Purification of quinoline yellow components using high-speed counter-current chromatography by stepwise increasing the flow-rate of the mobile phase

Nitrogen-doped carbon quantum dots as dual mode fluorescence sensors for the determination of food colorant quinoline yellow

Quinoline yellow (QY), as a food coloring agent, will consume a large number of detoxifying substances in the body after being ingested by the human body, interfering with the normal metabolic functions of the human body, and may cause allergies, diarrhea and other symptoms, as well as a certain degree of carcinogenicity, posing a great threat to human health. As a result, it is critical to develop a fast, sensitive, and effective approach to determining quinoline yellow in food. In this study, carbon dots (N-CQDs) with high fluorescence quantum yield were prepared and used to determine the QY content using the dual mode of internal filtering effect and fluorescence emission shift detection. Both methods showed good linearity in the range of QY concentration of 0.3-3.2 μM, and the detection limits were classified as 2.6 nM and 0.18 μM. In addition, in order to achieve visual detection of QY, fluorescent test strips were constructed using the carbon dots and non-fluorescent qualitative filter paper to make the detection of QY more convenient. This probe presents a novel way for detecting quinoline yellow in food analysis.

A cationic surfactant-decorated liquid crystal-based sensor for sensitive detection of quinoline yellow

Quinoline yellow (QY) is one of the popular synthetic food colorants and in food industry greatly used. Developing accurate and simple QY detection procedures is of major considerable importance in ensuring food safety. Hence, it is important to detect this food colorant effectively to reduce risk. Herein, an innovative liquid crystal (LC)-based sensor was designed for the label-free and ultra-sensitive detecting of the QY by means of a cationic surfactant-decorated LC interface. The nematic liquid crystal in touch with CTAB revealed a homeotropic alignment, when QY was injected into the LC-cell, the homeotropic alignment consequently altered to a planar one by electrostatic interactions between QY and CTAB. The designed LC-based sensor detected QY at the too much trace level as low as 0.5 fM with analogous selectivity. The suggested LC-based sensor is a rapid, convenient and simple procedure for label-free detection of QY in food industrial and safety control application.

Determination of sulphonated quinophthalones in Quinoline Yellow and its lakes using high-performance liquid chromatography

Quinoline Yellow (QY, Colour Index No. 47005) is internationally used as a colour additive in foods, drugs, and cosmetics. The manufacture of QY requires sulphonating quinophthalone, and depending on the degree of sulphonation, various forms of QY result, containing different proportions of quinophthalone mono-, di-, and trisulfonic acid sodium salts (monoSA, diSA, and triSA, respectively). Regulations on the specific composition and uses of QY differ across countries with associated differences in names for QY. The QY form certified for use in the U.S. in drugs and cosmetics is known as D&C Yellow No. 10 (Y10). The Code of Federal Regulations (CFR) specifies that Y10 and its lakes consist of predominantly monoSA's, the sum of whose levels is ≥ 75%, and that the sum level of diSA's is ≤ 15%, with one of them (6'8'diSA) at ≤ 3%. The present work reports the development of an HPLC method for determining those CFR-specified values and the level of a non-CFR-specified component, 6'8'5triSA. The selected analytes, 6'SA, 6'5diSA, 6'8'diSA, and 6'8'5triSA, were quantified by using five-point-calibration curves (R² > 0.999) with data-point ranges of 9.96-96.53%, 0.54-21.69%, 0.10-5.00%, and 0.11-5.53% by weight, respectively. The method was found to be precise (relative standard deviation values, 0.55-0.80%) and accurate (recovery values, 91.07-99.45%). LOD and LOQ values, respectively, were as follows: 1.23 and 3.70%, 6'SA; 0.42 and 1.26%, 6'5diSA; 0.11 and 0.34%, 6'8'diSA; and 0.01 and 0.04%, 6'8'5triSA. The HPLC method was applied successfully to the analysis of 20 Y10 and eight Y10 lake samples. It can be extended to other QY forms such as E104 and Yellow 203 because it enables analysis of 6'8'5triSA. This paper also addresses the implications of the varying structure depictions and CAS numbers of the QY components that are due to the existence of three tautomeric forms of quinophthalone.

Preparative separation of flavone dimers from Dysosma versipellis by counter-current chromatography: Trifluoroacetic acid as a solvent system modifier

The separation of natural products is grueling and time-consuming work with repeated isolations needed to obtain purified compounds. However, using counter-current chromatography, a unique liquid-liquid partition chromatography, constituents can usually be purified efficiently. During the separation of flavone dimers from Dysosma versipellis (Hance) by counter-current chromatography, the separation resolution and sample loading was impeded by the emulsification of the sample. By screening, trifluoroacetic acid was selected as the solvent modifier to eliminate the emulsification. Then, a quaternary solvent system of hexane/ethyl acetate/methanol/water (4:6:5:5 v/v/v/v) with trifluoroacetic acid at a low concentration of 0.5% v/v was used to purify the components from D. versipellis. Compared to that without trifluoroacetic acid, the separation resolution as well as the sample loading both increased greatly. In addition, flavone dimers in low concentrations could be enriched and purified at high sample loading. As a result, five podophyllotoxins and 11 flavonoids were purified and characterized by interpretation of spectroscopic data, in which two of eight flavone dimers were new and a known flavone dimer was first separated from this species.

High-speed countercurrent chromatography isolation of flavans from Ixeris chinensis and their identification by NMR spectroscopy

High-speed countercurrent chromatography, combined with macroporous resin chromatography were applied to the separation and purification of flavans from Ixeris chinensis. Four flavans, namely, 5-methoxy-7,4'-dihydroxyflavan-3-ol (1), 5,7-dimethoxy-4'-hydroxyflavan-3-ol (2), 5,7-dimethoxy-4'-hydroxyflavan (3), and 5,7-dimethoxy-8-methyl-4'-hydroxyflavan (4), were obtained from I. chinensis for the first time. Their chemical structural identification was carried out by spectroscopic methods, including 1D and 2D NMR spectroscopy. Amounts of 13.2 mg of compound 1, 6.4 mg of compound 2, 5.8 mg of compound 3, and 14.5 mg of compound 4 were separated from 120 mg 75% ethanol fraction. The purities of 1-4 were 99.1, 99.2, 97.3, and 98.6 %, respectively.

Preparative separation of di- and trisulfonated components of Quinoline Yellow using affinity-ligand pH-zone-refining counter-current chromatography

Four positionally isomeric 2-(2-quinolinyl)-1H-indene-1,3(2H)-dionedisulfonic acids (SA) and one triSA, components of the color additive Quinoline Yellow (QY, Color Index No. 47005), were isolated from the dye mixture by affinity-ligand pH-zone-refining counter-current chromatography (CCC) through complementary use of ion-exchange and ion-pair reagents as the ligand. The added ligands facilitated the partitioning of the very polar polysulfonated components into the organic stationary phase of the two-phase solvent systems that consisted of isoamyl alcohol-methyl tert-butyl ether-acetonitrile-water (3:5:1:7), (3:4:1:7) or (3:1:1:5). Thus, separation of a 5-g portion of QY using sulfuric acid as the retainer and dodecylamine as the ligand (an ion-exchange reagent, 20% in the stationary phase), resulted in 1.21g of 6',5-diSA and 1.69g of 6',8',5-triSA, both of over 99% purity. A minor component, 8',4-diSA, not previously reported was also obtained (4.8mg of over 94% purity) through a similar separation of a different batch of QY using hydrochloric acid as the retainer and 10% dodecylamine as the ligand in the stationary phase. Two components that co-eluted (0.55g) in the 5g separation were separated when trifluoroacetic acid was used as the retainer and tetrabutylammonium hydroxide (an ion-pair reagent) as the ligand. The separation resulted in 20.7mg of 6',4-diSA, not previously reported, and 111.8mg of 8',5-diSA, both of over 98% purity. The isolated compounds were characterized by high-resolution mass spectrometry and proton nuclear magnetic resonance with correlated spectroscopy assignments.

Application of analytical and preparative high-speed counter-current chromatography for the separation of Z-ligustilide from a crude extract of Angelica sinensis

Z-Ligustilide was separated and purified from the traditional Chinese medicinal plant Angelica sinensis by high-speed counter-current chromatography (HSCCC). Analytical HSCCC was first used for the systematic selection of the two-phase solvent system. Preparative HSCCC separation was performed with a two-phase solvent system composed of petroleum ether (60-90 degrees C)-ethanol-water at an optimum volume ratio of 10:17:10 (v/v). A total of 38 mg Z-ligustilide at 98.8% purity was obtained in one step from 200 mg crude extract as determined by HPLC analysis. The structure of the target compound was identified by electron impact ionisation mass spectrometry.

Rational development of solvent system families in counter-current chromatography

Application of a mixture of 21 commercially available natural products, termed the GUESSmix, established a standard test that allows for a systematic analysis and comparison of the properties of biphasic solvent systems in counter-current/partition chromatography. Because the GUESSmix is comprised of compounds with varying polarities, functional groups, and structural features, it proves to be a rational method for mapping the optimal resolution polarity range of a particular solvent system. The mapping of optimal resolution polarity ranges of solvent systems provided for the description of the overall optimal resolution polarity range of a solvent system family, comprised of the same solvents in different proportions. By comparing the GUESSmix performance in the individual members of a solvent system family, the solvent system that best functions as the representative of, or portal to, the solvent system families was determined. The GUESSmix also afforded a method to compare the overall optimal resolution polarity ranges of solvent system families. Based on performance of GUESSmix chromatograms, the counter-current chromatography (CCC) properties of a two ternary literature solvent systems, ethyl acetate/n-butanol/water (EBuWat) and t-butylmethylether/acetonitrile/water (terAcWat), were explored in order to contrast and compare their CCC potential. A quaternary solvent system, hexane/t-butylmethylether/acetonitrile/water (HterAcWat), was also formulated and studied. The results indicated that the GUESSmix is fit for the purpose of developing and evaluating CCC solvent system families with desired performance characteristics.

Orthogonal test design for optimization of supercritical fluid extraction of daphnoretin, 7-methoxy-daphnoretin and 1,5-diphenyl-1-pentanone from Stellera chamaejasme L. and subsequent isolation by high-speed counter-current chromatography

Supercritical fluid extraction (SFE) of daphnoretin, 7-methoxy-daphnoretin and 1,5-diphenyl-1- pentanone from Stellera chamaejasme L. was performed. An orthogonal L9 (3)4 test design was applied to select the optimum extraction parameters including pressure, temperature, modifier and sample particle size on yield using an analytical-scale SFE system. The process was then scaled up by 100 times using a preparative SFE system under the optimized conditions of 25 MPa of pressure, 45 degrees C of temperature, 40-60 mesh of sample particle size and modified CO2 with 20% methanol. The yield of the crude extract from preparative SFE was 2.65%, which contained daphnoretin 25.2%, 7-methoxy-daphnoretin 22.8% and 1,5-diphenyl-1-pentanone 21.1%, respectively. Then the crude extract was successfully isolated and separated by preparative high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (10:13:13:10, v/v) by increasing the flow-rate of the mobile phase stepwise from 1.0 to 2.0 ml/min after 90 min. The target compounds isolated and purified by HSCCC were analyzed by high-performance liquid chromatography (HPLC). The separation produced total of 69.2mg of daphnoretin at 99.2% purity, 63.4 mg of 7-methoxy-daphnoretin at 98.7% purity and 58.3 mg of 1,5-diphenyl-1-pentanone at 98.1% purity from 300 mg of the crude extract in one-step separation. The recoveries of daphnoretin, 7-methoxy-daphnoretin and 1,5-diphenyl-1-pentanone were 90.8, 91.5 and 90.4%, respectively, in HSCCC isolation step and the chemical structure identification was carried out by MS, 1H NMR and 13C NMR.

Preparative isolation of four new and two known flavonoids from the leaf of Patrinia villosa Juss. by counter-current chromatography and evaluation of their anticancer activities in vitro

A preparative counter-current chromatography (CCC) was used to isolate and separate chemical constituents from the leaf of Patrinia villosa, a famous traditional Chinese medicinal herb. Six flavonoids including two known and four novel compounds were successfully simultaneous purified by CCC with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (10: 13: 13: 10, v/v) by increasing the flow rate of the mobile phase from 1.0 ml/min to 2.0 ml/min after 110 min to bring out the late eluters. The separation produced total of 44.9 mg fraction I with 99.1% purity, 35.5 mg fraction II with 98.8% purity, 79.8 mg fraction III with 99.3% purity, 45.8 mg fraction IV with 98.8% purity, 39.8 mg fraction V with 98.6% purity and 9.6 mg fraction VI with 97.5% purity from 400 mg crude extract in one single isolation procedure and less than 10 h, and the obtained fractions were all analyzed by high performance liquid chromatography (HPLC). Their chemical structures were elucidated as (2S)-5,7,2',6'-tetrahydroxy-6,8-di (gamma,gamma-dimethylallyl) flavanone (1), (2S)-5,7,2',6'-tetrahydroxy-6-lavandulylated flavanone (2), (2S)-5,7,2',6'-tetrahydroxy-4'-lavandulylated flavanone (3), (2S)-5,2',6'-trihydroxy-2'',2''-dimethylpyrano [5'', 6'': 6, 7] flavanone (4), (2S, 3''S)-5,2',6'-trihydroxy-3''-gamma,gamma-dimethylallyl-2'',2''-dimethyl-3'',4''-dihydropyrano [5'', 6'': 6, 7] flavanone (5) and licoagrochalcone B (6), respectively, by spectrum methods including UV, IR, high resolution (HR)-electrospray ionization (ESI)-MS, 1-dimension (1D) and 2-dimension (2D) NMR techniques. Among them, compounds 2, 3, 4, and 5 were new compounds and discovered from nature for the first time. The recoveries of the six compounds were 91.2%, 91.4%, 92.1%, 90.5%, 90.3% and 89.7%, respectively, in CCC step. Subsequently, their anticancer activities were also examined to inhibit human cancer cells' growth including A549, BEL-7402, SGC-7901, MCF-7, HT-29, K562 and A498 cell lines by MTT method in vitro. The results indicated that the compounds 1, 2 and 3 exhibited high anticancer activities (IC50 < 7 microg/ml), especially to K562 cancer cell (IC50 < 3.1 microg/ml), and the compounds 4, 5 and 6 exhibited weaker inhibition effect (IC50 < 30 microg/ml).

Isolation and purification of canthaxanthin from the microalgaChlorella zofingiensis by high-speed counter-current chromatography

Certain microalgae are considered to be a potential source of canthaxanthin, which possesses strong antioxidant and anticancer activities. A high-speed counter-current chromatography (HSCCC) method was developed for the separation and purification of canthaxanthin from the microalga Chlorella zofingiensis. The crude canthaxanthin was obtained by extraction with organic solvents after the microalgal sample had been saponified. Preparative HSCCC, with a two-phase solvent system composed of n-hexane-ethanol-water (10:9:1 v/v), was successfully performed yielding canthaxanthin at 98.7% purity from 150 mg of the crude extract (2.1% canthaxanthin) in a one-step separation. The recovery of canthaxanthin was 92.3%. This was the first report that canthaxanthin was successfully separated and purified from microalgae.

Efficient new method for extraction and isolation of three flavonoids from Patrinia villosa Juss. by supercritical fluid extraction and high-speed counter-current chromatography

Supercritical fluid extraction (SFE) of orotinin, orotinin-5-methyl ether and licoagrochalcone B from Patrinia villosa was performed. The optimization of parameters including pressure, temperature, modifier and sample particle size on yield was carried out using an analytical-scale SFE system. The process was then scaled up by 100 times using a preparative SFE system under the optimized conditions of 25 MPa, 45 degrees C, a sample particle size 40-60 mesh and modified CO2 with 20% methanol. The yield of the preparative SFE was 2.82% (crude extract I) and the combined yield of orotinin, orotinin-5-methyl ether and licoagrochalcone B was 0.82 mg/g of dry sample mass. Then the crude extract I was re-dissolved in methanol and methanol soluble fraction (crude extract II, 0.17%) was obtained, which was successfully isolated and separated by a preparative high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (5:6:6:6, v/v/v/v) by increasing the flow-rate of the mobile phase stepwise from 1.0 to 2.0 ml/min after 3 h. The target compounds isolated and purified by HSCCC were analyzed by high performance liquid chromatography. The separation produced total of 38.2 mg of orotinin at 99.2% purity, 19.8 mg of orotinin-5-methyl ether at 98.5% purity and 21.5 mg of licoagrochalcone B at 97.6% purity from 400 mg of the crude extract in a one-step separation. The recoveries of orotinin, orotinin-5-methyl ether and licoagrochalcone B were 91.1, 91.6 and 90.3%, respectively, and the chemical structure identification was carried out by UV, IR, MS, 1H NMR and 13C NMR.

Preparative isolation and purification of trans-3,5,4′-trihydroxystilbene-4′-O-β-d-glucopyranoside and (+)catechin from Rheum tanguticum Maxim. ex Balf. using high-speed counter-current chromatography by stepwise elution and stepwise increasing the flow-rate of the mobile phase

Preparative high-speed counter-current chromatography (HSCCC) was successfully used for isolation and purification of trans-3,5,4'-trihydroxystilbene-4'-O-beta-D-glucopyranoside (compound 1) and (+)catechin (compound 2) from Rheum tanguticum Maxim. ex Balf. by stepwise elution with a pair of two-phase solvent system composed of ethyl acetate-ethanol-water (25:1:25, v/v) and (5:1:5, v/v), and stepwise increasing the flow-rate of the mobile phase from 0.8 to 2.0 mlmin(-1) after 5 h. The preparative HSCCC separation was performed on 250 mg of crude extract yielding pure compound 1 (10.2 mg) and compound 2 (26.7 mg) all at purities of over 96% in a single run. The structures of the two compounds have been elucidated by means of spectroscopic methods including MS and 1H, 13C nuclear magnetic resonance spectroscopy.

Isolation and purification of baicalein, wogonin and oroxylin A from the medicinal plant Scutellaria baicalensis by high-speed counter-current chromatography

The medicinal plant Scutellaria baicalensis Georgi has been used widely in traditional Chinese medicine for anti-inflammation, anticancer, antiviral and antibacterial infections, reducing the total cholesterol level and decreasing blood pressures. A high-speed counter-current chromatography (HSCCC) method was developed for the preparative separation and purification of three bioactive flavonoids, namely, baicalein, wogonin and oroxylin A, from S. baicalensis Georgi. Preparative HSCCC with a two-phase solvent system composed of n-hexane-ethyl acetate-n-butanol-water (1:1:8:10, v/v/v/v) was successfully performed by increasing the flow-rate of the mobile phase stepwise from 1.0 to 2.0 ml min(-1) after 4 h. The components purified and collected were analyzed by high-performance liquid chromatography. The method yielded 144.8 mg of baicalein at 95.7% purity, 50.2 mg of wogonin at 98.5% purity, and 12.4 mg of oroxylin A at 93.2% purity from 500 mg of the crude extract in a one-step separation. The recoveries of baicalein, wogonin and oroxylin A were 92.7%, 91.6% and 92.5%, respectively.

Isolation and purification of the bioactive carotenoid zeaxanthin from the microalga Microcystis aeruginosa by high-speed counter-current chromatography

High-speed counter-current chromatography was successfully applied for the first time to the isolation and purification of the bioactive carotenoid zeaxanthin from the cyanobacterium Microcystis aeruginosa. The crude zeaxanthin was obtained by extraction with organic solvents after the microalgal sample had been saponified. Preparative high-speed counter-current chromatography with a two-phase solvent system composed of n-hexane-ethyl acetate-ethanol-water (8:2:7:3, v/v/v/v) was successfully performed yielding zeaxanthin at 96.2% purity from 150 mg of the crude extract in a one-step separation. The recovery of zeaxanthin was 91.4%. This was also the first report that zeaxanthin was successfully separated and purified from microalgae.

Preparative isolation and purification of bergapten and imperatorin from the medicinal plant Cnidium monnieri using high-speed counter-current chromatography by stepwise increasing the flow-rate of the mobile phase

A high-speed counter-current chromatography (HSCCC) method was developed for the preparative separation and purification of bergapten and imperatorin from the Chinese medicinal plant Cnidium monnieri (L.) Cusson. The crude extract was obtained by extraction with ethanol from the dried fruits of Cnidium monnieri (L.) Cusson under sonication. Preparative HSCCC with a two-phase solvent system composed of n-hexane-ethyl acetate-ethanol-water (5:5:5:5, v/v/v/v) was successfully performed by increasing the flow-rate of the mobile phase stepwise from 1.0 to 2.0 ml min(-1) after 180 min. The components purified and collected were analyzed by high-performance liquid chromatography. The method yielded 45.8 mg of bergapten at 96.5% purity and 118.3 mg of imperatorin at 98.2% purity from 500 mg of the crude extract in a single run. The recoveries of bergapten and imperatorin were 92.1 and 93.7%, respectively.

Preparative isolation and purification of coumarins from Angelica dahurica (Fisch. ex Hoffm) Benth, et Hook. f (Chinese traditional medicinal herb) by high-speed counter-current chromatography

A preparative high-speed counter-current chromatography (HSCCC) method for isolation and purification of coumarins from Angelica dahurica (Fisch. ex Hoffin) Benth, et Hook. f(Baizhi in Chinese) was successfully established by using n-hexane-methanol-water as the two-phase solvent system in gradient elution mode. The upper phase of n-hexane-methanol-water (5:5:5, v/v) was used as the stationary phase of HSCCC. The mobile phase used in HSCCC was the lower phase of n-hexane-methanol-water (5:5:5, v/v) and n-hexane-methanol-water (5:7:3, v/v) that was changed in gradient. Three major components including imperatorin, isoimperatorin and oxypeucedanine were isolated, each at over 98% purity as determined by high-performance liquid chromatography (HPLC). The peak fractions of HSCCC were identified by 1H-NMR and 13C-NMR.

Purification of paeoniflorin from Paeonia lactiflora Pall. by high-speed counter-current chromatography

High-speed counter-current chromatography was successfully used for the first time for the preparative separation and purification of paeoniflorin from the Chinese medicinal plant Paeonia lactiflora Pall. using a two-phase solvent system composed of n-butanol-ethyl acetate-water (1:4:5, v/v) in a single run. From 160 mg of the crude sample containing 22.0% paeoniflorin, 33.2 mg of paeoniflorin was yielded at 98.2% purity as determined by HPLC analysis. The recovery of paeoniflorin was 94.3%.