Kinetic modelling for the assay of nortriptyline hydrochloride using potassium permanganate as oxidant

Response surface methodology combined Box-Behnken design optimized green kinetic spectrophotometric and HPLC methods to quantify angiotensin receptor blocker valsartan in pharmaceutical formulations

The high-performance liquid chromatographic (HPLC) and kinetic spectrophotometric methods were established to compute valsartan (VAL) in pharmaceutical formulations. The spectrophotometric procedures adopted initial rate, fixed time, and equilibrium strategies to assess VAL. The method was based on the carboxylic acid group of the oxidized VAL with a mixture of potassium iodate (KIO₃) and potassium iodide (KI) at room temperature, producing a stable, yellow-coloured absorb at 352 nm. The critical parameters were optimized using green process optimization methodology such as Box-Behnken design (BBD) which belongs to response surface methodology (RSM). After the screening, experiments identified them as significant, and then three crucial factors were optimised: KI volume, KIO₃ volume, and reaction time against response as absorbance. The HPLC procedure was also optimized based on the desirability function on RSM-BBD. The parameters such as pH, methanol (%), and flow rate (ml/min) were optimized with the best responses: peak area, symmetry, and theoretical plates. The linearity of spectrophotometric and HPLC methods was within the range of 2-24 and 0.25-11.25 µg/ml, respectively. The developed procedures produced excellent accuracy and precision. The design of the experiment (DoE) setting explained and discussed the individual steps and the importance of independent and dependent variables used to develop the model and optimization. The method was validated as per the International Conference on Harmonization (ICH) guidelines. Furthermore, Youden's robustness study was applied with factorial combinations of the preferred analytical parameters and explored their influence with alternative conditions. The analytical Eco-Scale score was calculated and was found a better option as green methods to quantify VAL. The results were reproducible with the analysis completed with biological fluid and wastewater samples.

Optimized Box-Behnken experimental design based response surface methodology and Youden's robustness test to develop and validate methods to determine nateglinide using kinetic spectrophotometry

Selective and straightforward kinetic spectrophotometric methods were developed to quantify nateglinide (NTG) in pharmaceutical dosage forms. Fixed time (ΔA) and the equilibrium methods utilized the reaction of NTG with 1-chloro-2,4-dinitrobenzene (CDNB) in dimethyl sulfoxide (DMSO) with heating at 80 °C for 25 min to form a stable yellow-coloured Meisenheimer complex, which absorbs maximally at 421 nm. The optimization was achieved by utilizing the Box-Behnken experimental design (BBD) combined with response surface methodology (RSM). In which three significant factors were studied, namely, CDNB volume (A), heating temperature (B) and heating time (C) against the absorbance as a response. Method validation presented the International Conference on Harmonisation (ICH) parameters such as specificity, selectivity, linearity, precision, accuracy, limit of detection (LOD), limit of quantitation (LOQ), robustness and solution stability. The LOD and LOQ values were 0.48, 1.46, and 0.21, 0.62 µg/ml, respectively, for a fixed time (ΔA) and equilibrium methods with the linear dynamic range of 1-15 µg/ml. Furthermore, Youden's robustness test using factorial combinations of the selected analytical parameters was performed and investigated its influence with alternative conditions. All results were reproducible and quickly adopted for routine analysis of NTG in pharmaceutical formulations and laboratory preparations.

In Vitro Kinetic Hydrolysis Study of Metronidazole Derivatives with Carvacrol and Eugenol Using Validated RP-HPLC Method

Background:

Prodrugs principle is widely used to improve the pharmacological and pharmacokinetic properties of some active drugs. Much effort was made to develop metronidazole prodrugs to enhance antibacterial activity and or to improve pharmacokinetic properties of the molecule or to lower the adverse effects of metronidazole.

Objective:

In this work, the pharmacokinetic properties of some of monoterpenes and eugenol pro metronidazole molecules that were developed earlier were evaluated in-vitro. The kinetic hydrolysis rate constants and half-life time estimation of the new metronidazole derivatives were calculated using the validated RP-HPLC method.

Method:

Chromatographic analysis was done using Zorbbax Eclipse eXtra Dense Bonding (XDB)-C18 column of dimensions (250 mm, 4.6 mm, 5 μm), at ambient column temperature. The mobile phase was a mixture of sodium dihydrogen phosphate buffer of pH 4.5 and methanol in gradient elution, at 1ml/min flow rate. The method was fully validated according to the International Council for Harmonization (ICH) guidelines. The hydrolysis process carried out in an acidic buffer pH 1.2 and in an alkaline buffer pH 7.4 in a thermostatic bath at 37ºC.

Results:

The results followed pseudo-first-order kinetics. All metronidazole prodrugs were stable in the acidic pH, while they were hydrolysed in the alkaline buffer within a few hours (6-8 hr). The rate constant and half-life values were calculated, and their values were found to be 0.082- 0.117 hr-1 and 5.9- 8.5 hr., respectively.

Conclusion:

The developed method was accurate, sensitive, and selective for the prodrugs. For most of the prodrugs, the hydrolysis followed pseudo-first-order kinetics; the method might be utilised to conduct an in-vivo study for the metronidazole derivatives with monoterpenes and eugenol.