Separation of betacyanins from Iresine herbstii Hook. ex Lindl. leaves by high-speed countercurrent chromatography in a polar solvent system

Rapid screening and target-guided isolation of antioxidants from German chamomile by 2,2-diphenyl-1-picrylhydrazyl-ultra-high-performance liquid chromatography-mass spectrometry coupled with off-line two-dimensional high-speed countercurrent chromatography

German chamomile is one of the most effective herbal elements used in anti-allergic products and as an antioxidant. Herein, the antioxidant activity of different extract fractions of German chamomile was initially evaluated using an off-line 2,2-diphenyl-1-picrylhydrazyl spectrophotometric assay. The ethyl acetate extract demonstrated the highest efficacy in scavenging free radicals. Based on this, a rapid screening and separation method using ultra-high-performance liquid chromatography combined with the 2,2-diphenyl-1-picrylhydrazyl assay was implemented to identify antioxidants in the ethyl acetate fraction of German chamomile flowers. Ten potential radical scavengers were tentatively screened from German chamomile using a target-guided isolating approach with off-line two-dimensional high-speed countercurrent chromatography and the structures of the compounds were analyzed and identified. Ultimately, 10 radical scavengers were obtained from the ethyl acetate extract with a purity quotient exceeding 90%. The results demonstrated the effectiveness and reproducibility of this method for isolating potential antioxidants from complex mixtures in a targeted manner. This strategy can be applied to the target-guided isolation of complex mixtures of natural products with broad K-values and similar structures.

In-depth analysis of the xanthine oxidase inhibitors of Cicer arietinum L.-based receptor-ligand affinity coupled with complex chromatography

INTRODUCTION

Cicer arietinum L. is the choice of health food for people with diabetes, hypertension, and hyperlipidemia. As an essential source of high-nutrition legumes, it is also an important source of dietary isoflavones.

OBJECTIVES

In order to improve the preparation efficiency of natural plants, a rapid biological activity screening and preparation of xanthine oxidase inhibitors from C. arietinum L. was established.

METHODS

Xanthine oxidase (XOD) inhibitors were rapidly screened using ultrafiltration liquid chromatography-mass spectrometry (UF-LC-MS) based on receptor-ligand affinity. The change in XOD activity was evaluated by enzymatic reaction kinetics measurement. The potential bioactive compounds were verified through molecular docking. In addition, the biological activity of ligands screened was separated and purified by complex chromatography. The structures of the compounds were identified by nuclear magnetic resonance spectroscopy.

RESULTS

Three active ingredients, namely daidzin, daidzein, calycosin with XOD binding affinities were identified and isolated from the raw plant materials via semi-preparative high-performance liquid chromatography (HPLC), 0-60 min, 5-50% B and countercurrent chromatography (CCC) (ethyl acetate/acetic acid/water [5:0.8:10, v/v/v]).

CONCLUSION

This study will help to elucidate the mechanisms of action of natural plants of interest at the molecular level and could also provide more opportunities for the discovery and development of new nutritional value from other natural resources.

Unveiling Alternative Oxidation Pathways and Antioxidant and Cardioprotective Potential of Amaranthin-Type Betacyanins from Spinach-like Atriplex hortensis var. 'Rubra'

A comprehensive oxidation mechanism was investigated for amaranthin-type betacyanins with a specific glucuronosylglucosyl moiety isolated from Atriplex hortensis 'rubra' using liquid chromatography coupled to diode array detection and electrospray ionization tandem mass spectrometry (LC-DAD-ESI-MS/MS) and LC-Quadrupole-Orbitrap-MS (LC-Q-Orbitrap-MS). By employing one-dimensional (1D) and two-dimensional (2D) NMR, this study elucidates the chemical structures of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS)-oxidized celosianins for the first time. These findings demonstrate alternative oxidation pathways for acylated betacyanins compared to well-known betanidin, betanin, and gomphrenin pigments. Contrary to previous research, we uncover the existence of 17-decarboxy-neo- and 2,17-bidecarboxy-xanneo-derivatives as the initial oxidation products without the expected 2-decarboxy-xan forms. These oxidized compounds demonstrated potent free radical scavenging properties. Celosianin (IC50 = 23 μg/mL) displayed slightly higher antioxidant activity compared to oxidized forms, 17-decarboxy-neocelosianin (IC50 = 34 μg/mL) and 2,17-bidecarboxy-xanneocelosianin (IC50 = 29 μg/mL). The oxidized compounds showed no cytotoxic effects on H9c2 rat cardiomyoblasts (0.1-100 μg/mL). Additionally, treatment of H9c2 cells with the oxidized compounds (0.1-10 μg/mL) elevated glutathione levels and exhibited protective effects against H2O2-induced cell death. These findings have significant implications for understanding the impact of oxidation processes on the structures and biological activities of acylated betalains, providing valuable insights for future studies of the bioavailability and biological mechanism of their action in vivo.

Betalains isolated from underexploited wild plant Atriplex hortensis var. rubra L. exert antioxidant and cardioprotective activity against H9c2 cells

Atriplex hortensis var. rubra L. extracts prepared from leaves, seeds with sheaths, and stems were characterized for betalainic profiles by spectrophotometry, LC-DAD-ESI-MS/MS and LC-Orbitrap-MS techniques. The presence of 12 betacyanins in the extracts was strongly correlated with high antioxidant activity measured by ABTS, FRAP, and ORAC assays. Comparative assessment between samples indicated the highest potential for celosianin and amaranthin (IC₅₀ 21.5 and 32.2 μg/ml, respectively). The chemical structure of celosianin was elucidated for the first time by complete 1D and 2D NMR analysis. Our findings also demonstrate that betalain-rich A. hortensis extracts and purified pigments (amaranthin and celosianin) do not induce cytotoxicity in a wide concentration range in rat cardiomyocytes model (up to 100 μg/ml for extracts and 1 mg/ml for pigments). Furthermore, tested samples effectively protect H9c2 cells from H₂O₂-induced cell death and prevent from apoptosis induced by Paclitaxel. The effects were observed at sample concentrations between 0.1 and 10 μg/ml.

A simple and practical solvent system selection strategy for high-speed countercurrent chromatography based on the HPLC polarity parameter model

The selection of an appropriate solvent system is the most crucial step in high-speed countercurrent chromatography (HSCCC) separation. The compound polarity plays an important role in HPLC analysis and HSCCC separation, and it can be calculated by the HPLC polarity parameter model and the average polarity of the HSCCC solvent system, respectively. However, flow rates, columns and methanol concentrations of the HPLC experiment can influence the calculation of the compound polarity. Therefore, the applicability and accuracy of the HPLC polarity parameter model still needed to be extensively validated. We chose 14 compounds to conduct the shake-flask experiments and HPLC analysis on, such as apigenin, honokiol, phloridzin and dihydromyricetin. The HPLC analysis results showed that different flow rates and columns have negligible effects on the calculated compound polarities. However, there was a certain variation trend in the calculated polarities with different methanol concentrations. Although the polarity values of some compounds showed a difference between the HPLC analysis and shake-flask experiments, their partition coefficients (K) in the HSCCC solvent systems were still located in the range of 0.5 < K < 2.0. Guided by the HPLC polarity parameter model, the appropriate HSCCC solvent systems for mangosteen peel and Hypericum sampsonii Hance were selected, and the two main components (mangostin and quercetin) were isolated from their extracts, respectively. The separation results showed that the predicted compound polarities were sufficient to meet the HSCCC separation requirements. Meanwhile, this method required only 1 to 2 HPLC analyses with reference compounds, greatly improved the efficiency of the HSCCC solvent system selection, and shortened the experimental time. The polarity parameter model was a fast and efficient analysis method for the selection of an appropriate HSCCC solvent system.

Efficient separation of anti-inflammatory isolates from Polygonti rhizome by three different modes of high-speed counter-current chromatography

Successful isolation of 15 compounds from Polygonti rhizome was obtained by an efficient technique combined with macroporous resin column chromatography pretreatment and three different modes of high-speed counter-current chromatography for the first time. For the pretreatment, AB-8 resin was applied to remove the polysaccharides and enrich four different parts (samples I, II, III, and IV) by polarities. For the separation, sample I was separated by pH-zone-refining counter-current chromatography and seven cycle recycling mode high-speed counter-current chromatography, yielding four alkaloids (1--4); samples II-IV were further separated by the conventional high-speed counter-current chromatography, yielding seven flavonoids (5-10, 12), one steroid saponin (11), and three terpenoids (13-15). Finally, the isolates were assayed for their anti-inflammatory activities against nitric oxide production with compounds 5, 9-10, 13 showing significant anti-inflammatory activities, IC₅₀ values which were 13.0, 16.2, 17.1, and 14.7 μM, respectively, while others showing moderate and weak anti-inflammatory activities, respectively.

Metabolite Profiling Analysis and the Correlation with Biological Activity of Betalain-Rich Portulaca grandiflora Hook. Extracts

The aim of the study was to evaluate the possible correlation between the bioactivity and the phytochemical profile of four betalain-rich extracts from Portulaca grandiflora Hook. The HPLC-DAD-ESI-MS analysis indicated the presence of 19 betaxanthins and two betacyanins. The highest concentrations of betaxanthins (982 mg/100 g DE) and betacyanins (650 mg/100 g DE) were noticed in orange and purple flowers extracts, respectively. The HPLC-DAD-ESI-HRMS/MS analyses revealed the presence of a total of 71 compounds. Fifteen new betaxanthins and fifty other metabolites were identified for the first time. The antioxidant activity of the studied flower extracts increased in the sequence of yellow < orange < purple < red (0.066−0.176 mM TE/g DE). Betalains showed less effect on the antioxidant activity of extracts than other metabolites did. Extracts from yellow and orange flowers were more active against Gram-positive bacteria (MIC = 4−16 mg/L), whereas extracts from red and purple flowers were slightly more active against Gram-negative bacteria (MIC = 16−32 mg/L). All the extracts showed the same activity against yeasts (MIC = 32 mg/L). Betaxanthins were active against Gram-positive bacteria, whereas betacyanins were active against Gram-negative bacteria. Remaining metabolites also exhibited antimicrobial activities. The cytotoxicity assessment showed that the P. grandiflora extracts were non-toxic to normal VERO cells. No significant antiviral activity towards Human Herpesvirus type 1 was observed (62 µg/mL). Among the tested varieties, the purple one showed anticancer selectivity towards colon carcinoma cells (RKO).

Isolation and purification of flavonoids from Euonymus alatus by high-speed countercurrent chromatography and neuroprotective effect of rhamnazin-3-O-rutinoside in vitro

The flavonoids from Euonymus alatus exhibit many biological activities including significant antioxidant, anti-inflammatory, anti-cancer. In this work, a high-speed countercurrent chromatography method for the isolation and purification of flavonoids from crude extracts of Euonymus alatus was established. The effects of several solvent systems on the separation efficiency of target compounds in the extract of Euonymus alatus were studied. The solvent system composed of n-hexane-ethyl acetate-methanol-water at a volume ratio of (3:5:3:5, v/v) was chosen, in which the lower phase was used as the mobile phase at the rotation speed of 800 rpm and flow rate of 2.0 mL/min. The three flavonoids were obtained and identified as patuletin-3-O-rutinoside, rhamnazin-3-O-rutinoside, and dehydrodicatechin A by mass spectroscopy and nuclear magnetic resonance, and the quantities of patuletin-3-O-rutinoside, rhamnazin-3-O-rutinoside, and dehydrodicatechin A were 2.2, 9.7, and 1.8 mg, respectively. The results indicated that high-speed countercurrent chromatography was a simple and efficient method for the isolation and purification of flavonoids from the crude extracts of Euonymus alatus. The cellular antioxidant activity experimental result indicated that rhamnazin-3-O-rutinoside could alleviate H₂ O₂ -induced oxidative stress.

High-speed countercurrent chromatography for isolation and enrichment of betacyanins from fresh and dried leaves of Atriplex hortensis L. var. "Rubra"

Betacyanins and their decarboxylated derivatives from fresh and dried edible leaves of Atriplex hortensis L. var. "Rubra" were fractionated for the first time by high-speed countercurrent chromatography. Pigments present in fresh leaf extract were separated in systems: ethanol - acetonitrile - n-propanol - ammonium sulphate - water (0.5:0.5:0.5:1.2:1.0, v/v/v/v/v) (tail-to-head mode) and tert-butyl methyl ether - n-butanol - acetonitrile - water with 0.7% heptafluorobutyric acid (2:2:1:5, v/v/v/v) (head-to-tail mode). The mobile phase flow rate was 2 mL/min and the retention of the stationary phase was 79.8 and 75.2%, respectively. Pigments from dried leaves were separated in a similar ion-pair system with heptafluorobutyric acid in different volume proportions 1:3:1:5 (head-to-tail mode) and the flow rate of the mobile phase 3 mL/min. The stationary phase retention was 64.0%. The application of the countercurrent chromatography for the fractionation of betacyanins from leaves of Atriplex hortensis enabled to isolate and pre-concentrate the pigments for further low- and high-resolution liquid chromatographic-tandem mass spectrometric detection. This study revealed the presence of 10 betacyanins in fresh and 16 in dried leaves of Atriplex hortensis. Two compounds were not previously identified in the whole Amaranthaceae family. Additionally, instead of (iso)amaranthin, celosianin and its epimer were dominant betacyanins in the Atriplex hortensis.

Multi-colored shades of betalains: recent advances in betacyanin chemistry

Covering: 2001 to 2021Betacyanins cover a class of remarkable natural red-violet plant pigments with prospective chemical and biological properties for wide-ranging applications in food, pharmaceuticals, and the cosmetic industry. Betacyanins, forming the betalain pigment group together with yellow betaxanthins, have gained much attention due to the increasing social awareness of the positive impact of natural products on human health. Betalains are commercially recognized as natural food colorants with preliminarily ascertained, but to be further investigated, health-promoting properties. In addition, they exhibit a remarkable structural diversity based on glycosylated and acylated varieties. The main research directions for natural plant pigments are focused on their structure elucidation, methods of their separation and analysis, biological activities, bioavailability, factors affecting their stability, industrial applications as a plant-based food, natural colorants, drugs, and cosmetics as well as methods for high-yield production and stabilization. This review covers period of the last two decades of betacyanin research. In the first part of the review, we present an updated classification of all known betacyanins and their derivatives identified by chemical means as well as by mass spectrometric and NMR techniques. In the second part, we review the current research reports focused on the chemical properties of the pigments (decarboxylation, oxidation, conjugation, and chlorination reactions as well as the acyl group migration phenomenon) and describe the semi-synthesis of natural and artificial fluorescent betalamic acid conjugates, showing various prospective research directions.

Development of active and smart packaging films based on starch, polyvinyl alcohol and betacyanins from different plant sources

In this study, active and smart packaging films were prepared by individually adding betacyanins-rich plant extracts (red pitaya flesh extract (RPFE), prickly pear fruit extract (PPFE), red beetroot extract (RBRE), globe amaranth flower extract (GAFE) and red amaranth leaf extract (RALE)) into starch/polyvinyl alcohol. The structural, physical and functional properties of the films containing betacyanins from different plant sources were compared for the first time. Results showed betacyanins from RPFE, PPFE and RBRE were betanin-type betacyanins. Betacyanins from GAFE and RALE were gomphrenin-type and amaranthin-type betacyanins, respectively. The films containing RPFE and PPFE presented more uniform cross-sections and had the highest water vapor barrier (9.37 and 9.26 × 10^-11 g m^-1 s^-1 Pa^-1) and mechanical strength (8.26 and 7.87 MPa). However, the film containing GAFE presented the lowest light transmittance but the highest 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (EC₅₀ = 0.47 mg/mL). All the films containing betacyanins are sensitive to pH 8-12 buffer solutions and volatile ammonia. Notably, the film containing RPFE exhibited distinct color changes (from purple-red to pink) when shrimp spoiled. Our results suggest the structural, physical and functional properties of betacyanins-rich films are closely related to the source and type of betacyanins.

A strategy based on isocratic and linear-gradient high-speed counter-current chromatography for the comprehensive separation of platycosides from Platycodi radix

Platycosides, the generally recognized main active constituents of Platycodi radix, have been studied extensively for their wide pharmacological activities. Herein, we have successfully developed an efficient method for the enrichment and comprehensive isolation of platycosides from Platycodi radix by MCI resin column chromatography (CC) and two different modes of high-speed counter-current chromatography (HSCCC). MCI resin CC was the preferable enrichment operation for platycosides from the 70%-ethanol extract of Platycodi radix and rendered target platycosides when eluted by 60% aqueous methanol solution. As for the separation, two different modes, including isocratic HSCCC and linear-gradient HSCCC, were applied together to separate the platycosides using a mixture of ethyl acetate, n-butanol and water coupled with evaporative light scattering detection, for the first time. Isocratic HSCCC was applied to separate crude platycosides from Platycodi radix using ethyl acetate-n-butanol-water (1 : 1 : 2, v/v), yielding seven pure platycosides (compounds 1-6, 8) and two fractions of enriched mixtures of compounds 7, 9, 10, and 11. Linear-gradient HSCCC was employed to rapidly separate compounds 7, 9, 10, and 11 by constantly changing the proportions of ethyl acetate and n-butanol in the ethyl acetate-n-butanol-water solvent system. Finally, platycoside E (1), deapio-platycodin D₃ (2), platycodin D₃ (3), deapio-platycodin D₂ (4), platycodin D₂ (5), platycodin D (6), polygalacin D₂ (7), polygalacin D (8), and three tautomers, namely 2''-O-acetylplatycodin D (9) and 3''-O-acetylplatycodin D (9'), 2''-O-acetylpolygalacin D₂ (10) and 3''-O-acetylpolygalacin D₂ (10'), and 2''-O-acetylpolygalacin D (11) and 3''-O-acetylpolygalacin D (11'), were obtained from 300 mg of crude platycosides from Platycodi radix.

Analytical, Preparative, and Industrial-Scale Separation of Substances by Methods of Countercurrent Liquid-Liquid Chromatography

Countercurrent liquid-liquid chromatographic techniques (CCC), similar to solvent extraction, are based on the different distribution of compounds between two immiscible liquids and have been most widely used in natural product separations. Due to its high load capacity, low solvent consumption, the diversity of separation methods, and easy scale-up, CCC provides an attractive tool to obtain pure compounds in the analytical, preparative, and industrial-scale separations. This review focuses on the steady-state and non-steady-state CCC separations ranging from conventional CCC to more novel methods such as different modifications of dual mode, closed-loop recycling, and closed-loop recycling dual modes. The design and modeling of various embodiments of CCC separation processes have been described.