The Role Seemingly of Amorphous Silica Gel Layers in Chiral Separations by Planar Chromatography

In planar chromatography, silica gel appears as the most frequently used adsorbent. Its preference as planar chromatographic stationary phase is due to its high specific surface area (ca. 700 m2 g-1) and relatively simple active sites (silanol groups, Si-OH). The high specific surface area of silica gel and a high density of coverage of its surface with the silanol active sites contribute jointly to an excellent separation performance of this adsorbent. In our experiments on chiral separation of the enantiomer pairs by planar chromatography, contradictory behavior of the silica gel layers versus the chiral compounds was observed. The migration tracks of chiral compounds in the ascending planar chromatographic mode were not vertical but bent on either side being a function of analyte chirality. This deviation of the analyte’s migration track was noticed, when using the densitometric scanner to quantify the respective chromatograms. In order to confirm the hypothesis as to the microcrystalline nature of silica gel used in liquid chromatography, it was further investigated through circular dichroism (CD) and the data thereof confirmed that the ‘chromatographic’ silica gels are not amorphous but microcrystalline, contributing to the (partial) horizontal enantioseparation of the antimer pairs. This paper summarizes the results of our investigation on the microcrystalline nature of silica gels used in planar chromatography and their impact on enantioseparation of the selected pairs of antimers

The Forty-Sixth Euro Congress on Drug Synthesis and Analysis: Snapshot

The 46th EuroCongress on Drug Synthesis and Analysis (ECDSA-2017) was arranged within the celebration of the 65th Anniversary of the Faculty of Pharmacy at Comenius University in Bratislava, Slovakia from 5-8 September 2017 to get together specialists in medicinal chemistry, organic synthesis, pharmaceutical analysis, screening of bioactive compounds, pharmacology and drug formulations; promote the exchange of scientific results, methods and ideas; and encourage cooperation between researchers from all over the world. The topic of the conference, Drug Synthesis and Analysis, meant that the symposium welcomed all pharmacists and/or researchers (chemists, analysts, biologists) and students interested in scientific work dealing with investigations of biologically active compounds as potential drugs. The authors of this manuscript were plenary speakers and other participants of the symposium and members of their research teams. The following summary highlights the major points/topics of the meeting

TLC-MS Versus TLC-LC-MS Fingerprints of Herbal Extracts. Part III. Application of the Reversed-Phase Liquid Chromatography Systems With C18 Stationary Phase

Free full text: [https://doi.org/10.1093/chrsci/49.7.560

TLC-MS Versus TLC-LC-MS Fingerprints of Herbal Extracts. Part III. Application of the Reversed-Phase liquid Chromatography Systems With C-18 Stationary Phase

Free full text: [https://doi.org/10.1093/chrsci/49.7.560

Tlc-Ms Versus Tlc-Lc-Ms Fingerprints of Herbal Extracts. Part Ii. Phenolic Acids and Flavonoids

In the previous paper from this series, we proposed mass spectrometric fingerprinting of a complex and volatile botanical sample upon an example of the essential oil derived from Salvia lavandulifolia. In that paper, we compared two variants of fractionation of such a mixture. A simpler one-dimensional variant consisted of the low-temperature thin-layer chromatographic fractionation coupled with mass spectrometric fingerprinting of each separated fraction (1D LT TLC-MS). A more sophisticated variant was the two-dimensional liquid chromatographic system composed of the low-temperature thin-layer chromatography, high-performance liquid chromatography, and mass spectrometric detection (2D LT TLC-LC-MS). In this study, we present an analogous approach to the non-volatile botanical mixtures upon an example of the pharmacologically important phenolic acids and flavonoids selectively extracted from Salvia lavandulifolia. With these non-volatile fractions, the thin-layer chromatographic separations were carried out at ambient temperature (21 +/- 0.5 degrees C). Once again, we compared two variants of fractionation. A simpler one-dimensional variant consisted of the thin-layer chromatographic mode coupled with mass spectrometric fingerprinting of each separated fraction (1D TLC-MS). A more sophisticated variant was the two-dimensional liquid chromatographic system composed of the thin-layer chromatography and high-performance liquid chromatography, with mass spectrometric detection (2D TLC-LC-MS). As expected, the two-dimensional mode proved better performing than the one-dimensional mode (1D TLC-MS). It was concluded that thin-layer chromatography directly or indirectly coupled with mass spectrometric detection can prove very useful in the analysis of the phenolic acid and flavonoid fraction selectively extracted from botanical material

Tlc-Ms Versus Tlc-Lc-Ms Fingerprints of Herbal Extracts. Part I. Essential Oils

In our earlier studies, we proposed the low-temperature thin-layer chromatography with densitometric and mass spectrometric detection for fingerprinting of essential oils derived from several different species from the Salvia genus. Development of the proposed LT-TLC-MS approach was only possible with use of the TLC-MS interface able to couple the chromatographic plate with mass spectrometer. The goal of this study was to develop for the same purpose the two-dimensional liquid chromatographic system, which was only possible with use of the TLC-MS interface. It included the low-temperature thin-layer chromatography coupled with high-performance liquid chromatography, to build an overall LT TLC-LC-MS system. We compared the fingerprinting results for the essential oil of Salvia lavandulifolia obtained with use of the one-dimensional system (1D LT TLC-MS) with those obtained with use of the two-dimensional system (2D LT TLC-LC-MS). It was shown that the 2D approach provides more fingerprints for further investigations than the 1D approach. Moreover, it is also clear that the 2D approach is better suited for identification of individual chemical species contained in a given mixture, due to the simpler patterns of mass spectra obtained from the 2D analytical mode than from the 1D one. However, with the constituents of the essential oil derived from Salvia lavandulifolia, a straightforward identification was not possible, basically due to numerous groups of isomers among the terpenes and terpenoids contained in the examined sample that have the same molecular weights and hence, can give identical m/z signals

Determination of hemin, protoporphyrin IX and zinc(II) protoporphyrin IX in Parma ham using thin layer chromatography

An effort was undertaken to investigate a possibility to quantify hemin, protoporphyrin IX (PPIX), and zinc(II) protoporphyrin IX (Zn(II)PPIX) by means of thin-layer chromatography (TLC). All these porphyrins naturally occur in meat and meat products, and they are known for being metabolically interrelated in a not yet fully understood fashion. In view of the results of a current research in meat chemistry, it seems most likely that Zn(II)PPIX is responsible for the red color of Parma ham (a traditional Italian dry ham). This discovery instigates a novel concept that Zn(II)PPIX might replace sodium nitrite and potassium nitrate in the function of the red color forming pigment, the latter two compounds traditionally used for the same purpose in meat industry, yet known for the formation of the carcinogenic N-nitrosamines as well. In this study, a novel analytical system was proposed for the successful baseline separation of hemin, PPIX, and Zn(II)PPIX, and a possibility was tested of quantifying these three porphyrins in Parma ham. To this effect, the calibration curves were established for the porphyrin standards. Due to the recognized photosensitivity of hemin, PPIX, and Zn(II)PPIX, extraction of these three compounds from Parma ham and the thin-layer chromatographic procedure were carried out in the darkness, although a complete blackout was not always possible. One problem remained unsolved in this study, namely the selection of a proper (preferably a visible light resistant, hence a non-porphyrin) internal standard (IS) for the performance of the recovery procedure for hemin, PPIX, and Zn(II)PPIX contained in the meat matrix. Finally, it was concluded that the elaborated TLC procedure can successfully be implemented to quantification of hemin and PPIX in Parma ham (and in the other meat products as well).peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=ljlc20status: publishe

Piperazinyl fragment improves anticancer activity of Triapine

<div><p>A new class of TSCs containing piperazine (piperazinylogs) of Triapine, was designed to fulfill the di-substitution pattern at the TSCs N4 position, which is a crucial prerequisite for the high activity of the previously obtained TSC compounds–DpC and Dp44mT. We tested the important physicochemical characteristics of the novel compounds L¹-L¹². The studied ligands are neutral at physiological pH, which allows them to permeate cell membranes and bind cellular Fe pools more readily than less lipid-soluble ligands, e.g. DFO. The selectivity and anti-cancer activity of the novel TSCs were examined in a variety of cancer cell types. In general, the novel compounds demonstrated the greatest promise as anti-cancer agents with both a potent and selective anti-proliferative activity. We investigated the mechanism of action more deeply, and revealed that studied compounds inhibit the cell cycle (G1/S phase). Additionally we detected apoptosis, which is dependent on cell line’s specific genetic profile. Accordingly, structure-activity relationship studies suggest that the combination of the piperazine ring with Triapine allows potent and selective anticancer chelators that warrant further <i>in vivo</i> examination to be identified. Significantly, this study proved the importance of the di-substitution pattern of the amine N4 function.</p></div

Piperazinyl fragment improves anticancer activity of Triapine - Fig 3

<p>(a) Absorption spectrophotometric titration vs. pH of the free L² ligand; (b) electronic spectra of the protonated species of L²; (c) concentration distribution curves for the L² species. (I = 0.1 M (KCl) in 80% (w/w) MeOH/H₂O; T = 25.0°C; [L²] = 5x10^-5M; pH 1.6–11.02).</p

Design strategy for novel TSCs (L¹-L¹²).

<p>All designed ligands are based on the Triapine skeleton, which is present in the active analogs Dp44mT, DpC and 1b, 1d that have been described as highly active analogs [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188767#pone.0188767.ref021" target="_blank">21</a>].</p