Offline preparative three-dimensional HPLC for systematic and efficient purification of alkaloids from Gelsemium elegans Benth

Dihydrokoumine, a dual-target analgesic with reduced side effects isolated from a traditional Chinese medicine

INTRODUCTION

Opioids are the most common antinociceptive drugs, but long-term administration causes serious adverse side effects. Gelsemium elegans Benth. is traditionally used as an analgesic agent and mainly contains indole alkaloids with structures different from those in common opioids, indicating distinct pharmacological properties. This work aims to find a new analgesic from Gelsemium elegans Benth. and evaluate it in vitro and in vivo.

METHODS

Dihydrokoumine was purified from Gelsemium elegans Benth. Binding to mu opioid receptor (MOR), M3 receptor (M3R) and other 15 G protein-coupled receptors were evaluated in vitro combined with molecular docking analysis. Analgesic efficacy and side effects were measured in vivo using hot-plate, formalin paw, and rotarod tests in mice. Cytotoxicity, acute toxicity in mice and pharmacokinetics were assessed.

RESULTS

A MOR agonist, dihydrokoumine, was first identified from Gelsemium elegans Benth. Further investigations showed that dihydrokoumine exhibited selective partial agonist action on the MOR and antagonist action on the M3R among other 15 GPCRs. In in vivo mouse models, dihydrokoumine could relieve acute pain and chronic inflammatory pain without drug tolerance and sedative side effects. Additionally, we observed a good safety profile and favorable pharmacokinetic properties.

CONCLUSION

A MOR partial agonist/M3R antagonist analgesic with reduced side effects was isolated from a traditional Chinese medicine. This study bestows dihydrokoumine as a new dual-target analgesic and as a potential lead compound in pain management.

An efficient method for the preparative isolation and purification of alkaloids from Gelsemium by using high speed counter-current chromatography and preparative HPLC

We established an efficient method using high-speed countercurrent chromatography (HSCCC) combined with preparative high-performance liquid chromatography (prep-HPLC) for isolating and purifying Gelsemium elegans (G. elegans) alkaloids. First, the two-phase solvent system composed of 1% triethylamine aqueous solution/n-hexane/ethyl acetate/ethanol (volume ratio 4:2:3:2) was employed to separate the crude extract (350 mg) using HSCCC. Subsequently, the mixture that resulted from HSCCC was further separated by Prep-HPLC, resulting in seven pure compounds including: 14-hydroxygelsenicine (1, 12.1 mg), sempervirine (2, 20.8 mg), 19-(R)-hydroxydihydrogelelsevirine (3, 10.1 mg), koumine (4, 50.5 mg), gelsemine (5, 32.2 mg), gelselvirine (6, 50.5 mg), and 11-hydroxyhumanmantenine (7, 12.5 mg). The purity of these seven compounds were 97.4, 98.9, 98.5, 99, 99.5, 96.8, and 85.5%, as determined by HPLC. The chemical structures of the seven compounds were analyzed and confirmed by electrospray ionization mass spectrometry (ESI-MS), 1H-nuclear magnetic resonance (1H NMR), and 13 C-nuclear magnetic resonance (13 C NMR) spectra. The results indicate that the HSCCC-prep-HPLC method can effectively separate the major alkaloids from the purified G. elegans, holding promising prospects for potential applications in the separation and identification of other traditional Chinese medicines.

Sequential purification of cannabidiol by two-dimensional liquid chromatography combined with modeling and simulation of elution profiles

Cannabidiol (CBD) has garnered significant attention for its neuroprotective properties, and research on its therapeutic effects has increased dramatically in recent years. However, the systematic purification of CBD through scalable processes has remained bottleneck due to the structural similarities of the cannabinoids. Although preparative chromatography is considered as a potential solution, it is usually time-consuming and expensive. Therefore, the development of scalable strategy via fast and accurate optimization approach is crucial. The present study aimed to develop a sequential process for the scalable purification of CBD through an eco-friendly ethanolic extraction using ultrasonic assisted extraction, decarboxylation of cannabidiolic acid optimized by response surface methodology, followed by the development of off-line two-dimensional semi-preparative chromatography, boosted with stacked injection overloading. In the first dimension, a column packed with macroporous resin allows to enrich the target substance and then, the behavior of resin column for scale-up procedure were predicted and optimized by developed mathematical model. A C18 column was used in the second dimension. The CBD purity and recovery obtained were 94.3 and 82.1 %, respectively. A robust and reliable method was employed for CBD enrichment/purification, which can be generalized to other bioactive compounds in complex matrices.

Molecular identification and functional characterization of a transcription factor GeRAV1 from Gelsemium elegans

BACKGROUND

Gelsemium elegans is a traditional Chinese medicinal plant and temperature is one of the key factors affecting its growth. RAV (related to ABI3/VP1) transcription factor plays multiple roles in higher plants, including the regulation of plant growth, development, and stress response. However, RAV transcription factor in G. elegans has not been reported.

RESULTS

In this study, three novel GeRAV genes (GeRAV1-GeRAV3) were identified from the transcriptome of G. elegans under low temperature stress. Phylogenetic analysis showed that GeRAV1-GeRAV3 proteins were clustered into groups II, IV, and V, respectively. RNA-sequencing (RNA-seq) and real-time quantitative PCR (qRT-PCR) analyses indicated that the expression of GeRAV1 and GeRAV2 was increased in response to cold stress. Furthermore, the GeRAV1 gene was successfully cloned from G. elegans leaf. It encoded a hydrophilic, unstable, and non-secretory protein that contained both AP2 and B3 domains. The amino acid sequence of GeRAV1 protein shared a high similarity of 81.97% with Camptotheca acuminata CaRAV. Subcellular localization and transcriptional self-activation experiments demonstrated that GeRAV1 was a nucleoprotein without self-activating activity. The GeRAV1 gene was constitutively expressed in the leaves, stems, and roots of the G. elegans, with the highest expression levels in roots. In addition, the expression of the GeRAV1 gene was rapidly up-regulated under abscisic acid (ABA), salicylic acid (SA), and methyl jasmonate (MeJA) stresses, suggesting that it may be involved in hormonal signaling pathways. Moreover, GeRAV1 conferred improved cold and sodium chloride tolerance in Escherichia coli Rosetta cells.

CONCLUSIONS

These findings provided a foundation for further understanding on the function and regulatory mechanism of the GeRAV1 gene in response to low-temperature stress in G. elegans.

Separation and structural characterization of unknown impurity in vancomycin by two-dimensional preparative liquid chromatography, LC-MS and NMR

Vancomycin is an effective antibiotic used for the treatment of Gram-positive bacterial infections. During the analysis of vancomycin, an unknown impurity at the level of 0.5% was detected by high-performance liquid chromatography (HPLC). To characterize the structure of the impurity, a new two-dimensional preparative liquid chromatography (2D-Prep-LC) method was developed to separate the impurity from the vancomycin sample. After further analysis including liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy, the structure of the unknown impurity was identified as a vancomycin analog in which the N-Methyl-leucine residue on the side chain is replaced by an N-methylmethionine residue. In this study, we established a reliable and efficient method for separating and identifying vancomycin impurities, which will provide a valuable contribution to the field of pharmaceutical analysis and quality control.

Targeted isolation of cyclooxygenase-2 inhibitors from Saussurea obvallata using affinity ultrafiltration combined with preparative liquid chromatography

Saussurea obvallata (S. obvallata) is widely used in Qinghai-Tibet Plateau with high medicinal and edible values of reducing inflammation. But, the individual components and mechanisms of action still ill-defined. In this work, an integrated method using affinity ultrafiltration combined with preparative liquid chromatography was developed to identify and separate cyclooxygenase-2 (COX-2) inhibitors from S. obvallata. The sample was pretreated using on-line medium pressure liquid chromatography to yield the active fraction. Then, the potential COX-2 ligands were screened out using affinity ultrafiltration from the targeted fraction and the identified compounds were isolated via preparative liquid chromatography. As a result, four main compounds, coniferin (1), syringin (2), roseoside (3) and grasshopper ketone (4) were targeted isolated with IC₅₀ values of 12.34 ± 1.81, 4.04 ± 0.43, 13.91 ± 2.46 and 7.97 ± 1.21 µM, respectively. Results of this work demonstrated that the developed strategy was effective for the targeted separation of COX-2 inhibitors from natural product extracts.

Optimizing the preparative capacity of two-dimensional liquid chromatography based on analytes retention behaviors

In this work, a solute retention optimization method (SRO) was proposed to exploit the purification potential of two-dimensional liquid chromatography (2D-LC). According to our findings, the complementarity of 2D-LC correlates with some specific impurities. In the two methods used in 2D-LC, the retention order of these impurities and target compound is completely opposite. Taking full advantage of the complementarity is crucial to enhance the saturation capacity (w_max) of 2D-LC by SRO. For the purpose of validating the effectiveness of SRO, a reverse-phase liquid chromatography (RPLC) coupled with hydrophilic interaction chromatography (HILIC) was developed to purify p-chlorobenzoic acid from substituted benzenes. By using the overloading effects of analytes as indicators, the w_max of RPLC × HILIC was determined by the bisection method, and finally defined by the extremely high loading volume of 4.9 mL. A touch-peak separation of impurities and the target compound occurred precisely during the secondary separation. The effectiveness of SRO was also verified by the greater purification efficiency of RPLC × HILIC than that of HILIC × RPLC. Subsequently, a RPLC × RPLC method was developed by SRO to prepare the reference materials of caffeine from tea extracts. Only by an analytical C18 column, 15.6 mg of caffeine with the purity of 98.3% was obtained at once with the recovery up to 82.3%. However, without the aid of SRO, the purity rapidly decreased to 62.0%. Compared to other methods, SRO-based 2D-LC offers certain advantages in terms of purity, recovery, and the purification efficiency, suggesting that it is particularly effective in developing preparative 2D-LC facing complex matrices.

Less Configuration and More Dimensionality: Preparative Heart-Cut Multidimensional Liquid Chromatography Based on Trapping Arrays

The resolving power of multiple dimensional liquid chromatography (mD-LC) is multiplicative as it adds dimensions. However, the issue in creating a preparative mD-LC system is that the higher the dimensionality, the more complicated the system configuration. Thus, we presented a new configuration of preparative mD-LC using one set of LC modules and trapping array-based multiple heart-cut interfaces. A preparative two-dimensional liquid chromatography (2D-LC) separation of herbal medicine formulation produced 40 compounds with a purity of >90%. During the separation process, the interface stores the fractions and allocates positions for the fractions from a different dimension; LC draws the fraction from the interface, makes ⁿD separation, and sends isolated fractions to the interface. By repeating this process, we achieved variable dimensionality of LC separations. We also presented a preparative 3D-LC separation of herbal medicines to validate the principle of "less configuration and more dimensionality". Thus, we can explore the higher dimensional preparative separations. The developed preparative mD-LC displayed exceptional power in the isolation of various compounds and has great potential in the application of natural products.

A mass spectrometry imaging approach on spatiotemporal distribution of multiple alkaloids in Gelsemium elegans

Gelsemium elegans contains multiple alkaloids with pharmacological effects, thus researchers focus on the identification and application of alkaloids extracted from G. elegans. Regretfully, the spatiotemporal distribution of alkaloids in G. elegans is still unclear. In this study, the desorption electrospray ionization mass spectrometry imaging (DESI-MSI) was applied to simultaneously analyze the distribution of pharmacologically important alkaloids in different organ/tissue sections of G. elegans at different growth stages. Finally, 23 alkaloids were visualized in roots, stems and leaves at seedling stage and 19 alkaloids were observed at mature stage. In mature G. elegans, 16 alkaloids were distributed in vascular bundle region of mature roots, 15 alkaloids were mainly located in the pith region of mature stems and 2 alkaloids were enriched in epidermis region of mature stems. A total of 16 alkaloids were detected in leaf veins of mature leaves and 17 alkaloids were detected in shoots. Interestingly, diffusion and transfer of multiple alkaloids in tissues have been observed along with the development and maturation. This study comprehensively characterized the spatial metabolomics of G. elegans alkaloids, and the spatiotemporal distribution of alkaloid synthesis. In addition, the results also have reference value for the development and application of Gelsemium elegans and other medicinal plants.

Bioactivity-guided isolation of cyclooxygenase-2 inhibitors from Saussurea obvallata (DC.) Edgew. Using affinity solid phase extraction assay

ETHNOPHARMACOLOGICAL RELEVANCE

Saussurea obvallata (DC.) Edgew. is a traditional Tibetan medicine used for the treatment of inflammation-related diseases, but the scientific validation was very limited.

AIM OF THE STUDY

This study aimed to rapid screen and targeted isolate cyclooxygenase-2 (COX-2) inhibitors from S. obvallata extract.

MATERIALS AND METHODS

An efficient ligand-fishing method based on affinity solid phase extraction (A-SPE) combining with HPLC was developed. The identified COX-2 inhibitors were separated using preparative liquid chromatography. In vitro COX-2 inhibition assays were employed to confirm the inhibitory activities of the isolated compounds. In addition, the effect of the isolated compounds on the production of prostaglandin E2 (PGE2) and the expression of COX-2 in LPS-induced RAW 264.7 were evaluated.

RESULTS

A total of four phenylpropanoids, isolariciresinol, syringaresinol, pinoresinol and balanophonin were targeted isolated as COX-2 inhibitors with IC₅₀ values of 36.4 ± 2.6 μM, 23.1 ± 1.8 μM, 3.6 ± 0.3 μM and 12.1 ± 0.9 μM, respectively. The isolated compounds significantly inhibited LPS-induced NO production in a dose-dependent manner. And, the results of the inhibitory effect on the release of PGE₂ and the expression of COX-2 in LPS-induced macrophages were consistent with A-SPE analysis.

CONCLUSION

The present work demonstrated that the developed A-SPE-HPLC method could successfully targeted isolated COX-2 inhibitors from S. obvallata extract. And, the isolation results indicated that the therapeutic effect of S. obvallata on inflammation-related diseases was partly based on the COX-2 active ingredients.

Isoquinoline alkaloid dimers with dopamine D1 receptor activities from Menispermum dauricum DC

A phytochemical investigation on chemical constituents from the rhizomes of Menispermum dauricum DC. identified eight undescribed dimeric alkaloids with structurally diverse monomeric isoquinoline. Alkaloid structures were elucidated by a combination of spectroscopic data analyses and time-dependent density functional theory (TDDFT) ECD calculation. The isolates were evaluated for inhibitory effect on dopamine D1 receptor and compound 1 exhibited potent D1 receptor antagonistic activity with an IC₅₀ value of 8.4 ± 2.0 μM.

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.