Borbála Boros

Determination of polyphenolic compounds by liquid chromatography-mass spectrometry in Thymus species

Polyphenolic compounds represent a wide group of phytochemicals, including well-known subgroups of phenolic acids, flavonoids, natural dyes, lignans etc., which are produced by plants. These natural bioactive compounds possess a variety of beneficial effects including antioxidant and anticarcinogenic activities, protection against coronary diseases as well as antimicrobial properties. Thymus species have already been reported as sources of different phenolic acids and flavonoids. Moreover, the composition and content of flavonoids in Thymus species play important role as taxonomic markers providing distinction of species. High-performance liquid chromatography (HPLC) coupled with diode array detector (DAD) and on-line mass spectrometry (ESI-MS) method was used for analysis. The method was evaluated for a number of validation characteristics (repeatability and intermediate precision, LOD, LOQ, calibration range, and recovery). The polyphenolic pattern of five native Hungarian Thymus species (T. glabrescens Willd., T. pannonicus All., T. praecox Opiz, T. pulegioides L., and T. serpyllum L.) was characterized. The dominant compound was rosmarinic acid, which ranged between 83.49 μg g(-1) and 1.436 mg g(-1). Other phenolic acids (ferulic acid, caffeic acid and its other derivatives, chlorogenic acid and p-coumaric acids) were present in every examined Thymus species, as well as flavanones: naringenin, eriodictyol and dihydroquercetin; flavones: apigenin and apigenin-7-glucoside, flavonols: quercetin and rutin. The polyphenolic pattern was found to be a useful additional chemotaxonomic tool for classification purposes and determination of the locality of origin.

Determination of tropane alkaloids atropine and scopolamine by liquid chromatography-mass spectrometry in plant organs of Datura species

Hyoscyamine (atropine) and scopolamine are the predominant tropane alkaloids in the Datura genus, occurring in all plant organs. The assessment of the alkaloid content of various plant parts is essential from the viewpoint of medical use, but also as a potential risk of toxicity for humans and animals. Therefore, a reliable method for the determination of tropane alkaloid content is of high importance. The present work aimed at the elaboration of a rapid method for determination of the most abundant Datura alkaloids by LC-MS technique using a new generation of core-shell particle packed column. Tropane alkaloid content was investigated in various plant organs of four Datura taxa (D. innoxia, D. metel, D. stramonium, and D. stramonium var. tatula), grown under the same conditions, in two developmental stages. We have developed a rapid LC-MS method for the quantitative determination of atropine and scopolamine, which was successfully applied to quantify the alkaloids in different plant organs (leaves, flowers, stems, seeds) of thorn apples after a simple sample preparation step. Elaboration and validation of the method and analysis of plant extracts were done by UFLC-MS technique, employing an Ascentis Express C18 column. Detection was done in positive ionization mode (ESI+) and the method suitability was evaluated by several validation characteristics. Quantitation limits are 333 and 167 pgmL(-1) for scopolamine and atropine, respectively, and the method shows very good repeatability. The analysis of Datura extracts revealed significant differences depending on the species, the organ and the sampling period. Atropine was found to be dominant over scopolamine in three out of the four taxa investigated. D. innoxia showed the highest concentrations of scopolamine in all organs examined, whereas D. metel accumulated the lowest scopolamine levels. Hyoscyamine, measured as atropine, was the highest in D. stramonium var. tatula, and the lowest in D. innoxia. Samples collected in summer had higher scopolamine levels than autumn samples, concerning both stems and leaves.

Effect of pressure on retention factors in HPLC using a non-porous stationary phase

SummaryPressure and temperature have significant influence on retention in HPLC. This study investigates the effect of pressure and temperature on the retention behavior of aromatic hydrocarbons (toluene, ethyl benzene, butyl benzene, pentyl benzene) and polar, acidic and basic samples (phenol, acetophenone, N,N-dimethyl aniline, benzophenone) on a reversed phase column. The effect has been studied on non-porous, tetradecyl (C14) coated silica particles. We found that the adsorption-induced decrease of the partial molar volume of the solutes investigated was between ΔVm=5–15 cm3 mol−1. The increment of the decrease of the partial molar volume due to the addition of one CH2 group, for the homologous series of the aromatic hydrocarbons is approximately ΔVCH2=2.3 cm3mol−1.

Effect of pressure on solute capacity factor in HPLC using a non-porous stationary phase

SummaryThe pressure applied in liquid chromatography (LC) can influence the capacity factor of analytes. Using commercial equipment, column (33×4.6 mm) and 1.5 μm non-porous, tetradecyl (C14) coated silica particles, a moderate but significant change in the capacity factor was observed with increasing pressure. Depending on the experimental conditions the relationship was found to be either linear or non-linear. In the latter case the retention increased at first, but later tended to decrease at still higher pressure. The results direct attention to the role of the pressure (and hence of flow rate and heat of friction) in determining capacity factors.

HPLC separation of opium alkaloids on porous and non-porous stationary phases

SummaryA new reversed-phase (RP) HPLC method has been developed and validated for the separation of the main opium alkaloids morphine, codeine, thebaine, papaverine and noscapine on a non-porous (micropellicular) stationary phase. On this phase quantification of the compounds by internal standardization with brucine was achieved extremely rapidly, in ca 1.5 min, only. Thus, the analysis time for the opium alkaloids was approximately one tenth of that on porous stationary phases. Different opium samples were investigated using non-porous and porous packings. The correlation between the results was excellent.

Quick and sensitive HPLC separations on non-porous reversed-phase packings

SummaryThe aim of this work was to evaluate reversed-phase chemically bonded non-porous (micropellicular)dp=1.5 μm stationary phases. On these modern phases the time for analysis of complex mixtures of solutes—whether monomeric or polymeric (e.g. drugs, vitamins, peptides, or protein)—is very short compared with that on porous phases. Different surface chemistries were elaborated for the separation of different types of sample. For the separation of small molecules a long-chain (C14) hydrocarbon-coated phase seems to be optimum; a short chain (C6) hydrocarbon bonded to the surface of the silica seems better for the separation of polymers.The efficiency, the low analysis times, and sensivities were demonstrated by separation of different proteins, peptides, drugs, alkaloids, and mixtures of water and fat-soluble vitamins.

The myth of data acquisition rate.

With the need for high-frequency data acquisition, the influence of the data acquisition rate on the quality of the digitized signal is often discussed and also misinterpreted. In this study we show that undersampling of the signal, i.e. low data acquisition rate will not cause band broadening. Users of modern instrumentation and authors are frequently misled by hidden features of the data handling software they use. Very often users are unaware of the noise filtering algorithms that run parallel with data acquisition and that lack of information misleads them. We also demonstrate that undersampled signals can be restored by a proper trigonometric interpolation.

Palladium-catalyzed diaminocarbonylation: synthesis of androstene dimers containing 3,3′- or 17,17′-dicarboxamide spacers

Novel androstene-based dimers linked through A- and D-ring with 3,3′- and 17,17′-dicarboxamide spacers, were synthesized via palladium-catalyzed aminocarbonylation. Androstane derivatives possessing either 3-iodo-3,5-diene or 17-iodo-16-ene functionality were used as substrates in the presence of palladium-phosphine in situ catalysts and aliphatic and aromatic diamines as N-nucleophiles. Since androst-4-ene-3,17-dione was used as starting material, a multistep synthesis including protection/deprotection of one of the keto functionalities (3-one or 17-one) as ethylene ketals, transformation of the other keto group to iodoalkene functionality via its hydrazone, and palladium-catalyzed aminocarbonylation of the iodoalkene functionality was used. In this way, new dimeric compounds possessing a keto functionality were obtained in moderate-to-good isolated yields, via highly chemoselective reactions, under relatively mild conditions.Graphical abstract

Development and Validation of an HPLC-DAD Analysis for Pharmacopoeial Qualification of Industrial Capsicum Extracts

A reverse-phase high-performance liquid chromatography method was developed to quantify capsaicin (trans-8-methyl-N-vanillyl-6-nonenamid), dihydrocapsaicin (8-methyl-N-vanillylnonanamide) and the main capsaicinoid contents of Capsicum extracts. The chromatographic separation was carried out on a C8 column using isocratic mobile phase consisting of 40% (v/v) acetonitrile and 60% (v/v) orthophosphoric acid solution with flow rate of 1.5 mL/min. The concentration of the eluting compounds was monitored by a diode-array detector at wavelength of 281 nm. The method was evaluated for number of validation characteristics (selectivity, accuracy (confidence intervals <1%), repeatability and intermediate precision (RSD% < 2.5%), limit of detection (LOD), limit of quantification (LOQ) and calibration range). The LOD was 0.25 µg/mL and the LOQ was 0.5 µg/mL. Using methanolic solutions of United States Pharmacopoeia (USP) Capsaicin and Dihydrocapsaicin Reference Standards, the method was linear over the concentration range 0.0005-0.5000 mg/mL for both capsaicinoids. The method was applied to qualify capsaicinoid content of two industrial capsicum extracts according to the USP 29.

Correction to: Use of non-living lyophilized Phanerochaete chrysosporium cultivated in various media for phenol removal

In the original publication of this paper, the Acknowledgements section is missing the statement below.