Tomislav Tosti

Salting-out thin-layer chromatography of some macrolide antibiotics

The chromatographic behavior of roxithromycin, midecamycin, erythromycin, azithromycin, and erythromycin ethylsuccinate has been studied by salting-out thin-layer chromatography (SOTLC) with cellulose as a adsorbent and aqueous ammonium sulfate solutions of different concentration as mobile phases. Hydrophobicity was determined from the linear relationships between solute RM values and the ammonium sulfate content of the mobile phase. Hydrophobicity values RM0 and C0 were calculated on the basis of the results obtained. Lipophilicity determined in this way was correlated with calculated log P values.

Lipophilicity of some guaianolides isolated from two endemic subspecies of Amphoricarpos neumayeri (Asteraceae) from Montenegro.

In this study 10 guaianolide-type sesquiterpene gamma-lactones named amphoricarpolides, isolated from the aerial parts of two endemic subspecies of Amphoricarpos neumayeri (ssp. neumayeri and ssp. murbeckii Bosnjak), were investigated by means of reversed-phase thin-layer chromatography. Methanol-water and tetrahydrofuran-water binary mixtures were used as mobile phase in order to determine lipophilicity parameters R (0) (M) and C(0). Some of the investigated compounds were screened for their cytotoxic activity against HeLa and B16 cells. Chromatographically obtained lipophilicity parameters were correlated with calculated logP values and IC(50) values. Principal component analysis identified the dominant pattern in the chromatographically obtained data.

Phytochemical fingerprints of lime honey collected in serbia.

Composition of phenolic compounds and the sugar content were determined as the basis for characterization of lime honey from Serbia. Particular attention was given to differences in phytochemical profiles of ripe and unripe lime honey and lime tree nectar. Melissopalynological analysis confirmed domination of Tilia nectar in all analyzed samples. Phenolic acids, abscisic acid, flavonoids, and flavonoid glycosides were determined by means of ultra-HPLC coupled with a hybrid mass spectrometer (UHPLC-OrbiTrap). Sugar content was determined using high-performance anion-exchange chromatography with amperometric detection. Similar phenolic compounds characterized unripe and ripe honeys, while the lime tree nectar profile showed notable differences. Compared to lime tree nectar, a high amount of chrysin, pinocembrin, and galangin were detected in both ripe and unripe lime honey. Fructose and glucose were the major constituents of all investigated samples, and amounts were within the limits established by European Union legislation. Sucrose content in the nectar sample was up to two-fold higher when compared to all honey samples. Isomaltose and gentiobiose with turanose content were different in analyzed production stages of lime honey.

Structure-retention relationship study of polyoxygenated steroids.

The chromatographic behavior of 31 newly synthesized polyoxygenated steroids was investigated by the means of reversed-phase planar chromatography. Retention data were correlated to molecular characteristics of the analytes with view to examine possible relationships by the means of multiple linear regression (MLR) and partial least square (PLS) regression. On the basis of comparison of the statistical parameters obtained for both MLR and PLS 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 MLR and PLS models.

Influence of frost damage on the sugars and sugar alcohol composition in quince (Cydonia oblonga Mill.) floral nectar

Cold stress adversely affects growth and productivity, and triggers a series of morphological, physiological, biochemical and molecular changes in plants. Since sugars are present in all floral nectars in greater amounts than any other constituent, the aim of this study was to examine how frost exposure changes sugar metabolism and how it affects on the content of sugar components in the nectar of quince. Three quince cultivars (‘Vranjska’, ‘Triumph’ and ‘Leskovačka’) were investigated in this study. The contents of sugars (glucose, fructose, sucrose, trehalose, maltose, isomaltose, rhamnose, arabinose, ribose, melezitose, raffinose, and panose) and sugar alcohols (sorbitol, erythritol, mannitol and galactitol) were analyzed by high performance anion exchange chromatography (HPAEC) with amperometric detection. The results showed that after late spring frosts and irreversible damage of flower parts, the nectar of the three quince cultivars contained elevated levels of fructose, trehalose, arabinose, ribose, rhamnose, raffinose, galactitol and mannitol, indicating an impairment of central carbohydrate metabolism. The ratios between individual sugars, such as the glucose/fructose ratio, were changed in the nectar of damaged flowers in all three quince cultivars. The examined cultivars showed similar sugar response to cold stress. The only exception was ‘Leskovačka’ for the glucose and melezitose pathway, which means that composition of those two sugars changed significantly according to the genotype. The larger are the carbohydrates reserves in different parts of a fruit tree, the higher is the tolerance to any form of frost damage, the results of this study could help in the understanding of how different quince cultivars react to this kind of stress and how they modulate their sugar metabolism.

Estimation of Lipophilicity of Some Polyoxygenated Steroids by the Means of Normal-Phase Thin-Layer Chromatography

Unmodified silica gel in combination with two mobile phases, acetone–n-hexane and acetonitrile–dichloromethane, was used in order to evaluate the capability of normal-phase (NP) chromatography on bare silica gel in estimation of lipophilicity of some polyoxygenated steroids. Soczewinski equation coefficients were employed as a measure of lipophilicity. The RM0 values obtained in NP-systems were correlated with those derived by extrapolation from reversed-phase (RP) systems. In addition, retention data, i.e., lipophilicity parameters determined in NP systems were compared with logP values calculated by use of several commercial computer programs. The results showed that chromatographic parameters RM0, and m obtained in NP system consisted of silica gel as stationary phase and acetone–n-hexane as mobile phase, are acceptable as the measures of lipophilicity of polyoxygenated steroids. The mechanism of retention was discussed.

Testosterone and dihydrotestosterone levels in the transition zone correlate with prostate volume

There is still no consensus regarding intraprostatic androgen levels and the accumulation of androgens in the hyperplastic prostatic tissue. The current opinion is that intraprostatic dihydrotestosterone (DHT) concentrations are maintained but not elevated in benign prostatic hyperplasia (BPH), while there is no similar data concerning intraprostatic testosterone (T).

TLC Retention Behavior of Brodifacoum, Bromadiolone, and Coumatetralyl and their Impurities on Different Adsorbents

The chromatographic behavior of three biocidal technical materials, rodenticide active ingredients brodifacoum, bromadiolone, and coumatetralyl, and impurities present in the technical material was investigated by both normal-phase (NP) and reversed-phase (RP) planar chromatography. The research was carried out using thinlayers of silica gel, alumina, cellulose, and C18 silica. Several solvents on their own or in various combinations and proportions were used for separation. The optimum chromatographic systems for separation of the substances from each other and from their impurities were selected. Under reversed-phase chromatographic (RPC) conditions a linear correlation between RM values and mobile phase composition was established. From results obtained, the lipophilicity RM° and C0 were determined. Possible separation mechanisms are discussed on the basis of the established retention behavior.

Relationship between ripening time and sugar content of apricot (Prunus armeniaca L.) kernels

Apricot seeds could be obtained as a byproduct in different juice or conserve producing industries. Disposal of large amount of apricot seeds is wasting of potentially precious sources of phytochemicals. This study encompassed apricot cultivars that have different origin and flowering time with the aim of providing valuable information about the sugar content in its kernels. High-performance anion-exchange chromatography with pulsed amperometric detection was used for the determination of 22 sugars in the kernels of 70 apricot cultivars. The most common sugars in the apricot kernels are sucrose, fructose, and glucose whose ratio proved to be ripening time dependent (1:1:1 in the early, 1:2:3 in medium and 1:3:3 in the late cultivars). The kernels of the apricot with shorter vegetation period had the highest sum of glucose and fructose compared to other groups. Other sugar components were present in different levels as minor constituents depending on the ripening time. Also, most common sugars and some low-level sugars were strongly correlated to each other, indicating the normal metabolic carbohydrate pathway. To understand the distribution modes of sugars, a principal component analysis was performed.

Characterization of sugar and polyphenolic diversity in floral nectar of different ‘Oblačinska’ sour cherry clones

‘Oblačinska’ sour cherry, an autochthonous cultivar, is the most planted cultivar in Serbian orchards. Since fruit trees in temperate zone reward insects by producing nectar which ‘quality’ affects the efficiency of insect pollination, the aim of this study was analyzing of sugars and polyphenolics in floral nectar of 16 ‘Oblačinska’ sour cherry clones with different yielding potential. The contents of sugars and sugar alcohols were analyzed by ion chromatography, while polyphenolic profile was established using liquid chromatography/mass spectrometry technique. Fourteen sugars and six sugar alcohols were detected in nectar samples and the most abundant were fructose, glucose, and sucrose. Eleven polyphenols were quantified using available standards, while another 17 were identified according to their exact masses and characteristic fragmentations. Among quantified polyphenols, rutin, naringenin, and chrysin were the most abundant in nectar. Principal component analysis showed that some polyphenol components (naringin, naringenin, and rutin) together with sugars had high impact of spatial distribution of nectar samples on score plot.