Cross-column density functional theory-based quantitative structure-retention relationship model development powered by machine learning.

Quantitative structure-retention relationship (QSRR) modeling has emerged as an efficient alternative to predict analyte retention times using molecular descriptors. However, most reported QSRR models are column-specific, requiring separate models for each high-performance liquid chromatography (HPLC) system. This study evaluates the potential of machine learning (ML) algorithms and quantum mechanical (QM) descriptors to develop QSRR models that can predict retention times across three different reversed-phase HPLC columns under varying conditions. Four machine learning methods-partial least squares (PLS) regression, ridge regression (RR), random forest (RF), and gradient boosting (GB)-were compared on a dataset of 360 retention times for 15 aromatic analytes. Molecular descriptors were calculated using density functional theory (DFT). Column characteristics like particle size and pore size and experimental conditions like temperature and gradient time were additionally used as descriptors. Results showed that the GB-QSRR model demonstrated the best predictive performance, with Q2 of 0.989 and root mean square error of prediction (RMSEP) of 0.749 min on the test set. Feature analysis revealed that solvation energy (SE), HOMO-LUMO energy gap (∆E HOMO-LUMO), total dipole moment (Mtot), and global hardness (η) are among the most influential predictors for retention time prediction, indicating the significance of electrostatic interactions and hydrophobicity. Our findings underscore the efficiency of ensemble methods, GB and RF models employing non-linear learners, in capturing local variations in retention times across diverse experimental setups. This study emphasizes the potential of cross-column QSRR modeling and highlights the utility of ML models in optimizing chromatographic analysis.

New methods for resolution of hydroxychloroquine by forming diastereomeric salt and adding chiral mobile phase agent on RP-HPLC.

Hydroxychloroquine (HCQ), 2-([4-([7-Chloro-4-quinolyl]amino)pentyl]ethylamino)ethanol, exhibited significant biological activity, while its side effects cannot be overlooked. The RP-HPLC enantio-separation was investigated for cost-effective and convenient optical purity analysis of HCQ. The thermodynamic resolution of Rac-HCQ, driven by enthalpy and entropy, was achieved on the C18 column using Carboxymethyl-ß-cyclodextrin (CM-ß-CD) as the chiral mobile phase agent (CMPA). The effects of CCM-ß-CD, pH, and triethylamine (TEA) V% on the enantio-separation process were explored. Under the optimum conditions at 24°C, the retention times for the two enantiomers were t R 1 = 29.39 min $$ {t}_{R1}=29.39\ \min $$ and t R 2 = 32.42 min $$ {t}_{R2}=32.42\ \min $$ , resulting in R s = 1.87 $$ {R}_s=1.87 $$ . The resolution via diastereomeric salt formation of Rac-HCQ was developed to obtain the active pharmaceutical ingredient of single enantiomer S-HCQ. Di-p-Anisoyl-L-Tartaric Acid (L-DATA) was proved effective as the resolution agent for Rac-HCQ. Surprisingly, it was found that refluxing time was a key fact affecting the resolution efficiency, which meant the kinetic dominate during the process of the resolution. Four factors-solvent volume, refluxing time, filtration temperature, and molar ratio-were optimized using the single-factor method and the response surface method. Two cubic models were established, and the reliability was subsequently verified. Under the optimal conditions, the less soluble salt of 2L-DATA:S-HCQ was obtained with a yield of 96.9% and optical purity of 63.0%. The optical purity of this less soluble salt increases to 99.0% with a yield of 74.2% after three rounds recrystallization.

Design of experiment-oriented development and validation of novel bioanalytical reverse phase high performance liquid chromatography method of palbociclib in rat plasma and tissues, and its application in pharmacokinetic studies.

The current research involved the development and validation of an easy, cost-effective, and sensitive bioanalytical reverse-phase high-performance liquid chromatography method for the assessment of palbociclib (PAL) in rat plasma and kidney, liver, spleen and heart. A response surface methodology-based Box-Behnken design was used to optimize critical chromatographic conditions such as buffer pH, organic phase concentration and flow rate to attain good sensitivity, tailing factor and retention time. The conditions were: pH of buffer, 4.5; organic phase concentration, 40%; Shimpac column with 1.0 ml/min flow rate. The responses were: tailing factor, 1.29 ± 0.03, sensitivity, 366,593 ± 8,592; and retention time, 4.5 ± 0.05 min. The samples were extracted by a protein precipitation method, and absolute recoveries were in the range of 88.99-95.08%. The linearity of the developed method was validated over the range 100-2,000 ng/ml (r2 ≥ 0.994) in all tested matrices. The developed bioanalytical method showed greater accuracy (0.98 and 4.01%) and precision (<4.88%). The method was optimized for the sensitive analysis of the PAL in rat plasma, and the kidney, liver, spleen and heart were effectively applied to pharmacokinetic studies.

Novel RP-HPLC method for estimation of a newly developed combination of tizanidine and etoricoxib in rat plasma: Eight criteria for greens evaluation.

A novel environmentally friendly reversed-phase high-performance liquid chromatography (RP-HPLC) method has been effectively validated for simultaneously measuring a prospective conjunction of tizanidine (TIZ) and etoricoxib (ETC), the combined medicine, in rat plasma. The technique employs diclofenac potassium as the internal standard, guaranteeing dependable and precise outcomes. This study aimed to assess the impact of the suggested combination therapy on treating inflammation resulting from rheumatoid arthritis (RA) in a rat model. The procedure was performed using an Agilent series 1200 model HPLC apparatus. The chromatographic conditions consist of isocratic elution mode, C18 column with dimensions of 150 mm × 4.6 mm × 5 µm, flow rate of 1.5 mL/min, wavelength of 230 nm, temperature of 50°C, and injection volume of 10 µL. The elution was performed using a mobile phase consisting of a phosphate buffer with a pH of 3.5 and acetonitrile in a ratio of 80:20 v/v. Calibration curves were conducted for TIZ and ETC within the 1-50 µg/mL range, demonstrating linear trends with R2 values over 0.999. The effectiveness and eco-friendliness of the proposed method were evaluated using eight separate environmentally conscious metrics. The addition of TIZ and ETC to arthritic rodents amplified these effects significantly. Furthermore, TIZ and ETC significantly reduced serum levels in arthritic rodents, and safety investigations revealed normal complete blood count, liver, and renal functions. TIZ and ETC appear to have antiarthritic, anti-inflammatory, and safe combinations, making them viable future treatment options for RA that are also safe and efficacious. Following validation by United States Food and Drug Administration (US-FDA) rules, all goods met the criteria.

Cutting-edge HPLC and MCR techniques for synchronically quantifying anticholinergic drugs in the presence of C12 and C14 homologs: Robust application to green and white chemistry.

Green and white chemistry are vital to revolutionizing the chemical industry through their unparalleled potential to enhance sustainability and efficiency. In this study, nine sustainability tools of both green and white metrics, including green analytical procedure index (GAPI), ComplexGAPI, analytical greenness, analytical greenness metric for sample preparation, Analytical Eco-Scale (ESA), analytical method greenness score, high-performance liquid chromatography- environmental assessment tool (HPLC-EAT), analytical method volume intensity, and blue applicability grade index (BAGI), have been developed for appraising environmental friendliness for both innovative and straightforward mean centering of ratio spectra (MCR) and reversed-phase high-performance liquid chromatography (RP-HPLC) strategies utilized for concurrent analysis and separation of cyclopentolate (CYC) and C12 and C14 homologs of benzalkonium chloride (BNZ) in pure and ophthalmic solution. The mobile phase, formed of buffer phosphate and acetonitrile (35:65, v/v), was adjusted to pH 6.3, and 215-nm UV detection was used. The experimental flow rate was 2.0 mL min-1, and the analytical column was L11 Inertsil Ph-3 (150 mm × 4.6 mm, 5 µm). All sequences were run at 25°C in the column oven. The MCR approach effectively resolved the drug's spectral overlapping. CYC and BNZ employed this approach at 227.5 and 220.4 nm, respectively. As part of the HPLC analysis, an isocratic method was employed with phosphate buffer and acetonitrile in the mobile phase at 35:65. A correlation coefficient greater than 0.999 was observed between the calibration curves for the HPLC and MCR methods in the ranges of 20-320 µg mL-1 and 5-30 µg mL-1 for all drugs. The technique yields excellent primary recovery rates, ranging from 97.2% to 100.5%. The recommended approach has been validated according to International Council for Harmonization guidelines.

Carotenoid characterization, fatty acid profiles, and antioxidant activities of haloarchaeal extracts.

Microorganisms that can survive in saline environments, known as halotolerant or halophilic organisms, have a wide range of current and potential uses in biotechnology. In this study, it was aimed to determine the carotenoids of halophilic archaea strains isolated from the brine samples taken from different points of Salt Lake (Turkey) and determine the antioxidant activities of their carotenoids. To identify the halophilic archaea strains, they were cultivated in MAM JCM 168 medium and subjected to antibiotic susceptibility, fatty acid, two-dimensional and three-dimensional imaging by scanning electron microscopy and atomic force microscopy, biochemical and phylogenetic assays. The findings show that five different halophilic archaea strains have been identified as Halorubrum lipolyticum, Halorubrum sodomense, Haloarcula salaria, Halorubrum chaoviator, and Haloarcula japonica with 98% and above similarity ratio. The main fatty acids of all haloarchaeal strains were octadecanoic acid (C18:0) and palmitic acid (C16:0). The major carotenoid of the species was determined as all-trans bacterioruberin, and different carotenoid types such as lycopene, ß-carotene, and 2-isopentenyl-3,4-dehydrorodopin were found as well as bacterioruberin isomers. The antioxidant activities of carotenoids extracted from the species were analyzed by the 2,2-diphenyl-1-picrylhydrazyl radical scavenging method and the extracts showed antioxidant activity statistically significantly higher than ascorbic acid and butylated hydroxytoluene as reference products (p < 0.05).

Development of an RP-HPLC Method for Quantifying Diclofenac Diethylamine, Methyl Salicylate, and Capsaicin in Pharmaceutical Formulation and Skin Samples.

An RP-HPLC method with a UV detector was developed for the simultaneous quantification of diclofenac diethylamine, methyl salicylate, and capsaicin in a pharmaceutical formulation and rabbit skin samples. The separation was achieved using a Thermo Scientific ACCLAIMTM 120 C18 column (Waltham, MA, USA, 4.6 mm × 150 mm, 5 µm). The optimized elution phase consisted of deionized water adjusted to pH = 3 using phosphoric acid mixed with acetonitrile in a 35:65% (v/v) ratio with isocratic elution. The flow rate was set at 0.7 mL/min, and the detection was performed at 205 nm and 25 °C. The method exhibits good linearity for capsaicin (0.05-70.0 µg/mL), methyl salicylate (0.05-100.0 µg/mL), and diclofenac diethylamine (0.05-100.0 µg/mL), with low LOD values (0.0249, 0.0271, and 0.0038 for capsaicin, methyl salicylate, and diclofenac diethylamine, respectively). The RSD% values were below 3.0%, indicating good precision. The overall greenness score of the method was 0.61, reflecting its environmentally friendly nature. The developed RP-HPLC method was successfully applied to analyze Omni Hot Gel® pharmaceutical formulation and rabbit skin permeation samples.

Production and characterization of anti-hypertensive and anti-diabetic peptides from fermented sheep milk with anti-inflammatory activity: in vitro and molecular docking studies.

BACKGROUND: The present study aimed to evaluate the anti-hypertensive and anti-diabetic activities from biologically active peptides produced by fermented sheep milk with Lacticaseibacillus paracasei M11 (MG027695), as well as to purify and characterize the angiotensin-converting enzyme (ACE) inhibitory and anti-diabetic peptides produced from fermented sheep milk. RESULTS: After 48 h of fermentation at 37 °C, sheep milk demonstrated significant changes in anti-diabetic effects and ACE-I effects, with inhibition percentages observed for ACE inhibition (76.32%), α-amylase (70.13%), α-glucosidase (70.11%) and lipase inhibition (68.22%). The highest level of peptides (9.77 mg mL-1) was produced by optimizing the growth conditions, which included an inoculation rate of 2.5% and a 48 h of incubation period. The comparison of molecular weight distributions among protein fractions was conducted through sodium dodecyl-sulfate polyacrylamide gel electrophoresis analysis, whereas spots were separated using 2D gel electrophoresis according to both the molecular weight and pH. Peptide characterization with ultra-filtration membranes at 3 and 10 kDa allowed the study to assess molecular weight-based separation. Nitric oxide generated by lipopolysaccharide and the secretion of pro-inflammatory cytokines in RAW 264.7 immune cells were both inhibited by sheep milk fermented with M11. Fourier-transform infrared spectroscopy was employed to assess changes in functional groups after fermentation, providing insights into the structural changes occurring during fermentation. CONCLUSION: The present study demonstrates that fermentation with L. paracasei (M11) led to significant changes in fermented sheep milk, enhancing its bioactive properties, notably in terms of ACE inhibition and anti-diabetic activities, and the generation of peptides with bioactive properties has potential health benefits. © 2024 Society of Chemical Industry.

Formulation of Saxagliptin Oral Films: Optimization, Physicochemical Characterization, In-Vivo Assessment, and In-Vitro Real-Time Release Monitoring via a Novel Polyaniline Nanoparticles-Based Solid-Contact Screen Printed Ion-Selective Electrode.

Oral dispersible films have received broad interest due to fast drug absorption and no first-path metabolism, leading to high bioavailability and better patient compliance. Saxagliptin (SXG) is an antidiabetic drug that undergoes first-path metabolism, resulting in a less active metabolite, so the development of SXG oral dispersible films (SXG-ODFs) improves SXG bioavailability. The formula optimisation included a response surface experimental design and the impact of three formulation factors, the type and concentration of polymer and plasticiser concentration on in-vitro disintegration time and folding endurance. Two optimised SXG-ODFs prepared using either polyvinyl alcohol (PVA) or hydroxypropyl methylcellulose were investigated. SXG-ODFs prepared with PVA demonstrated a superior rapid disintegration time, ranging from 17 to 890 s, with the fastest disintegration time recorded at 17 s. These short durations can be attributed to the hydrophilic nature of PVA, facilitating rapid hydration and disintegration upon contact with saliva. Additionally, PVA-based films displayed remarkable folding endurance, surpassing 200 folds without rupture, indicating flexibility and stability. The high tensile strength of PVA-based films further underscores their robust mechanical properties, with tensile strength values reaching up to 4.53 MPa. SXG exhibits a UV absorption wavelength of around 212 nm, posing challenges for traditional quantitative spectrophotometric analysis, so a polyaniline nanoparticles-based solid-contact screen-printed ion-selective electrode (SP-ISE) was employed for the determination of SXG release profile effectively in comparison to HPLC. SP-ISE showed a better real-time release profile of SXG-ODFs, and the optimised formula showed lower blood glucose levels than commercial tablets.

Greens appraisal of validated stability indicating RP-HPLC method and forced degradation study for quantification of Ebastine in wastewater and dosage form.

OBJECTIVES: Allergic rhinitis and chronic idiopathic urticaria are common conditions triggered by environmental irritants, stress, and certain foods. The FDA has recently announced that the efficacy and safety of Ebastine (EBS) have been thoroughly evaluated and confirmed. This study considered using various tools to assess their greenness. We used AGREEprep, analytical eco-scale (ESA), and analytical method volume intensity (AMVI) to evaluate the greenness of the validated stability-indicating method and a forced degradation study. This allowed for easy determination and quantitation of EBS in wastewater and dosage form. METHODS: The method was established on Symmetry RP-C18 (150mm×4.6mm,5µm) using mobile phase, which can be prepared by mixing buffer solution of pH 3 with acetonitrile in a ratio of (37.5: 62.5, v/v) in addition to dissolving 0.72 gm of sodium lauryl sulfate in the final solution. The separation process was executed at a flow rate of 1.5mL/min and 5µL injection volume with UV detection at 254nm. Linearity was conducted for EBS in the 5-50µg/mL range. Different validation parameters were investigated, including accuracy, precision, robustness, and specificity. RESULTS: The limits of both detection and quantification were 0.84µg/mL and 2.57µg/mL for EBS. The recovery percentages of EBS were found to be 101.01% and 101.02% for wastewater and pharmaceutical formulations, respectively. CONCLUSION: According to International Council for Harmonisation (ICH) guidelines, a forced degradation study of EBS was evaluated, including acid, base hydrolysis, and oxidative hydrolysis using hydrogen peroxide and photolytic and thermal degradation. The highest degradation was achieved by acid hydrolysis. The safety and efficacy of EBS were evaluated via a safety comparative profile study.

Development and validation of stability indicating RP-HPLC method for simultaneous estimation of silodosin and mirabegron in synthetic mixture.

The study focuses to validate and develop a precise, simple and accurate stability indicating RP-HPLC method for estimation simultaneously of and silodosin and mirabegron in synthetic mixture. The chromatographic separation was achieved by using Shimpack Solar C18 column (250×4.5mm, 5µm) with acetonitrile: 5mM ammonium acetate in ratio of 90:10% v/v as a mobile phase at a constant flow rate of about 1.2mL/min. The development and validation were carried out at detection wavelength of 229nm. We developed a robust RP-HPLC method, validated for linearity, precision, accuracy, specificity, and system suitability. The method demonstrated excellent linearity with correlation coefficient value r2 was nearly 0.998 with linearity range 8-18µg/mL for Silodosin and 24-54µg/mL for mirabegron. LOD and LOQ were found to be lower; hence, the method is sensitive. Percentage recovery was obtained 99.97% and 99.99% for silodosin and mirabegron, respectively. In case of precision, robustness and repeatability, RSD was found to be less than 2. The validated and developed RP-HPLC method offers an efficient and practical approach for the simultaneous quantification of silodosin and mirabegron in pharmaceutical formulations, making it a valuable tool for quality control and pharmaceutical research.

High-Throughput Venomics.

In this study, we present high-throughput (HT) venomics, a novel analytical strategy capable of performing a full proteomic analysis of a snake venom within 3 days. This methodology comprises a combination of RP-HPLC-nanofractionation analytics, mass spectrometry analysis, automated in-solution tryptic digestion, and high-throughput proteomics. In-house written scripts were developed to process all the obtained proteomics data by first compiling all Mascot search results for a single venom into a single Excel sheet. Then, a second script plots each of the identified toxins in so-called Protein Score Chromatograms (PSCs). For this, for each toxin, identified protein scores are plotted on the y-axis versus retention times of adjacent series of wells in which a toxin was fractionated on the x-axis. These PSCs allow correlation with parallel acquired intact toxin MS data. This same script integrates the PSC peaks from these chromatograms for semiquantitation purposes. This new HT venomics strategy was performed on venoms from diverse medically important biting species; Calloselasma rhodostoma, Echis ocellatus, Naja pallida, Bothrops asper, Bungarus multicinctus, Crotalus atrox, Daboia russelii, Naja naja, Naja nigricollis, Naja mossambica, and Ophiophagus hannah. Our data suggest that high-throughput venomics represents a valuable new analytical tool for increasing the throughput by which we can define venom variation and should greatly aid in the future development of new snakebite treatments by defining toxin composition.

Variation of tafamidis plasma levels during the treatment of TTR amyloidosis patients with Glu89Gln mutation.

PURPOSE: The transthyretin kinetic stabilizer tafamidis, used as a first-line therapy of amyloidosis patients, binds selectively to the transthyretin protein structure and thus prevents its dissociation. The limited information regarding tafamidis application in Glu89Gln amyloidosis patients imposed our research team to determine and evaluate its individual mean plasma levels and their biological variation. METHODS: The present cohort study investigated Bulgarian amyloidosis patients, grouped by gender, age, and therapy duration. A total of sixty patients aged 40-75 years and therapy duration up to 9 years were included. A precise and accurate high-performance liquid chromatography method with ultraviolet detection was used for plasma concentration measurement. RESULTS: Mean plasma concentrations were 5.13 ± 2.64 µmol/L and showed low intra-individual (18.50%) and high inter-individual variability (51.43%). No significant difference was observed between tafamidis plasma levels and therapy duration with p = 0.5941 (p < 0.05 considered significant), but a significant positive correlation was found between plasma concentration, gender, and age with obtained results about p-value 0.0001 and 0.0235, respectively. CONCLUSION: The summary results of the study showed differences that may be based on some specific clinical features of the Glu89Gln mutation.

Quercetin extraction from small onion skin (Allium cepa L. var. aggregatum Don.) and its antioxidant activity.

In the present study, the maximum yield of quercetin was optimized for the ethanol extraction of small onions (Allium cepa L. var. aggregatum Don.), and the antioxidant activity was investigated in vitro. The extraction of quercetin from the small onion skin was carried out through ethanol solvent extraction with different ratios of ethanol and water. Ethanol: water ratio produced the highest quercetin from the onion skin. RP-HPLC analysis of the extracted material showed 2, 122 mg/g of quercetin and 0.34 mg/g of isorhamnetin. A total of 301.03 mg GAE/g dry weight and 156 mg/g quercetin equivalents were found in the onion skin extract. DPPH and ABTS free radical scavenging potentials of the tested extract (90:10 v/v) were dose-dependent, with IC50 values of 62.27 µg/mL and 53.65 µg/mL, respectively. Therefore, the present study reports that small onion skin extract rich in quercetin may serve as a promising antioxidant and anticancer agent.

The unique C-mannosylated hypertrehalosemic hormone of Carausius morosus: Identity, release, and biological activity.

Previous studies had shown that the corpora cardiaca (CC) of the Indian stick insect, Carausius morosus, synthesizes two hypertrehalosemic hormones (HrTHs)-decapeptides which differ in the way that the chromatographically less-hydrophobic form, code-named Carmo-HrTH-I, is modified by an unique C-mannosylated tryptophan residue at position 8. The availability of milligram amounts of this modified peptide in synthetic form now makes it possible to study physico-chemical and physiological properties. This study revealed that the synthetic peptide co-elutes with the natural peptide from the CC chromatographically, is heat stable for at least 30 min at 100°C, and causes hyperlipemia in acceptor locusts (a heterologous bioassay) and hypertrehalosemia in ligated stick insects (conspecific bioassay). In vitro incubation of Carmo-HrTH-I together with stick insect hemolymph (a natural source of peptidases) demonstrated clearly via chromatographic separation that the C-mannosylated Trp bond is stable and is not broken down to Carmo-HrTH-II (the more-hydrophobic decapeptide with an unmodified Trp residue). This notwithstanding, breakdown of Carmo-HrTH-I did take place, and the half-life of the compound was calculated as about 5 min. Finally, the natural peptide is releasable when CC are treated in vitro with a depolarizing saline (high potassium concentration) suggesting its role as true HrTHs in the stick insect. In conclusion, the results indicate that Carmo-HrTH-I which is synthesized in the CC is released into the hemolymph, binds to a HrTH receptor in the fat body, activates the carbohydrate metabolism pathway and is quickly inactivated in the hemolymph by (an) as yet unknown peptidase(s).

Oxidation and reduction analysis of therapeutic recombinant human interleukin-15 by HPLC and LC-MS.

Being an important immune stimulant of T lymphocytes and NK cells, the recombinant human interleukin-15 (rhIL-15) has been extensively researched in tumor immunotherapy or as a vaccine adjuvant. However, the rhIL-15 manufacturing level lags far behind its growing clinical demand due to the lack of efficient and exact analysis methodologies to characterize the trace by-products, typically redox and deamidation. In order to improve the production and quality control of rhIL-15, here we developed an expanded resolution reverse-phase high-performance liquid chromatography (ExRP-HPLC) approach to quickly and accurately analyze the oxidation and reduction by-products of rhIL-15, which may appear during the purification processes. Firstly, we developed RP-HPLC methods which can separate rhIL-15 fractions with different levels of oxidization or reduction, respectively, and the redox status of each peak was then determined by measuring the intact mass with a high-resolution mass spectrometer (UPLC-MS). To further clarify the complex pattern of oxidization of specific residues, the peaks with various oxidation levels were digested into pieces for peptide mapping to pinpoint the exact changes of oxygen and hydrogen atoms in the rhIL-15 by-products. In addition, we performed the ExRP-HPLC and UPLC-MS analysis of partially deamidated rhIL-15 to characterize their oxidation and reduction. Our work is the first in-depth characterization of the redox by-products of rhIL-15, even for deamidated impurities. The ExRP-HPLC method we reported can facilitate the rapid and accurate quality analysis of rhIL-15, which is substantially helpful for streamlining the industrial manufacturing of rhIL-15 to better meet the demands of clinical applications. KEYPOINTS: • The oxidization and reduction rhIL-15 by-products were characterized for the first time. • The changes of oxygen and hydrogen atoms in rhIL-15 redox by-products were accurately determined by UPLC-MS. • Oxidation and reduction by-products of deamidated rhIL-15 were further analyzed.

Racemization rate and biomolecular characterization of D-serine synthesizing bacteria Bacillus tequilensis A1C1.

D-amino acids, the important components of the bacterial cell walls, are valuable molecular and genetic markers of bacterial-derived organic material in the environment. D-serine, a racemization product of L-serine is one such amino acid present in various prokaryotes and eukaryotes. It is a well-recognized regulator of various activities in the human nervous system. In plants, it has a role in the nitrogen cycle regulation and pollen tube growth. Serine enantiomers are present in different concentrations and few bacterial strains are reported to contribute to D-serine in the environment. During the present study, soil samples from different places in North India were collected and processed to isolate and screen the bacteria on M9 minimal media (Himedia) for D-serine synthesis. Thin-layer chromatography (TLC Silica gel 60 F 254 (20 × 20 cm, Merck, Darmstadt, Germany) and Mass spectroscopic analysis (Bruker MICROTOF II spectrometer) studies, etc were performed. D-serine-producing isolates were characterized as per standard procedures. Bacterial isolate A1C1 with maximum D-serine (0.919 ± 0.02 nM) synthesis under optimal growth conditions (37°C ± 0.5, 150 ± 0.5 RPM, and 7 ± 0.5 pH) was identified as Bacillus tequilensis based on 16sRNA sequencing. The isolate could be a valuable serine racemization tool for various industrial and environmental applications.

Method Development and Validation of Gallic Acid in Liquid Dosage Form by Using RP-HPLC Method.

A simple, rapid, precise, sensitive, and reproducible reverse-phase high-performance liquid chromatography (RP-HPLC) method has been developed for the quantitative analysis of gallic acid in the pharmaceutical dosage form. Chromatographic separation of gallic acid was achieved on Waters Alliance-e 2695, by using Waters X-Terra RP-18 (150 × 4.6 mm, 3.5 µ) column and the mobile phase containing 0.1% formic acid and ACN in the ratio of 70:30% v/v. The flow rate was 1.0 mL/min; detection was carried out by absorption at 275 nm using a photodiode array detector at ambient temperature. The number of theoretical plates and tailing factor for gallic acid was NLT 2000 and should not be more than 2 respectively. Percentage relative standard deviation of peak areas of all measurements is always less than 2.0. The proposed method was validated according to ICH guidelines. The method was found to be simple, economical, suitable, precise, accurate, and robust method for quantitative analysis of gallic acid.

QbD-based stability-indicating liquid chromatography (RP-HPLC) method for the determination of flurbiprofen in cataplasm.

A nonsteroidal drug called flurbiprofen (FBN) has analgesic, anti-inflammatory and antipyretic activity. Currently the determination of FBN in cataplasm does not have any pharmacopeial method. However, the drug substance, tablet and ophthalmic solution formulations do have pharmacopeial methods. The development and validation of an accurate, precise and stability-indicating analytical method for the determination of FBN in cataplasm formulations is reported. The gradient method was employed for the quantification of FBN in the presence of internal standards such as biphenyl. A nonpolar separation phase (C18 , 250 × 4.6 mm, 5 µm Inertsil column; GL Sciences) was used. The optimal flow rate, column oven temperature, injection volume and detector wavelengths were 1.0 ml/min, 40°C, 20 µl and 245 nm, respectively. Mobile phase A was a mixture of water and glacial acetic acid (30:1 v/v) pH adjusted to 2.20 with glacial acetic acid or 1 m NaOH; mobile phase B was methanol (100%). The gradient elution program was [time (min)/% B]: 5/60, 20/70, 25/70, 30/60 and 40/60. The obtained RSDs for the precision and intermediate precision were 0.7 and 0.5%. The percentage recovery ranged from 99.2 to 100.4%. The linear regression coefficient >0.9996 indicates that all peak responses were linear with the concentration. The sample and standard solutions were stable for up to 24 h on the benchtop and in the refrigerator. The critical peaks were well separated from the generated peaks owing to forced degradation, including diluent and placebo peaks. The method validation data and quality by design-based robustness study results indicate that the developed method is robust and fit for routine use in the quality control laboratory. The proposed method is specific, accurate and precise, and the quality by design utilized the first method for the determination of FBN in cataplasm formulations. Transdermal patches and gels have low extraction capacity and this method is applicable for quantification.

Identification and structural characterization of major stress degradation products of halcinonide by liquid chromatography-high-resolution mass spectrometry.

Halcinonide is a topical corticosteroid approved by the US Food and Drug Administration (FDA), known for its anti-inflammatory and antipruritic properties. The therapeutic benefits of halcinonide have rendered it an effective treatment regimen for various dermatological conditions such as psoriasis, dermatitis, and eczema. However, stability of the drug substance is a prerequisite in determining the therapeutic efficacy and plays a crucial role during formulation development and long-term storage. As corticosteroids are highly susceptible to degradation, the current study aims to expose halcinonide to different stress conditions and understand its stability behavior. An HPLC method was developed for the separation of halcinonide and its degradation products. Separation was accomplished in gradient mode using an Eclipse Plus C18 column (250 × 4.5 mm, 5 µm) with ammonium formate (10 mM, pH 6.5) and acetonitrile as the mobile phases. LC-Q-TOF/MS/MS studies were conducted on halcinonide, which led to the identification of degraded products using optimized mass parameters. A potential mechanistic degradation pathway for halcinonide, along with the major identified degradation products has been established. The chromatographic method that was developed has been validated in compliance with the Q2(R1) guideline of the International Council for Harmonization. ProTox-II was used to perform in silico toxicity studies in order to evaluate the toxicity potential of both halcinonide and the identified degradation products.