Enantiomeric separation of the antiuremic drug colchicine by electrokinetic chromatography. Method development and quantitative analysis

Sustainable solutions for direct TLC enantioseparation with in-home thought-out, prepared/modified chiral stationary phases

TLC is used globally, yet less attention has been paid to TLC (in enantioseparation) despite its advantages. The present paper describes/reviews successfully practiced direct approaches of 'chiral additive in achiral stationary phase' (as an application of in-home thought out, prepared, tested, and modified chiral stationary phase), 'pre-mixing of chiral reagent with the enantiomeric mixture' (an approach using both achiral phases during chromatographic separation) and 'chiral additive in mobile phase', and chiral ligand exchange for enantioseparation of DL-amino acids, their derivatives, and some active pharmaceutical ingredients. It provided efficient enantioseparation, quantitative determination, and isolation of native forms via in-situ formation of non-covalent diastereomeric pair. The mechanism of enantioseparation in these approaches has been discussed along with the isolation and establishment of the structure of diastereomers. This may help chemists gain useful insights into fields outside their specialization and the experts get brief accounts of recent key developments, providing solutions for sustainable development of less expensive methods for control of enantiomeric purity and isolation of native enantiomers.

Applications of electrophoresis for small enantiomeric drugs in real-world samples: Recent trends and future perspectives

Separation and identification of chiral molecules is a topic widely discussed in the literature and of fundamental importance, especially in the pharmaceutical and food fields, both from industrial and laboratory points of view. Several techniques are used to carry out these analyses, but high-performance liquid chromatography is often the "gold standard." The high costs of chiral columns, necessary for this technique, led researchers to look for an alternative, and capillary electrophoresis (CE) is a technique capable of overcoming some of the disadvantages of liquid chromatography, often providing comparable results in terms of sensitivity and robustness. We addressed this topic, already widely discussed in the literature, providing an overview of the last 6 years of the most frequent and recent applications of CE. To make the manuscript more effective, we decided to divide it into paragraphs that represent the main field of application, from enantioseparation in complex matrices (pharmacokinetic studies or toxicological dosage of drugs, analysis of environmental pollutants, and analyses of foods) to quality control analyses on pharmaceutical formulas. About these, which are the fields of most meaningful use, we mentioned some of the most innovative and performing methods, with a look to the future on the application of new materials used, such as chiral selectors, that can make these types of analyses accessible to all, reducing cost, time, and excessive use of toxic solvents.

From capillaries to microchips, green electrophoretic features for enantiomeric separations: A decade review (2013-2022)

Enantioseparation by the electromigration-based method is well-established and widely discussed in the literature. Electrophoretic strategies have been used to baseline resolve complex enantiomeric mixtures, typically using a selector substance into the background electrolyte (BGE) from capillaries to microchips. Along with developing new materials/substances for enantioseparations, it is the concern about the green analytical chemistry (GAC) principles for method development and application. This review article brings a last decade's update on the publications involving enantioseparation by electrophoresis for capillary and microchip systems. It also brings a critical discussion on GAC principles and new green metrics in the context of developing an enantioseparation method. Chemical and green features of native and modified cyclodextrins are discussed. Still, given the employment of greener substances, ionic liquids and deep-eutectic solvents are highlighted, and some new selectors are proposed. For all the mentioned selectors, green features about their production, application, and disposal are considered. Sample preparation and BGE composition in GAC perspective, as well as greener derivatization possibilities, were also addressed. Therefore, one of the goals of this review is to aid the electrophoretic researchers to look where they have not.

Capillary Electrophoresis Mass Spectrometry: Developments and Applications for Enantioselective Analysis from 2011-2020

It is now more than 25 years since the first report of enantioselective analysis by capillary electrophoresis-mass spectrometry (CE-MS) appeared. This article reviews the power of chiral CE-MS in resolving issues on the use of chiral selector incompatibility with MS and poor detectability encountered for chiral compounds by UV detection. The review begins with the general principles, requirements, and critical aspects of chiral CE-MS instrumentation. Next, the review provides a survey of MS-compatible chiral selectors (CSs) reported during the past decade, and the key achievements encountered in the time period using these CSs. Within the context of the strategies used to combine CE and MS, special attention is paid to the approaches that feature partial filling technique, counter-migration techniques, and direct use of CS, such as molecular micelles. In particular, the development and application of moving and fixed CS for EKC-MS, MEKC-MS, and CEC-MS demonstrate how various chiral compounds analyses were solved in a simple and elegant way during the 2010-2020 review period. The most noteworthy applications in the determination of chiral compounds are critically examined. The operating analytical conditions are detailed in the Tables, and the authors provide commentary on future trends of chiral separations by CE-MS.

Smart spectrophotometric methods for stability assessment of two co-formulated antigout drugs

Simple, sensitive and accurate stability indicating spectrophotometric methods have been developed for the simultaneous determination of probenecid, colchicine as well as colchicine degradation product in their ternary mixture. Probenecid was firstly assayed using the double divisor ratio spectra derivative method. On the other hand, three spectrophotometric methods, namely: ratio difference, derivative ratio and mean centering of ratio spectra, have been suggested for the simultaneous quantification of colchicine and its degradation product. The obtained calibration curves were linear at 2.5-30.0 μg/mL, 0.5-25.0 μg/mL and 1.0-13.0 μg/mL for probenecid, colchicine and colchicine degradation product, respectively. The investigated methods were validated in accordance with the International Council for Harmonisation guidelines and were effectively used for quantification of probenecid and colchicine in their bulk powders and combined pharmaceutical dosage form.

Chiral Capillary Electrokinetic Chromatography: Principle and Applications, Detection and Identification, Design of Experiment, and Exploration of Chiral Recognition Using Molecular Modeling

This work reviews the literature of chiral capillary electrokinetic chromatography from January 2016 to March 2021. This is done to explore the state-of-the-art approach and recent developments carried out in this field. The separation principle of the technique is described and supported with simple graphical illustrations, showing migration under normal and reversed polarity modes of the separation voltage. The most relevant applications of the technique for enantioseparation of drugs and other enantiomeric molecules in different fields using chiral selectors in single, dual, or multiple systems are highlighted. Measures to improve the detection sensitivity of chiral capillary electrokinetic chromatography with UV detector are discussed, and the alternative aspects are explored, besides special emphases to hyphenation compatibility to mass spectrometry. Partial filling and counter migration techniques are described. Indirect identification of the separated enantiomers and the determination of enantiomeric migration order are mentioned. The application of Quality by Design principles to facilitate method development, optimization, and validation is presented. The elucidation and explanation of chiral recognition in molecular bases are discussed with special focus on the role of molecular modeling.

Detection-confirmation-standardization-quantification: a novel method for the quantitative analysis of active components in traditional Chinese medicines

Background

Quantitative analysis of the active ingredients of Traditional Chinese Medicine is a research tendency. The objective of this study was to build a novel method, namely, Detection-confirmation-standardization-quantification (DCSQ), for the quantitative analysis of active components in traditional Chinese medicines, without individual reference standard.

Methods

Danshen (the dried root of Radix Salvia miltiorrhiza) was used as the matrix. The “extraction” function in high-performance liquid chromatography-mass (HPLC-MS) instrument was used to find the peaks corresponding to cryptotanshinone, tanshinone I, and tanshinone IIA in the total ion current (TIC) chromatogram of Danshen. The multicomponent reference standard (MCRS) containing the three tanshinones mainly was prepared by preparative HPLC. The contents of them in the resulting MCRS were determined by NMR; moreover, the constituents of the MCRS were confirmed. The MCRS containing known content of the three tanshinones was used as the reference standard for the quantitative analysis of cryptotanshinone, tanshinone I and tanshinone IIA in Danshen Samples by analytical HPLC.

Results

The optimized HPLC conditions for the quantitative analysis of the active components in Danshen were established, and the assignments of the extracted peaks were confirmed by analyzing the characteristic fragments in their MS/MS product ion spectra and UV spectra. Then, the MCRS containing the three tanshinones were successfully prepared. The results of determination about the contents by NMR showed linearity fitted with high likelihood and calibration curves possessed high linearity. The results of determination on Danshen Samples obtained through DCSQ exhibited minimal deviations, in contrast to those obtained through individual reference standards.

Conclusion

The establishing DCSQ is independent and convenient for the quantitative analysis of the active components in TCMs by MCRS, without individual reference standard. This method is a great advance in quantitative analysis for complex composition, especially TCMs.

Stability-Indicating Chromatographic Methods for the Simultaneous Determination of Probenecid and Colchicine in Their Combined Tablet

Two stability-indicating chromatographic methods have been established and validated for concurrent determination of probenecid (PRO), colchicine (COL) along with the degradation product of colchicine (COL deg). PRO and COL were exposed to a stress stability study, which includes acidic, alkaline, oxidative, photolytic and thermal degradations. Chromatographic methods included the use of thin layer chromatography (TLC-densitometry) and high performance liquid chromatography (HPLC). In the first method, separation was achieved by using aluminum TLC plates that were precoated with silica gel G.F254 as the stationary phase and ethyl acetate-methanol-33%ammonia (8:1:1, by volume) as a mobile phase. The obtained chromatograms were scanned at 254 nm. The second method was based on HPLC using a RP- C18 column with isocratic elution. Good separation was obtained through a mobile phase comprised of phosphate buffer pH 5-acetonitrile (70:30, v/v) at a flow rate of 1.0 mL min-1 and ultraviolet detection at 254 nm. Different parameters affecting efficiency of the two methods were studied accurately for optimum separation of the three cited components. The suggested methods were validated according to the International Conference on Harmonization (ICH) guidelines and were applied for bulk powder and commercial tablets.

Advances of capillary electrophoresis enantioseparations in pharmaceutical analysis (2017-2020)

Capillary electrophoresis is a powerful technique for the analysis of polar chiral compounds and has been widely accepted for analytical enantioseparations of drug compounds in pharmaceuticals and biological media. In addition, many mechanistic studies have been conducted in an attempt to rationalize enantioseparations in combination with spectroscopic and computational techniques. The present review will focus on recent examples of mechanistic aspects and summarize recent applications of stereoselective pharmaceutical and biomedical analysis published between January 2017 and November 2020. Various separation modes including electrokinetic chromatography in combination with several detection modes including laser-induced fluorescence, mass spectrometry and contactless conductivity detection will be discussed. A general trend also observed in other analytical techniques is the application of quality by design principles in method development and optimization.

Enantiomeric Separation of Colchicine and Lacosamide by Nano-LC. Quantitative Analysis in Pharmaceutical Formulations

A chiral analytical methodology was developed by nano-liquid chromatography (nano-LC) enabling the enantiomeric separation of two chiral drugs, lacosamide (novel antiepileptic drug) and colchicine (antiuremic drug), commercialized as pure enantiomers. A capillary column lab-packed with an amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase was used in a lab-assembled nano-LC system. Lacosamide and colchicine enantiomers were separated in less than 8.0 and 9.0 min, respectively, with resolution values of 1.6 and 2.3, using 20 nL of sample and 1.8 µL of mobile phase per analysis. The analytical characteristics of the proposed methodology were evaluated according to the International Council for Harmonisation (ICH) guidelines, showing good analytical performance with good recoveries (97–98% and 100–103%) and precision values (relative standard deviation (RSD) <10.5 and <3.0%) for lacosamide and colchicine enantiomers, respectively. LODs were 1.7 and 2.0 µg/mL for (S)- and (R)-lacosamide, respectively, and 1.0 µg/mL for both colchicine enantiomers. Additionally, the developed methodology enabled to detect a 0.1% of the enantiomeric impurities, fulfilling the ICH regulation requirements. The method was applied to the determination of lacosamide and colchicine enantiomers in different pharmaceutical formulations to ensure their quality control. The content of the enantiomeric impurities was below a 0.1% and the amount of (R)-lacosamide and (S)-colchicine agreed with their labeled contents.

Capillary electrophoretic methods for quality control analyses of pharmaceuticals: A review

Capillary electrophoresis represents a promising technique in the field of pharmaceutical analysis. The presented review provides a summary of capillary electrophoretic methods suitable for routine quality control analyses of small molecule drugs published since 2015. In total, more than 80 discussed methods are sorted into three main sections according to the applied electroseparation modes (capillary zone electrophoresis, electrokinetic chromatography, and micellar, microemulsion, and liposome-electrokinetic chromatography) and further subsections according to the applied detection techniques (UV, capacitively coupled contactless conductivity detection, and mass spectrometry). Key parameters of the procedures are summarized in four concise tables. The presented applications cover analyses of active pharmaceutical ingredients and their related substances such as degradation products or enantiomeric impurities. The contribution of reported results to the current knowledge of separation science and general aspects of the practical applications of capillary electrophoretic methods are also discussed.

Advances in Chiral Separations at Nano Level

Background::

Nano level chiral separation is necessary and demanding in the development of the drug, genomic, proteomic, and other chemical and the environmental sciences. Few drugs exist in human body cells for some days at nano level concentrations, that are out of the jurisdiction of the detection by standard separation techniques. Likewise, the separation and identification of xenobiotics and other environmental contaminants (at nano or low levels) are necessary for our healthiness.

Discussion:

Conclusion:

This article will be beneficial for chiral chromatographers, academicians, pharmaceutical industries, environmental researchers and Government regulation authorities.

Enantiomeric Determination of Drugs in Pharmaceutical Formulations and Biological Samples by Electrokinetic Chromatography

Chirality is a relevant issue in the pharmaceutical field due to the different biological activity that enantiomers of a chiral drug can show. In fact, the desired biological or pharmaceutical activity might be present in only one of the enantiomers, while the other enantiomer(s) may have different biological activity, be inactive or even toxic. This has motivated in recent years the development of drugs marketed as pure enantiomers to avoid exposing the organism to the action of enantiomers that may not be active or even harmful to health. Thus, it is of high interest to develop enantioselective analytical methodologies to control the presence of enantiomeric impurities and to understand the enantioselective metabolism of chiral drugs. This review gives an overview about the analytical strategies developed by electrokinetic chromatography (EKC) from 2010 to June 2019 for the enantiomeric determination of drugs in both pharmaceutical formulations and biological samples. The types of chiral selectors used, the migration order of enantiomers, their resolution, the detection technique employed and the sensitivity achieved are revised and compared. Also, applications to assess the enantiomeric purity control of pharmaceutical formulations and to determine chiral drugs in biological samples to study their metabolism are included. Advantages and limitations of the chiral methods developed by EKC are also discussed.

Enantiomeric separation of ivabradine by cyclodextrin-electrokinetic chromatography. Effect of amino acid chiral ionic liquids

A chiral methodology was developed for the first time to ensure the quality control of ivabradine, a novel anti-ischemic and heart rate lowering drug commercialized as a pure enantiomer. With this aim, electrokinetic chromatography (EKC) was employed and the enantiomeric separation of ivabradine was investigated using different anionic and neutral cyclodextrins (CDs) and amino acid-based chiral ionic liquids (CILs) as sole chiral selectors. Baseline separation was only achieved with sulfated CDs, and the best enantiomeric resolution was obtained with sulfated-γ-CD. Under the optimized conditions, ivabradine enantiomers were separated in 6 min with a resolution of 2.7. Nuclear magnetic resonance experiments showed a 1:1 stoichiometry for the enantiomer-CD complexes and apparent and averaged equilibrium constants were determined. The combined use of sulfated-γ-CD and different CILs as dual separation systems was investigated, resulting in a significant increase in the resolution. The use of 5 mM tetrabutylammonium-aspartic acid ([TBA][L-Asp]) in 50 mM formate buffer (pH 2.0) containing 4 mM sulfated-γ-CD were considered the best conditions in terms of resolution and migration times for ivabradine enantiomers. Nevertheless, as no inversion of the enantiomer migration order was observed when combining CILs and sulfated-γ-CD and a good enantiomeric resolution and efficiency were obtained using just sulfated-γ-CD as the sole chiral selector, the analytical characteristics of this method were evaluated, showing good recovery (98% and 103% for S- and R-ivabradine, respectively) and precision values (RSD < 5% for instrumental repeatability, < 6% for method repeatability and < 7% for intermediate precision). The limits of detection (LODs) were 0.22 and 0.28 μg mL^-1 for S- and R-ivabradine, respectively, and the method enabled to detect a 0.1% of the enantiomeric impurity, allowing to accomplish the requirements of the International Conference on Harmonisation (ICH) guidelines. Finally, the method was applied to the analysis of a pharmaceutical formulation of ivabradine. The content of R-ivabradine was below the LOD and the amount of S-ivabradine was in agreement to the labeled content.

Biorhizome: A Biosynthetic Platform for Colchicine Biomanufacturing

Colchicine is one of the oldest plant-based medicines used to treat gout and one of the most important alkaloid-based antimitotic drugs with anticancer potential, which is commercially extracted from Gloriosa superba. Clinical trials suggest that colchicine medication could prevent atrial fibrillation recurrence after cardiac surgery. In addition, therapeutic colchicine is undergoing clinical trials to treat non-diabetic metabolic syndrome and diabetic nephropathy. However, the industrial-scale biomanufacturing of colchicine have not yet been established. Clearly, further studies on detailed biorhizome-specific transcriptome analysis, gene expression, and candidate gene validation are required before uncover the mechanism of colchicine biosynthesis and biorhizome-based colchicine biomanufacturing. Annotation of 32312 assembled multiple-tissues transcripts of G. superba represented 15088 unigenes in known plant specific gene ontology. This could help understanding colchicine biosynthesis in G. superba. This review highlights the biorhizomes, rhizome specific genes or gene what expressed with high level in rhizomes, and deep fluid dynamics in a bioreactor specifically for the biomanufacture of colchicine.