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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Erzsébet Háznagy-Radnai, Szilvia Czigle, Gábor Janicsák, and Imre Máthé

Stachys species contain iridoids, for example harpagide, acetylharpagide, aucubin, harpagoside, and ajugoside. The iridoid composition and content of leaves, stems, and inflorescences of ten Stachys species have been compared by use of a TLC-densitometric method. Harpagoside, harpagide, and acetylharpagide proved to be the main iridoids in Stachys officinalis L., St. sylvatica L., St. grandiflora Host., St. macrantha (C. Koch.) Jalas I., St. alpina L., St. palustris L., St. recta L., St. byzantina Koch., and St. germanica L. No iridoids were detected in St. annua L.

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–25 ] is used to estimate the relation between the studied responses and these key variables. The objective of this study was to develop a simple and rapid reversed phase high pressure liquid chromatography (RP-HPLC) method with fluorescence detection by

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Cereal Research Communications
Authors: T. Abonyi, S. Tömösközi, M. Budai, Sz. Gergely, É. Scholz, D. Lásztity, and R. Lásztity

26 301 310 Daniel, C., Triboi, E. 2001. Effects of temperature and nitrogen nutrition on the accumulation of gliadins analysed by RP-HPLC. Austr. J

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Six, sensitive, precise and accurate methods have been developed for the determination of cefditoren pivoxil (CP). The first two methods were based on the formation of charge transfer colored complex between CP and p-chloranilic acid (p-CA) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in the concentration range of 50.00–225.00 μg mL−1 and 75.00–250.00 μg mL−1, respectively. The influence of different parameters on color formation was studied to determine optimum conditions for the visible spectrophotometric methods. The other four methods were adopted for determination of the studied drug in the presence of its acid degradation products including two spectrophotometric methods, namely, first derivative (D1) and first derivative of ratio spectra (DD1), and two chromatographic methods, namely, thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), as stabilityindicating techniques. The degradation products were identified by infrared and mass spectroscopy. All the proposed methods were validated and successfully applied for determination of CP in pure form and in pharmaceutical preparations with good recovery ranges between 99.19 and 100.62. The results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by the manufacturer method, and no significant difference was found.

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Summary

Oroxylin A (5,7-dihydroxy-6-methoxyflavone), which has showed multiple pharmacological effects, was semi-synthesized chemically as a pharmaceutical agent. Its impurities, degradation products and their formation pathways remain unknown. In the present study, two impurities (5,6,7-trihydroxyflavone, 5-hydroxy-6,7-dimethoxytlavone) and a degradation product (5,7-dihydroxy-8-methoxyflavone) in Oroxylin A bulk drug substance were identified, and their formation pathways were proposed. A reversed phase liquid chromatographic method for the simultaneous determination of Oroxylin A and the three compounds was developed on a C18 column using methanol-acetonitrile-0.1% acetic acid (54:23:23, v/v/v) as the mobile phase. The detection was performed at 271 nm. The method was validated to be robust, precise, specific and linear between 4 and 40 μg mL−1; the limits of detection and quantification of Oroxylin A were 0.01 and 0.04 μg mL−1, respectively. The developed method was found to be suitable to check the quality of bulk samples of Oroxylin A at the time of batch release and also during its stability studies (long term and accelerated stability).

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Acta Chromatographica
Authors: E.N. Fedorova, A.D. Kivero, N.V. Geraskina, and L.R. Ptitsyn

A simple and rapid ultra-performance liquid chromatographic (UPLC) method for analyzing acetoin in bacterial culture fluid was developed and validated for the first time. The samples were separated using an Acquity BEH C18 column (2.1 mm × 100 mm, 1.7 μm particle size) and isocratic elution with 30 mM phosphoric acid—1% acetonitrile as the mobile phase. A photodiode array detector (PDA) was used. The run time was 6 min, and the detection limit was 2.11 × 10−4 mg mL−1. The UPLC method was compared with high-pressure liquid chromatography (HPLC) for acetoin analysis. The proposed UPLC method is highly sensitive and was successfully applied to the analysis of acetoin in bacterial culture fluid.

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Selected cortisone derivatives (corticosterone acetate, 11-dehydrocorticosterone acetate, corticosterone, 11-dehydrocorticosterone, allo-dihydrocortisone, hydrocortisone, and cortisone) have been separated by reversed-phase thin-layer chromatography and reversed-phase high-performance liquid chromatography. Experimental partition coefficients (log P exp ) of the derivatives were determined for the n -octanol-water system. Chromatographic data ( R F , R M , t R , and log k ) were correlated with experimental (log P exp ) and with theoretical n -octanol-water partition coefficients ( A log P S , IA log P , log P Kowwin , x log P , C log P , mi log P , log P Rekker ) and with the hydrophilic-lipophilic balance ( HLB ) of the compounds. It was found that corticosterone acetate should have the highest lipophilicity whereas cortisone should have the lowest. It was found that the chromatographic retention data ( R F , R M , t R , and log k ) correlated best with mi log P and x log P . Because the experimental values (log P exp ) of all the cortisone derivatives investigated were closest to mi log P values ( r = 0.9915) we conclude that mi log P is the best theoretical partition coefficient for evaluation of the lipophilicity of these cortisone derivatives.

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Acta Chromatographica
Authors: K. Wróblewski, A. Petruczynik, I. Radzik, S. J. Czuczwar, and M. Waksmundzka-Hajnos

Three independent reversed phase high-performance liquid chromatography (HPLC) procedures with diode array detection (DAD) for the analysis of carbamazepine (CBZ), topiramate (TPM), and valproic acid (VPA) have been developed in order to determine drug penetration of the blood—brain barrier. Determination of CBZ was performed on C18 column with mobile phases containing methanol (55%, v/v), acetate buffer at pH 3.5 (20%, v/v), double distilled water (25%, v/v), and 0.025 M L−1 diethylamine (DEA). The mobile phase containing acetonitrile and water (8:2, v/v) or acetonitrile and phosphate—citrate buffer at pH 2.6 (1:1), respectively, for analysis of VPA and TPM was applied. Quantification of carbamazepine was performed at 285 nm without extraction procedure before the analysis. Determination of topiramate and valproic acid was performed using precolumn derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl). FMOC-Cl is a suitable agent, which reacts with both primary and secondary amines and also with acidic groups. Topiramate was determined at 263 nm and valproic acid at 300 nm. The proposed procedures are simple, not time-consuming, and suitable for the determination of investigated compounds in mouse brain homogenates.

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Summary

Two new structural variants of Marfey's reagent (1-fluoro-2,4-dinitrophenyl-5-l-alaninamide, FDNP-l-Ala-NH2) were synthesized by nucleophilic substitution of one fluorine atom in 1,5-difluoro-2,4-dinitrobenzene (DFDNB) by l-methioninamide or d-phenylglycinamide. The new variants FDNP-l-Met-NH2 and FDNP-d-Phg-NH2 were characterized and used for derivatization of twenty-six α-amino acids. The resulting diastereomeric derivatives were separated on a reversed-phase C18 HPLC column using a linear gradient of acetonitrile and aqueous trifluoroacetic acid (TFA) and the results were compared with those obtained by use of Marfey's reagent. To determine and establish the efficiency of both the new variants, separation results were compared for diastereomers of five representative amino acids (Ala, Phe, Ser, Asp, and Asn) prepared with MR, FDNP-l-Phe-NH2, FDNP-l-Val-NH2, FDNP-l-Leu-NH2, and FDNP-l-Pro-NH2, experiments being performed under identical conditions. Both the new chiral reagents enabled better separation of the diastereomers than Marfey's reagent for most of the amino acids. The reagent FDNP-d-Phg-NH2 enabled excellent separation for serine and asparagine whereas other reagents failed or provided poor results.

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The need for more environmentally sound strategies of plant protection has become a driving force in physiological entomology to combat insect pests more efficiently. Since neuropeptides regulate key biological processes, these “special agents” or their synthetic analogues, mimetics, agonists or antagonists may be useful tools. We examined brain-suboesophageal ganglia and corpora cardiaca-corpora allata complexes of the cabbage moth, Mamestra brassicae , in order to obtain clues about possible peptide candidates which may be appropriate for the biological control of this pest. With the aid of bioassays, reversed phase high performance liquid chromatography, and mass spectrometry, five neuropeptides were unequivocally identified and the presence of a further three were inferred solely by comparing mass spectra with known peptides. Only one neuropeptide with adipokinetic capability was identified in M. brassicae . Data from the established homologous bioassay indicated that the cabbage moths rely on a lipid-based metabolism which is aided by an adipokinetic hormone (viz. Manse-AKH) that had previously been isolated in many different lepidopterans. Other groups of neuropeptides identified in this study are: FLRFamides, corazonin, allatostatin and pheromonotropic peptide.

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