NMR spectroscopy study of the structure of hypromellose phthalate, a component of enteric coatings of medicinal products

Scientific relevance. Hypromellose phthalate is a component of enteric coatings used to modify active substance release from oral medicinal products in the small intestine. The release rate directly depends on the non-stoichiometric composition of the polymer, first of all, on the proportion of phthalate groups in the macromolecule. It is therefore necessary to develop reliable analytical procedures for determining the structure of hypromellose phthalate to evaluate the dissolution rate of medicinal products containing the polymer.Aim. The study aimed to develop an analytical procedure for quantifying the proportion of phthalate groups in hypromellose phthalate samples using NMR spectroscopy and to determine the relationship between the polymer dissolution rate in aqueous buffer solutions and its structural features (degree of molar substitution and molecular mass).Materials and methods. The study examined hypromellose phthalate samples isolated from enteric coatings of proton-pump inhibitors and used the reference standard for hypromellose phthalate. The non-stoichiometric composition of the polymer was determined by 13C NMR spectroscopy.Results. The authors established the conditions required to separate hypromellose phthalate from the other coating components and identified the characteristic 13C NMR signals that may be used to differentiate between the structural fragments of hypromellose phthalate. The study demonstrated the relationship between the dissolution rate and the structure of the polymer. Commercial grades of hypromellose phthalate were shown to differ in composition and, as a result, in their dissolution kinetics (in particular, the threshold pH for the onset of dissolution (5.0–5.5), as well as the dissolution rates at the same pH).Conclusions. The authors developed NMR-based procedures to determine the proportion of phthalate groups on the basis of their mass fraction in a weighted hypromellose phthalate sample and the degree of molar substitution of the polymer. The results support the applicability of these analytical procedures to the characterisation of sample composition in polymer dissolution rate studies. In principle, it is possible to derive a multiple linear regression equation that describes the dissolution rate of hypromellose phthalate as a function of the molecular mass and the molar substitution with phthalate groups. Further investigation of a larger number of polymer samples with different compositions is needed to improve the regression model and demonstrate its statistical significance. In addition to the proportion of phthalate groups, the pharmacopoeial analysis of hypromellose phthalate should also control the molecular mass of the polymer

Experimental Cell Line Models for Nephrotoxicity Screening

The aim of the study was to review literature data on cell models for experimental assessment of drug nephrotoxicity in vitro. Because of nephrotoxicity, 2% of new investigational medicinal products are discarded at the stage of preclinical in vivo studies in laboratory animals, and 19%—after phase 3 clinical trials. Prediction of toxicity in cell models could make drug development more cost-effective and help to reduce/avoid animal testing. At present, there are no official international guidelines for assessment of nephrotoxicity in vitro, but there is a lot of research underway. The main toxicity target in kidneys is renal proximal tubule epithelial cells, therefore the main research is focused on the development of renal proximal tubule epithelial cell lines with stable functional characteristics. Another important aspect in nephrotoxicity modeling is the choice of relevant test methods and end points which would reflect potential toxicity mechanisms. The paper reviews existing human renal proximal tubule epithelial cell lines and current test methods for assessing cytotoxicity. Promising areas for future development of cell models for nephrotoxicity assessment— are optimisation and standardisation of in vitro systems that would help to make preclinical predictions of drug nephrotoxicity in vivo

Comparative evaluation of recommendations for preclinical studies of transporter-mediated drug–drug interactions

Scientific relevance. Sound recommendations for preclinical studies of transporter- mediated pharmacokinetic interactions of medicinal products can help increase the likelihood of identifying potentially nephrotoxic and hepatotoxic medicinal products at the development and authorisation stages. However, overly strict requirements for the number of studies to be performed may lead to a significant increase in the cost of finished medicinal products.Aim. The aim was to compare regulatory documents on studying transporter-mediated drug–drug interactions (DDIs).Discussion. This review examines changes in regulatory requirements for studying DDIs in chronological order from the first guidelines that appeared in 1997. As exemplified in this article, the multiplicity of transporters and the lack of specific inhibitors pose significant challenges in assessing the role of a particular transporter in drug distribution and drug–drug interactions. This comparative review shows that extrapolating from in vitro transporter inhibition studies to in vivo pharmacokinetics can be misleading.Conclusions. A unified approach to studying transporter-mediated DDIs will increase the likelihood of identifying potentially toxic agents at the stage of new molecule screening. At the same time, it is advisable to limit the number of in vitro and in vivo transporter studies and recommend conducting these studies only for medicinal products with a narrow therapeutic index

Susceptibility of HEK293 and RPTEC Cell Lines to Nephrotoxic Effects of Cefuroxime and Cefepime: A Comparative Study

Researchers need to identify the nephrotoxic properties of medicinal products both during preclinical development and when exploring options to optimise pharmacotherapy. The main challenge is to find an experimental model for assessing drug-induced nephrotoxicity that reflects in vivo conditions as closely as possible.The aim of the study was to compare the susceptibility of HEK293 and RPTEC cell lines used as experimental models for assessing the nephrotoxicity of cefuroxime and cefepime.Materials and methods. The study investigated HEK293 and RPTEC cell lines cultured on plates with 0.4 µm pore membrane inserts. The cell lines were incubated for 3 days with cefuroxime and cefepime (cephalosporins excreted primarily by the kidneys). The medicinal products were added to the basal part of the well at concentrations of 50 and 150 µg/mL (cefuroxime) or 30 and 120 µg/mL (cefepime) twice a day. After incubating the cells with cefuroxime and cefepime for 24, 48, and 72 hours, the authors determined the expression levels of the SLC22A6 and SLC22A8 genes encoding organic anion transporters by a reverse transcription polymerase chain reaction. The authors considered caspase 3 and caspase 7 activation indicative of the nephrotoxic effect of cephalosporins; they evaluated this indicator by a fluorometric assay after 24, 48, and 72 hours of incubation.Results. According to the study, the expression of the SLC22A6 and SLC22A8 genes decreased with cephalosporin transport in both cell lines. The decrease occurred in the RPTEC cell line earlier than in the HEK293 cell line. The authors observed caspase 3 and caspase 7 activation only in the RPTEC cell line after incubation with cefuroxime and cefepime at low concentrations (50 and 30 µg/mL, respectively) for 72 hours and at high concentrations (150 and 120 µg/mL, respectively) for 24 hours.Conclusions. The RPTEC cell line exhibits higher susceptibility to cefuroxime and cefepime toxic effects than the HEK293 cell line due to higher transporter gene expression. Higher cephalosporin concentrations accelerate caspase 3 and caspase 7 activation in the RPTEC cell line. The experimental model based on the RPTEC cell line is a promising tool for the analysis of the nephrotoxic properties of a wide range of medicinal products

Determination of the Degree of Unsaturation in Essential Oils

Being widely used, medicinal products based on vegetable oils require strict regulation and evaluation of quality attributes, determination of shelf-life periods, and monitoring of storage conditions. The most common testing method for unsaturated compounds in vegetable oils is the iodine value determination, which has a range     of limitations. An alternative method for determining the degree of unsaturation is based on epoxidation.The aim of the study was to evaluate the possibility of determining the degree of unsaturation of terpenoids and essential oils using peroxycarboxylic acids.Materials and methods. The authors performed epoxidation of linalool, myrcene, and lemon oil with peroxydecanoic and peroxyoctanoic acids, followed by iodometric titration of the excess acid.Results. The study demonstrated the possibility of measuring the degree of unsaturation of the selected essential oil and terpenoids using peracid epoxidation.   The authors developed a procedure for determining the iodine value of essential oils and calculated the iodine values of linalool, myrcene, and lemon oil. Epoxidation proceeded as a second-order reaction. The authors obtained the following reaction rate constants: 3.9 L×mol–1×min–1 for linalool (298 К), 1.76 L×mol–1×min–1 for myrcene converting to monoxide (298 К), 0.044 L×mol–1×min–1 for myrcene epoxide converting to diepoxide (298 К), and 3.9 L×mol–1×min–1 for lemon oil (297 К).Conclusions. The suggested procedure involving peracid titration for rapid and efficient determination of the degree of unsaturation (iodine value) provides a potential basis for developing a quantification method for total unsaturated bioactive compounds in essential oils

Nephrotoxicity Biomarkers: Role and Significance in the Diagnosis of Drug-Induced Kidney Injury

Drug-induced kidney injury (DIKI) accounts for 8 to 60% of episodes of acute kidney injury (AKI) among hospital patients. Early DIKI detection and timely adjustment of therapy will help reduce the kidney injury incidence and mortality. The aim of the study was to analyse scientific literature on the biomarkers used in DIKI diagnosis. The study revealed that the use of such kidney damage markers as serum creatinine, urinary output, urea nitrogen, sodium excretion, urinary sediment microscopy is limited because they do not give a full picture of the kidney injury degree and progression and do not allow for early AKI diagnosis. It was demonstrated that some of the most promising biomarkers are KIM-1, L-FABP, NAG, NGAL, cystatin C, clusterin, β2-microglobulin, МСР-1, IGFBP7, and TIMP-2. However, recommendations for determination of these biomarkers’ urine or blood concentrations for AKI diagnosis are somewhat preliminary, because there have been insufficient clinical and preclinical studies to establish validity of such tests. No precise algorithms based on determination of the biomarkers levels in urea and/or blood serum have been developed for AKI risk assessment, diagnosis, monitoring, and treatment. Thus, further research is necessary to investigate different AKI biomarkers and improve experimental models (both in vivo and in vitro), which will support assessment of potential nephrotoxic properties of existing and new medicinal products

NMR Spectroscopy Study of the Effect of the Molecular Mass of Hypromellose Phthalate on Its Solubility

Scientific relevance. Hypromellose phthalate is used in enteric coatings for oral medicinal products. The proportion of phthalate groups in the polymer is standardised because it has a significant effect on solubility. Whereas, the molecular mass of hypromellose phthalate is not controlled, and its impact on solubility in media with different pH values is understudied.Aim. The study aimed to employ NMR spectroscopy to investigate the effect the molecular mass of hypromellose phthalate may have on the dissolution kinetics at the pH value declared by the polymer manufacturer.Materials and methods. The study analysed hypromellose phthalate isolated from proton-pump inhibitor enteric coatings and the hypromellose phthalate reference standard. The molecular mass of the polymer was estimated by diffusion-ordered NMR spectroscopy (DOSY) with polyethylene glycols of known molecular masses for calibration. The authors studied the dissolution profiles of hypromellose phthalates of different molecular masses using 1H NMR spectra.Results. The authors developed a procedure for estimating the average molecular mass of hypromellose phthalate by DOSY. The procedure showed variations in the molecular mass of the polymer in the test samples; the molecular mass scatter amounted to 10 kDa. The dissolution profile of the test samples in an aqueous buffer solution (pH 5.59) was described by a linear function during the first hour. The slope characterising the dissolution rate varied from 10° to 36°.Conclusions. The variation in the molecular mass of hypromellose phthalate significantly affects the dissolution rate of the test samples. The function of the dissolution rate against the molecular mass of hypromellose phthalate is non-linear. The article provides a compelling reason for further research to derive a correlation equation for the dissolution rate of hypromellose phthalate as a function of two variables (molecular mass and proportion of phthalate groups in the polymer)

Vitrification of a monatomic 2D simple liquid

A monatomic simple liquid in two dimensions, where atoms interact isotropically through the Lennard-Jones-Gauss potential [M. Engel and H.-R. Trebin, Phys. Rev. Lett. 98, 225505 (2007)], is vitrified by the use of a rapid cooling technique in a molecular dynamics simulation. Transformation to a crystalline state is investigated at various temperatures and the time-temperature-transformation (TTT) curve is determined. It is found that the transformation time to a crystalline state is the shortest at a temerature 14% below the melting temperature Tm and that at temperatures below Tv = 0.6 Tm the transformation time is much longer than the available CPU time. This indicates that a long-lived glassy state is realized for T < Tv.Comment: 5pages,5figures,accepted for publication in CEJ

ТЕОРЕТИЧЕСКОЕ ОБОСНОВАНИЕ НАПРАВЛЕННОГО ТРАНСПОРТА БИОЛОГИЧЕСКИ АКТИВНЫХ КОМПОНЕНТОВ В УСЛОВИЯХ МОДЕЛИРУЕМОГО ЖЕЛУДОЧНО-КИШЕЧНОГО ТРАКТА

In this paper, the results of studies on the release of biological active compounds from their encapsulated forms under conditions of enzymatic hydrolysis in vitro are presented. In the phase of the model «small intestine» swelling of the capsules and their subsequent decay occurs, which allows to speak about the controlled release of encapsulated bioactive components. It was revealed that almost 90 % of the residual quantity of essential ingredients was released from the capsules in the model phase of the artificial «small intestine». At the end of the experiment, the capsules released all the encapsulated biologically active substances, regardless of the content of fish oil and phenolic compounds in them. It was noted that the poly-capsules had the greatest propensity to withstand the aggressive environment of the «model stomach» and concentrate in themselves the maximum amount of biologically active substances. Mathematical modeling confirms the direct transport of biologically active compounds and the role of the swelling of capsules in the release of biologically active compounds. two mathematical models describing the classical theory of diffusion from capsules and incorporating the material relaxation coefficient demonstrate a combination of empirical and theoretical approaches in controlling the properties of encapsulated biologically active substances. the obtained data are promising in the field of development of improved and functional food products, as well as the dry ingredients and concentrates В работе приведены результаты исследований по изучению высвобождения биологических активных соединений из их инкапсулированных форм в условиях ферментативного гидролиза in vitro. В фазе модельного «кишечника» происходит набухание капсул и их последующий распад, что позволяет говорить о контролируемом высвобождении инкапсулированных биоактивных компонентов. Выявлено, что почти 90% от остаточного количества эссенциальных ингредиентов было высвобождено из капсул в модельной фазе «искусственного кишечника». В конце эксперимента капсулы высвобождали все инкапсулированные биологически активные вещества, независимо от содержания в них рыбьего жира и фенольных соединений.Отмечено, что полислойные капсулы имели наибольшую склонность противостоять агрессивной среде «модельного желудка» и сконцентрировать в себе максимальное количество биологически активных веществ. Математическое моделирование подтверждает направленный транспорт биологически активных соединений и роль набухания капсул в высвобождении биологически активных соединений. Две математические модели, описывающие классическую теорию диффузии из капсул и с включением коэффициента релаксации материалов, демонстрируют комбинацию эмпирического и теоретического подходов в управлении свойств инкапсулированных биологически активных веществ. Полученные данные перспективны в области разработки улучшенных и функциональных продуктов питания, а также сухих ингредиентов и концентратов.