An approach based upon the consecutive separation and the economical two-phase solvent system preparation using UNIFAC mathematical model for increasing the yield of high-speed counter-current chromatography

Purification of triterpenoid saponins and 25R/25S-inokosterone from Achyranthes bidentata Bl. by high-speed countercurrent chromatography coupled silver nitrate coordination

An effective method by high-speed countercurrent chromatography coordinated with silver nitrate for the preparative separation of sterones and triterpenoid saponins from Achyranthes bidentata Blume was developed. Methyl tert-butyl ether/n-butanol/acetonitrile/water (4:2:3:8, v/v/v/v) was selected for 20-hydroxyecdysone (compound 1), chikusetsusaponin IVa methyl ester (compound 4), 2'-glycan-11-keto-pigmented saponin V (compound 5), as well as a pair of isomers of 25S-inokosterone (compound 2) and 25R-inokosterone (compound 3), which were further purified by silver nitrate coordinated high-speed countercurrent chromatography. What is more, dichloromethane/methanol/isopropanol/water (6:6:1:4, v/v/v/v) was applied for calenduloside E (compound 6), 3β-[(O-β-d-glucuronopyranosyl)-oxy]-oleana-11,13-dien-28-oic acid (compound 7), zingibroside R1 (compound 8) and chikusetsusaponin IVa (compound 9). Adding Ag+ to the solvent system resulted in unique selectivity for 25R/25S isomers of inokosterone, which increased the complexing capability and stability of Ag+ coordinated 25S-inokosterone, as well as the α value between them. These results were further confirmed by the computational calculation of geometry optimization and frontier molecular orbitals assay. Comprehensive mass spectrometry and nuclear magnetic resonance analysis demonstrated the structures of the obtained compounds.

Rapid screening and isolation of 5-lipoxygenase inhibitors in Inonotus obliquus and mechanism of action in the treatment of asthma

Accurate screening and targeted preparative isolation of active substances in natural medicines have long been two technical challenges in natural medicine research. This study outlines a new approach to improve the efficiency of natural product preparation, focusing on rapidly and accurately screening potential active ingredients in Inonotus obliquus as well as efficiently preparing 5-lipoxidase (5-LOX) inhibitors, to provide new ideas for the treatment of asthma with Inonotus obliquus. First, we used ultrafiltration (UF) mass spectrometry to screen for three potential inhibitors of 5-LOX in Inonotus obliquus. Subsequently, the inhibitory effect of the active ingredients screened in the UF assay on 5-LOX was verified using the molecular docking technique, and the potential role of the active compounds in Inonotus obliquus for the treatment of asthma was analyzed by network pharmacology. Finally, based on the above activity screening guidelines, we used semi-preparative liquid chromatography and consecutive high-speed countercurrent chromatography to isolate three high-purity 5-LOX inhibitors such as betulin, lanosterol, and quercetin. Obviously, through the above approach, we have seamlessly combined rapid discovery, screening, and centralized preparation of the active ingredient with molecular-level interactions between the active ingredient and the protease.

A novel strategy by combining foam fractionation with high-speed countercurrent chromatography for the rapid and efficient isolation of antioxidants and cytostatics from Camellia oleifera cake

Camellia oleifera cake is a by-product, which is rich in functional chemical components. However, it is typically used as animal feed with no commercial value. The purpose of this study was to isolate and identify compounds from Camellia oleifera cake using a combination of foam fractionation and high-speed countercurrent chromatography (HSCCC) and to investigate their biological activities. Foam fractionation with enhanced drainage through a hollow regular decahedron (HRD) was first established for simultaneously enriching flavonoid glycosides and saponins for further separation of target compounds. Under suitable operating conditions, the introduction of HRD resulted in a threefold increase in enrichment ratio with no negative effect on recovery. A novel elution-extrusion countercurrent chromatography (EECCC) coupled with the consecutive injection mode was established for the successful simultaneous isolation of flavonoid glycosides and saponins. As a result, 38.7 mg of kaemferol-3-O-[2-O-D-glucopyranosyl-6-O-α-L-rhamnopyranosyl]-β-D-glucopyranoside (purity of 98.17%, FI), 70.8 mg of kaemferol-3-O-[2-O-β-D-xylopyranosyl-6-O-α-L-rhamnopyranosyl]-β-D-glucopyranoside (purity of 97.52%, FII), and 560 mg of an oleanane-type saponin (purity of 92.32%, FIII) were separated from the sample (900 mg). The present study clearly showed that FI and II were natural antioxidants (IC50 < 35 μg/mL) without hemolytic effect. FIII displayed the effect of inhibiting Hela cell proliferation (IC50 < 30 μg/mL). Further erythrocyte experiments showed that this correlated with the extremely strong hemolytic effect of FIII. Overall, this study offers a potential strategy for efficient and green isolation of natural products, and is beneficial to further expanding the application of by-products (Camellia oleifera cake) in food, cosmetics, and pharmacy.

Fermentation of Robinia pseudoacacia flower for improving the antioxidation: optimized conditions, active composition, mechanism, and biotransformation process

Robinia pseudoacacia flower is a natural product with many biological activities, including antioxidation. To further develop its antioxidation, the extract was fermented by Aspergillus niger FFCC 3112 in the medium with carbon to nitrogen ratio of 1.4:1 and initial pH of 4.2 for 3.5 days to form the best antioxidant activity of the fermentation product by strain screening, single factor optimization, and response surface methodology. Further analysis, isolation and activity determination showed that a main chemical component, kaempferol-3-O-α-L-rhamnopyranosyl-(1→6)-β-D-galactopyranosyl-7-O-α-L-rhamnopyranoside, in the extract was completely hydrolyzed to kaempferol-7-O-α-L-rhamnopyranoside and kaempferol with better antioxidant activity through biotransformation, which was the basis for improving the antioxidant activity of fermentation products. Moreover, the mechanism of antioxidant and the contribution of phenolic hydroxyl groups were investigated by density functional theory. The result indicated that the antioxidant capacity of kaempferol-7-O-α-L-rhamnopyranoside and kaempferol increased with the increase of solvent polarity. In high-polarity solvents, they mainly scavenge free radicals through single electron transfer followed by proton transfer.

Preparation of Isoquercetin From Toona sinensis by Liquid-Liquid-Refining Extraction And Consecutive Counter-Current Chromatography

A high-speed counter-current chromatographic (HSCCC) method using ethyl acetate-water as solvent system was established to separate isoquercetin from Toona sinensis. In an HSCCC single separation, the sample sizes of ethanol extract were optimized from 203 to 1200 mg. The results showed that the yield of the target compound increased from 4 to 26 mg, and the corresponding purity decreased from 93.30 to 81.82%. To further improve the yield and purity, liquid-liquid-refining extraction was introduced to pretreat the ethanol extract and enrich the target compound. The ethanol extract was extracted with n-hexane-ethyl acetate-method-water (1:5:1:5, v/v) and ethyl acetate-water in turn to remove the low-polarity and high-polarity impurities and obtain the crude sample. Under the similar conditions, 85.25 mg of the target compound with the purity of 95.12% was separated from 240 mg of the crude sample. Subsequently, a consecutive HSCCC was developed to obtain 257 mg of the target compound from 720 mg of crude sample, which was equivalent to 14.4 g of ethanol extract. This method improved the purity of the target compound, but more importantly, the sample size can reach 12 times of the maximum sample size of the ethanol extract in a single run.

Ellagic acid from pomegranate peel: Consecutive countercurrent chromatographic separation and antioxidant effect

Ellagic acid is one of the most representative natural antioxidants, and is rich in pomegranate peel. In this study, a consecutive countercurrent chromatographic (CCC) separation method was established to improve the preparative efficiency of ellagic acid from pomegranate peel. By optimizing the solvent system, sample size and flow rate, 280 mg of ellagic acid was obtained from 5 g of crude sample from pomegranate peel by CCC after six consecutive injections. Moreover, the values of EC50 for ellagic acid in scavenging ABTS·+ and DPPH· were 4.59 ± 0.07 and 10.54 ± 0.07 μg/ml, respectively, indicating a strong antioxidant activity. This study not only established a high-throughput method for the preparation of ellagic acid, but also provided a successful example for the development of and research on other natural antioxidants.

A novel and high-efficient method for the preparation of heat-stable antifungal factor from Lysobacter enzymogenes by high-speed counter-current chromatography

Heat-stable antifungal factor (HSAF) produced by the biocontrol bacterium Lysobacter enzymogenes shows considerable antifungal activity and has broad application potential in the agricultural and medical fields. There is a great demand for pure HSAF compounds in academic or industrial studies. However, an efficient preparation method that produces a high yield and high purity of HSAF is lacking, limiting the development of HSAF as a new drug. In the present study, high-speed counter-current chromatography (HSCCC) combined with column chromatography was successfully developed for the separation and preparation of HSAF from the crude extract of L. enzymogenes OH11. The crude extract was obtained by macroporous resin adsorption and desorption, and the main impurities were partly removed by ultraviolet light (254 nm) and gel filtration (Sephadex LH-20). In the HSCCC procedure, the selected suitable two-phase solvent system (n-hexane/ethyl acetate/methanol/water = 3:5:4:5, v/v, the lower phase added with 0.1% TFA) with a flow rate of 2.0 mL/min and a sample loading size of 100 mg was optimized for the separation. As a result, a total of 42 mg HSAF with a purity of 97.6% and recovery of 91.7% was yielded in one separation. The structure elucidation based on HR-TOF-MS, 1H and 13C NMR, and antifungal activities revealed that the isolated compound was unambiguously identified as HSAF. These results are helpful for separating and producing HSAF at an industrial scale, and they further demonstrate that HSCCC is a useful tool for isolating bioactive constituents from beneficial microorganisms.

Preparation of 5-hydroxymethylfurfural from Schisandra chinensis (Turcz.) Baill by high-speed counter-current chromatography: Comparison of conventional and consecutive separation

Schisandra chinensis is a kind of plant with high medicinal value, which contains many medicinal ingredients, including 5-hydroxymethylfurfural. In the present study, an efficient method based on high-speed counter-current chromatography was established for the preparation of 5-hydroxymethylfurfural from Schisandra chinensis. Petroleum ether-ethyl acetate-methanol-water (2:5:2:5, v/v) was selected as the solvent system for high-speed counter-current chromatography. In order to improve the yield of single separation, the sample size was continuously optimized and improved. The result showed that 1250 mg was the most suitable sample size, and 41 mg of the target compound with 97% purity was obtained by a single run. To further improve the yield, consecutive high-speed counter-current chromatography was introduced and compared with the results of high-speed counter-current chromatography single run. The results showed that although the purity was reduced to 92%, 430 mg of the target compound was obtained from 12.5 g of ethanol extract within 670 min after 10 consecutive injections. It indicated that consecutive separation not only increased the yield of the target compound, but also saved the separation time and greatly improved the separation efficiency of high-speed counter-current chromatography.

Characterization, Large-Scale HSCCC Separation and Neuroprotective Effects of Polyphenols from Moringa oleifera Leaves

Moringa oleifera leaves have been widely used for the treatment of inflammation, diabetes, high blood pressure, and other diseases, due to being rich in polyphenols. The main objective of this work was to largely separate the main polyphenols from Moringa oleifera leaves using the technique of high-speed counter-current chromatography (HSCCC). The phenolic composition in Moringa oleifera leaves was first analyzed qualitatively and quantitatively by UPLC-Q-Exactive Orbitrap/MS and UPLC-QqQ/MS, respectively, indicating that quercetin and kaempferol derivatives, phenolic acid and apigenin are the main polyphenols in Moringa oleifera leaves, with quercetin and kaempferol derivatives predominating. Furthermore, the conditions of HSCCC for large-scale separation of polyphenols from Moringa oleifera leaves were optimized, which included the selection of the solvent system, flow rate and the sample load. Only by one-step HSCCC separation (within 120 min) under the optimized conditions, six quercetin and kaempferol derivatives, a phenolic acid and an apigenin could be individually isolated at a large scale (yield from 10% to 98%), each of which possessed high purity. Finally, the isolated polyphenols and phenolic extract from Moringa oleifera leaves (MLPE) were verified to have strong neuroprotective activities against H₂O₂-induced oxidative stress in PC-12 cells, suggesting that these compounds would contribute to the main beneficial effects of Moringa oleifera leaves.

A strategy to process hundred-gram level complex sample using liquid-liquid-refining extraction and consecutive counter-current chromatography: Toona sinensis case study

Large-scale preparation of target compounds from complex samples is facing great challenges. In the present study, an efficient strategy for large-scale preparation of target compound was proposed and successfully applied in the separation of active components from Toona sinensis. The pretreatment technology of liquid-liquid refining extraction (LLRE) combined with consecutive high-speed counter-current chromatography (HSCCC) was used to process hundred grams of extractions. Firstly, two phase solvent systems composed of n-hexane-ethyl acetate-methanol-water (5:5:5:5, v/v) and (2:5:2:5, v/v) were used to remove low polar and high polar impurities from 100 g crude extracts of T. sinensis, respectively, and 9.25 g of crude sample was obtained. And then, n-hexane-ethyl acetate-methanol-water (2.5:5:2.5:5, v/v) was used as the solvent system for HSCCC separation. The isocratic elution mode with max loading and consecutive injections mode were investigated to obtain more target compound. As a result, ethyl gallate with purity of 97% was successfully separated by 5 times consecutive counter-current chromatography. The separation was repeated once. Finally, ethyl gallate (3.73 g) was isolated from 9.25 g of crude sample (100 g crude extracts). The results demonstrated that the yield increased from 0.26 g/h/L of untreated crude extract to 0.93 g/h/L of LLRE pre-treated sample for single injection, and further increased to 1.62 g/h/L for 5 consecutive injections mode with the present method.

Isolation of potential α-glucosidase inhibitor from Inonotus obliquus by combining ultrafiltration-liquid chromatography and consecutive high-speed countercurrent chromatography

Inonotus obliquus is a rare medicinal fungus that contains several potential therapeutic ingredients. In this study, the α-glucosidase inhibitory activity of I. obliquus was examined, and a potential α-glucosidase inhibitor, (E)-4-(3,4-dihydroxyphenyl)but-3-en-2-one, was isolated from the I. obliquus extract through ultrafiltration-liquid chromatography (UF-LC). Consecutive high-speed countercurrent chromatography (HSCCC) was used for separation to obtain large quantities of the target compound. The universal quasi-chemical functional group activity coefficient (UNIFAC) model was utilized to prepare a two-phase solvent system, n-hexane/ethyl acetate/ethanol/water (4 : 4.5 : 3.5 : 5, v/v/v/v), wherein the proportions of n-hexane/ethyl acetate/ethanol/water in the stationary and mobile phases were 19.8 : 19.7 : 7.9 : 2.2 (v/v/v/v) and 1 : 16.4 : 57.5 : 136.6 (v/v/v/v), respectively. A flow rate of 2.5 mL min^-1 and a column speed of 860 rpm were maintained. Consequently, 10.3 mg of the target compound (95.9% purity) was obtained from 900 mg (6 × 150 mg) of the I. obliquus extract. The use of the UNIFAC model, in combination with consecutive HSCCC separations, allows the purification of large quantities of samples over a short time. Furthermore, the volume of the organic solvent required is reduced. Thus, UF-LC is an effective technique for screening potential α-glucosidase inhibitors isolated from I. obliquus. This can ultimately aid in the discovery of bioactive compounds for the prevention and treatment of diabetes.

Counter-current fractionation-assisted bioassay-guided separation of active composition from the edible medicinal insect Blaps rynchopetera Fairmaire

An efficient strategy for the selection of active components based on counter-current fractionation and bioassay-guided separation was established in the present work. Blaps rynchopetera Fairmaire was an edible medicinal insect. Its extract showed the potential RAW264.7 macrophage cell inhibitory activity. After extraction with different solvents, the active components were enriched in ethyl acetate. In order to further track the active compounds, the ethyl acetate extraction was divided into 14 fractions by means of HSCCC. The results showed that the activities of F6 and F7 were significant higher than the others. Two compounds, hydroxytyrosol and 4-ethylbenzene-1,3-diol, were separated from the mixture of F6 and F7 by column chromatography and their chemical structures were confirmed by MS, ¹H NMR and ¹³C NMR. The IC₅₀ of hydroxytyrosol and 4-ethylbenzene-1,3-diol against RAW264.7 macrophage cell were 38.24 ± 0.26 μg/mL and 103.26 ± 0.29 μg/mL, respectively, indicating that hydroxytyrosol was the major active ingredient responsible for the RAW264.7 inhibitory activity of Blaps rynchopetera Fairmaire.

Improved separation with the intermittently pressed tubing of multilayer coil in type-I counter-current chromatography

The intermittently pressed tubing was introduced in type-I counter-current chromatographic system as the separation column to improve the separation performance in the present study. The separations were performed with two different solvent systems composed of 1-butanol-acetic acid-water (4:1:5, v/v) (BAW) and hexane-ethyl acetate-methanol-0.1 M HCl (1:1:1:1, v/v) (HEMW) using dipeptides and DNP-amino acids as test samples, respectively. The chromatographic performance was evaluated in terms of retention of the stationary phase (Sf), theoretical plate (N) and peak resolution (Rs). In general, the type-I planetary motion with the multilayer coil of non-modified standard tubing can yield the best separation at a low revolution speed of 200 rpm with lower flow rate. The present results with intermittently pressed tubing indicated that the performance was also optimal at the revolution speed of 200 rpm where the lower flow rate was more beneficial to retention of stationary phase and resolution. In the moderately hydrophobic two-phase solvent system composed of hexane-ethyl acetate-metanol-0.1 M hydrochloric acid (1:1:1:1, v/v), DNP-amino acids were separated with Rs at 1.67 and 1.47, respectively, with 12.66% of stationary phase retention at a flow rate of 0.25 ml/min. In the polar solvent system composed of 1-butanol-acetic acid-water (4:1:5, v/v), dipeptide samples were resolved with Rs at 2.18 and 18.75% of stationary phase retention at a flow rate of 0.25 ml/min. These results indicate that the present system substantially improves the separation efficiency of type-I counter-current chromatographic system.

A multilayer coil in type-I counter-current chromatography

In the present study, a novel model of type-I counter-current chromatography was developed to simplify the separation column manufacture and extend its application ranges. In this system, a multilayer coil was used as the separation column of type-I counter-current chromatography for the first time. The chromatographic performance of this apparatus was evaluated in terms of retention of the stationary phase (Sf), theoretical plate (N) and peak resolution (Rs) using dipeptides and DNP-amino acids as test samples with two classic solvent systems composed of 1-butanol-acetic acid-water (4:1:5, v/v) (BAW) and hexane-ethyl acetate-methanol-0.1 M HCl (1:1:1:1, v/v) (HEMW), respectively. The results indicated that the performance was optimal at the revolution speed of 200 rpm. The lower flow rate was more beneficial to retention of stationary phase and peak resolution. Over all results of our study revealed that the new type-I counter-current chromatography with a multilayer coil has a high application potential.

Rapid prediction and identification of lipase inhibitors in volatile oil from Pinus massoniana L. needles

A facile method based on gas chromatography-mass spectrometry (GC-MS) and molecular docking was established to analyze, identify, and predict lipase inhibitors in volatile oil from Pinus massoniana L. needles (PMLN). The volatile oil, with an IC₅₀ value of 15.25 ± 0.06 μg/mL, exhibited potential inhibitory activity against lipase in vitro. In total, 33 compounds were identified from the volatile oil through GC-MS analysis. The major compounds in the volatile oil were β-pinene (39.24%), α-pinene (14.68%), germacrene D (9.08%), caryophyllene (6.94%), α-terpineol (5.39%), β-phellandrene (4.82%), and D-limonene (3.93%). The identified compounds were individually docked with lipase as the target through molecular docking. Among the compounds, longifolene characterized by preferable binding energy and the good inhibition constant exhibited potential lipase inhibitory activity. The IC₅₀ value of longifolene was 25.10 ± 0.49 μM, indicating that this compound is the active ingredient responsible for the lipase inhibitory activity of PMLN volatile oil.

An Efficient Method for the Preparative Isolation and Purification of Flavonoids from Leaves of Crataegus pinnatifida by HSCCC and Pre-HPLC

In this work, flavonoid fraction from the leaves of Crataegus pinnatifida was separated into its seven main constituents using a combination of HSCCC coupled with pre-HPLC. In the first step, the total flavonoid extract was subjected to HSCCC with a two-solvent system of chloroform/methanol/water/n-butanol (4:3:2:1.5, v/v), yielding four pure compounds, namely (-)-epicatechin (1), quercetin-3-O-(2,6-di-α-l-rhamnopyranosyl)-β-d-galactopyranoside (2), 4''-O-glucosylvitexin (3) and 2''-O-rhamnosylvitexin (4) as well as a mixture of three further flavonoids. An extrusion mode was used to rapidly separate quercetin-3-O-(2,6-di-α-l-rhamnopyranosyl)-β-d-galactopyranoside with a big K_D-value. In the second step, the mixture that resulted from HSCCC was separated by pre-HPLC, resulting in three pure compounds including: vitexin (5), hyperoside (6) and isoquercitrin (7). The purities of the isolated compounds were established to be over 98%, as determined by HPLC. The structures of these seven flavonoids were elucidated by ESI-MS and NMR spectroscopic analyses.

An Efficient Method for the Preparative Isolation and Purification of Flavonoid Glycosides and Caffeoylquinic Acid Derivatives from Leaves of Lonicera japonica Thunb. Using High Speed Counter-Current Chromatography (HSCCC) and Prep-HPLC Guided by DPPH-HPLC Experiments

In this work, the n-butanol extract from leaves of Lonicera japonica Thunb. (L. japonica) was reacted with DPPH and subjected to a HPLC analysis for the guided screening antioxidants (DPPH-HPLC experiments). Then, nine antioxidants, including flavonoid glycosides and caffeoylquinic acid derivatives, were isolated and purified from leaves of L. japonica using high speed counter-current chromatography (HSCCC) and prep-HPLC. The n-butanol extract was firstly isolated by HSCCC using methyl tert-butyl ether/n-butanol/acetonitrile/water (0.5% acetic acid) (2:2:1:5, v/v), yielding five fractions F1, F2 (rhoifolin), F3 (luteoloside), F4 and F5 (collected from the column after the separation). The sub-fractions F1, F4 and F5 were successfully separated by prep-HPLC. Finally, nine compounds, including chlorogenic acid (1), lonicerin (2), rutin (3), rhoifolin (4), luteoloside (5), 3,4-O-dicaffeoylquinic acid (6), hyperoside (7), 3,5-O-dicaffeoylquinic acid (8), and 4,5-O-dicaffeoylquinic acid (9) were obtained, respectively, with the purities over 94% as determined by HPLC. The structures were identified by electrospray ionization mass spectrometry (ESI-MS), ¹H- and ¹³C-NMR. Antioxidant activities were tested, and the isolated compounds showed strong antioxidant activities.

An Efficient Method for the Preparative Isolation and Purification of Flavonoid Glycosides and Caffeoylquinic Acid Derivatives from Leaves of Lonicera japonica Thunb. Using High Speed Counter-Current Chromatography (HSCCC) and Prep-HPLC Guided by DPPH-HPLC Experiments

In this work, the n-butanol extract from leaves of Lonicera japonica Thunb. (L. japonica) was reacted with DPPH and subjected to a HPLC analysis for the guided screening antioxidants (DPPH-HPLC experiments). Then, nine antioxidants, including flavonoid glycosides and caffeoylquinic acid derivatives, were isolated and purified from leaves of L. japonica using high speed counter-current chromatography (HSCCC) and prep-HPLC. The n-butanol extract was firstly isolated by HSCCC using methyl tert-butyl ether/n-butanol/acetonitrile/water (0.5% acetic acid) (2:2:1:5, v/v), yielding five fractions F1, F2 (rhoifolin), F3 (luteoloside), F4 and F5 (collected from the column after the separation). The sub-fractions F1, F4 and F5 were successfully separated by prep-HPLC. Finally, nine compounds, including chlorogenic acid (1), lonicerin (2), rutin (3), rhoifolin (4), luteoloside (5), 3,4-Odicaffeoylquinic acid (6), hyperoside (7), 3,5-O-dicaffeoylquinic acid (8), and 4,5-O-dicaffeoylquinic acid (9) were obtained, respectively, with the purities over 94% as determined by HPLC. The structures were identified by electrospray ionization mass spectrometry (ESI-MS), 1H- and 13C-NMR. Antioxidant activities were tested, and the isolated compounds showed strong antioxidant activities.

Preparative separation of quaternary ammonium alkaloids from Caulis Mahoniae by conventional and pH-zone-refining counter-current chromatography

Compared with the conventional HSCCC, PZRCCC is an efficient and rapid method for separation of quaternary ammonium alkaloids because of the high concentration of fractions and large sample loading capacity.