Online comprehensive two-dimensional hydrophilic interaction chromatography × reversed-phase liquid chromatography coupled with hybrid linear ion trap Orbitrap mass spectrometry for the analysis of phenolic acids in Salvia miltiorrhiza

Protection against myocardial ischemia/reperfusion injury in mice by 3-caffeoylquinic acid isomers isolated from Saxifraga tangutica

The development of ischemic heart disease (IHD) involves a variety of pathophysiological responses, such as mitochondrial dysfunction. Many compounds with antioxidant activity isolated from natural products have been shown to have significant effects on the prevention and treatment of cardiovascular diseases. However, little is known about the palliative effects of 3-caffeoylquinic acid isomers isolated from Saxifraga tangutica (S. tangutica) on myocardial ischemia/reperfusion injury (MIRI). Three isomers of 3-caffeoylquinic acid were isolated from S. tangutica and identified as neochlorogenic acid (Fr2-4-1-1, 18.5 mg), chlorogenic acid (Fr2-5-1-1, 81.7 mg) and cryptochlorogenic acid (Fr2-5-2-1, 15.0 mg) using medium-pressure liquid chromatography-high-pressure two-dimensional liquid chromatography. An in vitro DPPH assay showed that cryptochlorogenic acid (CCGA), neochlorogenic acid (NCGA) and chlorogenic acid (CGA) (in order of activity from strongest to weakest) possessed superior antioxidant activity. Langendorff's in vitro model was utilized to explore the protective effects of 3 caffeoylquinic acid isomers against MIRI. The ex vivo MIRI assay demonstrated that CCGA significantly improved hemodynamic function (P < 0.05), hemodynamic function-related indices (LVDP, RPP, +dP/dt and -dP/dt), and cell morphology in I/R myocardium tissues. In addition, the results of western blot analysis showed that mitochondrial biogenesis was significantly increased in I/R myocardial tissues after treatment with CCGA. In contrast, the activities of CGA and NCGA were lower. This is the first demonstration of efficient preparative isolation of 3-caffeoylquinic acid isomers (CGA, NCGA and CCGA) from S. tangutica. CCGA may be a promising approach for the treatment of cardiac I/R injury, especially for the regulation of mitochondrial biogenesis after MIRI.

Two Multidimensional Chromatography/High-Resolution Mass Spectrometry Approaches Enabling the In-Depth Metabolite Characterization Simultaneously from Three Glycyrrhiza Species: Method Development, Comparison, and Integration

Two offline multidimensional chromatography/high-resolution mass spectrometry systems (method 1: fractionation and online two-dimensional liquid chromatography, 2D-LC; method 2: fractionation and offline 2D-LC) were established to characterize the metabolites simultaneously from three Glycyrrhiza species. Ion exchange chromatography in the first-dimensional (1D) separation was well fractionated between the acidic (mainly triterpenoids) and weakly acidic components (flavonoids). These obtained subsamples got sophisticated separation by the second (2D) and third dimension (3D) of chromatography either by online reversed-phase chromatography × reversed-phase chromatography (RPC × RPC) or offline hydrophilic interaction chromatography × RPC (HILIC × RPC). Orthogonality for the 2D/3D separations reached 0.73 for method 1 and 0.81 for method 2, respectively. We could characterize 1097 compounds from three Glycyrrhiza species based on an in-house library and 33 reference standards, involving 618 by method 1 and 668 by method 2, respectively. They exhibited a differentiated performance and complementarity in identifying the multiple subclasses of Glycyrrhiza components.

Development of a column switching for direct online enrichment and separation of polar and nonpolar analytes from aqueous matrices

Trace substances in surface waters may threaten health and pose a risk for the aquatic environment. Moreover, separation and detection by instrumental analysis is challenging due to the low concentration and the wide range of polarities. Separation of polar and nonpolar analytes can be achieved by using stationary phases with different selectivity. Lower limits of detection of trace substances can be obtained by offline enrichment on solid phase materials. However, these practices require substantial effort and are time consuming and costly. Therefore, in this study, a column switching was developed to enrich and separate both polar and nonpolar analytes by an on-column large volume injection of aqueous samples. The column switching can significantly reduce the effort and time for analyzing trace substances without compromising on separation and detection. A reversed phase (RP) column is used to trap the nonpolar analytes. The polar analytes are enriched on a porous graphitized carbon column (PGC) coupled serially behind the RP column. A novel valve switching system is implemented to enable elution of the nonpolar analytes from the RP column and, subsequently, elution of polar analytes from the PGC column and separation on a hydrophilic interaction liquid chromatography (HILIC) column. To enable separation of polar analytes dissolved in an aqueous matrix by HILIC, the water plug that is flushed from the PGC column is diluted by dosing organic solvent directly upstream of the HILIC column. The developed method was tested by applying target analysis and non-target screening, highlighting the advantage to effectively separate and detect both polar and nonpolar compounds in a single chromatographic run. In the target analysis, the analytes, with a logD at pH 3 ranging from -2.8 to + 4.5, could be enriched and separated. Besides the 965 features in the RP phase, 572 features from real wastewater were observed in the HILIC phase which would otherwise elute in the void time in conventional one-dimensional RP methods.

Detailed comparison of in-house developed and commercially available heart-cutting and selective comprehensive two-dimensional liquid chromatography systems

Recently, two-dimensional liquid chromatography (2D-LC) has become a popular approach to analyze complex samples. This is partly due to the introduction of commercial 2D-LC systems. In the past, 2D-LC was carried out on in-house developed setups, typically consisting of several switching valves and sample loops as the interface between the two dimensions. Commercial systems usually offer different 2D-LC modes in combination with specialized software to operate the instrument and analyze the data. This makes them highly user-friendly, however, at an increased cost compared to in-house developed setups. This study aims to make a comparison between an in-house developed 2D-LC setup and a commercially available 2D-LC instrument. The comparison is made based on experimental differences, in addition to more general differences, including cost price, flexibility, and ease of operation. Special attention is also paid to the different strategies to deal with the mobile phase incompatibility between the highly orthogonal separation mechanisms considered in this work: hydrophilic interaction liquid chromatography (HILIC) and reversed-phase LC (RPLC). For the commercial 2D-LC instrument, this is done using active solvent modulation (ASM), a valve-based approach allowing the on-line dilution of the effluent eluting from the first dimension column before transfer to the second dimension (2D) column. For the in-house developed setup, a combination of restriction capillaries and a trap column is used. Using a sample of 28 compounds with a large polarity range, peak shapes and recoveries of the 2D-chromatograms are compared for both setups. For early eluting compounds, the selective comprehensive approach, currently only possible on the commercial 2D-LC instrument, results in the best peak shapes and recoveries, however, at the cost of an increased analysis time. In general, depending on the analytical goal (single heart-cut versus full-comprehensive 2D-LC), an in-house developed system can be satisfactory for the analysis of specific target compounds/samples. For more complex problems, it can be interesting to use a more specialized commercial 2D-LC instrument. Overall, this comparison study provides advice for analytical scientists, who are considering to use 2D-LC, on the type of equipment to consider, depending on the needs of their particular applications.

Gain deeper insights into traditional Chinese medicines using multidimensional chromatography combined with chemometric approaches

Traditional Chinese medicines (TCMs) possess a rich historical background, unique theoretical framework, remarkable therapeutic efficacy, and abundant resources. However, the modernization and internationalization of TCMs have faced significant obstacles due to their diverse ingredients and unknown mechanisms. To gain deeper insights into the phytochemicals and ensure the quality control of TCMs, there is an urgent need to enhance analytical techniques. Currently, two-dimensional (2D) chromatography, which incorporates two independent separation mechanisms, demonstrates superior separation capabilities compared to the traditional one-dimensional (1D) separation system when analyzing TCMs samples. Over the past decade, new techniques have been continuously developed to gain actionable insights from complex samples. This review presents the recent advancements in the application of multidimensional chromatography for the quality evaluation of TCMs, encompassing 2D-gas chromatography (GC), 2D-liquid chromatography (LC), as well as emerging three-dimensional (3D)-GC, 3D-LC, and their associated data-processing approaches. These studies highlight the promising potential of multidimensional chromatographic separation for future phytochemical analysis. Nevertheless, the increased separation capability has resulted in higher-order data sets and greater demands for data-processing tools. Considering that multidimensional chromatography is still a relatively nascent research field, further hardware enhancements and the implementation of chemometric methods are necessary to foster its robust development.

Systematical targeted multicomponent characterization and comparison of Arnebiae Radix and its three confusing species by offline two-dimensional liquid chromatography/LTQ-Orbitrap mass spectrometry

Arnebiae Radix, commonly known as "Zicao," can be easily confused with other compounding species, posing challenges for its clinical use. Here, we developed a comprehensive strategy to systematically characterize the diverse components across Arnebiae Radix and its three confusing species. First, an offline two-dimensional liquid chromatography (2D-LC) system integrating hydrophilic interaction chromatography (HILIC) and reverse phase (RP) separations was established, enabling effective separation and detection of more trace constituents. Second, a polygonal mass defect filtering (MDF) workflow was implemented to screen target ions and generate a precursor ion list (PIL) to guide multistage mass (MSn) data acquisition. Third, a three-step characterization strategy utilizing diagnostic ions and neutral losses was developed for rapid determination of molecular formulas, structure classes, and compound identification. This approach enabled systematic characterization of Arnebiae Radix and its three confusing species, with 437 components characterized including 112 shikonins, 22 shikonfurans, 144 phenolic acids, 131 glycosides, 18 flavonoids, and 10 other compounds. Additionally, 361, 230, 340, and 328 components were identified from RZC, YZC, DZC, and ZZC, respectively, with 142 common components and 30 characteristic components that may serve as potential markers for distinguishing the four species. In summary, this is the first comprehensive characterization and comparison of the phytochemical profiles of Arnebiae Radix and its three confusing species, advancing our understanding of this herbal medicine for quality control.

Identification of potential quality markers of Zishen Yutai pill based on spectrum-effect relationship analysis

Introduction: The current quality evaluation of traditional Chinese medicine (TCM) is difficult to attribute to clinical efficacy due to the complexity of TCM. Zishen Yutai pill (ZYP), a well-known traditional Chinese patent medicine, has been widely used to prevent recurrent miscarriage and treat threatened abortion. However, the chemical components of ZYP are unknown, and there is no convincing quality control method applied on ZYP. Although ZYP has been found to promote endometrial receptivity and treat impending abortion, the substantial basis of the therapeutic effects is unclear. The aim of this study was to clarify the quality markers correlated with the potential medicinal activities and provide a theoretical foundation for scientific quality control and product quality improvement of ZYP. Methods: The chemical constituents of ZYP were comprehensively analyzed by offline two-dimensional liquid chromatography-mass spectrometry (2DLC-LTQ-Orbitrap-MS). The efficacy of the 27 ZYP orthogonal groups was investigated using the HTR-8/SVneo oxidative damage model and migration model in vitro, as well as the endometrial receptivity disorder mouse model and premature ovarian failure mouse model in vivo. Based on the efficacy and mass spectral results, spectrum-effect relationship analysis was used to identify the chemical components with corresponding pharmacological activities. Results: A total of 589 chemical components were found in ZYP, of which 139 were not identified in the literature. The potential quality markers for ZYP were successfully identified through orthogonal design and spectrum-effect relationship analysis. By combining mass spectrum data and pharmacological results of 27 orthogonal groups, 39 substances were identified as potential quality markers. Conclusion: The approaches used in this study will provide a feasible strategy for the discovery of quality markers with bioactivity and further investigation into the quality evaluation of TCM.

Potential Mechanisms of Imidacloprid-Induced Neurotoxicity in Adult Rats with Attempts on Protection Using Origanum majorana L. Oil/Extract: In Vivo and In Silico Studies

Imidacloprid (IMI) insecticide is rapidly metabolized in mammals and contributes to neurotoxicity via the blocking of nicotinic acetylcholine receptors, as in insects. Origanum majorana retains its great antioxidant potential in both fresh and dry forms. No data is available on the neuroprotective effect of this plant in laboratory animals. In this context, aerial parts of O. majorana were used to prepare the essential oil (OMO) and methanol extract (OME). The potential neuroprotective impact of both OMO and OME against IMI-induced neurotoxicity in rats was explored. Forty-two rats were divided into 6 groups, with 7 rats in each one. Rats were daily administered the oral treatments: normal saline, OMO, OME, IMI, IMI + OMO, and IMI + OME. Our results revealed the identification of 55 components in O. majorana essential oil, most belonging to the oxygenated and hydrocarbon monoterpenoid group. Moreover, 37 constituents were identified in the methanol extract, mostly phenolics. The potent neurotoxic effect of IMI on rats was confirmed by neurobehavioral and neuropathological alterations and a reduction of both acetylcholine esterase (AchE) activity and dopamine (DA), serotonin (5HT), and γ-aminobutyric acid (GABA) levels in the brain. Exposure of rats to IMI elevates the malondialdehyde (MDA) levels and reduces the antioxidant capacity. IMI could upregulate the transcription levels of nuclear factor-κB (NF-κB), interleukin-1 β (IL-1β), and tumor necrosis factor (TNF-α) genes and express strong caspase-3 and inducible nitric oxide synthase (iNOS) immunostaining in most examined brain areas. On the other hand, rats coadministered OMO or OME with IMI showed a marked improvement in all of the studied toxicological parameters. In conclusion, cotreatment of O. majorana extracts with IMI can protect against IMI neurotoxicity via their potent antioxidant, anti-inflammatory, and anti-apoptotic effects. Thus, we recommend a daily intake of O. majorana to protect against insecticide's oxidative stress-mediated neuroinflammatory stress and apoptosis. The molecular docking study of linalool, rosmarinic acid, γ-terpene, and terpene-4-ol justify the observed normalization of the elevated iNOS and TNF-α levels induced after exposure to IMI.

Optimizing transfer and dilution processes when using active solvent modulation in on-line two-dimensional liquid chromatography

Two-dimensional liquid chromatography (2D-LC) is becoming increasingly popular for the analysis of complex samples, which is partly due to the recent introduction of commercial 2D-LC systems. To deal with the mobile phase incompatibility between highly orthogonal retention mechanisms, such as hydrophilic interaction liquid chromatography (HILIC) and reversed-phase LC (RPLC), several strategies have been introduced over the years. One of these strategies is active solvent modulation (ASM), a valve-based approach allowing the on-line dilution of the effluent eluting from the first dimension before transfer to the second dimension. This strategy has gained a lot of attention and holds great potential, however, no clear guidelines are currently in place for its use. Therefore, this study aims to investigate how the ASM process can be optimized when using highly incompatible LC combinations, such as HILIC and RPLC, in a simplified selective comprehensive 2D-LC set-up (sHILIC x RPLC) to suggest guidelines for future users. Using a representative sample, the dilution factor (DF), the duration of the ASM phase, the filling percentage of the sample loops, and their unloading configuration are investigated and optimized. It is observed that a DF of 10 with an optimal ASM phase duration, a sample loop filling of maximum 25%, and an unloading configuration in backflush mode, result in the best peak shapes, intensities, and recoveries for early eluting compounds, while keeping the total analysis time minimal. Based on these results, some general recommendations are made that could also be applied in other 2D-LC modes, such as comprehensive 2D-LC (LC x LC), heart-cutting 2D-LC (LC-LC), and other chromatographic combinations with mobile phase incompatibility issues.

Comprehensive and heart-cutting multidimensional liquid chromatography-mass spectrometry and its applications in food analysis

In food analysis, conventional one-dimensional liquid chromatography methods sometimes lack sufficient separation power due to the complexity and heterogeneity of the analyzed matrices. Therefore, the use of two-dimensional liquid chromatography (2D-LC) turns out to be a powerful tool to consider, especially when coupled to mass spectrometry (MS). This review presents the most remarkable 2D-LC-MS food applications reported in the last 10 years, including a critical discussion of the multiple approaches, modulation strategies as well as the importance of the optimization of the different analytical aspects that will condition the 2D-LC-MS performance. The presence of contaminants in food (food safety), the food quality, and authenticity or the relationship between the beneficial effects of food and human health are some of the fields in which most of the 2D-LC-MS applications are mainly focused. Both heart-cutting and comprehensive applications are described and discussed in this review, highlighting the potential of 2D-LC-MS for the analysis of such complex samples.

Comprehensive and heart-cutting multidimensional liquid chromatography-mass spectrometry and its applications in food analysis

In food analysis, conventional one-dimensional liquid chromatography methods sometimes lack sufficient separation power due to the complexity and heterogeneity of the analysed matrices. Therefore, the use of two-dimensional liquid chromatography (2D-LC) turns out to be a powerful tool to consider, especially when coupled to mass spectrometry (MS). This review presents the most remarkable 2D-LC-MS food applications reported in the last 10 years, including a critical discussion of the multiple approaches, modulation strategies as well as the importance of the optimisation of the different analytical aspects that will condition the 2D-LC-MS performance. The presence of contaminants in food (food safety), the food quality and authenticity or the relationship between the beneficial effects of food and human health are some of the fields in which most of the 2D-LC-MS applications are mainly focused. Both heart-cutting and comprehensive applications are described and discussed in this review, highlighting the potential of 2D-LC-MS for the analysis of such complex samples.

Bottom-Up Proteomics: Advancements in Sample Preparation

Liquid chromatography–tandem mass spectrometry (LC–MS/MS)-based proteomics is a powerful technique for profiling proteomes of cells, tissues, and body fluids. Typical bottom-up proteomic workflows consist of the following three major steps: sample preparation, LC–MS/MS analysis, and data analysis. LC–MS/MS and data analysis techniques have been intensively developed, whereas sample preparation, a laborious process, remains a difficult task and the main challenge in different applications. Sample preparation is a crucial stage that affects the overall efficiency of a proteomic study; however, it is prone to errors and has low reproducibility and throughput. In-solution digestion and filter-aided sample preparation are the typical and widely used methods. In the past decade, novel methods to improve and facilitate the entire sample preparation process or integrate sample preparation and fractionation have been reported to reduce time, increase throughput, and improve reproducibility. In this review, we have outlined the current methods used for sample preparation in proteomics, including on-membrane digestion, bead-based digestion, immobilized enzymatic digestion, and suspension trapping. Additionally, we have summarized and discussed current devices and methods for integrating different steps of sample preparation and peptide fractionation.

Enhancing the compatibility of normal-phase chromatography x reversed-phase chromatography by combination of low-temperature sensitive aqueous-phase compatible normal- phase chromatography and at-column dilution modulation

The nearly opposite retention mechanism in the two-dimensional liquid chromatography (2D-LC), which combines normal phase liquid chromatography (NPLC) and reversed phase liquid chromatography (RPLC), shows extremely high orthogonality and theoretical peak capacity. However, peak breakthrough and peak distortion caused by the highly incompatible 2D mobile phases counteracts the advantages offered by high orthogonality. To address this difficulty, this study proposes a comprehensive two-dimensional NPLC × RPLC integrating temperature-sensitive aqueous-phase compatible normal-phase chromatography (TSACNPLC) and at-column dilution modulation (ACDM). The proposed 2D-LC system uses an aqueous-miscible acetonitrile/methanol eluent in the 1st D NPLC, instead of an aqueous-phase immiscible eluent, such as n-hexane/methanol, to increase the miscibility with the RP mobile phase system. Additionally, the system exploits temperature-sensitive retention behavior to enhance the retention ability of aqueous-phase compatible NPLC. To verify the feasibility of the proposed 2D-LC, this study selected three multi-component samples with mid-to-low polarity, including ethoxylated (n ≈ 6) bisphenol A (BPA-6EO), ethoxylated (n ≈ 6) tristearylphenol (TSP-6EO), and safflower methanol extract. Next, the effectiveness of the constructed 2D-LC was systematically investigated, including low temperature-induced retention enhancement of NPLC, overcoming solvent incompatibility by ACDM, and optimization of 2 D separation conditions, was systematically investigated.

A multidimensional chromatography/high-resolution mass spectrometry approach for the in-depth metabolites characterization of two Astragalus species

To address the chemical complexity is indispensable in a number of research fields. Herb metabolome is typically composed by more than one class of structure analogs produced via different biosynthetic pathways. Multidimensional chromatography (MDC), due to the greatly enhanced separation space, offers the potential solution to comprehensive characterization of herbal metabolites. Here, we presented a strategy, by integrating MDC and quadrupole time-of-flight mass spectrometry (QTOF-MS), to accomplish the in-depth herbal metabolites characterization. Using the metabolome of two Astragalus species (A. membranaceus var. mongholicus,AMM; A. membranaceus, AM) as the case, an off-line three-dimensional liquid chromatography (3D-LC) system was established: hydrophilic interaction chromatography using an XAmide column as the first dimension (¹D) for fractionating the total extract, on-line reversed-phase × reversed-phase liquid chromatography separately configuring a CSH Fluoro-Phenyl column and a Cosmocore C18 column as the second dimension (²D) and the third dimension (³D) of chromatography to enable the explicit separation of three well fractionated samples. Moreover, the negative-mode collision-induced dissociation by QTOF-MS under the optimized condition could provide diversified fragments that were useful for the structural elucidation of AMM and AM. An in-house library (composed by 247 known compounds) and comparison with 43 reference standards were utilized to assist more reliable characterization. We could characterize 513 compounds from two Astragalus species (344 from AMM and 323 from AM), including 236 flavonoids, 150 triterpenoids, 18 organic acids, and 109 others. Conclusively, the established MDC approach gained excellent performance favoring the analogs-oriented in-depth characterization of herbal metabolites, but received uncompromising analytical efficiency.

Integrating HPLC-Q-TOF-MS/MS, network pharmacology and experimental validation to decipher the chemical substances and mechanism of modified Gui-shao-liu-jun-zi decoction against gastric cancer

Background and aim

Gastric cancer (GC) is a common malignant tumor worldwide. Modified Gui-shao-liu-jun-zi decoction (mGSLJZ) is a clinically effective traditional Chinese medicine (TCM) compound in GC treatment. This study aimed to analyze main chemical substances of mGSLJZ and investigate active ingredients and molecular mechanism of mGSLJZ against GC.

Experimental procedure

HPLC-Q-TOF-MS/MS was used to analyze chemical substances of mGSLJZ, and potential active ingredients were screened from TCMSP. The target set of mGSLJZ for GC was obtained based on SwissTargetPrediction. The PPI network was constructed to screen out core targets. GO and KEGG enrichment analyses were conducted to identify BPs, CCs, MFs and pathways. The "active ingredient-core target-pathway" regulatory network was constructed to obtain core substances. Subsequently, Oncomine, Proteinatlas and molecular docking were performed to validate these findings. The cell experiments were conducted to confirm the anti-GC effects of mGLSJZ.

Results and conclusion

Forty-one potential active ingredients were filtered out from 120 chemical substances in mGSLJZ, including various organic acids and flavonoids. The top 10 key targets, 20 related pathways and 6 core medicinal substances were obtained based on network pharmacology analysis. Molecular docking results indicated that the core substances and key targets had good binding activities. The cell experiments validated that mGSLJZ and the core substances inhibited the proliferation in multiple GC cells and that mGLSJZ restrained the migration of GC. Meanwhile, the top 5 targets and top 2 pathways were verified. The rescue experiments demonstrated that mGSLJZ suppressed the proliferation and migration of GC through the PI3K/AKT/HIF-1 pathway.

Rapid Profiling of Metabolites Combined with Network Pharmacology to Explore the Potential Mechanism of Sanguisorba officinalis L. against Thrombocytopenia

Sanguisorba officinalis L. (SO), a well-known herbal medicine, has been proven to show effect against thrombocytopenia. However, metabolites of SO in vivo are still unclear, and the underlying mechanism of SO against thrombocytopenia from the aspect of metabolites have not been well elucidated. In this study, an improved analytical method combined with UHPLC-QTOF MS and a molecular network was developed for the rapid characterization of metabolites in vivo based on fragmentation patterns. Then, network pharmacology (NP) was used to elucidate the potential mechanism of SO against thrombocytopenia. As a result, a total of 1678 exogenous metabolites were detected in urine, feces, plasma, and bone marrow, in which 104 metabolites were tentatively characterized. These characterized metabolites that originated from plasma, urine, and feces were then imported to the NP analysis. The results showed that the metabolites from plasma, urine, and feces could be responsible for the pharmacological activity against thrombocytopenia by regulating the PI3K-Akt, MAPK, JAK-STAT, VEGF, chemokine, actin cytoskeleton, HIF-1, and pluripotency of stem cells. This study provides a rapid method for metabolite characterization and a new perspective of underlying mechanism study from the aspect of active metabolites in vivo.

Anthocyanins in Different Food Matrices: Recent Updates on Extraction, Purification and Analysis Techniques

Anthocyanins (ANCs), a kind of natural pigments, are widely present in food substrates. Evidence has shown that ANCs can promote health in terms of anti-oxidation, anti-tumor, and anti-inflammation. However, the oxidative stability of ANCs limits accurate quantitation and analysis. Therefore, faster, more accurate, and highly sensitive extraction and determination methods are necessary for understanding the role of ANCs in medicine and food. This review presents an updated overview of pretreatment and detection techniques for ANCs in various food substrates since 2015. Liquid-liquid extraction and various green solvent extraction methods, such as accelerated solvents extraction, deep eutectic solvents extraction, ionic liquids extraction, and supercritical fluid extraction, are commonly used pretreatment methods for extraction and purification of ANCs. Liquid chromatography coupled with different detectors (tandem mass spectrometry and UV detectors) and spectrophotometry methods are some of the determination methods for ANC. This study has updated, compared, and discussed different pretreatment and analysis methods. Moreover, the advanced methods and development prospects in this field are comprehensively summarized, which can provide references for further utilization of ANCs.

Determination of the polyphenolic content of berry juices using focusing-modulated comprehensive two-dimensional liquid chromatography coupled to mass spectrometry detection

In this work, a comprehensive two-dimensional liquid chromatography system, comprised of a ZIC-HILIC and C18 columns in the first and second dimensions, respectively, was tuned and employed for attaining high resolution profiles of the polyphenolic pattern in seven commercial berry juices. The developed HILIC × RP-LC method was validated in terms of linearity range, correlation coefficients, limit of detection, limit of quantification, precision (intra- and inter-day), and recovery. A total of 104 polyphenolic compounds belonging to different chemical classes (hydroxybenzoic and cinnamic acid derivatives, flavone glycosides, flavonols, flavonol glycosides, dihydroflavonols, and anthocyanin glycosides) have been characterized and quantified in the juices investigated. Despite the constituents being similar, a notable quantitative variation among the analyzed berry species was observed. Elderberry contained the highest amount of polyphenols (918 ± 1.10 mg 100 mL^-1), followed by chokeberry (516 ± 0.08 mg 100 mL^-1). On the other hand, raspberry contained the lowest amount (104 ± 1.21 mg 100 mL^-1). Further, total phenolic, flavonoid, and anthocyanin contents were determined spectrophotometrically, yielding consistent results. The free-radical scavenging activity (DPPH test) and reducing power of the juices, expressed as IC₅₀ (μL mL^-1) and mg ASE mL^-1, varied from 2.79 ± 0.03 (honeyberry) to 31.66 ± 0.02 (blueberry) and from 1.71 ± 0.01 (blueberry) to 8.89 ± 0.12 (chokeberry), respectively. Such a ZIC-HILIC × C18 platform based on focusing modulation, never employed so far for berry juices, showed a remarkable separation capability with high values of corrected peak capacity (up to 1372) and orthogonality (A_o up to 0.80), thus providing a great applicability to be advantageously employed for other complex food samples.

Comprehensive profiling of Sanguisorba officinalis using off-line two-dimensional mixed-mode liquid chromatography × reversed-phase liquid chromatography, tandem high-resolution mass spectrometry, and molecular network

The profiling of natural products is important in modern biological sciences and new drug development. However, the separation and characterization of complex herbal extracts are significantly challenging for researchers in the biochemical field. Herein, an off-line two-dimensional mixed-mode LC × reversed-phase LC system is developed. Our system exhibits high orthogonality and is composed of a newly prepared stationary phase in the first dimension and a traditional C₁₈ phase in the second dimension, and is operated in combination with high-resolution MS and molecular network. Sanguisorba officinalis L. is studied using the proposed method owing to its bioactivity. With the aid of orthogonal separation, the ionization of the individual components is improved. The number of detected compounds and separated peaks are significantly increased when one-dimensional-LC is upgraded to two-dimensional-LC. In addition, 270 compounds (127 of which are tentatively characterized as new compounds, and further confirmation is needed) are successfully characterized based on their fragmentation patterns under the guidance of molecular network, while only 95 compounds are characterized using one-dimensional-LC and high-resolution MS. The results indicate that the developed off-line two-dimensional mixed-mode LC × reversed-phase LC, tandem high-resolution MS, and molecular network method is effective for profiling complex samples. This article is protected by copyright. All rights reserved.

A spectrum-effect based method for screening antibacterial constituents in Niuhuang Shangqing Pill using comprehensive two-dimensional liquid chromatography

To investigate and screen the active antibacterial constituents of Niuhuang Shangqing Pill (NSP), the current study developed a two-dimensional liquid chromatography (2DLC) method combining microcalorimetry technique. 60% ethanol extracts from 10 batches of different commercial NSP samples were analyzed and their chemical fingerprint were developed by the comprehensive 2DLC system of Shimadzu Nexera X2. Anti-streptococcus pneumoniae (SP) constituents were determined by microcalorimetry. Thermal kinetic parameters of the SP thermogram affected by 60% ethanol extracts from 10 NSP samples were analyzed by principal component analysis. Spectrum-effect correlation between comprehensive 2DLC fingerprint and the antibacterial activity were analyzed by orthogonal partial least squares (OPLS) and orthogonal partial least squares discriminant analysis (OPLS-DA). Findings showed that peak X1 (unknown), X9 (aloe-emodin), X10 (baicalein), X11 (unknown), X14 (wogonin), X15 (glycyrrhizic acid) and X17 (unknown) are the relevant components that are in positive correlation with inhibitory rate. Regarding inhibitory rate, X17 is the most powerful one, followed by X14, X15, X10, X11, X1 and X9, suggesting that compound X17, wogonin, glycyrrhizic acid and baicalein are the major active antibacterial components of NSP. The current method employing 2DLC with microcalorimetry technique proposes a new insight for screening and identifying antibacterial components in complex herbal formula.

Chemical characterization of flavonoids and alkaloids in safflower (Carthamus tinctorius L.) by comprehensive two-dimensional hydrophilic interaction chromatography coupled with hybrid linear ion trap Orbitrap mass spectrometry

Safflower (Carthamus tinctorius L.) is a famous food additive and herbal medicine in China. In the present research, an online comprehensive two-dimensional hydrophilic interaction chromatography coupled to a diode array detector and a hybrid linear ion trap-Orbitrap mass spectrometry (HILIC × HILIC-DAD-ESI/HRMS/MS ⁿ ) platform was developed to analyze the flavonoids and alkaloids in safflower. By combining with an XBridge Amide column (150 mm × 4.6 mm, 3.5 μm) and an Ultimate amide column (50 mm × 4.6 mm, 5 μm), the system orthogonality reached 88% and a total of 231 peaks were detected. Altogether 93 compounds, including 75 flavonoids and their glycosides and 10 alkaloids were unambiguously or tentatively identified in both negative and positive ion modes, using accurate mass and MS fragment data. Among them, 5 compounds were discovered and reported from safflower for the first time. The established HILIC × HILIC platform should be a powerful tool for the separation and characterization of complicated matrices in natural herbs.

Analysis of alkaloids in Gelsemium elegans Benth. Using an online heart-cutting + comprehensive RPLC×RPLC system tandem mass spectrometry

Characterization of alkaloids and new compound discovery become increasing challenging for Gelsemium elegans Benth. (G. elegans), due to the lack of an effective separation method. In this study, we developed a new online heart-cutting + comprehensive (HC) RPLC × RPLC system with pH difference, which was coupled to a mass detector to realize the separation and characterization of alkaloids from G. elegans. 18 Gelsemium standards were used to construct the RPLC × RPLC system with pH difference (pH 3 and 11), and good orthogonality (correlation coefficient 0.3) was obtained. A heart-cutting valve was introduced into the traditional online comprehensive RPLC × RPLC system to remove principal components and improve detection of minor components. The online HC RPLC × RPLC system achieved good resolving power (effective peak capacity 687) in condition of optimized practical factors, like the first- and second-dimension flow rates, modulation period and elution gradient et al. Finally, a total of 256 alkaloids were grouped and tentatively identified, among which 156 were unreported, including a new alkaloid type in G. elegans and many dimeric indole alkaloids, which was an important supplement to the study on chemical constituents of G. elegans.

Non-volatile compounds of Hyssopus cuspidatus Boriss and their antioxidant and antimicrobial activities

Hyssopus cuspidatus is a famous spice and an aromatic vegetable. Few information could be available concerning its non-volatile chemical composition and bioactivities. Preliminary bioactive evaluations on the crude ethanol extract and its four fractions disclosed that the ethyl acetate fraction (EAF) exhibited antioxidant and antimicrobial bioactivities. LC-MS/MS analysis of EAF helped to identify sixty-four compounds, and phenolic compounds were the dominant components. Systematic separation and purification of EAF led to the isolation of thirty-four compounds. Six compounds were identified to be new and eighteen compounds were discovered from H. cuspidatus for the first time. Rosmarinic acid, methyl rosmarinate, butyl rosmarinate and salvigenin were the major components of EAF and their contents were determined. Most of isolated compounds exhibited significant or moderate antioxidant and antimicrobial activities. This research supported the edible application of H. cuspidatus and disclosed the potency of it as a natural antioxidant and antimicrobial food additive.

Strategies to circumvent the solvent strength mismatch problem in online comprehensive two-dimensional liquid chromatography

On-line comprehensive two-dimensional liquid chromatography is a powerful technique for the separation of highly complex samples. Due to the addition of the second dimension of separation, impressive peak capacities can be obtained within a reasonable analysis time compared to one-dimensional liquid chromatography. In online comprehensive two-dimensional liquid chromatography, the separation power is maximized by selecting two separation dimensions as orthogonal as possible, which most often requires the combination of different mobile phases and stationary phases. The online transfer of a given solvent from the first dimension to the second dimension may cause severe injection effects in the second dimension, mostly due to solvent strength mismatch. Those injection effects may include peak broadening, peak distortion, peak splitting or breakthrough phenomenon. They are often found to reduce significantly the peak capacity and the peak intensity. To overcome such effects, arising specifically in online comprehensive two-dimensional liquid chromatography, different methods have been developed over the years. In this review, we focused on the most recently reported ones. A critical discussion, supported by a theoretical approach, gives an overview of their advantages and drawbacks.

A comprehensive study on the phenomenon of total breakthrough in liquid chromatography

Differences in elution strength between the sample solvent and the mobile phase usually give rise to undesirable effects on the chromatographic separation, which may range from slight broadening to severe peak deformation or even splitting. In the most extreme case, the retention factor of the analyte at the head of the column is so small at the time of injection that part of the analyte goes through the column with very little interaction with the stationary phase and hence elutes very close to the column dead time. This phenomenon is known as breakthrough. Usually, during breakthrough, the retained peak displays a wide array of deformations and it is not rare that multiple retained peaks appear for a given injected analyte. However, under certain conditions, it has been demonstrated that these deleterious effects could fully disappear, leaving only one breakthrough peak and one symmetrical peak on the chromatogram. This so-called "total breakthrough" phenomenon was recently highlighted in the specific context of the 2D-LC separation of peptides but has yet to be explained. In the present paper, we describe the results of a comprehensive study aiming to better understand and define the conditions of emergence of both breakthrough and total breakthrough phenomena in liquid chromatography. The effects of a broad range of parameters, including the nature of the solute, the retention mechanism, the injection and elution conditions, the column temperature, and the injected sample concentration on the occurrence of both phenomena were investigated. While breakthrough was found to occur for all studied compounds, it appears that the presence of positive charges on the molecule is a prerequisite for observing a total breakthrough phenomenon. Among all the parameters investigated in this work, only the injection conditions and the analyte retention were found to be impactful on the onset of both phenomena. This finding allowed us to suggest one necessary and sufficient condition, relying on the injection of critical volumes to observe each respective phenomenon. These critical volumes only depend on the column dead volume and the retention factor of the analyte in the injection solvent.

Reversed phase versus hydrophilic interaction liquid chromatography as first dimension of comprehensive two-dimensional liquid chromatography systems for the elucidation of the polyphenolic content of food and natural products

Comprehensive two-dimensional liquid chromatography is a well-established method for the unraveling of very complex real-world samples. With regard to food and natural products such a technique turned out to be a very promising approach due to its high resolving power and improved identification capability, especially in combination with mass spectrometry. In this context, polyphenols comprise a particular complex class of bioactive compounds, due to their nature and content in commonly consumed foodstuffs, making their analysis challenging. The present contribution shows an overview of the two commonly employed approaches used for polyphenol analysis, viz. RP-LC × RP-LC and HILIC × RP-LC. Furthermore, the latest implementations as well as limitations and future perspectives are critically reported.

Phytochemical profile and rosmarinic acid purification from two Peruvian Lepechinia Willd. species (Salviinae, Mentheae, Lamiaceae)

The phytochemical profile of Lepechinia meyenii (Walp.) Epling and Lepechina floribunda (Benth.) Epling obtained by liquid chromatography associated with high-resolution mass spectrometry is presented. Forty eight compounds were detected exhibiting a variety of salvianolic acids and abietane phenolic diterpenoids. A simple procedure by cold evaporative crystallization to purify rosmarinic acid from these botanical species was also shown.

Hydrophilic Interaction Liquid Chromatography (HILIC): Latest Applications in the Pharmaceutical Researches

Background:

Significant advances have been occurred in analytical research since the 1970s by Liquid Chromatography (LC) as the separation method. Reverse Phase Liquid Chromatography (RPLC) method, using hydrophobic stationary phases and polar mobile phases, is the most commonly used chromatographic method. However, it is difficult to analyze some polar compounds with this method. Another separation method is the Normal Phase Liquid Chromatography (NPLC), which involves polar stationary phases with organic eluents. NPLC presents low-efficiency separations and asymmetric chromatographic peak shapes when analyzing polar compounds. Hydrophilic Interaction Liquid Chromatography (HILIC) is an interesting and promising alternative method for the analysis of polar compounds. HILIC is defined as a separation method that combines stationary phases used in the NPLC method and mobile phases used in the RPLC method. HILIC can be successfully applied to all types of liquid chromatographic separations such as pharmaceutical compounds, small molecules, metabolites, drugs of abuse, carbohydrates, toxins, oligosaccharides, peptides, amino acids and proteins.

Objective:

This paper provides a general overview of the recent application of HILIC in the pharmaceutical research in the different sample matrices such as pharmaceutical dosage form, plasma, serum, environmental samples, animal origin samples, plant origin samples, etc. Also, this review focuses on the most recent and selected papers in the drug research from 2009 to the submission date in 2020, dealing with the analysis of different components using HILIC.

Results and Conclusion:

The literature survey showed that HILIC applications are increasing every year in pharmaceutical research. It was found that HILIC allows simultaneous analysis of many compounds using different detectors.

A systematic strategy integrating solid-phase extraction, full scan range splitting, mass defect filter and precursor ion list for comprehensive metabolite profiling of Danqi Tongmai tablet in rats

In vivo metabolite profiling of herbal medicines remains a challenge due to the complex chemical composition and drastic interference from biological matrix. In this study, a systematic strategy was established for comprehensive metabolite profiling of Danqi Tongmai (DQTM) tablet, a combination of salvianolic acids and notoginsenosides, in rats after oral administration. This strategy was composed of six steps. Firstly, the rat plasma and tissue samples were collected at multiple time points to increase the representativeness of samples. Secondly, different sample preparation methods were systematically investigated including protein precipitation, liquid-liquid extraction and solid-phase extraction to obtain superior extraction efficiency for both salvianolic acids and notoginsenosides. Thirdly, the MS acquisition method was optimized by splitting the full scan range into two separate segments to improve the detection capability for minor components. Fourthly, an extended polygonal mass defect filter (EP-MDF) model was constructed to filter potential metabolites of salvianolic acids and notoginsenosides, and remove large amounts of interference ions. Fifthly, ion intensity-based time point-staggered precursor ion list (IITPS-PIL) was generated to trigger more targeted MS/MS acquisition for potential metabolites at the highest concentration. Finally, the absorbed prototypes and metabolites were comprehensively characterized by reference standards and MS/MS fragmentation. The proposed strategy significantly improved the detection ability for trace prototypes and metabolites in vivo. A total of 370 components, including 94 prototypes (38 confirmed with reference standards) and 276 metabolites, were tentatively characterized in rat plasma and tissue samples after oral administration of DQTM. Collectively, this paper provided an applicable reference for comprehensive metabolite profiling of herbal medicines in complex biological samples.

Comparison of existing strategies for keeping symmetrical peaks in on-line Hydrophilic Interaction Liquid Chromatography x Reversed-Phase Liquid Chromatography despite solvent strength mismatch

In two-dimensional liquid chromatography, the combination of hydrophilic interaction liquid chromatography (HILIC) and reversed-phase liquid chromatography (RPLC) is very attractive due to the complementarity of their separation mechanisms. On-line comprehensive HILIC x RPLC is well-known to give rise to a large retention space coverage when dealing with ionisable compounds. However, method development in on-line HILIC x RPLC is challenging due to the reversed solvent strength between both dimensions, which can greatly affect the peak shapes in the second RPLC dimension, and thus the separation quality and the method sensitivity. In the present contribution, we compared four strategies designed to avoid this problem: (1) flow splitting, which consists in reducing the injection volume in the second dimension (²D), (2) on-line dilution with a make-up flow and (3) on-line dilution with Active Solvent Modulation (ASM), which both consist in reducing the solvent strength of the injected fractions, and (4) Total Breakthrough Strategy, which we recently proposed. Unlike the three preceding strategies, this latter one consists in injecting large volumes of strong solvent in ²D. The performance of each strategy was evaluated for sub-hour separations of a tryptic digest in on-line HILIC x RPLC. In this work, we considered the critical case for which the same column internal diameters (i.e. 2.1 mm here) are used in both dimensions. Peak capacity, peak shapes and peak intensities were considered for this evaluation. The highest peak capacity could be achieved with Total Breakthrough Strategy while the lowest one with on-line dilution using ASM. Peak intensities were usually higher with on-line dilution approaches (make-up flow and ASM). However, despite the presence of breakthrough, peak intensities were approximately 7-fold higher with Total Breakthrough Strategy than with flow splitting.

Development of an Online 2D Ultrahigh-Pressure Nano-LC System for High-pH and Low-pH Reversed Phase Separation in Top-Down Proteomics

The development of novel high-resolution separation techniques is crucial for advancing the complex sample analysis necessary for high-throughput top-down proteomics. Recently, our group developed an offline 2D high-pH RPLC/low-pH RPLC separation method and demonstrated good orthogonality between these two RPLC formats. Specifically, ultrahigh-pressure long capillary column RPLC separation has been applied as the second dimensional low-pH RPLC separation for the improvement of separation resolution. To further improve the throughput and sensitivity of the offline approach, we developed an online 2D ultrahigh-pressure nano-LC system for high-pH and low-pH RPLC separations in top-down proteomics. An online microtrap column with a dilution setup was used to collect eluted proteins from the first dimension high-pH separation and inject the fractions for ultrahigh-pressure long capillary column low-pH RPLC separation in the second dimension. This automatic platform enables the characterization of 1000+ intact proteoforms from 5 μg of intact E. coli cell lysate in 10 online-collected fractions. Here, we have demonstrated that our online 2D pH RP/RPLC system coupled with top-down proteomics holds the potential for deep proteome characterization of mass-limited samples because it allows the identification of hundreds of intact proteoforms from complex biological samples at low microgram sample amounts.

Review of Three-Dimensional Liquid Chromatography Platforms for Bottom-Up Proteomics

Proteomics is a large-scale study of proteins, aiming at the description and characterization of all expressed proteins in biological systems. The expressed proteins are typically highly complex and large in abundance range. To fulfill high accuracy and sensitivity of proteome analysis, the hybrid platforms of multidimensional (MD) separations and mass spectrometry have provided the most powerful solution. Multidimensional separations provide enhanced peak capacity and reduce sample complexity, which enables mass spectrometry to analyze more proteins with high sensitivity. Although two-dimensional (2D) separations have been widely used since the early period of proteomics, three-dimensional (3D) separation was barely used by low reproducibility of separation, increased analysis time in mass spectrometry. With developments of novel microscale techniques such as nano-UPLC and improvements of mass spectrometry, the 3D separation becomes a reliable and practical selection. This review summarizes existing offline and online 3D-LC platforms developed for proteomics and their applications. In detail, setups and implementation of those systems as well as their advances are outlined. The performance of those platforms is also discussed and compared with the state-of-the-art 2D-LC. In addition, we provide some perspectives on the future developments and applications of 3D-LC in proteomics.

Vacuum-assisted evaporative concentration combined with LC-HRMS/MS for ultra-trace-level screening of organic micropollutants in environmental water samples

Vacuum-assisted evaporative concentration (VEC) was successfully applied and validated for the enrichment of 590 organic substances from river water and wastewater. Different volumes of water samples (6 mL wastewater influent, 15 mL wastewater effluent, and 60 mL river water) were evaporated to 0.3 mL and finally adjusted to 0.4 mL. 0.1 mL of the concentrate were injected into a polar reversed-phase C18 liquid chromatography column coupled with electrospray ionization to high-resolution tandem mass spectrometry. Analyte recoveries were determined for VEC and compared against a mixed-bed multilayer solid-phase extraction (SPE). Both approaches performed equally well (≥ 70% recovery) for a vast number of analytes (n = 327), whereas certain substances were especially amenable to enrichment by either SPE (e.g., 4-chlorobenzophenone, logD_ow,pH7 4) or VEC (e.g., TRIS, logD_ow,pH7 − 4.6). Overall, VEC was more suitable for the enrichment of polar analytes, albeit considerable signal suppression (up to 74% in river water) was observed for the VEC-enriched sample matrix. Nevertheless, VEC allowed for accurate and precise quantification down to the sub-nanogram per liter level and required no more than 60 mL of the sample, as demonstrated by its application to several environmental water matrices. By contrast, SPE is typically constrained by high sample volumes ranging from 100 mL (wastewater influent) to 1000 mL (river water). The developed VEC workflow not only requires low labor cost and minimum supervision but is also a rapid, convenient, and environmentally safe alternative to SPE and highly suitable for target and non-target analysis.