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Summary

The merits of chemometrics in categorizing different Egyptian olive chemovarieties based on their compositional integrity were implemented in this study. Fingerprints of 9 different olive leaves varieties cultivated in Egypt were established using reversed-phase high-performance thin-layer chromatography (RP-HPTLC) prior to and after post-chromatographic derivatization with natural product-polyethylene glycol (NP/PEG) reagent and image analysis using ImageJ® software in order to build 2 separate data matrices. The chromatographic fingerprints were separately subjected to unsupervised pattern recognition multivariate analysis to build 2 separate models using principal component analysis (PCA) and hierarchical clustering analysis (HCA) algorithms to explore the distribution pattern of different chemovarieties. The second model which involved olive samples’ fingerprints after post-chromatographic derivatization exhibited greater ability to reveal a broader spectrum of phytoconstituents with enhanced sensitivity. Densitometric RP-HPTLC quantification of oleuropein marker was compared to image analysis approach using Sorbfil TLC Videodensitometer® by newly developed and validated methods. Densitometry exhibited better performance characteristics than image analysis method and therefore was executed for determination of oleuropein concentration in the 9 Egyptian olive varieties. Oleuropein marker solely was found to be inadequate for standardization of olive leaves varieties. This study demonstrated a comprehensive approach for the rapid classification of different Egyptian olive varieties, which is crucial to warranting their chemical-consistency and, thereafter, effective consistency.

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Gradient preparative-layer chromatography and RP-HPTLC have been used for analysis of anthocyanin extracts from Malve arborae L. flos and Vaccinium myrtillus L. fructus. Malvidine was identified in the extract from Malve arborae L. flos. Compounds in the anthocyanin extracts were separated on silica gel 60 F 254 PLC plates by five-step gradient elution with mobile phases containing different amounts of methyl tert -butyl ether (MTBE) as modifier. A chamber with a mobile phase reservoir/injector was used in gradient clution. Preparative chromatography experiments were followed by rechromatography on RP-HPTLC plates with a mobile phase gradient prepared from methanol, water, and formic acid. The procedure reported can be used for preparation of anthocyanin standards in the laboratory.

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A sensitive, simple, and accurate reversed-phase high-performance thin-layer chromatographic method has been established for determination of protodioscin in fruit powder from Tribulus terrestris L. A methanol extract of the fruit powder was used for experimental work. Separation was performed on RP-18F 254s HPTLC plates with 0.1 m KH 2 PO 4 -acetonitrile-methanol-triethylamine, 5 + 4 + 1 + 0.1 ( v/v ), as mobile phase. After development, plates were treated with 0.1 m H 2 SO 4 and detection and quantification were performed by densitometry at λ = 366 nm. Detection and quantitation limits were 0.03 μg and 0.05 μg, respectively. Response was a linearly dependent on amount of protodioscin in the range 0.05 to 1.00 μg. The validated RP-HPTLC method can be used for a routine quality-control analysis of Tribulus terrestris L. fruit powder and quantitative determination of protodioscin.

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Summary

We have recently reported on the effect of the environmental conditions on the quantity of diosgenin. Attempts for the simultaneous quantification of trigonelline and diosgenin using normal-phase silica gel plates were not successful. A high-performance thin-layer chromatography (HPTLC) method was developed using glass-backed plates coated with RP-18 silica gel 60 F254S and acetonitrile-water (7.5:2.5, V/V) as the mobile phase. Trigonelline and diosgenin peaks were well separated with R F values 0.29 ± 0.02 and 0.17 ± 0.01, respectively. The TLC plates were directly scanned at 267 nm for trigonelline and at 430 nm after derivatization with vanillin-sulfuric acid for diosgenin. Linear regression analysis revealed a good linear relationship between the peak area and the amounts of trigonelline and diosgenin in the range of 200–1400 and 50–300 ng per band, respectively. The method was validated in accordance with the International Conference on Harmonization (ICH) guidelines for precision, accuracy, and robustness.

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Influence of the following variables such as adsorbent type, type and concentration of organic modifier in mobile phase, type and concentration of ion-pairing reagent, or pH of the mobile phase buffer on retention of some synthetic peptides in reversed-phase high-performance thin-layer chromatography systems has been investigated. The investigations have been also focused on influence of the variables mentioned on solute zone shape regarding optimization of their separation. Remarks about solute retention mechanism have been also provided.

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A comparative QSAR and QSRR study has been conducted by multiple linear regression (MLR), principal-component regression (PCR), and partial least-squares (PLS) analysis. Comparisons based on these regression methods have been used to model the chromatographic retention (lipophilicity) of thirteen new oxadiazoline derivatives by means of descriptors obtained by use of the Alchemy software package. Retention indices were determined by reversed-phased high-performance thin-layer chromatography on C 18 plates. The retention indices predicted were quite satisfactory and in very good agreement with the molecular structure of the compounds investigated.

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A precise and sensitive reversed phase high-performance thin-layer chromatography (RP-HPLC) method was developed for the determination of nilotinib (NTB) in spiked plasma, urine, and pharmaceutical capsule formulation. The method was based on derivatization NTB with 4-chloro-7-nitrobenzofurazan (NBD-Cl) in the borax buffer (pH 9). The method employs an isocratic elution using acetonitrile and 10 mM orthophosphoric acid (40:60 v/v) as a mobile phase and an C18 column (4.6 mm × 250 mm, 5 μm, Waters Symmetry), with a fluorescence detector (λ ex: 447 nm, λ em: 530 nm). The method validation was performed with respect to linearity, recovery, accuracy, precision, and stability. The linear ranges were 100–600 ng mL−1 in standard solution, plasma, and urine. Correlation coefficients (r 2) were higher than 0.9997 for all of the analytes, indicating good linear relationship. The percentage recovery was 87.89% for plasma, 95.35% for urine, and 96.07% for capsules.

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A simple, rapid, specific, and accurate reverse-phase high-performance thin-layer chromatography (RP-HPTLC) method was developed and validated for simultaneous quantification of levodopa, carbidopa, and entacapone in their combined dosage form. Due to the structural similarity between levodopa and carbidopa, and vast difference in their polarity with that of entacapone, it is very challenging to carry out the simultaneous estimation of all three drugs together. In the developed method, chromatography was performed on TLC plates with precoated silica gel 60 RP-18 F254 using acetonitrile-n-butanol-water-triethylamine (0.5:9.5:1:0.001, ν/ν/ν/ν), pH adjusted to 3.6 with o-phosphoric acid, as the mobile phase. Densitometric evaluation was performed at 282 nm. The R F values were 0.46, 0.64, and 0.87 for levodopa, carbidopa, and entacapone, respectively. The polynomial regression data for the calibration plots showed good linear relationship in the concentration range 300–1500 ng per spot for levodopa, 200–1000 ng per spot for carbidopa, and 200–2000 ng per spot for entacapone. The suitability of this HPTLC method for quantitative determination of drugs was proved by validation in accordance with the requirements of the International Conference on Harmonization (ICH) guidelines (Q2B).

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A reversed-phase high-performance thin-layer chromatography (RP-HPTLC) method was developed for the determination of flavonoids (quercetin and kaempferol) and biflavonoids (sciadopitysin, ginkgetin, and bilobetin) in the aqueous methanolic extract of Ginkgo biloba. There have been a number of reports on the quantification of flavonoids in G. biloba using different analytical techniques, but the reported methods are not suitable for routine analysis and also for the simultaneous quantification of flavonoids and biflavonoids in G. biloba. The method employed here used precoated plates of silica gel 60F254 as the stationary phase with dual-run acetonitrile-water-methanol-formic acid (20:20:1:0.005, ν/ν/ν/ν) and acetonitrile-water-methanol-formic acid (20:17:1:0.005, ν/ν/ν/ν) as mobile phases with densitometric determination of flavonoids and biflavonoids at 254 nm in reflection/absorption mode. The linear regression analysis data for the calibration plots showed a linear relationship (r 2 from 0.9706 to 0.9990). The method was validated for accuracy, precision, and robustness. The limits of detection (LOD) and quantification (LOQ) were in the range of 0.12–0.37 μg and 0.60–1.85 μg, respectively, for the analytes. The method is reproducible and convenient for quantitative analysis of these compounds in the leaves of G. biloba. This is the first report of simultaneous densitometry quantification of major flavonoids and biflavonoids in G. biloba using the newly developed and validated RP-HPTLC method.

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