Determination of tryptophan in raw materials, rat brain and human plasma by RP-HPLC technique

This paper describes tryptophan (TRP) estimation in raw human plasma and rat brain by reversed-phase high-performance liquid chromatography (RP-HPLC). Estimation was carried out on a Purospher STAR C18 column using water-acetonitrile (90:10 v/v, at pH 2.7) mixture at a rate of 1.5 mL/min as mobile phase. Eluents were monitored at 273 nm by an ultraviolet detector. The method was linear (R(2) > 0.999), precise (intra-day and inter-day precision <2%) in the range of 0.25-20 μg/mL. The detection and quantification limits were 0.0144 μg/mL and 0.0437 μg/mL, respectively. In human plasma, Day 1 and Day 2 precision were 0.054-2.29% and 1.66-3.7%; whereas precisions in rat brain were 1.23-2.3% and 0.677-4.2%, respectively. The method was applied to study TRP level in human smokers and in arthritic rat brain. An efficient RP-HPLC method was developed for TRP determination that worked for clinical and research purposes.     

Development and Validation of a Liquid Chromatographic Method for the Determination of Leflunomide: Application to in vitro Drug Metal Interactions

Leflunomide is a leading drug for the treatment of rheumatoid arthritis. The principle aim of this study was to develop and validate an RP‐HPLC method for the determination of leflunomide in bulk and pharmaceutical dosage form using diclofenac sodium as an internal standard. For this purpose, chromatography was accomplished on a Purospher Start, C₁₈ (5 (m, 12.5 cm×0.46 cm) column at ambient temperature. Methanol:water (80:20, V/V) solvent system was selected as mobile phase, the pH of which was adjusted to 3.4 by ortho‐phosphoric acid and delivered at a flow rate of 1.2 mL·min⁻¹. Seperation of leflunomide and diclofenac sodium was carried out on a Purospher Start, C₁₈ equipped with a UV‐visible detector at 248 nm. The suitability of the method for the quantitative determination of the drugs is proven by validation in accordance with the requirements laid down by the International Conference on Harmonization (ICH) guidelines. The method was accurate (99.55%–100.03%), specific, linear (R²>0.999) and precise (intra‐day precision 0.023%–0.93% and inter‐day precision 0.26%–0.944%) in the range of 0.5–20 (g·mL⁻¹. The minimum limit of detection and quantification in pharmaceutical formulation were 0.05 and 0.15 (g·mL⁻¹, respectively. Thus the proposed method is simple, accurate, reproducible and suitable for the routine analysis of leflunomide in pharmaceutical formulations and was applied to study in vitro drug‐metal interactions.     

One-pot synthesis of novel pyrido[2,3-d]pyrimidines using HAp-encapsulated-γ-Fe2O3 supported sulfonic acid nanocatalyst under solvent-free conditions

Novel pyrido[2,3-d]pyrimidine derivatives were synthesized through a one-pot three-component approach using HAp-encapsulated-γ-Fe2O3[γ-Fe2O3@HAp-SO3H]catalyzed condensation of 6-arnino-2-（methylthio or ethylthio）pyrimidin-4（3H）-one,Meldrum＇s acid and aryl aldehydes at 60 ℃ and under solvent-free conditions.In this protocol the use of nanocatalyst provided a green,useful and rapid method to generate the products in short reaction times and excellent yields（88%-94%）.     

Retention time prediction of polycyclic aromatic hydrocarbons in gas chromatography–mass spectrometry using QSPR based on random forests and artificial neural network

Structural Chemistry - In this study, a quantitative structure–property relationship (QSPR) was proposed using the random forests (RF) and artificial neural network (ANN) for determining the...