Comprehensive separation of secondary metabolites in natural products by high-speed counter-current chromatography using a three-phase solvent system

High-speed counter-current chromatography (HSCCC) using the three-phase solvent system n-hexane-methyl acetate-acetonitrile-water at a volume ratio of 4:4:3:4 was applied to the comprehensive separation of secondary metabolites in several natural product extracts. A wide variety of secondary metabolites in each natural product was effectively extracted with the three-phase solvent system, and the filtered extract was directly submitted to the HSCCC separation using the same three-phase system. In the HSCCC profiles of crude natural drugs listed in the Japanese Pharmacopoeia, several physiologically active compounds were clearly separated from other components in the extracts. The HSCCC profiles of several tea products, each manufactured by a different process, clearly showed their compositional difference in main compounds such as catechins, caffeine, and pigments. These HSCCC profiles also provide useful information about hydrophobic diversity of whole components present in each natural product.     

Application of supercritical fluid extraction coupled with counter–current chromatography for extraction and online isolation of unstable chemical components from Rosa damascena

Supercritical fluid extraction (SFE) coupled with high‐speed counter‐current chromatography (HSCCC) was successfully used for the extraction and online isolation of the unstable compounds from Rosa damascene in a single extraction and separation operation in two stages. The solvent systems of SFE/HSCCC were optimized with the help of multiexponential function model. At the first stage, the upper phase of the solvent system of n‐butanol–tert‐butyl methyl ether–acetonitrile–0.1% aqueous TFA (1.7:1.0:0.8:4.0, v/v/v/v) was used as both the SFE entrainer and the HSCCC stationary phase, and the target compounds were eluted with the corresponding lower phase to separate the hydrophobic compounds. At the second stage, the upper phase of the solvent system of n‐hexane–ethyl acetate–methanol–water (3.2:1.0:2.8:2.6, v/v/v/v) was used as both the SFE entrainer and the HSCCC stationary phase, followed by elution with the corresponding lower phase to separate the moderate hydrophobic compounds. Six compounds including formononetin, delphinidin, cyaniding, 5,6,4′‐trihydroxy‐7,8‐dimethoxy flavone, 5,3′‐dihydroxy‐7,8‐dimethoxy flavone, and 5‐hydroxy‐6,7,8,3′,4′‐pentamethoxy flavone were successfully separated in one extraction–separation operation within 300 min. The targeted compounds were identified by MS and NMR spectroscopy. This research has opened up great prospects for industrial application of SFE/HSCCC to the extraction and separation of unstable compounds.     

Preparative isolation and purification of two benzoxazinoid glucosides from Acanthus ilicifolius L. by high-speed counter-current chromatography

The first preparative separation of two benzoxazinoids, (2R)-2-O-beta-d-glucopyranosyl-2H-1,4-benzoxazin-3(4H)-one (HBOA-Glc) and (2R)-2-O-beta-d-glucopyranosyl-4-hydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA-Glc), by means of high-speed counter-current chromatography (HSCCC) from the n-butanol extract of Acanthus ilicifolius L. is presented. The two-phase solvent system containing ethyl acetate-n-butanol-0.5%NH(4)OH (2:3:5, v/v/v, system B) was selected for the one-step HSCCC separation of HBOA-Glc and DIBOA-Glc according to the partition coefficient values (K) for target compounds and the separation factor (alpha) between the two target compounds. In the one-step HSCCC separation using solvent B, from 100mg n-butanol extract of A. ilicifolius, 6.3 mg HBOA-Glc and 6.8 mg DIBOA-Glc were isolated with purities of 90.3% and 80.2%, respectively. In order to obtain the two target compounds with higher purity, a second separation process was developed comprising two steps. In the two-step separation, the sample was first pre-purified by HSCCC using ethyl acetate-n-butanol-water (2:3:5, v/v/v, system A) solvent system and then purified using solvent system B. A 100-mg amount of the n-butanol extracts of A. ilicifolius was separated to yield 5.8 mg of HBOA-Glc and 4.8 mg of DIBOA-Glc with purities of 97.1% and 94.8%, respectively, which were directly used for NMR analyses.     

High throughput qualitative analysis of polyphenols in tea samples by ultra-high pressure liquid chromatography coupled to UV and mass spectrometry detectors

The analysis of polyphenols in tea extracts is important due to their potential health benefits. Therefore, efficient and high throughput analytical methods have been developed for the separation of seven predominant polyphenols, also known as catechin derivatives, present in tea extracts. Columns packed with sub-2-μm particles operating at elevated pressure (UHPLC strategy) were selected to improve chromatographic performance. The potential of UHPLC–UV was demonstrated with baseline resolution of all standard catechins in only 30 s using a 50-mm column packed with 1.7-μm particles. When dealing with real samples such as tea extracts, however, longer columns of up to 150 mm in length were employed to enhance the separation of catechin derivatives and other constituents within the tea samples while maintaining an acceptable analysis time. Two strategies based on 2-D experiments were proposed to clearly identify catechins. Firstly, a liquid–liquid extraction procedure was added prior to the UHPLC–UV analysis to decrease the complexity of the sample. Secondly, UHPLC was coupled to ESI-MS/MS to attain sufficient sensitivity and selectivity between catechin derivatives and other constituents of tea extract. These two strategies were found extremely promising as a clear discrimination of catechins from the matrix could be attained.     

Separation and identification of polyphenols in apple pomace by high-speed counter-current chromatography and high-performance liquid chromatography coupled with mass spectrometry

Apple pomace, a by-product in the processing of apple juice, was investigated as a potential source of polyphenols. Two methods of separation and purification of polyphenols from apple pomace extract were established by combination of gel chromatography with high-speed counter-current chromatography (HSCCC) and solvent extraction with HSCCC, respectively. The optimal separation was performed on a Sephadex LH-20 column using gradient aqueous ethanol as eluting solvent from 0% to 100% in increments of 10%. HPLC analysis indicated that main polyphenols existed in fractions eluted between 40% and 50% aqueous ethanol. The fractions of interest from column were separated by HSCCC with the solvent system hexane–ethyl acetate–1% aqueous acetic acid (0.5:9.5:10, v/v/v). Ethyl acetate fractionation of the apple pomace extract followed by direct HSCCC separation by the same solvent system in the volume ratio of 1:9:10 also produced a good separation of the main polyphenols of interest. Six high-purity polyphenols were achieved tentatively and identified by HPLC/MS: chlorogenic acid (1, m/z 354), quercetin-3-glucoside/quercetin-3-glacaside (2, m/z 464), quercetin-3-xyloside (3, m/z 434), phloridzin (4, m/z 436), quercetin-3-arabinoside (5, m/z 434), and quercetin-3-rhamnoside (6, m/z 448). These results provided a preliminary foundation for further development and exploration of apple pomace.     

Three-phase solvent systems for comprehensive separation of a wide variety of compounds by high-speed counter-current chromatography

Three-phase solvent systems were efficiently utilized for high-speed counter-current chromatography (HSCCC) to separate multiple components with a wide range of hydrophobicity. The compositions of three-phase systems were optimized according to their physical parameters such as volume ratio, viscosity and specific gravity of upper (UP), middle (MP) and lower (LP) phases. The three-phase systems composed of n-hexane-methyl acetate-acetonitrile-water (4:4:3:4, v/v/v/v) was selected for HSCCC separation of a mixture of 15 standard compounds with a wide range in hydrophobicity from beta-carotene to tryptophan. The separation was initiated by filling the column with a mixture of MP and LP both as a stationary phase followed by elution with UP to separate the hydrophobic compounds. Then the mobile phase was switched to MP to elute the moderately hydrophobic compounds, and finally the polar compounds still retained in the column were fractionated by eluting the column with LP. The system successfully resolved all 15 compounds in one-step operation in 70 min.     

SEPARATION OF THE MINOR FLAVONOLS FROM FLOS GOSSYPII BY HIGH-SPEED COUNTERCURRENT CHROMATOGRAPHY

An effective high-speed countercurrent chromatography (HSCCC) method was established for further separation and purification of four minor flavonols in addition to five major flavonols which were reported by our previous study from extracts of Flos Gossypii. HSCCC was performed with three two-phase solvent systems composed of n-hexane-ethyl acetate-methanol-water (7.5:15:6:7, v/v), (2.5:15:2:7, v/v) and (0:1:0:1, v/v). The separation was repeated 3 times, and 3.8 mg of 8-methoxyl-kaempferol-7-O-β-D-rhamnoside (HPLC purity 98.27%), 6.7 mg of astragalin (HPLC purity 94.18%), 3.3 mg of 4'-methoxyl-quercetin-7-O-β-D-glucoside (HPLC purity 94.30%) and 8.2 mg of hyperoside (HPLC purity 93.48%) were separated from 150 mg of the crude sample. The chemical structures of the flavonols were confirmed by MS, (1)H NMR and (13)C NMR. Meanwhile, the results indicated that the target compound with smaller K value (<0.5) can be separated by increasing column length of HSCCC. And four separation rules of flavonols according to the present study and references were summarized, which can be used as a useful guide for separation of flavonols by HSCCC.     

Combination of supercritical fluid extraction with counter‐current chromatography to isolate anthocyanidins from the petals of Chaenomeles sinensis based on mathematical calculations

Supercritical fluid extraction (SFE) coupled with high‐speed counter‐current chromatography (HSCCC) was successfully used for the extraction and on‐line isolation of the anthocyanidins from the petals of Chaenomeles sinensis in two stages. The SFE parameters were optimized by an orthogonal test, and the solvent systems of SFE and HSCCC were calculated and optimized with the help of a multiexponential function model. In the first stage, the lower phase of the solvent system of n‐butanol/tert‐butyl methyl ether/acetonitrile/0.1% aqueous TFA (0.715:1.0:0.134:1.592, v/v/v/v) was used as both the SFE modifier and the HSCCC stationary phase, after extraction, the extractants were pumped into HSCCC column, and then eluted with the corresponding upper phase to isolate the moderately hydrophobic compounds. In the second stage, the upper phase of the solvent system of n‐butanol/ethyl acetate/acetonitrile/0.1% aqueous TFA (1.348:1.0:0.605:2.156, v/v/v/v) was used as both the SFE modifier and the HSCCC stationary phase, followed by elution with the corresponding lower phase to separate the hydrophobic compounds. With the help of two‐stage SFE/HSCCC, six compounds including delphinidin‐3‐O‐glucoside (Dp3G), cyanidin‐3‐O‐glucoside (Cy3G), peonidin‐3‐O‐glucoside (Pn3G), delphinidin (Dp), peonidin (Pn), and malvidin (Mv) were successfully separated within 300 min. The targeted compounds were identified by UV spectrophotometry, MS, and NMR spectroscopy. This research has opened up great prospects for the industrial application of SFE–HSCCC for the automatic extraction and separation of unstable compounds.     

Preparative isolation and purification of five compounds from the Chinese medicinal herb Polygonum cuspidatum Sieb. et Zucc by high-speed counter-current chromatography

High-speed counter-current chromatography (HSCCC) was applied to the separation and purification of five compounds from the Chinese medicinal herb Polygonum cuspidatum Sieb. et Zucc. The crude extracts from P. cuspidatum Sieb. et Zucc were treated with light petroleum-ethyl acetate-methanol-water (2:5:4:6, v/v). Sample 1 was obtained from the lower phase and sample 2 from the upper phase. The sample 1 was separated with light petroleum-ethyl acetate-water (1:5:5, v/v) and yielded 19.3mg of piceid, 17.6 mg of anthraglycoside B from 200mg of sample 1. The sample 2 was separated with light petroleum-ethyl acetate-methanol-water (3:5:4:6, v/v) and light petroleum-ethyl acetate-methanol-water (3:5:7:3, v/v) in a gradient elution and yielded 18.5mg of resveratrol, 35.3mg of emodin and 8.2mg of physcion from 220 mg of sample 2. The purity of each compound is over 95% as determined by HPLC. The chemical structures of these components were identified by (1)H NMR and (13)C NMR.     

High-speed counter-current chromatography separation and purification of resveratrol and piceid from Polygonum cuspidatum

High-speed counter-current chromatography (HSCCC) was applied to the separation and purification of resveratrol and piceid from the dried roots (20.0 g) of Polygonum cuspidatium. The EtOAc extracts were separated with chloroform-methanol-water (4:3:2, v/v). Resveratrol was identified in fraction 5. The water extracts were separated first with EtOAc-EtOH-water (10:1:10, v/v) and then with the same solvent system at the modified volume ratio of 70:1:70. Yields of resveratrol and piceid obtained were 2.18% and 1.07%. Chemical structures of the purified resveratrol and piceid were confirmed by electrospray ionization MS and 1H nuclear magnetic resonance spectroscopy.     

高速逆流色谱结合制备液相色谱法分离制备葡萄籽中的多酚

采用高速逆流色谱结合制备液相色谱法从葡萄籽乙醇提取物中分离得到了8种多酚。高速逆流色谱以上相为固定相,下相为流动相,主机转速为900 r/min,流速为2 mL/min,分离温度为25℃,检测波长为280 nm,利用正向和反向洗脱相结合的模式,在正丁醇-乙酸乙酯-水（1∶14∶15,v/v/v）和正己烷-乙酸乙酯-水（1∶10∶10,v/v/v）溶剂系统下从葡萄籽提取物中分离得到了5种多酚。原花青素B₁、原花青素B₂、没食子酸、表儿茶素没食子酸酯和儿茶素的纯度分别为98.5%、97.2%、98.3%、98.9%和96.7%。利用制备液相色谱法对高速逆流色谱分离成分进一步分离纯化,获得了表儿茶素、表没食子儿茶素没食子酸酯和没食子儿茶素没食子酸酯,纯度分别99.2%、99.3%和99.2%。该方法单次制备量均达到毫克级,简便、快速、分离纯度高,适合于葡萄籽中多酚的分离制备。     

Isolation of dammarane saponins from Panax notoginseng by high-speed counter-current chromatography

The Chinese phytomedicinal formulation Sanqi Zongdai Pian, traditionally prepared from crude extracts from roots of Panax notoginseng (Araliaceae), contains highly polar dammarane saponins which were separated at a preparative scale using high-speed counter-current chromatography (HSCCC). In each operation, 283 mg methanolic extract of five tablets was separated and yielded pure 157, 17, 13 and 56 mg of ginsenoside-Rb1, notoginsenoside-R1, ginsenoside-Re and ginsenoside-Rg1, respectively, n-hexane-n-butanol-water (3:4:7, v/v/v) was used for the two-phase solvent system of the HSCCC separation. The chemical structures of three ginsenosides and one notoginsenoside were elaborated by means of electrospray ionization MS-MS and NMR analysis.     

A consecutive preparation method based upon accelerated solvent extraction and high‐speed counter‐current chromatography for isolation of aesculin from Cortex fraxinus

A consecutive preparation method based upon accelerated solvent extraction (ASE) coupled with high‐speed counter‐current chromatography (HSCCC) was presented and aesculin was obtained from Cortex fraxinus. The extraction condition of ASE was optimized with response surface methodology; some significant parameters such as the solvent system and its stability, the amount of loading sample in HSCCC were also investigated. The original sample was first extracted with methanol at 105°C and 104 bar for 7 min using ASE, then the extracts were consecutively introduced into the HSCCC system and separated and purified with the same ethyl acetate/n‐butanol/water (7:3:10, v/v/v) solvent system for five times without further exchange and equilibrium. About 3.1 ± 0.2 mg/g in each time and total of 15.4 mg/g aesculin with purity over 95% was isolated from Cortex fraxinus. The results demonstrated that the consecutive preparation method was time and solvent saving and high throughput, it was suitable for isolation of aesculin from Cortex fraxinus, and also has good potential on the separation and purification of effective compounds from natural product.     

PREPARATIVE ISOLATION AND PURIFICATION OF FIVE FLAVONOIDS FROM POGOSTEMON CABLIN BENTH BY HIGH-SPEED COUNTERCURRENT CHROMATOGRAPHY AND PREPARATIVE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

High-speed countercurrent chromatography (HSCCC) and preparative high-performance liquid chromatography (prep-HPLC) were successively used for the separation of pogostone and four flavonoids from Pogostemon cablin (Blanco) Benth. An efficient HSCCC separation was achieved on a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (11:5:11:5, v/v/v/v). Three well-separated peaks were obtained in the HSCCC chromatogram. The first and the second fractions each contained two flavonoids which were further separated by preparative HPLC. Consequently, the separation yielded 11.5 mg of 4', 5-Dihydroxy-3', 7-dimethoxyflavanone at a purity of 99%, 20.3 mg of 5- Hydroxy-7, 3', 4'-trimethoxyflavanone at a purity of 98%, 18 mg of 5, 4'-Dihydroxy-3, 7, 3'-trimethoxyflavone at a purity of 96%, and 8 mg of 5-Hydroxy-3, 7, 4'-tetramethoxyflvone at a purity of 98%. The third HSCCC fraction yielded 18.5 mg of pogostone at a purity of 95%. The chemical structures of these compounds were identified by ESI-MS(n), (1)H-NMR, and (13)C-NMR.     

Preparative isolation and purification of two amides from Mallotus lianus Croiz by high-speed counter-current chromatography

High-speed counter-current chromatography (HSCCC) was applied to the preparative isolation and purification of two amides from Mallotus lianus Croiz. In a single HSCCC separation, using the two-phase solvent system composed of n-hexane/ethyl acetate/methanol/water (5:1:5:1 v/v), 247.5 mg of the enriched crude sample was separated to afford 10.3 mg of N-isobutyl-2E,4E,12Z-octadecatrienamide and 15.7 mg of (7Z,10Z,18Z)tricosa-7,10,18-trienamide, a novel compound, with the purities of 98.0 and 94.6%, respectively. The HSCCC fractions were analyzed by HPLC and chemical structures of the compounds were identified by 1D- and 2D-NMR, ESI-, and GC-MS.     

Separation and purification of verticine and verticinone from Bulbus Fritillariae Thunbergii by high-speed counter-current chromatography coupled with evaporative light scattering detection

High-speed counter-current chromatography (HSCCC) coupled with evaporative light scattering detection (ELSD) was successfully applied to preparative separation and purification of verticine and verticinone from crude extracts of Bulbus Fritillariae Thunbergii by a one-step separation, using chloroform–ethanol–0.2 mol L⁻¹ hydrochloric acid (3:2:2, v/v/v) as a solvent system. HPLC analysis of the fractions collected on the preparative HSCCC of 200 mg of crude extracts showed that the purity of verticine (25.6 mg) was 96.8% and that of verticinone (10.3 mg) was 95.4%. The chemical identities of these components were confirmed by ¹H NMR and EI–MS.     

A high performance liquid chromatography method for simultaneous detection of 20 bioactive components in tea extracts

Tea is the second most widely consumed beverage and contains various bioactive compounds. A simple method to analyze these compounds is of great scientific and commercial interest. In this work, a 30 min HPLC method was developed using a simple gradient elution system, and the mobile phases and elution gradients were optimized. This method separated 17 polyphenols and three alkaloid compounds in tea extracts, including catechins, alkaloids, phenolic acids, flavonols, and flavone, which are responsible for the bioactivity and flavor of tea. Excellent linearity was observed for all standard calibration curves, and correlation coefficients were above 0.9994. Heatmap analysis demonstrated significant separation between green, black, and pu‐erh tea samples. The method described here is accurate and sensitive enough for the determination of active components in tea and could potentially be applied to other food products for the comprehensive investigation of their quality.     

Ten marker compounds-based comparative study of green tea and guava leaf by HPTLC densitometry methods: antioxidant activity profiling

High-performance thin layer chromatography (HPTLC) method for the separation and quantitative determination of ten markers (catechins, flavonoids, and phenolics) in different extracts of green tea and guava leaf has been developed and the antioxidant activity profiles of the two plant extracts have been determined. Ten marker compounds have been resolved using silica gel 60 F(254) plates, toluene/acetone/formic acid (5:4:1 v/v/v) for markers 1-6, and toluene/ethyl acetate/formic acid/methanol (3:3:0.8:0.2 v/v/v/v) for markers 7-10 as the mobile phases. The high-performance thin layer chromatography densitometry was performed at wavelengths of 282 and 285 nm for the markers 1-6 and 7-10, respectively. Potent antioxidant activity and the presence of phenolics and flavan-3-ols has been observed for the guava leaf extracts suggestive of its use as an alternate economical source of antioxidants over green tea--the well-established food additive/nutraceutical agent.     

Sample capacity in preparative high-speed counter-current chromatography

High-speed counter-current chromatography (HSCCC) is a versatile technique in preparative separation and purification of pure compounds from complex matrices. As a preparative chromatography, there is a need to maximize the column production. Based on the plate theory of Van Deemter, the effect of the sample load on the separation was investigated in a preparative HSCCC with a 1000 ml column capacity. The test samples of hydroquinone, pyrocatechol and phenol were separated using a two-phase solvent system of n-hexane-ethyl acetate-ethanol-water (1:1:1:1, v/v/v/v) at different sample loads. The results showed that for the case of HSCCC, the agreement of the effect of sample load on peak height and peak width between the Van Deemter's theory and the experiments is excellent. Furthermore, the factors limiting the mass load, including the resolution between the peaks, the partition isotherm and the solute solubility were also discussed.     

Flow rate gradient high-speed counter-current chromatography separation of five diterpenoids from Triperygium wilfordii and scale-up

In this paper, high-speed counter-current chromatography (HSCCC) instruments with different gravitational forces were applied for the separation of bioactive compounds from Triperygium wilfordii Hook.f. The critical parameters including sample concentration, sample volume and flow rate were first optimized on an analytical Mini-DE HSCCC system, and then scaled up to a preparative TBE 300A HSCCC system. Although this scale-up process was performed using different CCC instruments with different centrifuges and gravitational forces, the same resolutions were obtained and the elution time could be predictable. Five diterpenoid compounds and one unknown compound were separated from Triperygium wilfordii Hook.f. by HSCCC with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (HEMW) (3:2:3:2, v/v/v/v). This one-step flow gradient separation produced triptonide (25 mg), isoneotriptophenolide (77 mg), hypolide (83 mg), unknown compound (1 mg), triptophenolide (42 mg), triptonoterpene methyl ether VI (37 mg) from 320 mg crude extract with purities of 98.2%, 96.6%, 98.1%, 95.3%, 95.1%, and 96.5%, respectively. Their purities and structures were identified by high-performance liquid chromatography, mass spectrometry and NMR. This paper demonstrates that analytical CCC plays an important role in optimizing parameters and scale-up process when analytical CCC and preparative CCC are supplied by different manufacturers with different gravitational forces, and the scale-up process from analytical CCC to preparative CCC is still predictable.