Synthesis of Cyclopentenone Isoprostanes and Highly Functionalized Cyclopentanes

Cyclopentane ring itself or as an element of bicyclic or polycyclic systems is not only ubiquitous in nature but also an increasingly recognized structural motif for biomedical research and drug discovery. In this context, the first part of the thesis describes our efforts towards synthetic analogs of a natural epoxy cyclopentenone isoprostane known to possess anti-inflammatory bioactivity. Employing reported strategies seven novel cyclopentenone isoprostanes were provided to our collaborators to examine their bioactivity. Additionally, preliminary studies demonstrated that the analog bearing an azide functionality could be labeled with an alkyne-containing cyanine (Cy5) and thus could serve as a valuable tool to further study the signaling pathway of related isoprostanes. While numerous methodologies have been developed for the synthesis of this structural entity, the employment of known strategies to access relevant structural analogs can still be tedious and challenging. Acknowledging that, the second part of the thesis covers our investigations towards the use of vinylboron derivatives in radical-mediated [3 + 2] annulation reactions. The development of an efficient route giving access to 1,1-diborylethene in gram scale allowed us to extend the scope of this reaction allowing the synthesis of substituted cyclopentanes flanked with two boronic ester moieties. The established processes are operationally simple, convergent, atom economical, and mild. Thus, the synthesis of cyclopentanes presenting sensitive functional groups is enabled. Additionally, the utility of the synthesized cyclopentane platforms was demonstrated by taking advantage of the presence of either the iodine atom, the boron atom(s), or both functionalities. These functionalization products include intriguing and applicable bicyclo[3.1.0]hexanes decorated with a boronic ester moiety, allylic gem-diboronates, and homoallyiodides among others, and are all easily accessible in one or two steps

LC-MS/MS method for simultaneous quantification of the first-line anti-tuberculosis drugs and six primary metabolites in patient plasma : Implications for therapeutic drug monitoring

Funding Information: This study was funded by the Latvian Council of Science. Project No: lzp-2020/1-0050. Publisher Copyright: © 2021 The AuthorsThe pharmacokinetic profiling of drug substances and corresponding metabolites in the biological matrix is one of the most informative tools for the treatment efficacy assessment. Therefore, to satisfy the need for comprehensive monitoring of anti-tuberculosis drugs in human plasma, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for simultaneous quantification of first-line anti-tuberculosis drugs (ethambutol, isoniazid, pyrazinamide, and rifampicin) along with their six primary metabolites. Simple single-step protein precipitation with methanol was chosen as the most convenient sample pre-treatment method. Chromatographic separation of the ten analyte mixture was achieved within 10 minutes on a reverse-phase C8 column using mobile phase gradient mode. The multiple reaction monitoring mode (MRM) was used for analyte detection and quantification in patient samples. The chosen quantification ranges fully covered expected plasma concentrations. The method exhibited acceptable selectivity; the within- and between-run accuracy ranged from 87.2 to 113.6%, but within- and between-run precision was between 1.6 and 14.9% (at the LLOQ level CV < 20%). Although the response of the isonicotinic acid varied depending on the matrix source (CV 21.8%), validation results proved that such inconsistency does not affect the accuracy and precision of results. If stored at room temperature plasma samples should be processed within 4 h after collection, temporary storage at −20 °C up to 24 h is acceptable due to stability issues of analytes. The developed method was applied for the patient sample analysis (n = 34) receiving anti-tuberculosis treatment with the first-line drugs.publishersversionPeer reviewe

Penetration of Wood Preservatives into Thermally Modified Birch and Pine Wood

The objective of the present study was to investigate the interaction between Cu-containing preservatives and birch (Betula spp.) and pine (Pinus sylvestris L.) wood, modified at a relatively mild temperatures (150 – 180ºC). The disposition of wood to absorb water was evaluated by capillary absorption (CA) tests through the specimens’ tangential and radial surface. Changes in wood drying characteristics due to thermal modification (TM) were evaluated by monitoring wood moisture dynamics after impregnation. In order to assess the capacity of wood to absorb preservatives, a vacuum/pressure process was used to impregnate small specimens for which uniform saturation into the entire volume can easily be reached. Quantitative determination of copper Cu content in the specimens was performed by using atomic absorption spectroscopy (AAS). The fixation of the absorbed Cu was evaluated by subjecting the specimens to leaching procedures according to EN 84 and assessing the ratio of retained Cu in the specimens. The CA test showed deceleration of capillary absorption in TM birch wood through both surfaces, with similar absorption rates regardless of treatment temperatures. A significant increase in the absorption rate through the tangential surface was recorded for TM pine wood and the increase was greater for specimens treated at higher temperatures. The results of moisture content monitoring showed a similar reduction in the drying rate due to thermal modification regardless of species. Comparing wood of one species with similar densities, less preservative was absorbed by TM wood. However, the results of AAS showed that, in comparison with unmodified wood, 10% (birch) and 25% (pine) more Cu per one gram of wood was introduced during impregnation. Nevertheless, TM also resulted in higher Cu leaching rates for both species

Effect of NAT2, GSTM1 and CYP2E1 genetic polymorphisms on plasma concentration of isoniazid and its metabolites in patients with tuberculosis, and the assessment of exposure-response relationships

Publisher Copyright: Copyright © 2024 Ulanova, Kivrane, Viksna, Pahirko, Freimane, Sadovska, Ozere, Cirule, Sevostjanovs, Grinberga, Bandere and Ranka.Objectives: Isoniazid is a key drug in the chemotherapy of tuberculosis (TB), however, interindividual variability in pharmacokinetic parameters and drug plasma levels may affect drug responses including drug induced hepatotoxicity. The current study investigated the relationships between isoniazid exposure and isoniazid metabolism-related genetic factors in the context of occurrence of drug induced hepatotoxicity and TB treatment outcomes.  Methods: Demographic characteristics and clinical information were collected in a prospective TB cohort study in Latvia ( N = 34). Time to sputum culture conversion (tSCC) was used as a treatment response marker. Blood plasma concentrations of isoniazid (INH) and its metabolites acetylisoniazid (AcINH) and isonicotinic acid (INA) were determined at three time points (pre-dose (0 h), 2 h and 6 h after drug intake) using liquid chromatography-tandem mass spectrometry. Genetic variations of three key INH-metabolizing enzymes (NAT2, CYP2E1, and GSTM1) were investigated by application PCR- and Next-generation sequencing-based methods. Depending on variables, group comparisons were performed by Student's t-test, one-way ANOVA, Mann-Whitney-Wilcoxon, and Kruskal-Wallis tests. Pearson correlation coefficient was calculated for the pairs of normally distributed variables; model with rank transformations were used for non-normally distributed variables. Time-to-event analysis was performed to analyze the tSCC data. The cumulative probability of tSCC was obtained using Kaplan-Meier estimators. Cox proportional hazards models were fitted to estimate hazard rate ratios of successful tSCC.  Results: High TB treatment success rate (94.1%) was achieved despite the variability in INH exposure. Clinical and demographic factors were not associated with either tSCC, hepatotoxicity, or INH pharmacokinetics parameters. Correlations between plasma concentrations of INH and its metabolites were NAT2 phenotype-dependent, while GSTM1 genetic variants did not showed any effects. CYP2E1*6 (T > A) allelic variant was associated with INH pharmacokinetic parameters. Decreased level of AcINH was associated with hepatotoxicity, while decreased values of INA/INH and AcINH/INH were associated with month two sputum culture positivity. Conclusion: Our findings suggest that CYP2E1, but not GSTM1, significantly affects the INH pharmacokinetics along with NAT2. AcINH plasma level could serve as a biomarker for INH-related hepatotoxicity, and the inclusion of INH metabolite screening in TB therapeutic drug monitoring could be beneficial in clinical studies for determination of optimal dosing strategies.Peer reviewe

Effect of NAT2, GSTM1 and CYP2E1 genetic polymorphisms on plasma concentration of isoniazid and its metabolites in patients with tuberculosis, and the assessment of exposure-response relationships

Objectives: Isoniazid is a key drug in the chemotherapy of tuberculosis (TB), however, interindividual variability in pharmacokinetic parameters and drug plasma levels may affect drug responses including drug induced hepatotoxicity. The current study investigated the relationships between isoniazid exposure and isoniazid metabolism-related genetic factors in the context of occurrence of drug induced hepatotoxicity and TB treatment outcomes.Methods: Demographic characteristics and clinical information were collected in a prospective TB cohort study in Latvia (N = 34). Time to sputum culture conversion (tSCC) was used as a treatment response marker. Blood plasma concentrations of isoniazid (INH) and its metabolites acetylisoniazid (AcINH) and isonicotinic acid (INA) were determined at three time points (pre-dose (0 h), 2 h and 6 h after drug intake) using liquid chromatography-tandem mass spectrometry. Genetic variations of three key INH-metabolizing enzymes (NAT2, CYP2E1, and GSTM1) were investigated by application PCR- and Next-generation sequencing-based methods. Depending on variables, group comparisons were performed by Student’s t-test, one-way ANOVA, Mann-Whitney-Wilcoxon, and Kruskal-Wallis tests. Pearson correlation coefficient was calculated for the pairs of normally distributed variables; model with rank transformations were used for non-normally distributed variables. Time-to-event analysis was performed to analyze the tSCC data. The cumulative probability of tSCC was obtained using Kaplan-Meier estimators. Cox proportional hazards models were fitted to estimate hazard rate ratios of successful tSCC.Results: High TB treatment success rate (94.1%) was achieved despite the variability in INH exposure. Clinical and demographic factors were not associated with either tSCC, hepatotoxicity, or INH pharmacokinetics parameters. Correlations between plasma concentrations of INH and its metabolites were NAT2 phenotype-dependent, while GSTM1 genetic variants did not showed any effects. CYP2E1*6 (T &gt; A) allelic variant was associated with INH pharmacokinetic parameters. Decreased level of AcINH was associated with hepatotoxicity, while decreased values of INA/INH and AcINH/INH were associated with month two sputum culture positivity.Conclusion: Our findings suggest that CYP2E1, but not GSTM1, significantly affects the INH pharmacokinetics along with NAT2. AcINH plasma level could serve as a biomarker for INH-related hepatotoxicity, and the inclusion of INH metabolite screening in TB therapeutic drug monitoring could be beneficial in clinical studies for determination of optimal dosing strategies

Easy Access to γ-Iodo-gem-Diborylated-Cyclopentanes and Bicyclic Cyclopropanes

A formal atom transfer radical [3+2] annulation (ATRAn) reaction between different homoallyl radical precursors and 1,1-diborylethene was developed. It provides a rapid access to polysubstituted cyclopentanes containing a gem-diboronic ester moiety. The synthetic utility of theses uniquely functionalized 5-membered rings is highlighted by their easy conversion to attractive borylated building blocks such as 1-borylated bicyclo[3.1.0]hexanes. The ATRAn reaction was extended to homopropagylic radicals giving access to unique allylic gem-diboronic esters that could be used in allylboration of aldehydes

Conditions Influencing Mould Growth for Effective Prevention of Wood Deterioration Indoors

Effective prevention of mould growth indoors is still an important topic considering that mould growth is frequently observed in buildings, it causes serious health hazards and can irreversibly damage infected objects. Several studies have been conducted and mould growth models developed. Despite that, some potentially important aspects such as water damage and spore contamination have received only little attention. The objective of the present study was to investigate the effect of the initial moisture content of wood and spore contamination on mould development indoors. The mould tests were performed in constant temperature (10, 20 and 30 &deg;C) and relative humidity (91% and 97%) conditions. The results show that wetting of wood specimens prior to the test significantly accelerates mould growth at a temperature of 10 &deg;C. For the other temperatures, the effect was insignificant. Similar results were obtained for the test involving dry (conditioned at RH 50%) and conditioned specimens (RH 91% or RH 97%). The results regarding initial spore contamination show that significantly longer periods are required for mould to develop without spore contamination at 10 &deg;C and 20 &deg;C, while at 30 &deg;C the effect is relatively small

Enhancing Thermally Modified Wood Stability against Discoloration

Thermal modification of wood has gained its niche in the production of materials that are mainly used for outdoor applications, where the stability of aesthetic appearances is very important. In the present research, spectral sensitivity to discoloration of thermally modified (TM) aspen wood was assessed and, based on these results, the possibility to delay discoloration due to weathering by non-film forming coating containing transparent iron oxides in the formulation was studied. The effect of including organic light stabilizers (UVA and HALS) in coatings as well as pretreatment with lignin stabilizer (HALS) was evaluated. Artificial and outdoor weathering was used for testing the efficiency of different coating formulations on TM wood discoloration. For color measurements and discoloration assessment, the CIELAB color model was used. Significant differences between the spectral sensitivity of unmodified and TM wood was observed by implying that different strategies could be effective for their photostabilization. From the studied concepts, the inclusion of the transparent red iron oxide into the base formulation of the non-film forming coating was found to be the most effective approach for enhancing TM wood photostability against discoloration due to weathering

Life cycle inventory for currently harvested birch roundwood

The knowledge of the environmental performance of different products and services is vital in the modern world because of the climate change and other environmental problems that we are facing. Life cycle assessment is a valuable tool that allows to determine the environmental performance and compare products and services with the same function. There is no doubt that the importance of forests is crucial in the environmental protection, despite that raw wood products (roundwood, pulpwood and fuelwood) are not carbon neutral as previously thought because of the human activities during forest management processes. Apart from climate change, production of raw wood products also contribute to other environmental impact categories: acidification, eutrophication, photochemical oxidant formation and abiotic resource depletion. Previous studies have shown that the life cycle inventory (LCI) data for raw wood products should be collected from the site-specific not from more generic sources because of the significant differences in several geography and technology related factors. However, less discussed are time-related factors, which should also be acknowledged especially because of the long growing time of trees. The main objective of the present study was to determine which forest management processes should be included in the LCI for currently harvested birch (Betula spp.) roundwood in Latvia and based on these results compile the required data for the LCI. The results of forest management history analysis showed that for currently produced birch roundwood only logging operations should be included in the system boundary. Subsystems such as seed production, seedling production and silvicultural operations were not practiced or had only minor impact due to low mechanization level in the past. By taking into account the time-related factors, the LCI was developed and can be used in further calculations of environmental impacts for different wood-based products that are manufactured from currently harvested birch roundwood

Borylated Cyclopentanes via Atom Transfer Radical [3+2] Annulation

Abstract. An atom transfer radical [3+2] annulation (ATRAn) reaction involving alkenyl boronic esters and homoallylic iodides provides a rapid access to polysubstituted borylated cyclopentanes. A variety of α-substituted vinylboronic esters are suitable substrates and offer unique opportunities for further modification of the formed 5-membered ring. For instance, the oxidation of the boronic ester to an alcohol allows to prepare products that corresponds to an annulation involving the enol form of acetone. Substitution of the iodide by a nucleophile such as lithium methoxide without modifying the boronic ester moiety is also feasible. Finally, by using a (3-acetoxyprop-1-en-2-yl)boronic ester, a facile 1,2-elimination reaction provided a methylenecyclopentane. In this case, the alkenylboronate radical trap acts as an equivalent to allene, a building block so far elusive for preparative radical reactions