Fast separation of triterpenoid saponins using supercritical fluid chromatography coupled with single quadrupole mass spectrometry

Development and Validation of the UPLC-DAD Methodology for the Detection of Triterpenoids and Phytosterols in Fruit Samples of Vaccinium macrocarpon Aiton and Vaccinium oxycoccos L

Cranberries are used in the production of medicinal preparations and food supplements, which highlights the importance of triterpene compounds determination in cranberry fruit raw material. The aim of our study was to develop and validate for routine testing suitable UPLC-DAD methodology for the evaluation of triterpene acids, neutral triterpenoids, phytosterols, and squalene content in cranberry samples. The developed and optimized UPLC-DAD methodology was validated according to the guidelines of the International Council for Harmonization (ICH), evaluating the following parameters: range, specificity, linearity (R2 > 0.999), precision, LOD (0.27−1.86 µg/mL), LOQ (0.90−6.18 µg/mL), and recovery (80−110%). The developed and validated technique was used for the evaluation of triterpenic compounds in samples of Vaccinium macrocarpon and Vaccinium oxycoccos fruits, and their peels, pulp and seeds. The studied chromatogram profiles of Vaccinium macrocarpon and Vaccinium oxycoccos were identical but differed in the areas of the analytical peaks. Ursolic acid was the dominant compound in fruit samples of Vaccinium macrocarpon and Vaccinium oxycoccos. The highest amounts of triterpenic compounds were detected in the cranberry peels samples. The developed method for the detection of triterpene compounds can be applied in further studies for routine testing on the qualitative and quantitative composition of fruit samples of Vaccinium macrocarpon and Vaccinium oxycoccos species and cultivars.

Advanced Development of Supercritical Fluid Chromatography in Herbal Medicine Analysis

The greatest challenge in the analysis of herbal components lies in their variety and complexity. Therefore, efficient analytical tools for the separation and qualitative and quantitative analysis of multi-components are essential. In recent years, various emerging analytical techniques have offered significant support for complicated component analysis, with breakthroughs in selectivity, sensitivity, and rapid analysis. Among these techniques, supercritical fluid chromatography (SFC) has attracted much attention because of its high column efficiency and environmental protection. SFC can be used to analyze a wide range of compounds, including non-polar and polar compounds, making it a prominent analytical platform. The applicability of SFC for the separation and determination of natural products in herbal medicines is overviewed in this article. The range of applications was expanded through the selection and optimization of stationary phases and mobile phases. We also focus on the two-dimensional SFC analysis. This paper provides new insight into SFC method development for herbal medicine analysis.

Recent Advances in Separation and Analysis of Saponins in Natural Products

To better control the quality of saponins, ensure their biological activity and clinical therapeutic effect, and expand the development and application of saponins, this paper systematically and comprehensively reviews the separation and analytical methods of saponins in the past decade. Since 2010, the electronic databases of PubMed, Google Scholar, ISI Web of Science, Science Direct, Wiley, Springer, CNKI (National Knowledge Infrastructure, CNKI), Wanfang Med online, and other databases have been searched systematically. As a result, it is found that ionic liquids and high-performance countercurrent chromatography are the most popular extraction and separation techniques for saponins, and the combined chromatography technique is the most widely used method for the analysis of saponins. Liquid chromatography can be used in combination with different detectors to achieve qualitative or quantitative analysis and quality control of saponin compounds in medicinal materials and their preparations. This paper provides the latest valuable insights and references for the analytical methods and continued development and application of saponins.

Simultaneous Quantitative Analysis of the Major Bioactive Compounds in Gentianae Radix and its Beverages by UHPSFC-DAD

This study presents the first ultra-high performance supercritical fluid chromatography-diode array detector (UHPSFC-DAD) assay for simultaneous quantitation of secoiridoids, iridoids, xanthones, and xanthone glycosides in Gentiana lutea L. Separation was reached within 12 min on an Acquity UPC2 BEH 2-EP column using CO2 and methanol with 5.5% water as mobile phases. Method validation for nine selected marker compounds (gentisin, isogentisin, swertiamarin, sweroside, gentiopicroside, loganic acid, amarogentin, gentioside, and its isomer) confirmed the assay's sensitivity, linearity, precision, and accuracy. The practical applicability was proven by the analysis of 13 root specimens and 10 commercial liquid preparations (seven liqueurs and three clear spirits). In all root batches, the secoiridoid gentiopicroside dominated (2.1-5.6%) clearly over all other metabolites. In the liqueurs, the metabolite content and distribution were extremely variable: while gentiopicroside was the main compound in four liqueurs, sweroside dominated in one preparation and loganic acid in two others. In contrast, measurable amounts of the metabolites were not detected in any of the examined clear spirits.

Oleanolic Acid: Extraction, Characterization and Biological Activity

Oleanolic acid, a pentacyclic triterpenoid ubiquitously present in the plant kingdom, is receiving outstanding attention from the scientific community due to its biological activity against multiple diseases. Oleanolic acid is endowed with a wide range of biological activities with therapeutic potential by means of complex and multifactorial mechanisms. There is evidence suggesting that oleanolic acid might be effective against dyslipidemia, diabetes and metabolic syndrome, through enhancing insulin response, preserving the functionality and survival of β-cells and protecting against diabetes complications. In addition, several other functions have been proposed, including antiviral, anti-HIV, antibacterial, antifungal, anticarcinogenic, anti-inflammatory, hepatoprotective, gastroprotective, hypolipidemic and anti-atherosclerotic activities, as well as interfering in several stages of the development of different types of cancer; however, due to its hydrophobic nature, oleanolic acid is almost insoluble in water, which has led to a number of approaches to enhance its biopharmaceutical properties. In this scenario, the present review aimed to summarize the current knowledge and the research progress made in the last years on the extraction and characterization of oleanolic acid and its biological activities and the underlying mechanisms of action.

Separation and characterization of phenylamides from Piper kadsura using preparative supercritical fluid chromatography and ultra-high-performance supercritical fluid chromatography-tandem mass spectrometry

A preparative supercritical fluid chromatography method for the separation of Piper kadsura obtained five phenylamide compounds, which had the same structural skeleton, but changed in the number and position of methoxyl substituents. To improve the separation selectivity of these structural analogues, silica, phenyl, and chiral stationary phases were screened. Only through the combination of Chiral C and phenyl columns could the separation of the five phenylamides be solved. The two-step strategy using preparative supercritical fluid chromatography presented good orthogonality that ensured the purity of the phenylamides. Then, an ultra-high-performance supercritical fluid chromatography hyphened tandem mass spectrometry method was developed, and the fragmentation pattern of phenylamides was summarized. It mainly cleaved in the amide bond to produce the fragment ion, which could help to judge the substituent positions. Twenty-eight possible molecular weights of hydroxyl and methoxyl substituted phenylamides were calculated and screened. Nine compounds were extracted in three [M + H]⁺ ions at m/z 284.13, 314.13, and 344.13, including five purified compounds and the other four positional or trans-cis phenylamide isomers in low content. The methods developed in this research were useful in the separation and characterization of phenylamide analogues.

Supercritical fluid chromatography using methacrylate-based monolithic column for the separation of polar analytes

A poly(N,N-dimethyl-N-methacryloyloxyethyl-N-(3-sulfopropyl) ammonium betaine-co-ethylene dimethacrylate) monolith was prepared in a 100 × 2.0 mm id stainless-steel column and was investigated for supercritical fluid chromatography. Optimization of its porosity was performed by changing the conditions of polymerization. Then, the chemical group of this column was confirmed by Fourier transform infrared spectroscopy and elemental analysis. The morphology was characterized by scanning electron microscopy. The prepared column showed good repeatability based on the retention factor of adenine, uracil and cytosine to calculate their run-to-run, day-to-day, column-to-column, and batch-to-batch relative standard deviations. Those values were less than 1.9% (n = 10), 6.5% (n = 3), 5.6% (n = 3), and 1.7% (n = 3), respectively. In addition, the column was found to be stable within 3 and 10 days with relative standard deviations less than 6.5 and 8.5%, respectively. These results indicated that the columns showed good reproducibility and stability. Compared with liquid chromatogaphy, supercritical fluid chromatography provided better kinetic performance and selectivity. Finally, several neutral, acid, and basic polar analytes were utilized to test its application. The results demonstrated that the prepared column exhibited a good separation performance and showed great potential in supercritical fluid chromatography.

An integrated strategy for holistic quality identification of Chinese patent medicine: Liuwei Dihuang Pills as a case study

INTRODUCTION

Liuwei Dihuang Pills (concentrated pills, simplified as LWDHP), one of the most famous classic Chinese Patent Medicine (CPM), is produced by hundreds of pharmaceutical manufacturers with billions of Chinese yuan (CNY) in annual sales. However, current quality identification of LWDHP mainly relies on a thin-layer chromatography (TLC) method that is complicated and deficient.

OBJECTIVE

The goal of this study is to simplify the identification process and provide a more comprehensive quality assessment method of LWDHP by developing an integrated strategy based on liquid chromatography coupled with mass spectrometry (LC-MS) and multivariate statistical analysis.

METHOD

Ultra-high-performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UHPLC/QTOF-MS) was employed to perform qualitative analyses of a home-made LWDHP and to establish a stably characteristic compound library by analysis of batches of its component herbs. Then selective ion monitoring (SIM) of single MS was utilised to develop a rapid identification method based on the UHPLC/QTOF-MS analysis result. Multivariate statistical analysis was subsequently used for the quality assessment of different commercial samples.

RESULTS

Seventy-eight characteristic compounds were characterised, and 68 of them were recorded to establish a stably characteristic compound library. Thirty-one compounds were selected from the library for the establishment of SIM identification method. Good specificity, capability, and feasibility had been respectively verified by the analysis of blank sample, negative control (NC) preparation samples, home-made LWDHP sample, and commercial sample. Multivariate statistical analysis of 20 batches of commercial LWDHP samples revealed the quality consistency of the same vendor's product and quality difference between diverse vendors' products.

CONCLUSION

The SIM identification method by a single analysis could significantly simplify the identification process of LWDHP, and it was performed in a holistic mode for no less than two compounds of each component herb monitored. Moreover, it could also be combined with multivariate statistical analysis to conduct quality assessments of batches of samples. The integrated strategy used in the study of LWDHP could be applied for the identification of other CPM as well.

Ultra-high performance supercritical fluid chromatography method for separation and quantitation of saikosaponins in herbal medicine

Saikosaponins are the main active ingredients of Bupleuri Radix and have been shown to have hepatoprotective, immunomodulatory and anti-viral activities. Among the saikosaponins, saikosaponin a (SSa), saikosaponin b₁ (SSb₁) and saikosaponin b₂ (SSb₂) are a group of isomers, which are difficult to separate by HPLC. In this study, a new method for separation and quantitation of saikosaponins was established by using ultra-high performance supercritical fluid chromatography (UHPSFC). A Torus Diol column (100 mm × 3 mm, 1.7 μm) was applied in this study. The mobile phase CO₂ (A) was the main solvent with MeOH (B) as co-solvent. The results showed that the five saikosaponins were successfully separated within 22 min through optimization of chromatographic conditions. Besides, the UHPSFC method was applied for the quantitation of saikosaponins in a patent medicine Chaihu Dropping Pills, and demonstrated a good correlation coefficient (R²) ≥ 0.9990 in the range of 0.025 - 0.25 mg/mL. The recoveries of the five saikosaponins at three different concentrations were in the range of 90.23-99.84%. This study indicates that the proposed method has high separation efficiency in analyzing saikosaponins, which provides a new way for the separation and quantitation of saikosaponins in herbal medicines.

Development of a novel method for polar metabolite profiling by supercritical fluid chromatography/tandem mass spectrometry

Supercritical carbon dioxide (scCO₂), the main fluid in the mobile phase for supercritical fluid chromatography (SFC), is non-polar. The majority of polar compounds are little soluble in scCO₂, thereby rendering them poor candidates for achieving separation by carbon dioxide-based SFC. There is no reported method for the comprehensive analysis of hydrophilic metabolites by SFC with mobile phases comprising a high CO₂ ratio. In this study, we investigated the effect of additives in the modifier for enabling the application of SFC to profile diverse polar compounds for metabolomics. Eleven types of columns were screened by using proteinogenic amino acids as the model compounds. The addition of water and acids (formic acid and trifluoroacetic acid (TFA)) to the modifier was also investigated to improve the solubility of the polar compounds and mitigate the unfavorable interaction between the stationary phase and the polar compounds. A significant improvement in the peak shapes of the amino acids was observed upon addition of TFA. The CO₂/modifier ratio and TFA concentration in the mobile phases were investigated using the CROWNPAK CR-I (+) column, which showed the best performance during the column-screening. The CO₂/methanol/water/TFA ratio of 70/27/3/0.15 (v/v/v/v) was determined as the optimized mobile phase composition. Furthermore, the applicability of the optimized analytical method to other polar compounds was examined; 100 cationic and amphoteric compounds with predicted logP_ow values that ranged from -5.9 to 1.7 could be simultaneously analyzed without derivatization. Anionic compounds such as organic acids, phosphates, and sugars were excluded from the target analytes. Most of the previously reported SFC methods for analyzing polar compounds employ a gradient elution and require the use of high modifier ratios at 40% or more. In the proposed method, the use of water and TFA enabled the rapid and simultaneous analysis under isocratic elution within 10 min, even with a high CO₂ ratio of 70%. Additionally, a rat serum extract was analyzed using the optimized conditions, and 43 polar metabolites were successfully detected. This result demonstrates the applicability of the SFC/tandem mass spectrometry method to real samples.

Towards eco-friendly secondary plant metabolite quantitation: Ultra high performance supercritical fluid chromatography applied to common vervain (Verbena officinalis L.)

This report presents the first ultra high performance supercritical fluid chromatography diode array detector based assay for simultaneous determination of iridoid glucosides, flavonoid glucuronides, and phenylpropanoid glycosides in Verbena officinalis (Verbenaceae) extracts. Separation of the key metabolites was achieved in less than 7 min on an Acquity UPC² Torus Diol column using a mobile phase gradient comprising subcritical carbon dioxide and methanol with 0.15% phosphoric acid. Method validation for seven selected marker compounds (hastatoside, verbenalin, apigenin‐7‐O‐glucuronide, luteolin‐7‐O‐glucuronide, apigenin‐7‐O‐diglucuronide, verbascoside, and luteolin‐7‐O‐diglucuronide) confirmed the assay to be sensitive, linear, precise, and accurate. Head‐to‐head comparison to an ultra high performance liquid chromatography comparator assay did prove the high orthogonality of the methods. Quantitative result equivalence was evaluated by Passing‐Bablok‐correlation and Bland‐Altman‐plot analysis. This cross‐validation revealed, that one of the investigated marker compound peaks was contaminated in the ultra high performance liquid chromatography assay by a structurally related congener. Taken together, it was proven that the ultra high performance supercritical fluid chromatography instrument setup with its orthogonal selectivity is a true alternative to conventional reversed phase liquid chromatography in quantitative secondary metabolite analysis. For regulatory purposes, assay cross‐validation with highly orthogonal methods seems a viable approach to avoid analyte overestimation due to coeluting, analytically indistinguishable contaminants.

Quality Evaluation of Mahonia bealei (Fort.) Carr. Using Supercritical Fluid Chromatography with Chemical Pattern Recognition

Mahonia bealei (Fort.) Carr. (M. bealei) plays an important role in the treatment of many diseases. In the present study, a comprehensive method combining supercritical fluid chromatography (SFC) fingerprints and chemical pattern recognition (CPR) for quality evaluation of M. bealei was developed. Similarity analysis, hierarchical cluster analysis (HCA), principal component analysis (PCA) were applied to classify and evaluate the samples of wild M. bealei, cultivated M. bealei and its substitutes according to the peak area of 11 components but an accurate classification could not be achieved. PLS-DA was then adopted to select the characteristic variables based on variable importance in projection (VIP) values that responsible for accurate classification. Six characteristics peaks with higher VIP values (≥1) were selected for building the CPR model. Based on the six variables, three types of samples were accurately classified into three related clusters. The model was further validated by a testing set samples and predication set samples. The results indicated the model was successfully established and predictive ability was also verified satisfactory. The established model demonstrated that the developed SFC coupled with PLS-DA method showed a great potential application for quality assessment of M. bealei.

Supercritical fluid chromatography-a technical overview and its applications in medicinal plant analysis: an update covering 2012-2018

Medicinal plants with complex matrices are endowed with a wide scope of biological activities. The separation, quantification, characterization and purification of bioactive components from herbal medicine extracts have always challenged analysts. Fortunately, the advancement of various emerging techniques has provided potent support for improving the method selectivity, sensitivity and run speeds in medicinal plant analyses. In recent years, the advent of new-generation supercritical fluid chromatography (SFC) instruments and a wide diversity of column chemistries, coupled with the intrinsic technical features of SFC, have made it an alternative and prominent analytical platform in the medicinal plant research area. This work aims to give a comprehensive overview of the fundamentals, technical advancement and investigating parameters of SFC in combination with three prevalent detectors. Moreover, the latest research progress of SFC applications in medicinal plant analyses is illuminated, with focus on herbal medicine-related SFC papers on the analytical and preparative scale that were published during the period of 2012 to December 2018. The most relevant applications were classified based on the constituents to be analysed. As for the respective research cases, analytical protocols and data processing strategies were provided, along with the indicated restrictions or superiority of the method; thus, the current status of SFC in medicinal plant analysis was presented.

Simultaneous determination of amino acids in different teas using supercritical fluid chromatography coupled with single quadrupole mass spectrometry

Tea is a widely consumed beverage and has many important physiological properties and potential health benefits. In this study, a novel method based on supercritical fluid chromatography coupled with mass spectrometry (SFC-MS) was developed to simultaneously determine 11 amino acids in different types of tea (green teas, Oolong tea, black tea and Pu-erh tea). The separation conditions for the analysis of the selected amino acids including the column type, temperature and backpressure as well as the type of additive, were carefully optimized. The best separation of the 11 amino acids was obtained by adding water (5%, v/v) and trifluoroacetic acid (0.4%, v/v) to the organic modifier (methanol). Finally, the developed SFC-MS method was fully validated and successfully applied to the determination of these amino acids in six different tea samples. Good linearity (r ≥ 0.993), precision (RSDs ≤ 2.99%), accuracy (91.95%–107.09%) as well as good sample stability were observed. The limits of detection ranged from 1.42 to 14.69 ng/mL, while the limits of quantification were between 4.53 and 47.0 ng/mL. The results indicate that the contents of the 11 amino acids in the six different tea samples are greatly influenced by the degree of fermentation. The proposed SFC-MS method shows a great potential for further investigation of tea varieties.

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A SFC-MS approach was developed for the determination of amino acids.

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Water and trifluoroacetic acid are interesting additives for the SFC separation of amino acids.

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The SFC-MS method shows a good potential to differentiate the types of tea based on the content of amino acids.

Selective Profiling of Saponins from Gypsophila trichotoma Wend. by HILIC Separation and HRMS Detection

INTRODUCTION

Roots of Gypsophila trichotoma Wend. (Caryophyllaceae) are rich sources of glucuronide oleanane-type triterpenoid carboxylic acid 3,28-O-bidesmosides (GOTCABs). These saponins have been reported to possess synergistic cytotoxicity in combination with type I ribosome-inactivating protein saporin.

OBJECTIVE

To develop ultra high-performance liquid chromatography - electrospray ionisation/high resolution mass spectrometry (UHPLC-ESI/HRMS) acquisition strategy for the recognition of Gypsophila GOTCAB saponins.

METHODOLOGY

A highly-selective hydrophilic interaction UHPLC method (Si-HILIC UHPLC) was developed for the separation of GOTCAB saponins from the methanol-aqueous root extract of G. trichotoma (GTR). UHPLC was coupled to an Orbitrap mass spectrometer equipped with heated electrospray ionisation (HESI) probe. ESI-HRMS and tandem mass spectrometry (MS/MS) data of the separated compounds was used for saponins structure assignment.

RESULTS

Based on the conformity of the fragmentation of 11 previously identified GTR saponins, 21 GOTCAB forming between two and four isobaric and positional isomers are identified with proposals for their structures. Tables with assignment of characteristic fragment ions and more than 10 newly identified saponins in GTR were described. Fragmentation rules for tentative identification of three major types of saponins from GTR were summarised and possible fragmentation pathways were proposed. Type I and II consisted of acylated and sulphated GOTCABs, respectively, while type III included acylated and sulphated saponins. The type II sulphated GOTCAB saponins were all previously not described.

CONCLUSIONS

The study demonstrates the potential of the coupling of highly-selective (Si)-HILIC UHPLC with HRMS and MS/MS detection for analysis and identification of triterpenoid saponins. Copyright © 2017 John Wiley & Sons, Ltd.