Search

In this work, we synthesized and confirmed the structure of several alkaloid N-oxides using mass spectrometry and Fourier-transform infrared spectroscopy. We also investigated their reduction mechanisms using voltammetry. For the first time, we obtained alkaloid N-oxides using an oxidation reaction with potassium peroxymonosulfate as an oxidant. The structure was established based on the obtained fragmentation mass spectra recorded by LC-Q-ToF-MS. In the FT-IR spectra of the alkaloid N-oxides, characteristic signals of N-O group vibrations were recorded (bands in the range of 928 cm⁻1 to 971 cm⁻1), confirming the presence of this functional group. Electrochemical reduction studies demonstrated the reduction of alkaloid N-oxides at mercury-based electrodes back to the original form of the alkaloid. For the first time, the products of the electrochemical reduction of alkaloid N-oxides were detected by mass spectrometry. The findings provide insights into the structural characteristics and reduction behaviors of alkaloid N-oxides, offering implications for pharmacological and biochemical applications. This research contributes to a better understanding of alkaloid metabolism and degradation processes, with potential implications for drug development and environmental science. [ABSTRACT FROM AUTHOR]

Local anesthetics (LAs) are widely used in anesthesiology, ophthalmology, and otolaryngology as well as for treatment of chronic and oncological pain. However, anesthetics can cause adverse effects up to lethal ones. In this work, we cited reviews on chromatographic and spectroscopic methods of local anesthetics determination published earlier, and the main purpose was to review the possibilities and advantages of voltammetric methods used for the LAs determination. The electrochemical behavior, mechanism of LAs transformation on the various working electrodes and analytical parameters of voltammetric methods used for their determination were reviewed in the work. Vast majority of these methods were developed for the most widely used anesthetics in medicine like benzocaine, lidocaine and procaine. Special attention was paid to possible mechanisms of electrochemical oxidation and in some cases reduction of LAs or their derivatives. Voltammetry is used for the determination of LAs in pharmaceutical formulations and in biological fluids. The analytical characteristics in terms of sensitivity, selectivity, reproducibility also were discussed in the article. [ABSTRACT FROM AUTHOR]

In present paper we described a new simple voltammetric method of determination of nefopam alkaloid and its metabolite – N‐oxide. N‐oxide of nefopam is reduced at the dropping mercury electrode (DME) and silver solid amalgam electrodes (AgSAE), which can effectively replace mercury and chemically modified electrodes. The reduction consists of two one‐electron stages each accompanied with one proton transfer. N‐oxide of nefopam can be obtained from nefopam substance by oxidation with potassium peroxymonosulfate. It was studied the effect of various factors on N‐oxide quantitative yield (pH, oxidation duration, reagents concentration) as well as on the reduction of N‐oxide at DME and p‐AgSAE (pH, the nature of background electrolyte, potential and time of accumulation). It was showed that the reduction current linearly increased with increasing of concentration of analgesic. Limit of quantiation is 10−6 mol L−1 at DME and 10−7 mol L−1 at p‐AgSAE. The developed method was applied for the analysis of commercial drug solution for injection "Nefopam" with recovery of 96.7 %, as well as for the spiked human urine samples. Excellent repeatability with a relative standard deviation below 5 % was achieved. [ABSTRACT FROM AUTHOR]

Aims: The kinetic studies of Famotidine (FMT) pure substance and medicinal preparation have been carried out in buffer solutions under second-order conditions at the temperature 293 K for the first time. New titrimetric procedures are described for the FMT determination. Materials and Methods: FMT pure substance and tablets have been used in analytical reaction with of KHSO5. The kinetic behavior has been studied by the iodometric method in different pH medium. Results: FMT oxidation reaction has been studied for the S-oxide product under pH=2.0-5.0 and Sulfone product under pH=7.0-8.4. The reaction studied corresponds to the total second order. The Sulfone formation from FMT S-oxide reaction rate constant is in the interval from 14.49 to 32 min-1 L mol-1. FMT has been treated with a measured excess of standard potassium caroate in buffer solution with pH 7, after a contact time of 20 min, the residual oxidant back has been determined by the iodometric titration method. The titrimetric method is applicable over 1-10 mg mL-1 concentration range and the reaction follows 1:2 (FMT:KHSO5) stoichiometry. The method has been validated for precision, accuracy, linearity, robustness and LOQ. The recovery percent ranged from 99.2 to 100.5%, RSD from 1.09 to 1.70 %, LOQ = 0.03 mg mL-1 for pure substance. RSD for tablet formulations has been in the limits from 1.17-2.87 %. Conclusions: The conditions of FMT S-oxide and Sulfone formation have been optimized. The developed procedures are rapid, simple and inexpensive and could be applied to pharmaceutical preparation.