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Summary

Silica-gel column chromatography and preparative reversed-phase high-performance liquid chromatography (RP-HPLC) were sequentially employed for the isolation of two antioxidants including gallic acid and methyl gallate from Folium Toonea Sinensis. An RP-HPLC-UV method was then developed and validated to rapidly determine their content in this herb with ethyl gallate as internal standard. The quantitation was performed on an XBridge Shield RP18 column (150 mm × 4.6 mm, 5 μm) under 40°C. The mobile phase consisting of acetonitrile and 0.1% formic acid aqueous solution was driven at 1.0 mL min−1 under gradient elution, and 270 nm was selected to monitor the separation. To evaluate the fitness for purpose of the method and to investigate the difference in the content of analytes among different samples, the leaves collected from five production sites were analyzed. The newly established method is suitable for routine analysis of gallic acid and methyl gallate in the herb and, hence, can assist in its quality assessment. It was also found that not only the content of two antioxidants but also the ratio varied significantly among different geographical origins. In addition, three samples from Yantai, Zumadian, and Zhenjiang were distinguished as they have a much higher content ratio than the other two.

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The separation and estimation of natural products by chromatographic techniques such as high-performance liquid chromatography (HPLC) and high-performance thin-layer chromatography (HPTLC) are widely preferred. The present work reveals the quantification of morphine (a regulated narcotic agent) in the Ayurvedic formulation ̀Kamini Vidrawan Raś using reversed-phase HPLC (RP-HPLC). The results obtained herein were compared with the results of earlier reported work using HPTLC. The HPTLC separation of morphine was performed on an aluminum-backed layer of silica gel 60 F254 using ethyl acetate–methanol–ammonia solution as the mobile phase, while RP-HPLC was performed on Kromasil C8-column (150 mm × 4.6 mm, 5 µm) using a mobile phase comprising of N-heptane sulfonate sodium salt–acetonitrile (70:30, v/v) at a flow rate of 1.5 mL min-1. The International Conference on Harmonisation (ICH) guidelines were followed for validation of both the chromatographic methods. Both the developed chromatographic methods are simple, rapid, accurate, and sensitive.

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Two sensitive, specific, and selective stability-indicating chromatographic methods were developed for the determination of cyclobenzaprine HCl (CZ) and asenapine maleate (AS) in pure forms, in the presence of their degradation products and in their pharmaceutical formulations. The first method was an isocratic reversed-phase high-performance liquid chromatography (RP-HPLC). Analysis was performed on cyano column using a mobile phase consisting of acetonitrile–(0.05 m) potassium dihydrogen phosphate buffer (pH 3 ± 0.1) (70:30, v/v) with a flow rate of 1.5 mL min−1 and ultraviolet (UV) detection at 290 nm for the determination of CZ, and methanol–(0.05 m) potassium dihydrogen phosphate buffer (pH 6 ± 0.1) (70:30, v/v) with a flow rate of 1.5 mL min−1 and UV detection at 220 nm for the determination of AS. The second method was thin-layer chromatography (TLC), using silica gel 60 F254 plates and toluene–methanol–chloroform-ammonia solution 33% (5:3:6:0.1, by volume) as the mobile phase for the two drugs. The spots were scanned densitometrically at 290 and 220 nm for the determination of CZ and AS, respectively. The methods were validated according to the International Conference on Harmonization (ICH) guidelines, and the acceptance criteria for linearity, accuracy, precision, specificity, and system suitability were met in all cases. The linearity ranges were 2.5–25 μg mL−1 for the RP-HPLC method and 5–50 μg band−1 for the TLC method for both drugs. The limits of detection for the RP-HPLC method were 0.250 and 0.578 for CZ and AS, respectively, while the limits of quantification were 0.758 and 1.572 for CZ and AS, respectively. The limits of detection for the TLC method were 1.355 and 1.284 for CZ and AS, respectively, while the limits of quantification were 4.472 and 3.891 for CZ and AS, respectively. The results were compared statistically at a 95% confidence level with the reported methods. There were no significant differences between the mean percentage recoveries and the precisions of the two methods.

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Abstract  

Citronellol and citronellyl acetate have been entrapped with α-, β- and γ-cyclodextrin (CD). Evolved gas detection and TG-MS coupling was applied to prove the actual inclusion complex formation between monoterpens and CDs. The terpene content was determined by UV-VIS specrophotometry and RP-HPLC and the effect of storage time on the terpene content was also investigated. The α- and γ-cyclodextrin inclusion complexes showed higher thermal stabilities vs. dynamic heating compared to the β-CD complexes. On the contray, the retention of guest using β-cyclodextrin even after 10 years of storage was much more pronounced. Experimental data other than 1:1 complex compositions are assumed. Molecular modeling experiments also suggested multiple complex compositions.

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This paper reports an investigation of physicochemical properties of four series of carbamates of 3-hydroxy and 4-hydroxyphenyl-acetamides of 4-benzylpiperidine and 1-benzylpiperazine which act as inhibitors of acetyl- and butyryl-cholinesterases. Two experimental methods, reversed-phase high-performance liquid chromatography (RP-HPLC) and reversed-phase thin-layer chromatography (RPTLC), were used to determine the lipophilicity of the selected compounds. The results obtained were compared with theoretical lipophilicity calculated by use of ChemOffice, QikProp, and Pallas software. Correlation with the experimental data was the best for log P COMB values calculated with Pallas and QPlog P calculated with QikProp. The QikProp software was also used to estimate several physicochemical properties for all the compounds; these were then used for preliminary analysis of quantitative structure-activity relationships.

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Thirteen carbonyl derivatives of imidazo [2,1- c ][1,2,4]triazine have been synthesized as a new bioactive set of substances. Investigations of chromatographic retention with use of mobile phases containing different concentrations of modifier enable derivation of several characteristics indicative of lipophilicity differences among the compounds. The lipophilicity ( R MW ) of the solutes was determined by reversed-phase thin-layer chromatography (RPTLC) with aqueous mobile-phases containing organic modifiers (methanol or dioxane) on water-wettable octadecyl silica. Reversed-phase high-performance liquid chromatography (RP HPLC) systems with aqueous mobile phases and different organic modifiers (methanol, dioxane, acetonitrile, tetrahydrofuran) on octadecyl silica columns was also used for determination of the lipophilicity (log k w ) of the thirteen derivatives. Correlations between ϕ 0 (MeOH) values and ϕ 0 (modifier) were established for all the compounds with high values of correlation coefficients ( r > 0.93).

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Summary

A stability-indicating LC assay method was developed and validated for the quantitative determination of doripenem and biapenem in pharmaceutical dosage forms in the presence of degradation products formed during forced degradation studies. An isocratic RP-HPLC method was developed with a C-18 (250 mm × 4.6 mm, 5 μm) column and 12 mM ammonium acetate-acetonitrile (96:4 υ/υ) as mobile phase. The flow rate of the mobile phase was 1.0 mL min−1 for doripenem and biapenem. The determination was carried out at the wavelength of 295 nm. The carbapenems were subjected to stress conditions of degradation in aqueous solutions including hydrolysis, oxidation, photolysis, and thermal degradation. The developed method was validated with respect to linearity, accuracy, precision, selectivity, and robustness.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Małgorzata Kozyra, Kazimierz Głowniak, Andrzej Zabża, Grażyna Zgórka, Tomasz Mroczek, Tomasz Cierpicki, Joanna Kulesza, and Iwona Mudło

Preparative separation and isolation of coumarins from petroleum ether and methanol extracts of the fruits and roots of Peucedanum verticillare L. Koch ex DC ( Umbelliferae = Apiaceae ) have been achieved by column chromatography and normal- and reversed-phase TLC with gradient elution. Isolated coumarins were identified by comparison with standards in analytical TLC and in RP HPLC with gradient elution, by melting point (m.p.) measurement, by UV spectroscopy, by MS, and by 1 H and 13 C NMR spectroscopy. Esculin, umbeliferone, bergapten, xanthotoxin, isoimperatorin, imperatorin, psoralen, and cis -kellactone were isolated for the first time from P. verticillare L. Koch ex DC. Two angular-type pyranocoumarins isolated from the roots and fruits of Peucedanum verticillare L. Koch ex DC. were identified as pteryxin and epoxypteryxin by MS and 1 H and 13 C NMR.

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The purpose of this paper was to assess the suitability of thin-layer chromatography (TLC) as a pilot method for high-performance liquid chromatography (HPLC). The new 1,2,4-triazole and thiosemicarbazide derivatives were analyzed by use of reversed-phase (RP)-TLC and RP-HPLC techniques, applying octadecyl silica adsorbents and aqueous-organic mobile phases. Organic modifiers: methanol and acetonitrile were used at appropriate concentrations providing optimal retention factors. For both techniques, retention coefficient k in column chromatography and the retardation factor R F expressing retention in TLC were determined. The experimentally measured parameters were presented in a logarithmic scale as log k and R M, respectively. The constructed relationships between log k and R M allowed determining the possibility of TLC for anticipating HPLC retention behavior.

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Summary

Qualitative and quantitative analysis was performed on supercritical-fluid and conventional Soxhlet extracts of Betula pendula Roth., Alnus glutinosa (L.) Gaertn., and Platanus hybrida Brot. bark. The effect of the two extraction methods on extraction yields was compared. Lupeol and β-sitosterol were identified in the bark extracts by TLC and by GC-MS. The main components were betulin and lupeol followed by β-sitosterol; betulinic acid seemed to be a minor constituent. Betulin content was determined by RP-HPLC, with acetonitrile-water 80:20 (v/v) as mobile phase. Comparison of the extraction methods showed that supercritical-fluid (scCO2 + EtOH) and ethanolic Soxhlet extraction resulted in the highest extraction yields. Accumulation of betulin derivatives was higher in supercritical-fluid extracts (scCO2 + EtOH) than in conventional Soxhlet extracts.

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