Evaluation of UV Spectrophotometry for the Analysis of a Novel Antihypoxic Compound

Relevance. The provision of the population with effective and safe medicines has always been a top priority, making the search for new promising molecules a relevant task. A research group led by Professor I.A. Volchegorsky at the South Ural State Medical University has synthesized «Thioxipine» (TOP) – a new complex ester exhibiting antihypoxic activity (Russian Patent No. 2797949, dated June 13, 2023). Aim. To study the possibility of using ultraviolet spectrophotometry (UV spectrophotometry) for the analysis of 2-ethyl-6-methylpyridinol-3-yl thiooctanoate and to develop methods for its quantitative determination. Materials and methods. The test substance is an intense yellow oily liquid; it is insoluble in water but soluble in 95% ethyl alcohol, which was used as the solvent. Samples were weighed on an OHAUS EX224/AD analytical balance (USA). Measurements were performed using an SF-56 spectrophotometer («LOMOSPEKTR», Russia) equipped with quartz cuvettes (l = 1.00 cm) at room temperature. Pure solvent was used as the reference solution. Class A volumetric glassware was used at all stages of the study. Results. Two methods for the quantitative determination of the new ester using ultraviolet spectrophotometry are proposed. The first method involves direct spectrophotometric determination of the test substance at λ=269 nm. The method demonstrates linearity in the concentration range of 0-200 µM (r=0.9999), and the recovery rate falls within 98.14–101.41%. The repeatability of the determination is indicated by an RSD value of 1.41%. The probability of an erroneous result is p<0.05, indicating the absence of significant systematic error in the determination. The second method is a variant of differential spectrophotometry and allows for avoiding errors in the quantitative determination of Thioxipine in the presence of its hydrolysis products. The optical density of model solutions containing Thioxipine and its hydrolysis products was measured at λ=269 nm and λ=287 nm against the pure solvent. The value ΔD = D₂₆₉ – D₂₈₇ was used to calculate the ester content in the sample. A linear dependence of ΔD on the Thioxipine concentration is observed in the range from 0 to 300 µM (r=0.9997), and the recovery rate for Thioxipine remains within 100.8–101.4%. The maximum value of the relative error in a series of determinations using the differential spectrophotometry method was 1.45%, which is lower than the value of 2.02% obtained with the first method. Conclusions. The preferred applications of the developed methods are indicated. Their metrological assessment demonstrates the feasibility of using the UV spectrophotometry method for the analysis of 2-ethyl-6-methylpyridinol-3-yl thiooctanoate (Thioxipine).