Enantioseparation of S,R‐(±)‐Ketoprofen on Plain Silica Gel Layers with Achiral Mobile Phase

Surface Interactions between Ketoprofen and Silica-Based Biomaterials as Drug Delivery System Synthesized via Sol–Gel: A Molecular Dynamics Study

Biomaterial-based drug delivery systems for a controlled drug release are drawing increasing attention thanks to their possible pharmaceutical and biomedical applications. It is important to control the local administration of drugs, especially when the drug exhibits problems diffusing across biological barriers. Thus, in an appropriate concentration, it would be released in situ, reducing side effects due to interactions with the biological environment after implantation. A theoretical study based on Molecular Mechanics and Molecular Dynamics methods is performed to investigate possible surface interactions between the amorphous SiO₂ surface and the ketoprofen molecules, an anti-inflammatory drug, considering the role of drug concentration. These theoretical results are compared with experimental data obtained by analyzing, through Fourier transform infrared spectroscopy (FT-IR), the interaction between the SiO₂ amorphous surface and two percentages of the ketoprofen drug entrapped in a silica matrix obtained via the sol–gel method and dried materials. The loaded drug in these amorphous bioactive material forms hydrogen bonds with the silica surface, as found in this theoretical study. The surface interactions are essential to have a new generation of biomaterials not only important for biocompatibility, with specific structural and functional properties, but also able to incorporate anti-inflammatory agents for release into the human body.

Development of a Novel Thin-Layer Chromatographic Method of Screening the Red Beet (Beta vulgaris L.) Pigments in Alimentary Products

The aim of this study was to develop a thin-layer chromatographic method of qualitative analysis, aiming to confirm the presence of the red beetroot pigments in a given sample. The TLC system developed for this purpose consists of the precoated RP-18 F254s TLC plates and the acetonitrile + methanol + water + glacial acetic acid, 2:7:1:0.1 (v/v/v/v) mobile phase. With the use of this system, a striking horizontal separation of betacyanin pigments is obtained for both the red beetroot juice and the commercial betanin sample (with the left-to-right resolution distance of the two bands equal to ca. 6 mm), and a unique pattern of the two skewed chromatographic bands is observed. This striking phenomenon has been given a thorough consideration, and its tentative physicochemical justification was provided, based on analogical cases reported and extensively discussed in our earlier studies. Characteristic fingerprint obtained both for the beetroot juice and the commercial sample of betanin (resembling two slant butterfly wings) can prove very helpful for qualitative confirmation of the presence (or otherwise) of the betanin pigment in the red color juices and beverages, as it was demonstrated upon an example of elderberry juice with a confirmed fortification with the betanin pigment.

Chromatographic Enantioseparations in Achiral Environments: Myth or Truth?

Direct chromatographic enantioseparations are among the most important practical tasks of chromatography. The accepted rules and concepts of stereochemistry anticipated one type of chromatographic systems applicable only to such enantioseparations consisting either of chiral stationary phase, or chiral selector present in mobile phase. In such a model of chromatographic system, both racemic and non-racemic mixtures could be enantioseparated. Over the years, however, reports on successful chiral enantioseparations in non-chiral chromatographic systems have cumulated as well. To adapt the initial model to novel experimental evidence, an assumption had to be added stating that these were only non-racemic mixtures (and not racemic ones), which could be enantioseparated in achiral chromatographic systems, by granting them an inevitable chirality from the enantiomeric excess of a more abundant enantiomer. There still exists an overlooked portion of experimental evidence for successful enantioseparations of racemic mixtures in the non-chiral chromatographic systems, which cannot be explained by the accepted model. Facing this incompatibility between the model and practical results, we reflect on how to reconcile these two by questioning the possibility of pinpointing a true racemate with the help of our imperfect analytical tools.

Dynamics of Spontaneous Peptidization of l-, d- and dl-Serine in an Abiotic Solution as Investigated with Use of TLC-Densitometry and the Auxiliary Chromatographic Techniques

From our earlier investigations, it comes out that proteinogenic amino acids can undergo spontaneous oscillatory reactions of chiral inversion and peptidization. l-Serine (l-Ser) is an important proteinogenic amino acid with many vital functions in human and mammalian organisms, e.g., it is responsible for good condition of the nervous cell membranes. It undergoes spontaneous oscillatory processes of chiral inversion and peptidization, and the goal of this study was to compare the dynamics of its peptidization with that of d-Ser and dl-Ser (racemate). The main analytical technique used in our experiment was TLC-densitometry, and the auxiliary chromatographic techniques were HPLC-evaporative light scattering detector and LC-MS. The results obtained witness to the differences in peptidization dynamics of the two Ser enantiomers (l and d) and of the racemic mixture thereof (dl). It was shown that dl-Ser characterizes with the higher, and l- and d-Ser with the lower peptidization yields.