Correlation of structure and chromatographic behavior of the polioxygenated steroids by the means of thin-layer chromatography

U okviru ove doktorske disertacije detaljno je proučavan uticaj supstituenata vezanih za A prsten na hromatografsko ponašanje serije polioksigenovanih steroida u uslovima tankoslojne hromatografije. U cilju proučavanja uticaja polarnosti sorbenta na retenciju ispitivanih jedinjenja upotrebljena su dva veoma različita sorbenta: polarni nemodifikovani silika-gel i nepolarni C-18 modifikovani silika-gel. Posebna pažnja posvećena je razmatranju uticaja sastava primenjenih mobilnih faza na retenciju radi što boljeg razumevanja odnosa hromatografskog ponašanja i lipofilnosti ispitivanih jedinjenja. Uzimajući u obzir svojstva sorbenta kao i korišćenih mobilnih faza, retenciono ponašanje je izučavano u uslovima normalno-fazne i reverzno-fazne hromatografije. Kao tipični normalnofazni sistemi upotrebljeni su polarni silika-gel kao stacionarna faza i manje polarni rastvarači (aceton, heksan, acetonitril, dihlormetan) kao mobilna faza. Reverzno-fazni sistemi sastojali su se od smeše voda ˗ organski rastvarač (aceton, metanol ili acetonitril) i oktadecil modifikovanog silika-gela kao stacionarne faze. U uslovima normalno-fazne hromatografije sistem aceton/nheksan se pokazao kao pogodan za ispitivanje uticaja sastava mobilne faze na hromatografsko ponašanje polioksigenovanih steroidnih jedinjenja. U uslovima reverzno-fazne hromatografije najbolja selektivnost je postignuta primenom mobilne faze metanol - voda. U okviru ovog rada proučena je i mogućnost primene tankoslojne hromatografije za brzo i jednostavno određivanje lipofilnosti kao važnog parametra biološke aktivnosti ispitivanih steroida. Utvrđeno je da postoji linearna zavisnost između retencionih parametara ispitivanih jedinjenja i sastava dvokomponetnih mobilnih faza. Ispitivanjem korelacije između hromatografski određenih parametara lipofilnosti i teorijski izračunatih logP vrednosti utvrđeno je da je reverzno-fazna hromatografija pogodnija za procenu lipofilnosti ispitivanih jedinjenja.Takođe pokazano je da ispitivani polioksigenovani steroidi sa supstituisanim A prstenom predstavljaju kongenernu seriju. Primenom višestruke linearne regresije (multiple linear regression, MLR) i metode parcijalne regresije najmanjih kvadrata (partial least squares, PLS) proučavane su moguće zavisnosti između hromatografskog ponašanja i molekulskih svojstava analita. Na osnovu statističkih parametara dobijenih za tri reverzno-fazna hromatografska sistema najbolje korelacije između RM 0 i deskriptora bile su u sistemu C-18 / metanol-voda što izdvaja ovaj hromatografski sistem kao najpogodniji za određivanje lipofilnosti analita. Na osnovu regresionih modela određeni su deskriptori koji najbolje opisuju ponašanje analita u odnosu na utvrđene retencione parametre. Dobijeni su statistički značajni modeli kvantitativnog odnosa strukture i retencije (QSRR). Izračunata lipofilnost izražena kao XlogP, površinski napon (ST) i Hansenovo vodonično vezivanje (HHB) su deskriptori koji najbolje opisuju QSRR i u višestrukoj linearnoj regresiji i u parcijalnoj regresiji najmanjih kvadrata.The framework of this thesis was to thoroughly investigate influence of structural moiety attached to A ring on chromatographic behavior of series polyoxigenated steroids under thin-layer chromatography conditions. In order to examine the effect of sorbent polarity on retention behavior of the investigated substances, two different sorbents were selected: polar unmodified silica gel and non-polar C-18 modified silica. In addition, influence of the mobile phase composition was discussed with view to determine relationship between chromatographic behavior and lipophilicity. Taking into account the nature of both sorbents and chromatographic solvents used, the chromatographic behavior of the substances was investigated under normal- and reversed-phase conditions. Polar silica gel with less polar solvents was used as typical normal-phase systems, whereas alkyl modified silica gel (RP-18 silica) in combination with polar water–organic mobile phases (methanol, acetone or acetonitrile) - for typical reversed-phase separation. It was found that in normal-phase chromatography acetone/n-hexane was more suitable for studying relationship between chromatographic behavior of the polioxigenated steroids and mobile phase composition. Under reversed-phase condition the best selectivity was achieved by the use of methanol-water mobile phase. An additional goal of this thesis was to investigate possibility of application of thin-layer chromatography for rapid and simple determination of lipophilicity as parameter of special importance for biologically active substances. A linear relationship between retention parameters of the investigated compounds and composition of the binary mobile phase used was established. On the basis of correlation between chromatographically determined lipophilicity and calculated logP values it was found that reversed-phase chromatography is useful method for lipophilicity estimation. In addition, it is appear that investigated polyoxigenated steroids represent a congeneric series of compounds. Chromatographically determined parameters of lipophilicity (RM 0) were used for developing appropriate models for structure-retention relationships by multivariate statistical analysis. The retention data for system methanol-water on C-18 silica phase has the most significant correlation between RM 0 and descriptors indicating this chromatographic system as most suitable for lipophilicity determination of the studied compounds. Retention data were correlated to molecular characteristics of the analytes with view to examine possible relationships by the means of multiple linear regression and partial least square regression. On the basis of comparison of the statistical parameters obtained for both multiple linear regression and partial least square regression models, descriptors best describing the analyte behavior were selected. Statistically significant and physically meaningful structure-retention relationships were obtained. Calculated lipophilicity expressed as XlogP as well surface tension and Hansen hydrogen bonding was included in both multiple linear regression and partial least square regression models

Supplementary data for the article: Waisi, H.; Janković, B.; Nikolić, B.; Dragičević, V.; Panić, I.; Tosti, T.; Trifković, J. Influence of Various Concentrations of 24-Epibrassinolide on the Kinetic Parameters during Isothermal Dehydration of Two Maize Hybrids. South African Journal of Botany 2018, 119, 69–79. https://doi.org/10.1016/j.sajb.2018.08.006

Supplementary material for: [https://doi.org/10.1016/j.sajb.2018.08.006]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/342

Grape seed flour of different grape pomaces: Fatty acid profile, soluble sugar profile and nutritional value

The aim of this study was to determine fatty acid and soluble sugar profiles of the grape seed flour originated from non-fermented dried pomace of international and autochthonous grape varieties in order to estimate their potential nutritional value. The grape seed flours were obtained from the grapes harvested in technological maturity. It has been shown that grape seed flours contained significant quantities of unsaturated fatty acids (UFAs), especially linoleic fatty acids, whose content ranged from 61.15 - 83.47 %. Oleic acid mostly contributed to the content of monounsaturated fatty acids, while the stearic acid was the most abundant saturated fatty acid (SFA). Among polyunsaturated fatty acids, mainly ω-6 FAs, were the most represented. The tested grape seed flours had the high UFA/SFA ratio (3.63-11.09), low atherogenicity (0.04-0.13) and thrombogenicity (0.16-0.47) indices. Fifteen different sugars were found in analysed samples with the total concentration ranging from 40588 to 91319 mg/kg seed with fructose and glucose as the most abundant. Principal component analysis based on the content of FAs and soluble sugars revealed unique composition of the seed flour of Prokupac variety. These findings indicate that the tested grape seed flours is a good source of nutritionally valuable FAs and sugars that can play an important role in the formulation of a new functional food products

Decolorization of reactive black 5 using dielectric barrier discharge in the presence of inorganic salts

Inorganic salts improve the coloration of textiles, which increase pollution load on dyehouse effluent in general. Decolorization of reactive textile dye C.I. Reactive Black 5 was studied using Advanced Oxidation Processes (AOPs) in a non-thermal plasma reactor, based on coaxial water falling film Dielectric Barrier Discharge (DBD). Initial dye concentration in the solution was 40.0 mg L-1. The effects of addition of inorganic salt different high concentrations (NaCl, Na2SO4 and Na2CO3) on the degree of decolorization were studied. Recirculation of dye solution through the DBD reactor with applied energy density 45-315 kJ L-1 was used. The influence of residence time was investigated after 5 minutes and 24 hours of plasma treatment. Decolorization of the dyes was monitored by spectrophotometric measurement. Changes of pH values and the conductivity of dye solution after each recirculation were tested. The most effective decolorization of over 90% was obtained with the addition of NaCl (50 g L-1), applied energy density of 135 kJ L-1 and after residence time of 24 hours of plasma treatment. Decolorization of solutions containing inorganic salts Na2SO4 and Na2CO3 were lower than for the solution without salt

Supplementary data for the article: Waisi, H.; Janković, B.; Nikolić, B.; Dragičević, V.; Panić, I.; Tosti, T.; Trifković, J. Influence of Various Concentrations of 24-Epibrassinolide on the Kinetic Parameters during Isothermal Dehydration of Two Maize Hybrids. South African Journal of Botany 2018, 119, 69–79. https://doi.org/10.1016/j.sajb.2018.08.006

Supplementary material for: [https://doi.org/10.1016/j.sajb.2018.08.006]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/342

An insight into seasonal changes of carbohydrates and phenolic compounds within the moss Polytrichum formosum (Polytrichaceae)

The same population of the polytrichaceous moss Polytrichum formosum was studied over four different periods of the year, analysing its carbohydrate and polyphenolic content and dynamics related to environmental seasonal changes. A total of 18 different types of sugars (including mono-, di-, tri- and tetra-saccharides) and four sugar alcohols were determined. Chlorogenic acid was the most represented among the 10 detected phenolic compounds. As inferred by the sugar content, sucrose, fructose and glucose were the most dominant sugars, but it is worth mentioning the abundance of trehalose and turanose at least during one of the observed seasons. The presence of four trisaccharides and one tetrasaccharide within P. formosum should be highlighted, as well as the first reports of turanose, isomaltotriose, panose and rhamnose within this species. The quantitative changes over the year clearly demonstrate carbohydrate dynamics in relation to seasonal climatic variation. Sugars are shown to be significant constitutive molecules within P. formosum, but also physiologically active compounds, i.e. signalling and energy storage and supplier molecules. We assume that phenolics have moss-supportive effects during oxidative stress and biotic interaction

The Effects of a Meldonium Pre-Treatment on the Course of the LPS-Induced Sepsis in Rats

A dysregulated and overwhelming response to an infection accompanied by the exaggerated pro-inflammatory state and metabolism disturbance leads to the fatal outcome in sepsis. Previously we showed that meldonium, an anti-ischemic drug clinically used to treat myocardial and cerebral ischemia, strongly increases mortality in faecal-induced peritonitis (FIP) in rats. We postulated that the same mechanism that is responsible for the otherwise strong anti-inflammatory effects of meldonium could be the culprit of the increased mortality. In the present study, we applied the LPS-induced model of sepsis to explore the presence of any differences from and/or similarities to the FIP model. When it comes to energy production, despite some shared similarities, it is evident that LPS and FIP models of sepsis differ greatly. A different profile of sympathoadrenal activation may account for this observation, as it was lacking in the FIP model, whereas in the LPS model it was strong enough to overcome the effects of meldonium. Therefore, choosing the appropriate model of sepsis induction is of great importance, especially if energy homeostasis is the main focus of the study. Even when differences in the experimental design of the two models are acknowledged, the role of different patterns of energy production cannot be excluded. On that account, our results draw attention to the importance of uninterrupted energy production in sepsis but also call for much-needed revisions of the current recommendations for its treatment. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Study of Retention of 31 Polyoxygenated Steroids by Normal- and Reversed-Phase Thin-Layer Chromatography

The chromatographic behavior of 31 steroidal compounds on both silica gel and RP-18 silica thin layers using nonaqueous and aqueous-organic mobile phases was investigated. It was found that an application of more polar solvent systems such as acetonitrile-dichloromethane in comparison to acetone-n-hexane resulted in stronger elution of the investigated substances in all investigated cases. Under normal-phase conditions better selectivity was achieved in acetonitrile-dichloromethane and the best in binary mixture with component ratio 1: 9 (v/v). The selectivity of the separation under reversed-phase conditions was increased with the increased fraction of water in mobile phases used. A conclusion on the influence of substance moiety on the retention behavior of the investigated substances under reversed-phase conditions could not be drawn due to complex retention mechanism. In order to find similarities and dissimilarities between normal-and reversed-phase systems used, retention parameters were investigated by principal component analysis and cluster analysis