Enantioselective potential of teicoplanin- and vancomycin-based superficially porous particles-packed columns for supercritical fluid chromatography

Application of the superficially porous particles (SPPs) grafted with chiral selectors can substantially improve resolution in chromatographic techniques. In this work, we carried out a deeper study on supercritical fluid chromatography systems with 2.7 µm SPPs bonded with teicoplanin and vancomycin. Fast separations of the majority of enantiomers of phytoalexins, substituted tryptophans, and ketamine derivatives, as representatives of important biologically active and structurally diverse chiral compounds have been achieved. The chromatographic behavior of the structurally different analytes served to characterize these separation systems. The influence of separation conditions, namely mobile phase composition, i.e. type of co-solvent and additive on retention, enantioselective resolution and enantioselectivity was examined. The success rate of baseline and partial separations in individual groups of compounds differed with the chiral stationary phase and also with mobile phase composition. The best, baseline separations for the phytoalexins were achieved on the TeicoShell column using methanol as a co-solvent and trifluoroacetic acid as an additive if used. Mostly partial separations were achieved on the vancomycin-based column for all groups of analytes. Complementary separation behavior of these CSPs was confirmed for the majority of the chiral compounds examined in this work.

Fast enantioseparation of indole phytoalexins in additive free supercritical fluid chromatography

A series of chiral indole phytoalexins with potential anticancer and antimicrobial activity were enantioseparated in supercritical fluid chromatography. Two polysaccharide-based chiral stationary phases composed of tris-(3,5-dimethylphenylcarbamate) derivatives of amylose or cellulose coated on 2.5 μm silica particles were successfully used. The influences of the polysaccharide backbone, co-solvent type and co-solvent content in the mobile phase on retention, enantioselectivity and enantioresolution of indole phytoalexins were investigated. Fast baseline separations were achieved for 26 from 27 tested compounds. Amylose-based chiral stationary phase provided higher number of baseline resolutions of the indole phytoalexins than the cellulose-based one. However, certain complementary enantioresolution results towards the studied compounds were observed between the investigated columns. The relationship between structure of the indole phytoalexins and their chromatographic behavior in supercritical fluid chromatography was discussed.

PROSPECTIVE NON-RANDOMIZED CASE-CONTROL STUDY: IMMEDIATE RESULTS OF RADICAL LAPAROSCOPIC INTERVENTIONS FOR GASTRIC CANCER, THE EXPERIENCE OF A SINGLE CENTER

The aim of this study was to define safety and oncological adequacy of radical laparoscopic interventions in gastric cancer (GC) in the conditions of a specialized oncology center. Materials and methods. The study included 193 (108 men and 85 women) with a histologically verified gastric adenocarcinoma of varying degrees of differentiation or cricoid-cell carcinoma with stage T1b-T4a cN0-N1 according to the UICC / TNM classification (7th edition). The study was prospective. The main group (laparoscopic interventions) included 81 patients: 54 underwent distal subtotal resections of the stomach (DSRS) and 27 underwent gastrectomies (GE); 101 patients (66 DSRSs and 35 GEs) contained the control group (open interventions). Separate group of 11 patients were with a conversion access. Results. The average duration of the laparoscopic DSRS was 209.6 ± 50.4 minutes, the open DSRS - 168.9 ± 44.1 minutes (p <0.05). The mean duration of laparoscopic GE was 241.7 ± 60.3 min, while the open GE was 185.1 ± 48.9 min (p <0.05). The average volume of intraoperative blood loss for laparoscopic DSRS was 100 ± 65.4 ml, with open DSRS - 217.4 ± 102.5 ml (p <0.05) and for laparoscopic and open GE it was 105.5 ± 45.2 ml and 247.1 ± 87.4 ml, respectively (p <0.05). The average number of removed lymph nodes in laparoscopic DSRS was 24,7 ± 5,1, with open DSRS - 25,4 ± 6,7 (p> 0,05), while in laparoscopic and open GE it was 25,1 ± 6, 4 and 26.8 ± 5.3, respectively (p> 0.05). In all cases of laparoscopic interventions R0 resection was performed. In the structure of postoperative complications the specific gravity of severe complications (IIIb - V degree according to the classification of Clavien-Dindo) in the subgroup of laparoscopic DSRS was 5.6%, in the subgroup of open DSRS - 6% (p> 0.05), and in subgroups of laparoscopic and open GE - 11.1% and 8.6%, respectively (p> 0.05). Postoperative lethality in the group of laparoscopic interventions was 1.2%, in the open surgery group - 2.9% (p> 0.05). The analysis of training curves in the performance of laparoscopic interventions demonstrated that the experience of 30 laparoscopic DSRSs and 15 laparoscopic GEs did not allow promoting an access to the plateau but it demonstrated the trend in reducing the duration of operations when accumulating experience. Conclusions. Radical laparoscopic operations for stomach cancer are safe and oncologically adequate. The absence of long-term results of treatment dictates the necessity of continuing the study.

Comprehensive Single-Platform Lipidomic/Metabolomic Analysis Using Supercritical Fluid Chromatography-Mass Spectrometry

Supercritical fluid chromatography (SFC) is a rapidly expanding technique in the analysis of nonpolar to moderately polar substances and, more recently, also in the analysis of compounds with higher polarity. Herein, we demonstrate a proof of concept for the application of a commercial SFC instrument with electrospray ionization-mass spectrometry (MS) detection as a platform for the comprehensive analysis of metabolites with the full range of polarities, from nonpolar lipids up to highly polar metabolites. The developed single-platform SFC-MS lipidomic/metabolomic method is based on two consecutive injections of lipid and polar metabolite extracts from biphase methyl tert-butyl ether extraction using a diol column and two different gradient programs of methanol-water-ammonium formate modifier. Detailed development of the method focused mainly on the pressure limits of the system, the long-term repeatability of results, and the chromatographic performance, including optimization of the flow rate program, modifier composition and gradient, and injection solvent selection. The developed method enabled fast and comprehensive analysis of lipids and polar metabolites from plasma within a 24 min cycle with two injections using a simple analytical platform based on a single instrument, column, and mobile phase. Finally, the results from SFC-MS analysis of polar metabolites were compared with widely established liquid chromatography MS analysis in metabolomics. The comparison showed different separation selectivity of metabolites using both methods and overall lower sensitivity of the SFC-MS due to the higher flow rate and worse chromatographic performance.

DEFINITION OF ETIOLOGICAL ANTIBIOTIC SENSITIVITY FACTORS IN PURULENT-INFLAMMATORY PROCESSES

The purpose of the study - assessment of purulent-inflammatory processes etiologic factors and determination of microbial agents' in forms of plankton and biofilms sensitivity to antibiotics. Clinical microbial strains isolated from patients with purulent-inflammatory processes were the subject of the study. The study material comprised of wound tissue, pus, bandage and suture, catheters and drainage devices. Sensitivity of isolates to antimicrobial preparations with various mechanism of activity on the microbial cells was studied with the help of micro-test system. Formation of biofilms was studied with the help of definition of bacteria strains ability to adhesion to the surface of polystyrene flatbeds. It was revealed that one of the leading factors of purulent-inflammatory process development is S.aureus, which disseminated in 36,5% of cases; E.coli disseminated in 17,3% of cases. Among the agents of purulent-inflammatory processes the specific gravity attributed to: Proteus spp. - 14,6%, S.рyogenes - 12,8%, P.aeruginosa - 6,9%, K.pneumoniae - 6,7%. It was revealed that all isolates formed dense biofilms. It was demonstrated that most isolates in plankton form were sensitive to Novapime, Cefepime, Gatifloxacin, Imipenem; sensitive strains were registered in a smaller quantity to Gentamicin, Clindamycin and Doxycycline. In terms of sensitivity of isolates in the form of biofilm to antibacterial preparations it was revealed that most isolates were polyresistant to them. Thus, the study of the sensitivity of allotted microbial strains to antimicrobial preparations demonstrated, that there were strains among cultures with multiple resistances which was the consequence of a wide and not always effective use of antimicrobial preparations.

Chiral supercritical fluid chromatography of monoacylglycerol and diacylglycerol enantiomers in biological samples: Adjusting selectivity via column coupling

The distinction of lipid isomers is gaining more attention in lipidomics due to their different biochemical properties in the organism. Herein, we aimed to develop a method for the analysis of monoacylglycerol (MG) and diacylglycerol (DG) enantiomers in biological samples using chiral supercritical fluid chromatography and mass spectrometry (SFC-MS). Amylose-based chiral columns showed a certain degree of separation of MG and DG isomers, but low selectivity for the acylglycerol classes in total lipid extracts, which could not be improved by modifier composition or other chromatographic conditions. The coelution of MG and DG enantiomers with highly concentrated triacylglycerols (TGs) negatively affected their MS determination based on the peak area ratio, therefore the interclass selectivity of chiral SFC was adjusted by coupling with an achiral column. The connection of the amylose tris-(3,5-dimethylphenylcarbamate) chiral column with octadecyl achiral column using a methanol as a modifier provided an excellent interclass separation of acylglycerols with the resolution of 5.53 and 15.17 for oleic acid-based MG/DG and DG/TG classes, respectively. The developed method enabled the determination of MG and DG enantiomers in complex total lipid extracts of biological samples in a 15 min gradient without time-consuming sample prefractionation. Chiral SFC-MS analysis of egg yolk, human plasma, and porcine brain samples showed different ratios of enantiomers, suggesting their unique roles within each sample type.

Chiral supercritical fluid chromatography-mass spectrometry with liquid chromatography fractionation for the characterization of enantiomeric composition of fatty acid esters of hydroxy fatty acids

BACKGROUND

Fatty acid esters of hydroxy fatty acids (FAHFAs) are a recently discovered class of endogenous bioactive lipids with promising therapeutic potential for diabetes and inflammation. They represent complex mixtures of different isomers whose biological functions are the subject of investigation. Highly selective methods are required to characterize the composition of enantiomers in biological samples composed of many isobars and regioisomers. We aimed to develop a method for characterizing the enantiomeric composition of FAHFAs in biological samples using supercritical fluid chromatography-mass spectrometry (SFC-MS).

RESULTS

The influence of key chromatographic parameters, such as column chemistry, mobile phase composition, and gradient, on the separation efficiency of 21 commercially available FAHFA regioisomers without stated absolute configuration and 4 FAHFA enantiomers was assessed. The optimized SFC-MS method utilizes a chiral column based on a tris-(3-chloro-5-methylphenylcarbamate) derivative of amylose (Lux i-Amylose-3) and acetonitrile-methanol mobile phase modifier, enabling fast enantioseparation of most FAHFA racemic pairs in 5 min. However, the SFC separation of FAHFA regioisomers was less effective, limiting its applicability to complex biological samples. To address this, we propose an offline two-dimensional separation approach with reversed-phase liquid chromatography for isolating FAHFA regioisomers, followed by chiral SFC-MS analysis of fractions. The suitability of the method was demonstrated by characterizing the enantiomeric composition of FAHFA in white adipose tissue and rice samples. The chiral analysis revealed the presence of both R- and S-FAHFA isomers in the samples, with one enantiomer being predominant.

SIGNIFICANCE

The developed approach represents a proof of concept for the use of SFC-MS with LC prefractionation for the characterization of FAHFA enantiomeric composition in complex biological samples, providing a valuable tool for future research on the biological roles of bioactive lipids in health and disease.

Direct Chiral Supercritical Fluid Chromatography-Mass Spectrometry Analysis of Monoacylglycerol and Diacylglycerol Isomers for the Study of Lipase-Catalyzed Hydrolysis of Triacylglycerols

The fast and selective separation method of intact monoacylglycerol (MG) and diacylglycerol (DG) isomers using chiral supercritical fluid chromatography-mass spectrometry (SFC-MS) was developed and employed to study lipase selectivity in the hydrolysis of triacylglycerols (TGs). The synthesis of 28 enantiomerically pure MG and DG isomers was performed in the first stage using the most commonly occurring fatty acids in biological samples such as palmitic, stearic, oleic, linoleic, linolenic, arachidonic, and docosahexaenoic acids. To develop the SFC separation method, different chromatographic conditions such as column chemistry, mobile phase composition and gradient, flow rate, backpressure, and temperature were carefully assessed. Our SFC-MS method used a chiral column based on a tris(3,5-dimethylphenylcarbamate) derivative of amylose and neat methanol as a mobile phase modifier, which provides baseline separation of all the tested enantiomers in 5 min. This method was used to evaluate hydrolysis selectivity of lipases from porcine pancreas (PPL) and Pseudomonas fluorescens (PFL) using nine TGs differing in acyl chain length (14-22 carbon atoms) and number of double bonds (0-6) and three DG regioisomer/enantiomers as hydrolysis intermediate products. PFL exhibited preference of the fatty acyl hydrolysis from the sn-1 position of TG more pronounced for the substrates with long polyunsaturated acyls, while PPL did not show considerable stereoselectivity to TGs. Conversely, PPL preferred hydrolysis from the sn-1 position of prochiral sn-1,3-DG regioisomer, whereas PFL exhibited no preference. Both lipases showed selectivity for the hydrolysis of outer positions of DG enantiomers. The results show complex reaction kinetics of lipase-catalyzed hydrolysis given by different stereoselectivities for substrates.