitive 2,5-dihydroxybenzoic acid formed. Several natural essential oils as well as active plastic films including in their formulation such oils have been subjected to oxidation. Polymers containing clove and oregano were the most efficient ones (up to 7.2 and 4.7 times, respectively, more antioxidant than blanks), whereas rosemary, citronella and propolis showed average efficiency. On the other hand, active materials containing ferulic acid, quercetin, catechin and thymol, as well as commercial active bags with ethylene-absorption properties, showed limited or none antioxidant protection. Experimental results and full details about experimental assembly are given.     

Aromatic amines from polyurethane adhesives in food packaging: The challenge of identification and pattern recognition using Quadrupole-Time of Flight-Mass Spectrometry

Toxic primary aromatic amines (PAAs) are reaction products from residual isocyanates in polyurethane adhesives. The maximum migration level of the total sum of PAAs is 10 ng g⁻¹ of food. This paper reports on a method for quantification of 18 PAAs by UHPLC–MS/MS that was optimised and applied to a series of industrial laminates prepared from polyurethane adhesives. Non-intentionally added substances (NIAS), impurities and other migrants were identified by Q-TOF/MS^E. A comparison of the quantitative values obtained by the colorimetric method using NEDA and by UHPLC–MS/MS confirmed that the first method can overestimate the quantification of PAAs. This could be attributed to the impurities and other NIAS present in the plastic laminate. Values of R² in the analytical characteristics of UHPLC–MS/MS were obtained, the best value being 0.9964 and the most unfavourable 0.7626. The detection limit (LOD) and the quantification limit (LOQ) were 2 pg g⁻¹ and 7 pg g⁻¹, respectively. The stability of the PAAs over time in the acidic simulant in contact with the plastic laminate is also reported.     

Chemical Characterization and Antibacterial Activity of Essential Oil of Medicinal Plants from Eastern Serbia

The objective of this study was to evaluate wild growing Satureja kitaibelii, Thymus serpyllum, Origanum vulgare, Achillea millefolium and Achillea clypeolata with respect to their essential oil (EO) content, composition and antimicrobial activity. The five species were collected at Mt. Rtanj and the village of Sesalac, Eastern Serbia. The main EO constituents of Lamiaceae plants were p-cymene (24.4%), geraniol (63.4%) and germacrene D (21.5%) in Satureja kitaibelii, Thymus serpyllum and Origanum vulgare ssp. vulgare, respectively. A. millefolium EO had multiple constituents with major ones being camphor (9.8%), caryophyllene oxide (6.5%), terpinen-4-ol (6.3%) and 1,8-cineole (5.6%), while the main EO constituents of A. clypeolata were 1,8-cineole (45.1%) and camphor (18.2%). Antimicrobial testing of the EO showed that Staphylococcus aureus (Gram-positive) was more sensitive to all of the tested EOs than Escherichia coli (Gram-negative). S. kitaibelii EO showed the highest antimicrobial activity against both tested bacterial strains. This is the first study to characterize the EO composition and antimicrobial activity of these five medicinal species from Eastern Serbia in comparison with comprehensive literature data. The results can be utilized by the perfumery, cosmetics, food and pharmaceutical industries, but also for healing purposes in self-medication.     

Screening chemical libraries for nucleic-acid-binding drugs by in vitro selection: A test case with lividomycin

Summary Screening new drugs is a costly and time-consuming process. Identifying new targets for existing therapeutics is often a particularly effective avenue for drug development. We have investigated whether in vitro selection can be used for target acquisition. Aminoglycoside antibiotics are known to bind to and inactivate functional natural nucleic acids, such as ribosomal RNA. As an example of how new targets for aminoglycosides could be identified, a lividomycin aptamer was iteratively isolated from a random sequence pool. The consensus sequence of this and other anti-aminoglycoside aptamers was used as the basis for a comprehensive search of natural sequence databases. Surprisingly, a high degree of similarity was found between aptamers and genomic sequences from a variety of organisms. While many of the similarities found are in regions of unknown or nonessential function, some of the sequences are found in critical genes in pathogenic organisms.