Pharmacological differences between the optical isomers of ibuprofen: evidence for metabolic inversion of the (-)-isomer

Bioequivalence risk assessment of oral formulations containing racemic ibuprofen through a chiral physiologically based pharmacokinetic model of ibuprofen enantiomers

The characterization of the time course of ibuprofen enantiomers can be useful in the selection of the most sensitive analyte in bioequivalence studies. Physiologically based pharmacokinetic (PBPK) modelling and simulation represents the most efficient methodology to virtually assess bioequivalence outcomes. In this work, we aim to develop and verify a PBPK model for ibuprofen enantiomers administered as a racemic mixture with different immediate release dosage forms to anticipate bioequivalence outcomes based on different particle size distributions. A PBPK model incorporating stereoselectivity and non-linearity in plasma protein binding and metabolism as well as R-to-S unidirectional inversion has been developed in Simcyp®. A dataset composed of 11 Phase I clinical trials with 54 scenarios (27 per enantiomer) and 14,452 observations (7129 for R-ibuprofen and 7323 for S-ibuprofen) was used. Prediction errors for AUC0-t and Cmax for both enantiomers fell within the 0.8-1.25 range in 50/54 (93 %) and 42/54 (78 %) of scenarios, respectively. Outstanding model performance, with 10/10 (100 %) of Cmax and 9/10 (90 %) of AUC0-t within the 0.9-1.1 range, was demonstrated for oral suspensions, which strongly supported its use for bioequivalence risk assessment. The deterministic bioequivalence risk assessment has revealed R-ibuprofen as the most sensitive analyte to detect differences in particle size distribution for oral suspensions containing 400 mg of racemic ibuprofen, suggesting that achiral bioanalytical methods would increase type II error and declare non-bioequivalence for formulations that are bioequivalent for the eutomer.

The Role of the Transient Atropisomerism and Chirality of Flurbiprofen Unveiled by Laser-Ablation Rotational Spectroscopy

The combination of atropisomerism and chirality in flurbiprofen is shown to be relevant concerning its pharmacological activity. The two most stable conformers of a total of eight theoretically predicted for each R- or S- flurbiprofen enantiomers have been isolated in the cooling conditions of a supersonic jet and structurally characterized by laser ablation Fourier transform microwave spectroscopy. The detected conformers, whose structure is mainly defined by three dihedral angles, only differ in the sign of the phenyl torsion angle giving rise to S_a and R_a atropisomers. A comparison with the structures available for the R- and S- enantiomers complexed to COX isoforms reveals that the enzymes select only the S_a atropisomers, resulting in a diastereoisomer-specific recognition. The most stable gas phase conformer is exclusively selected when using the S- enantiomer while the second is recognized only for the R- enantiomer. These experimental results highlight the importance of atropisomerism in drug design.

An in silico analysis of Ibuprofen enantiomers in high concentrations of sodium chloride with SARS-CoV-2 main protease

2020 will be remembered worldwide for the outbreak of Coronavirus disease (COVID-19), which quickly spread until it was declared as a global pandemic. The main protease (Mpro) of SARS-CoV-2, a key enzyme in coronavirus, represents an attractive pharmacological target for inhibition of SARS-CoV-2 replication. Here, we evaluated whether the anti-inflammatory drug Ibuprofen, may act as a potential SARS-CoV-2 Mpro inhibitor, using an in silico study. From molecular dynamics (MD) simulations, we also evaluated the influence of ionic strength on the affinity and stability of the Ibuprofen-Mpro complexes. The docking analysis shows that R(-)Ibuprofen and S(+)Ibuprofen isomers can interact with multiple key residues of the main protease, through hydrophobic interactions and hydrogen bonds, with favourable binding energies (-6.2 and -5.7 kcal/mol, respectively). MM-GBSA and MM-PBSA calculations confirm the affinity of these complexes, in terms of binding energies. It also demonstrates that the ionic strength modifies significantly their binding affinities. Different structural parameters calculated from the MD simulations (120 ns) reveal that these complexes are conformational stable in the different conditions analysed. In this context, the results suggest that the condition 2 (0.25 NaCl) bind more tightly the Ibuprofen to Mpro than the others conditions. From the frustration analysis, we could characterize two important regions (Cys44-Pro52 and Linker loop) of this protein involved in the interaction with Ibuprofen. In conclusion, our findings allow us to propose that racemic mixtures of the Ibuprofen enantiomers might be a potential treatment option against SARS-CoV-2 Mpro. However, further research is necessary to determinate their possible medicinal use.Communicated by Ramaswamy H. Sarma.

Chiral Inversion of 2-Arylpropionic Acid Enantiomers under Anaerobic Conditions

This work examined the chiral inversion of 2-arylpropionic acids (2-APAs) under anaerobic conditions and the associated microbial community. The anaerobic condition was simulated by two identical anaerobic digesters. Each digester was fed with the substrate containing 11 either pure (R)- or pure (S)-2-APA enantiomers. Chiral inversion was evidenced by the concentration increase of the other enantiomer in the digestate and the changes in the enantiomeric fraction between the two enantiomers. Both digesters showed similar and poor removal of 2-APAs (≤30%, except for naproxen) and diverse chiral inversion behaviors under anaerobic conditions. Four compounds exhibited (S → R) unidirectional inversion [flurbiprofen, ketoprofen, naproxen, and 2-(4-tert-butylphenyl)propionic acid], and the remaining seven compounds showed bidirectional inversion. Several aerobic and facultative anaerobic bacterial genera (Candidatus Microthrix, Rhodococcus, Mycobacterium, Gordonia, and Sphingobium) were identified in both digesters and predicted to harbor the 2-arylpropionyl-CoA epimerase (enzyme involved in chiral inversion) encoding gene. These genera presented at low abundances, <0.5% in the digester dosed with (R)-2-APAs and <0.2% in the digester dosed with (S)-2-APAs. The low abundances of these genera explain the limited extent of chiral inversion observed in this study.

Expanding Access to Optically Active Non-Steroidal Anti-Inflammatory Drugs via Lipase-Catalyzed KR of Racemic Acids Using Trialkyl Orthoesters as Irreversible Alkoxy Group Donors

Studies into the enzymatic kinetic resolution (EKR) of 2-arylpropanoic acids (‘profens’), as the active pharmaceutical ingredients (APIs) of blockbuster non-steroidal anti-inflammatory drugs (NSAIDs), by using various trialkyl orthoesters as irreversible alkoxy group donors in organic media, were performed. The enzymatic reactions of target substrates were optimized using several different immobilized preparations of lipase type B from the yeast Candida antarctica (CAL-B). The influence of crucial parameters, including the type of enzyme and alkoxy agent, as well as the nature of the organic co-solvent and time of the process on the conversion and enantioselectivity of the enzymatic kinetic resolution, is described. The optimal EKR procedure for the racemic profens consisted of a Novozym 435-STREM lipase preparation suspended in a mixture of 3 equiv of trimethyl or triethyl orthoacetate as alkoxy donor and toluene or n-hexane as co-solvent, depending on the employed racemic NSAIDs. The reported biocatalytic system provided optically active products with moderate-to-good enantioselectivity upon esterification lasting for 7–48 h, with most promising results in terms of enantiomeric purity of the pharmacologically active enantiomers of title APIs obtained on the analytical scale for: (S)-flurbiprofen (97% ee), (S)-ibuprofen (91% ee), (S)-ketoprofen (69% ee), and (S)-naproxen (63% ee), respectively. In turn, the employment of optimal conditions on a preparative-scale enabled us to obtain the (S)-enantiomers of: flurbiprofen in 28% yield and 97% ee, ibuprofen in 45% yield and 56% ee, (S)-ketoprofen in 23% yield and 69% ee, and naproxen in 42% yield and 57% ee, respectively. The devised method turned out to be inefficient toward racemic etodolac regardless of the lipase and alkoxy group donor used, proving that it is unsuitable for carboxylic acids possessing tertiary chiral centers.

Preclinical Investigations to Explore the Difference between the Diastereomers [177Lu]Lu-SibuDAB and [177Lu]Lu-RibuDAB toward Prostate Cancer Therapy

[¹⁷⁷Lu]Lu-Ibu-DAB-PSMA, a radioligand modified with ibuprofen as the albumin binder, showed higher accumulation in PSMA-positive tumors of mice than the clinically used [¹⁷⁷Lu]Lu-PSMA-617 but lower retention in non-targeted tissues than previously developed albumin-binding PSMA radioligands. The aim of this study was to investigate whether the stereochemistry of the incorporated ibuprofen affects the radioligand's in vitro and in vivo properties and to select the more favorable radioligand for further development. For this purpose, SibuDAB and RibuDAB containing (S)- and (R)-ibuprofen, respectively, were synthesized and labeled with lutetium-177. In vitro, the two isomers had similar properties; however, [¹⁷⁷Lu]Lu-SibuDAB showed increased binding to mouse and human plasma proteins (91 ± 1 and 88 ± 2%, respectively) compared to [¹⁷⁷Lu]Lu-RibuDAB (75 ± 2 and 79 ± 2%, respectively). In vivo, [¹⁷⁷Lu]Lu-SibuDAB was metabolically more stable than [¹⁷⁷Lu]Lu-RibuDAB with ∼90 vs ∼67% intact radioligand detected in the blood at 4 h post injection (p.i.). In line with the lower albumin-binding affinity, the blood clearance of [¹⁷⁷Lu]Lu-RibuDAB in mice was considerably faster [27% of injected activity (% IA), 1 h p.i.] than for [¹⁷⁷Lu]Lu-SibuDAB (50% IA, 1 h p.i.). Time-dependent biodistribution studies performed in tumor-bearing athymic nude mice showed high PSMA-specific tumor uptake for both isomers. A twofold increased area under the curve (AUC_0→8d) of the blood retention was determined for [¹⁷⁷Lu]Lu-SibuDAB as compared to [¹⁷⁷Lu]Lu-RibuDAB, whereas the kidney AUC_0→8d value of [¹⁷⁷Lu]Lu-SibuDAB was only half as high as for [¹⁷⁷Lu]Lu-RibuDAB. As a result, a more favorable tumor-to-kidney AUC_0→8d ratio was obtained for [¹⁷⁷Lu]Lu-SibuDAB, which was also visualized on SPECT/CT images. Based on its improved kidney clearance and higher metabolic stability, [¹⁷⁷Lu]Lu-SibuDAB was selected as the more favorable radioligand. Therapy studies performed with [¹⁷⁷Lu]Lu-SibuDAB (5 MBq/mouse) demonstrated the anticipated therapeutic superiority over the current gold-standard [¹⁷⁷Lu]Lu-PSMA-617 (5 MBq/mouse). The significantly increased survival time of mice treated with [¹⁷⁷Lu]Lu-SibuDAB as compared to those injected with [¹⁷⁷Lu]Lu-PSMA-617 justifies further development of this novel radioligand toward clinical application.

Stereoselectivity of Interaction of Nonsteroidal Anti-Inflammatory Drug S-Ketoprofen with L/D-Tryptophan in Phospholipid Membranes

The mechanisms of stereoselectivity of the interaction of chiral drugs with active sites of enzymes and cell receptors attract significant attention. The first reason is the difference in therapeutic activity of the enantiomers of the common drugs. Another reason is the interest in the role of chiral inversion of amino acids involved in various peptides in the development of many diseases including Alzheimer’s, Parkinson’s, type II diabetes, and a number of other pathological conditions. In our study we use elementary chemical process—electron transfer (ET) to simulate individual stages of ligand–receptor and enzyme–substrate interactions. In particular, previous studies of photoinduced ET in chiral donor-acceptor dyads consisting of the nonsteroidal anti-inflammatory drug (R/S)-ketoprofen and (L)-tryptophan show the stereo and spin selectivity of ET in diastereomers. The present study is devoted to the interaction of (S)-ketoprofen with L- and D-enantiomers of tryptophan in homogeneous aqueous solution and in phospholipid membranes. The study was done using the NMR technique and molecular modeling. These approaches confirm efficient penetration of ketoprofen into the lipid bilayer and binding with tryptophan molecule. The short-lived paramagnetic intermediates formed during the photoinduced ET from electron donor tryptophan to ketoprofen have been detected using the chemically induced dynamic nuclear polarization (CIDNP) technique. It was found that S-ketoprofen interacts stereoselectively with tryptophan enantiomers in the lipid membrane. The formation of the ketyl radical of ketoprofen under irradiation leads to the oxidation of membrane lipids and may be the cause of ketoprofen phototoxicity. However, in contrast to a homogeneous solution in phosphate buffer saline, where the amino acid tryptophan accelerates the photodecomposition of KP due to intramolecular hydrogen transfer, tryptophan in a lipid membrane significantly reduces the rate of photodegradation due to a reversible electron (or hydrogen) transfer reaction. The stereoselectivity in the rate of KP and lipids decomposition under UV irradiation of S-ketoprofen in the presence of tryptophan enantiomers in lipid bilayer has been detected.

Xylitol as a Hydrophilization Moiety for a Biocatalytically Synthesized Ibuprofen Prodrug

Biocatalyzed synthesis can be exploited to produce high-value products, such as prodrugs. The replacement of chemical approaches with biocatalytic processes is advantageous in terms of environmental prevention, embracing the principles of green chemistry. In this work, we propose the covalent attachment of xylitol to ibuprofen to produce an IBU-xylitol ester prodrug. Xylitol was chosen as a hydrophilizer for the final prodrug, enhancing the water solubility of ibuprofen. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) extensively used as an analgesic, anti-inflammatory, and antipyretic. Despite being the third-most-prescribed medicine in the world, the aqueous solubility of ibuprofen is just 21 mg/L. This poor water solubility greatly limits the bioavailability of ibuprofen. We aimed to functionalize ibuprofen with xylitol using the reusable immobilized N435 biocatalyst. Instead of a biphasic media, we proposed a monophasic reaction environment. The characterization of the IBU-xylitol ester was performed by ¹H, ¹³C-NMR, DEPT, COSY, HMQC, HMBC, FTIR, and MS spectroscopy. Preliminary in vitro tests showed that this enzymatically synthesized prodrug of ibuprofen reduced the expression of the interleukin 8 genes in human bronchial epithelial cells (IB3-1) from cystic fibrosis (CF) patients.

Is it possible to predict the stability of a crystal structure under the influence of pressure? Quantum chemical study of ibuprofen crystals

Quantum chemical modeling was used to analyze the crystalline structure of ibuprofen under atmospheric pressure to determine the structural features, providing its stability under pressure.

Scalemic mixtures preparation for optimized composition of ibuprofen solid dosage forms

The stable and metastable phase diagrams between the sinister and the rectus ibuprofen enantiomers were established by means of thermal analysis and X-ray powder diffraction experiments as a function of temperature. The results obtained allow proving for the first time the existence, for the stable system, of a solid solution by mixing the racemic ibuprofen with one of its enantiomers for low concentration of the enantiomer. Since the rectus ibuprofen is a non-active pharmaceutical agent which can be partially bio-converted into the sinister enantiomer, the present work offers a new approach for scalemic mixtures preparation in order to improve the benefit/risk ratio related to ibuprofen solid dosage form administration.

Chemical derivatization in combination with supercritical fluid chromatography to improve resolution of stereoisomers

Aim: Quantification of stereoisomers in biological matrices is of pivotal importance for drug development. Supercritical fluid chromatography paired with chiral stationary phases is the gold standard for resolution of enantiomers. However, this technique often proves inadequate for resolution of polar stereoisomers. Materials & methods: A combination of achiral chemical derivatization with supercritical fluid chromatography using chiral stationary columns to improve enantiomeric resolution is described. Results: Separation of four possible stereoisomers of linerixibat was achieved after derivatization with 3N HCl in n-butanol within 12 min (case1). Derivatization with acetic, propionic, butyric, isobutyric, valeric and isovaleric anhydrides significantly improved the separation of stereoisomers (case 2 and 3) within 10 min. The best stereoisomeric resolution was achieved using valeric and isovaleric anhydrides.

Ibuprofen-based advanced therapeutics: breaking the inflammatory link in cancer, neurodegeneration, and diseases

Ibuprofen is a classical nonsteroidal anti-inflammatory drug (NSAID) highly prescribed to reduce acute pain and inflammation under an array of conditions, including rheumatoid arthritis, osteoarthritis, dysmenorrhea, and gout. Ibuprofen acts as a potential inhibitor for cyclooxygenase enzymes (COX-1 and COX-2). In the past few decades, research on this small molecule has led to identifying other possible therapeutic benefits. Anti-tumorigenic and neuroprotective functions of Ibuprofen are majorly recognized in recent literature and need further consideration. Additionally, several other roles of this anti-inflammatory molecule have been discovered and subjected to experimental assessment in various diseases. However, the major challenge faced by Ibuprofen and other drugs of similar classes is their side effects, and tendency to cause gastrointestinal injury, generate cardiovascular risks, modulate hepatic and acute kidney diseases. Future research should also be conducted to deduce new methods and approaches of suppressing the unwanted toxic changes mediated by these drugs and develop new therapeutic avenues so that these small molecules continue to serve the purposes. This article primarily aims to develop a comprehensive and better understanding of Ibuprofen, its pharmacological features, therapeutic benefits, and possible but less understood medicinal properties apart from major challenges in its future application.KEY POINTSIbuprofen, an NSAID, is a classical anti-inflammatory therapeutic agent.Pro-apoptotic roles of NSAIDs have been explored in detail in the past, holding the key in anti-cancer therapies.Excessive and continuous use of NSAIDs may have several side effects and multiple organ damage.Hyperactivated Inflammation initiates multifold detrimental changes in multiple pathological conditions.Targeting inflammatory pathways hold the key to several therapeutic strategies against many diseases, including cancer, microbial infections, multiple sclerosis, and many other brain diseases.

Biocatalytic Approach for Direct Esterification of Ibuprofen with Sorbitol in Biphasic Media

Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) introduced in the 1960s and widely used as an analgesic, anti-inflammatory, and antipyretic. In its acid form, the solubility of 21 mg/L greatly limits its bioavailability. Since the bioavailability of a drug product plays a critical role in the design of oral administration dosage, this study investigated the enzymatic esterification of ibuprofen as a strategy for hydrophilization. This work proposes an enzymatic strategy for the covalent attack of highly hydrophilic molecules using acidic functions of commercially available bioactive compounds. The poorly water-soluble drug ibuprofen was esterified in a hexane/water biphasic system by direct esterification with sorbitol using the cheap biocatalyst porcine pancreas lipase (PPL), which demonstrated itself to be a suitable enzyme for the effective production of the IBU-sorbitol ester. This work reports the optimization of the esterification reaction.

Investigation of isomerization of dexibuprofen in a ball mill using chiral capillary electrophoresis

Besides the racemate, the S-enantiomer of ibuprofen (Ibu) is used for the treatment of inflammation and pain. Since the configurational stability of S-Ibu in solid state is of interest, it was studied by means of ball milling experiments. For the evaluation of the enantiomeric composition, a chiral CE method was developed and validated according to the ICH guideline Q2(R1). The addition of Mg²⁺ , Ca²⁺ , or Zn²⁺ ions to the background electrolyte (BGE) was found to improve Ibu enantioresolution. Chiral separation of Ibu enantiomers was achieved on a 60.2 cm (50.0 cm effective length) x 75 μm fused-silica capillary using a background electrolyte (BGE) composed of 50 mM sodium acetate, 10 mM magnesium acetate tetrahydrate, and 35 mM heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD) as chiral selector. The quantification of R-Ibu in the mixture was performed using the normalization procedure. Linearity was evaluated in the range of 0.68-5.49% R-Ibu (R² = 0.999), recovery was found to range between 97 and 103%, the RSD of intra- and interday precision below 2.5%, and the limit of quantification for R- in S-Ibu was calculated to be 0.21% (extrapolated) and 0.15% (dilution of racemic ibuprofen), respectively. Isomerization of S-Ibu was observed under basic conditions by applying long milling times and high milling frequencies.

Recovery of Active Pharmaceutical Ingredients from Unused Solid Dosage-Form Drugs

The concept of drug recycle by recovering active pharmaceutical ingredients (APIs) from unused tablets and capsules was demonstrated using acetaminophen, tetracycline HCl, and (R,S)-(±)-ibuprofen as case examples. The recovery process comprised three core unit operations: solid-liquid extraction, filtration, and crystallization. Recovery yields of 58.7 wt %, 73.1 wt %, and 67.6 wt % for acetaminophen, tetracycline HCl, and (R,S)-(±)-ibuprofen were achieved, respectively. More importantly, all of the APIs were of high purity based on high-performance liquid chromatography assay. The crystal forms of the recovered APIs were in conformity with the standards.

Magnetic Levitation in Chemistry, Materials Science, and Biochemistry

All matter has density. The recorded uses of density to characterize matter date back to as early as ca. 250 BC, when Archimedes was believed to have solved "The Puzzle of The King's Crown" using density.^[1] Today, measurements of density are used to separate and characterize a range of materials (including cells and organisms), and their chemical and/or physical changes in time and space. This Review describes a density-based technique-magnetic levitation (which we call "MagLev" for simplicity)-developed and used to solve problems in the fields of chemistry, materials science, and biochemistry. MagLev has two principal characteristics-simplicity, and applicability to a wide range of materials-that make it useful for a number of applications (for example, characterization of materials, quality control of manufactured plastic parts, self-assembly of objects in 3D, separation of different types of biological cells, and bioanalyses). Its simplicity and breadth of applications also enable its use in low-resource settings (for example-in economically developing regions-in evaluating water/food quality, and in diagnosing disease).

Chiral bioanalytical methods in bioequivalence studies of intravenous vs. oral formulations of ibuprofen

According to the Ibuprofen Product-Specific Bioequivalence Guidance of the European Medicines Agency, achiral bioanalytical methods are considered acceptable for demonstration of bioequivalence of ibuprofen-containing products. The aim of this investigation is to compare the bioequivalence outcomes obtained with individual R and S ibuprofen enantiomers and the sum of both enantiomers from bioequivalence studies in which new intravenous ibuprofen products were compared with oral ibuprofen products. Bioequivalence was assessed for S and R enantiomers of ibuprofen and the sum of both enantiomers, which was calculated to represent the results that would have been obtained with an achiral assay. The infusion rates of 15, 20, and 30 minutes modify the maximum concentration (C_max ) of the intravenous administrations. In contrast, the time when the maximum concentration is observed (T_max ) was insensitive to detect differences in input rate within this range of infusion times. The eutomer S-ibuprofen is the least sensitive analyte to detect differences in input rate; therefore, the regulatory acceptance of achiral bioanalytical methods for ibuprofen bioequivalence studies is justified because the sum of both enantiomers is more discriminative than the chiral methods where only the eutomer is used for regulatory decisions.

Dissecting intermolecular interactions in the condensed phase of ibuprofen and related compounds: the specific role and quantification of hydrogen bonding and dispersion forces

Ibuprofen is a well-established non-steroidal anti-inflammatory drug, inhibiting the prostaglandin-endoperoxide synthase. One of the key features defining the ibuprofen structure is the doubly intermolecular O-HO[double bond, length as m-dash]C hydrogen bond in cyclic dimers as know from carboxylic acids and confirmed by X-ray analysis. Until now, there was neither information about the vaporization enthalpy of ibuprofen nor about how this thermal property is determined by the subtle balance between different types of intermolecular interaction. In this study we derive the vaporization enthalpy of ibuprofen from thermochemical experiments to be . We dissected the hydrogen bond energy, EHB = 45.0 kJ mol-1, exclusively from measured vaporization enthalpies of related aliphatic carboxylic acids, their homomorph methyl esters and alkyl acetates, respectively. This contribution from hydrogen bonding could be confirmed almost quantitatively from quantum chemical calculations of ibuprofen clusters, which also suggest dispersion interaction of similar order (Edisp = 47 kJ mol-1). Following the full analysis of the gas-vapor transition enthalpy, we studied the changing structural components from the solid to the liquid phase of ibuprofen by means of Attenuated Total Reflection Infrared (ATR-IR) spectroscopy. The cyclic dimers as observed in the X-ray patterns are essentially preserved in the liquid state just above the melting point. However, with increasing temperature the doubly hydrogen-bonded cyclic dimers are replaced by singly hydrogen-bonded linear dimers in the liquid ibuprofen. The transfer enthalpy from the temperature-dependent equilibria of both dimers as obtained from the IR intensity ratios of the vibrational bands quantifies for the first time the energy of the released, single hydrogen bond to be EHB = 21.0 kJ mol-1. Overall, we show that a combination of thermodynamics, infrared spectroscopy and quantum chemistry provides quantification and detailed understanding of structure and molecular interaction in ibuprofen and related compounds.

Stereoisomeric profiling of chiral pharmaceutically active compounds in wastewaters and the receiving environment - A catchment-scale and a laboratory study

Chiral pharmaceutically active compounds (cPACs) are not currently governed by environmental regulation yet are expected to be in the future. As cPACs can exert stereospecific toxicity in the aquatic environment, it is essential to better understand their stereoselective behaviour here. Therefore, this study aims to provide a new perspective towards comprehensive evaluation of cPACs at a river catchment level, including their stereochemistry as a chemical phenomenon driving fate of chiral molecules in the environment. A large spatial and temporal monitoring program was performed in Southwest England. It included 5 sewage treatment works and the receiving waters of the largest river catchment in Southwest England. Simultaneously, lab-scale microcosm studies in simulated activated sludge bioreactors and river water microcosm were performed to evaluate stereoselective degradation of cPACs. A multi-residue enantioselective method allowed the analysis of a total of 18 pairs of enantiomers and 3 single enantiomers in wastewater and river water samples. Our monitoring program revealed: (1) spatial and temporal variations of cPACs in influent wastewaters resulting from different patterns of usage as well as an (2) enantiomeric enrichment of cPACs, likely due to human metabolism, despite their commercialization as racemic mixtures. A similar chiral signature was observed in effluent and receiving waters. Stereoselective degradation was observed in trickling filters (TF) for naproxen, ketoprofen, cetirizine and 10,11-dihydroxy-10-hydroxycarbamazepine, in sequencing batch reactors (SBR) for ifosfamide and in activated sludge (AS) for cetirizine. The extent of enantiomer-specific fate was wastewater treatment dependent in the case of naproxen (TF showed higher stereoselectivity than AS and SBR) and cetirizine (TF and AS showed higher stereoselectivity than SBR) due to differing microbial population. Furthermore, stereoselective degradation of naproxen was highly variable among STWs using similar treatments (TF) and operating in the same region. Microbial stereoselective degradation was also confirmed by both activated and river water simulated microcosm for chloramphenicol, ketoprofen, indoprofen, naproxen and 10,11-dihydroxy-10-hydroxycarbamazepine. Results from our large scale river catchment monitoring study and lab simulated microcosm show wide-ranging implications of enantiomerism of cPACs on environmental risk assessment (ERA). As two enantiomers of the same compound show different biological effects (e.g. toxicity), their non-racemic presence in the environment might lead to inaccurate ERA. This is because current ERA approaches do not require analysis at enantiomeric level.

Simultaneous Determination of Over-the-Counter Pain Relievers in Commercial Pharmaceutical Products Utilizing Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) Multivariate Calibration Model

The quality of over-the-counter (OTC) pain relievers is important to ensure the safety of the marketed products in order to maintain the overall health care of patients. In this study, the multivariate curve resolution-alternating least squares (MCR-ALS) chemometric method was developed and validated for the resolution and quantification of the most commonly consumed OTC pain relievers (acetaminophen, acetylsalicylic acid, ibuprofen, naproxen, and caffeine) in commercial drug formulations. The analytical performance of the developed chemometric methods such as root mean square error of prediction, bias, standard error of prediction, relative error of prediction, and coefficients of determination was calculated for the developed model. The obtained results are linear with concentration in the range of 0.5-7 μg/mL for acetaminophen and 0.5-3.5 and 0.5-3 μg/mL for naproxen and caffeine, respectively, while the linearity ranges for acetyl salicylic acid and ibuprofen were 1-15 μg/mL. High values of coefficients of determination ≥0.9995 reflected high predictive ability of the developed model. Good recoveries ranging from 98.0% to 99.7% were obtained for all analytes with relative standard deviations (RSDs) not higher than 1.62%. The optimized method was successfully applied for the analysis of the studied drugs either in their single or coformulated pharmaceutical products without any separation step. The optimized method was also compared with a reported HPLC method using paired t-test and F-ratio at 95% confidence level, and the results showed no significant difference regarding accuracy and precision. The developed method is eco-friendly, simple, fast, and amenable for routine analysis. It could be used as a cost-effective alternative to chromatographic techniques for the analysis of the studied drugs in commercial formulations.

Upcycling a plastic cup: one-pot synthesis of lactate containing metal organic frameworks from polylactic acid

A visual representation of waste PLA being upcycled to a lactate containing MOF, ZnBLD–dPLA.

Femtosecond Vibrational Sum-Frequency Generation Spectroscopy of Chiral Molecules in Isotropic Liquid

Vibrationally resonant optically active (VOA) sum-frequency generation (SFG) is a second-order nonlinear process sensitive to the stereospecific vibrational structure of chiral molecules. We demonstrate that a femtosecond VOA SFG signal can be measured in the isotropic bulk of a chiral liquid. The chiral, achiral, and VOA SFG spectra of R- and S-limonene and their racemic mixture in the C-H stretching frequency region are characterized. In particular, it is shown that the observed circular intensity difference (CID) signal, which can provide distinguishable stereochemical vibrational information between enantiomers, arises from interference of the electric-dipole allowed antisymmetric Raman tensor-induced and Raman optical activity (ROA) tensor-induced SFG fields. Furthermore, we show that the CID and linear polarization intensity difference (LID) SFG spectra are connected to the real and imaginary parts of the effective chiral VOA SFG susceptibility, respectively. We anticipate that the present technique will be of use in transient chiroptical spectroscopy and stereochemical vibrational imaging studies.

Essential chemistry for biochemists

Within every living organism, countless reactions occur every second. These reactions typically occur more rapidly and with greater efficiency than would be possible under the same conditions in the chemical laboratory, and while using only the subset of elements that are readily available in nature. Despite these apparent differences between life and the laboratory, biological reactions are governed by the same rules as any other chemical reaction. Thus, a firm understanding of the fundamentals of chemistry is invaluable in biochemistry. There are entire textbooks devoted to the application of chemical principles in biological systems and so it is not possible to cover all of the relevant topics in depth in this short article. The aim is instead to provide a brief overview of those areas in chemistry that are most relevant to biochemistry. We summarize the basic principles, give examples of how these principles are applied in biological systems and suggest further reading on individual topics.

Encapsulation of Ibuprofen in CD-MOF and Related Bioavailability Studies

Although ibuprofen is one of the most widely used nonsteroidal anti-inflammatory drugs (NSAIDs), it exhibits poor solubility in aqueous and physiological environments as a free acid. In order to improve its oral bioavailability and rate of uptake, extensive research into the development of new formulations of ibuprofen has been undertaken, including the use of excipients as well as ibuprofen salts, such as ibuprofen lysinate and ibuprofen, sodium salt. The ultimate goals of these studies are to reduce the time required for maximum uptake of ibuprofen, as this period of time is directly proportional to the rate of onset of analgesic/anti-inflammatory effects, and to increase the half-life of the drug within the body; that is, the duration of action of the effects of the drug. Herein, we present a pharmaceutical cocrystal of ibuprofen and the biocompatible metal-organic framework called CD-MOF. This metal-organic framework (MOF) is based upon γ-cyclodextrin (γ-CD) tori that are coordinated to alkali metal cations (e.g., K⁺ ions) on both their primary and secondary faces in an alternating manner to form a porous framework built up from (γ-CD)₆ cubes. We show that ibuprofen can be incorporated within CD-MOF-1 either by (i) a crystallization process using the potassium salt of ibuprofen as the alkali cation source for production of the MOF or by (ii) absorption and deprotonation of the free-acid, leading to an uptake of 23-26 wt % of ibuprofen within the CD-MOF. In vitro viability studies revealed that the CD-MOF is inherently not affecting the viability of the cells with no IC₅₀ value determined up to a concentration of 100 μM. Bioavailability investigations were conducted on mice, and the ibuprofen/CD-MOF pharmaceutical cocrystal was compared to control samples of the potassium salt of ibuprofen in the presence and absence of γ-CD. From these animal studies, we observed that the ibuprofen/CD-MOF-1 cocrystal exhibits the same rapid uptake of ibuprofen as the ibuprofen potassium salt control sample with a peak plasma concentration observed within 20 min, and the cocrystal has the added benefit of a 100% longer half-life in blood plasma samples and is intrinsically less hygroscopic than the pure salt form.

Stereoselective Pharmacokinetics and Chiral Inversion of Ibuprofen in Adjuvant-induced Arthritic Rats

2-Arylpropionic acid (2-APA) nonsteroidal anti-inflammatory drugs are commonly used in racemic mixtures (rac) for clinical use. 2-APA undergoes unidirectional chiral inversion of the in vivo inactive R-enantiomer to the active S-enantiomer. Inflammation causes the reduction of metabolic activities of drug-metabolizing enzymes such as cytochrome P450 (P450) and UDP-glucuronosyltransferase. However, it is unclear whether inflammation affects the stereoselective pharmacokinetics and chiral inversion of 2-APA such as ibuprofen (IB). We examined the effects of inflammation on the pharmacokinetics of R-IB and S-IB after intravenous administration of rac-IB, R-IB, and S-IB to adjuvant-induced arthritic (AA) rats, an animal model of inflammation. The plasma protein binding of rac-IB, glucuronidation activities for R-IB and S-IB, and P450 contents of liver microsomes in AA rats were determined. Total clearance (CL_tot) of IB significantly increased in AA rats, although the glucuronidation activities for IB, and P450 contents of liver microsomes decreased in AA rats. We presumed that the increased CL_tot of IB in AA rats was caused by the elevated plasma unbound fraction of IB due to decreased plasma albumin levels in AA rats. Notably, CL_tot of R-IB but not S-IB significantly increased in AA rats after intravenous administration of rac-IB. These results suggested that AA could affect drug efficacies after stereoselective changes in the pharmacokinetics of R-IB and S-IB.

Determination of ibuprofen enantiomers in human plasma by HPLC–MS/MS: validation and application in neonates

Aim: An adaptive method to determine ibuprofen enantiomers with limited volume of plasma required is necessary for investigating PK of ibuprofen in neonates. Results: Enantiomer separation was achieved on a Lux cellulose 3 column with mobile phase consisting of methanol water (85:15, v/v) and formic acid (0.0075%) at isocratic rate of 0.2 ml/min. Calibration curve is linear for each enantiomer at the range of 0.1–60 μg/ml. Validation was conducted and results met requirements regarding to intra- and inter-run precision, accuracy and recovery. No matrix effect or interference was observed from neonatal plasma or comedications. Only 20 μl of plasma was requested in this study. Conclusion: This assay was specific and reliable to quantify ibuprofen enantiomers in neonate plasma.

Ultrasound-Assisted Enantioselective Esterification of Ibuprofen Catalyzed by a Flower-Like Nanobioreactor

A flower-like nanobioreactor was prepared for resolution of ibuprofen in organic solvents. Ultrasound irradiation has been used to improve the enzyme performance of APE1547 (a thermophilic esterase from the archaeon Aeropyrum pernix K1) in the enantioselective esterification. Under optimum reaction conditions (ultrasound power, 225 W; temperature, 45 °C; water activity, 0.21), the immobilized APE1547 showed an excellent catalytic performance (enzyme activity, 13.26 μmol/h/mg; E value, 147.1). After ten repeated reaction batches, the nanobioreactor retained almost 100% of its initial enzyme activity and enantioselectivity. These results indicated that the combination of the immobilization method and ultrasound irradiation can enhance the enzyme performance dramatically.

Separation and enrichment of enantiopure from racemic compounds using magnetic levitation

Crystallization of a solution with high enantiomeric excess can generate a mixture of crystals of the desired enantiomer and the racemic compound. Using a mixture of S-/RS-ibuprofen crystals as a model, we demonstrated that magnetic levitation (MagLev) is a useful technique for analysis, separation and enantioenrichment of chiral/racemic products.