RP-HPLC Method for the Determination and Quantification of Artesunate

A simple, rapid and cost-effective reverse phase high-performance liquid chromatographic (RP-HPLC) method was developed for the quantification of artesunate. C18 Promosil (ODS, 150 × 4.6 mm, 5 μm) column was used as stationary phase to separate the drug. Mobile phase comprised of ethanol: water (65:35) having pH 4.5 was run isocratically at a flow rate of 1 mL/min at 27°C. The method was validated according to ICH guidelines for linearity, precision, accuracy, robustness, specificity, limit of detection (LOD) and limit of quantification (LOQ). The method was found accurate, precise and robust with an average retention time of 4.509 min and 0.5357 %RSD. Good linearity was observed in the concentration range of 2–10 mg/ml with regression coefficient R2 value of 0.9995 and slope value of 369,928. Conclusively, as per ICH norms, the developed method was successfully validated and used for the quantification of artesunate in fast dissolving tablets (FDTs).

OPTIMIZATION AND VALIDATION OF AN ANALYTICAL METHOD FOR TRANEXAMIC ACID IN WHITENING CREAMS BY RP-HPLC WITH PRECOLUMN DERIVATIZATION

Objective: An efficient and selective analytical method with precolumn derivatization using reverse-phase high-performance liquid chromatography(RP-HPLC) was developed for the analysis of tranexamic acid in whitening creams.Methods: Derivatization was performed using 1% ninhydrin solution in methanol as a derivation agent to form a colored Ruhemann’s purple product.The analytical conditions included the use of a C18 column as the stationary phase and a methanol: acetate (20 mM) buffer at pH 4 (75:25) as themobile phase, with a flow rate of 0.8 mL/min and UV–visible detection at a wavelength of 570 nm.Results: The average retention time of the tranexamic acid derivative was 5.413 min. The results of the calibration curves were linear, with acorrelation coefficient (r) of 0.9993 at a concentration ranging from 8 to 48 μg/mL. The recovery was between 99.26% and 101.77%. The limits ofdetection and quantification were 1.87 μg/mL and 6.25 μg/mL, respectively.Conclusion: The analytical method developed in this study met the validation requirements and included a simple and efficient derivatization methodapplicable for the selective analysis of tranexamic acid in whitening creams.

Some pharmacokinetics aspects of new analgetics from hexaazaisiowuritsitane class in rats

An important stage in the preclinical study of a new drug is the study of its pharmacokinetics: absorption, distribution, metabolism, and excretion of the drug compound. The purpose of this study was to study the pharmacokinetics in healthy animals of a new analgesic based on hexaazaisowurtzitane (thiowurtzine). Materials and methods. A technique for determining the concentration of thiowurtzine in the blood plasma and rat excreta has been developed and validated. Using high-performance liquid chromatography and tandem mass spectrometry, concentrations of thiowurtzine in plasma and rat excreta were determined after a single intragastric dose of 100 mg/kg. Results. The peak concentration of thiowurtzine in the blood plasma of rats accounts for 2 hours, which is consistent with the pharmacodynamic data of the analgesic, the average retention time of the substance in the body reached 17.15 h after administration. Thiowurtzine is believed to be actively metabolized.

Production of protected amino acids using the reaction between hydroxycarboxylic acids and amino acids as well as binding on the bentonite

We have developed methods for the production of protected methionine and protected lysine, making use of the reaction between citric acid and malic acid as well as methionine and lysine, on the one hand, and of the interaction between swollen bentonite and the two amino acids, on the other hand. Our in vivo and in vitro experiments have demonstrated that one part of the amino acids transformed during the reaction, while another part bound on the bentonite’s surface to a significant degree. Assisted by the reaction between hydroxycarboxylic acids and amino acids, we achieved a protection of about 75% for methionine and 60% for lysine, that is, 25% of the methionine and 40% of the lysine appeared in the free amino acid fraction. The swollen bentonite bound 75% of the added methionine and 60% of the added lysine. Our chemical analyses have demonstrated that through the time–temperature combinations applied by us the methionine and lysine do not undergo significant degradation and can be fully released from the protected form. Further, our in vitro experiments using rumen fluid from fistulated cattle showed that during the average retention time of the fodder in the rumen the protected amino acids will resist microbial enzymes and maintain their protected status during their presence in the rumen.

A Stability-Indicating RP-HPLC-UV Method for Determination and Chemical Hydrolysis Study of a Novel Naproxen Prodrug

A new naproxen amide prodrug was synthesized and spectrally characterized and a simple, precise, and accurate stability-indicating RP-HPLC method was developed and validated for determination and chemical hydrolysis study of the prodrug. Forced degradation studies were conducted as per the International Conference on Harmonization (ICH) guidelines to establish the stability-indicating power of the method. Separations were performed on a C18 column (150 × 4.6 mm i.d., 5 μm p.s.). The mobile phase consisted of acetonitrile and phosphate buffer pH 4.0 in the ratio 60 : 40. The flow rate and injection volume were 1.0 mL/min and 15 μL, respectively. The peaks were monitored at 272 nm. The average retention time is 5.136 min. The linearity of the method was investigated in the range of 10–50 μg/mL and r2 was found to be larger than 0.9987. The LOD and LOQ were found to be 1.853 and 5.615 μg/mL, respectively. Results indicated that the degradants are well resolved and separated from the prodrug. Hydrolysis kinetics studies were carried out in buffer solutions (pH 1.2, 5.5 and 7.4) to establish the fate of the prodrug. The half-lives in the respective buffers were 23.5, 262, and 334 hours indicating sufficient stability to attain the goal of oral delivery.

Kinetics of ruminal passage rate of particles of signal grass silage, maize and intercropped

<p>The purpose of this study was to evaluate the kinetics of ruminal passage rate of particles from the subsequent associations: corn and signal grass; corn, signal grass and Calopogônio; corn, signal grass and Macrotiloma; and corn, signal grass and Estilosantes. It was used four crossbred holstein-zebu cattle with the rumen tubed in order to determine the the kinetics of ruminal passage rate of particles. The feces were collected at the times zero (immediately after addition of fibers complexed with chromium), 1, 2, 4, 6, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 56 , 64, 72, 80, 88, 96, 120, 132, 144 and 192 hours. The profile parameters of passage rate estimative were adjusted according to robust regression procedures. The average time of particles retention in the raft (ATPR1); the average time in the rumen liquid phase (ATRLP2) and the average time of total ruminal retention (ATTRR) were adjusted for the passage kinetics and estimated with the NLIN procedure of SAS. From the observed results, may be suggested that the transference rate <italic>λ</italic> has an inverse behavior to the escape rate <italic>κ</italic>, the <italic>τ</italic> average values, the average retention time and average particles retention time in the rumen liquid phase (ATRLP2) were not statistically different. The feed characteristics after the raft escape and reach to ATRLP2, were very similar; (ATTRR), related to treatments, were not statistically different (P<0,05). There were observed small TMRR numerical differences in different foods. The corn and signal grass; corn, signal grass and calopogônio; corn, signal grass and macrotiloma, corn, signal grass and estilosantes silage fibers had similar rates of<italic>λ</italic>, k, ATPR1, ATRLP2 and ATTRR. Therefore, the the kinetics of ruminal passage rate of particles is similar. Thus, the choice of the system should be based on other factors, such as viability of the management ease and silage cost.</p>

An evaluation of retention time and short-circuiting in waste stabilisation ponds using Serratia marcescens bacteriophage as a tracer

A single dose of 10 litres of Serratia marcescens bacteriophage was introduced at the inlet of the Cayman Islands waste stabilisation ponds to trace residence time and dispersion through facultative and maturation ponds. The design retention time of the facultative ponds was 11.5 days for a daily flow of 2600 m3. However the study demonstrated that the average retention time was &lt;2 days and the tracer's peak, representing about 1% of the total dose, was detected at the outlet after 3-6 hours. This short-circuiting was attributed mainly to the prevailing wind direction and the orientation of the lagoons including inlet-outlet arrangements. The residence time and short-circuiting was confirmed independently using a numerical model developed by Fares and based on the theory of shallow water equations for the simulation of spatial wind-driven circulation in a natural marine basin. The close agreement of the results of this experimental study with the numerical model, has fundamental implications for improving performance of ponds at the design stage. Given local wind conditions the model permits a rigorous pre-testing of design configurations which is likely to impact on dimensions and orientation in the future.