Xueli Cao

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Organization: Beijing Technology and Business University

Department: Beijing Key Laboratory of Plant Resources Research and Development

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Organic Chemistry

Ionic Liquid

Chemicals
References

Separation of the potential G-quadruplex ligands from the butanol extract of Zanthoxylum ailanthoides Sieb. & Zucc. by countercurrent chromatography and preparative high performance liquid chromatography

Co-reporter:Tian Han, Xueli Cao, Jing Xu, Hairun Pei, Hong Zhang, Yalin Tang

Journal of Chromatography A 2017 Volume 1507(Volume 1507) pp:

Publication Date(Web):21 July 2017

DOI:10.1016/j.chroma.2017.05.058

•PH-zone refining CCC was firstly applied in the research of alkaloids in Z. ailanthoides.•A seldom used solvent system composed of CH2Cl2-methanol-water was applied in pH-zone refining CCC.•Three tetrahydroprotoberberine alkaloids were firstly isolated in this species and two are new compounds.•The remarkable stabilization effect on G-quadruplex by the three tetrahydroprotoberberines was firstly reported.G-quadruplex DNA structure is considered to be a very attractive target for antitumor drug design due to its unique role in maintaining telomerase activities. Therefore, discovering ligands with high stability of G-quadruplex structure is of great interest. In this paper, pH-zone refining counter current chromatography (CCC) and preparative high performance liquid chromatography (HPLC) were employed for the separation of potent G-quadruplex ligands from the n-butanol fraction of the crude extract of Zanthoxylum ailanthoides, which is a traditional Chinese medicine recently found to display high inhibitory activity against several human cancer cells. The 75% aqueous ethanol extract of the stem bark of Z. ailanthoides and its fractions with petroleum ether, ethyl acetate and n-butanol displayed almost the same G-quadruplex stabilization ability. Here, pH-zone refining CCC was used for the separation of the alkaloids from the n-butanol fraction by a seldom used solvent system composed of dichloromethane-methanol-water (4:1:2.5) with 10 mM TEA in the organic stationary phase as retainer and 10 mM HCl in the aqueous mobile phase as eluter. Compounds I, II and III were obtained, with purity greater than 95%, in the quantities of 31.2, 94.0, and 26.4 mg respectively from 300 mg of lipophilic fraction within 80 min, which were identified as three tetrahydroprotoberberines isolated for the first time in this plant. In addition, a phenylpropanoid glycoside compound IV (Syringin), an isoquinoline (Magnoflorine, V), and two lignin isomers (+)-lyoniresiol-3α-O-β-d-glucopyranoside (VI) and (−)-lyoniresinol −3α-O-β-D −glucopyranoside (VII) were isolated by traditional CCC together with preparative HPLC. Compounds IV, V, VI and VII were obtained, with purity greater than 95%, in the quantities of 4.0, 13.2, 6.7, and 6.5 mg respectively from 960 mg of hydrophilic fraction. Among the seven isolated compounds, tetrahydroprotoberberine I, II and III were found to display remarkable stabilization effects on G-quadruplex by increasing G-quadruplex's Tm approximately 10 °C, which may be the most potent G-quadruplex ligands in Z. ailanthoides.

Determination of Alternaria mycotoxins in wine and juice using ionic liquid modified countercurrent chromatography as a pretreatment method followed by high-performance liquid chromatography

Co-reporter:Chen Fan, Xueli Cao, Man Liu, Wei Wang

Journal of Chromatography A 2016 Volume 1436() pp:133-140

Publication Date(Web):4 March 2016

DOI:10.1016/j.chroma.2016.01.069

•A novel IL modified CCC pretreatment method was developed.•It can be used for the determination of trace Alternaria mycotoxins in liquid food samples.•The enrichment strategy is unique by employing [HOOCMIM][Cl] to modify the solvent system.•The elution of targets by reversing the original stationary phase to mobile phase is quite artful.•The method can provide high recoveries with good reproducibility and low LOD.Alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA) are some of the main Alternaria mycotoxins that can be found as contaminants in food materials. The objective of this study was to develop a pretreatment method with countercurrent chromatography (CCC) for enrichment and cleanup of trace Alternaria mycotoxins in food samples prior to high-performance liquid chromatography (HPLC) analysis. An Analytical CCC instrument with a column volume 22.5 mL was used, and a two-phase solvent system composed of ethyl acetate and water modified with 6% [HOOMIM][Cl] in mass to volume ratio was selected. Under the optimized CCC operation conditions, trace amounts of AOH, AME, and TeA in large volume of liquid sample were efficiently extracted and enriched in the stationary phase, and then eluted out just by reversing the stationary phase as mobile phase in the opposite flowing direction tail-to-head. The enrichment and elution strategies are unique and can be fulfilled online with high enrichment factors (87–114) and high recoveries (81.14–110.94%). The method has been successively applied to the determination of Alternaria mycotoxins in real apple juice and wine samples with the limits of detection (LOD) in the range of 0.03–0.14 μg L−1. Totally 12 wine samples and 15 apple juice samples from the local market were analyzed. The detection rate of AOH and AME in both kinds of the samples were more than 50%, while TeA was found in relatively high level of 1.75–49.61 μg L−1 in some of the apple juice samples. The proposed method is simple, rapid, and sensitive and could also be used for the analysis and monitoring of Alternaria mycotoxin in other food samples.

Determination of chlorophenols in red wine using ionic liquid countercurrent chromatography as a new pretreatment method followed by high-performance liquid chromatography

Co-reporter:Chen Fan;Nai Li

Journal of Separation Science 2015 Volume 38( Issue 12) pp:2109-2116

Publication Date(Web):

DOI:10.1002/jssc.201500172

A countercurrent chromatography method for the enrichment and cleanup of chlorophenols from food samples was successfully established by using an ionic-liquid-modified two-phase solvent system composed of dichloromethane containing 2% 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and water. The column was firstly filled with the organic stationary phase, and then a large volume of sample was pumped into the column after it was equilibrated with pure water at the rotation speed. Finally, the trace amounts of chlorophenols extracted and enriched in the stationary phase were eluted out by an alkaline mobile phase and determined by high-performance liquid chromatography. Under optimized conditions, the enrichment and cleanup of the chlorophenols can be fulfilled online with enrichment factors (34–65) and high recoveries (84.69–95.23%). The method has been applied to the determination of chlorophenols in real red wine samples with the limits of detection in the range of 1.89–4.21 μg/L. The present method is highly suitable for the pretreatment of large volume of aqueous sample for the determination of trace amounts of contaminants in food and environmental samples.

Isolation of anti-tumor compounds from the stem bark of Zanthoxylum ailanthoides Sieb. & Zucc. by silica gel column and counter-current chromatography

Co-reporter:Xue-li Cao, Jing Xu, Ge Bai, Hong Zhang, Yan Liu, Jun-feng Xiang, Ya-lin Tang

Journal of Chromatography B 2013 Volume 929() pp:6-10

Publication Date(Web):15 June 2013

DOI:10.1016/j.jchromb.2013.04.006

•The potent anti-tumor components in Z. ailanthoides were investigated.•The silica gel chromatography and HPCCC were used successively.•Luvangetin, xanthyletin, hinokinin and asarinin were isolated and identified.•Asarinin was firstly isolated from this plant to the best of our knowledge.Silica gel column chromatography combined with high performance counter-current chromatography (HPCCC) was employed for the separation of potential anti-tumor compounds from a petroleum ether fraction of a crude extract of Zanthoxylum ailanthoides Sieb. & Zucc. This traditional Chinese medicine was recently found to display high inhibitory activity against A-549 human cancer cells in vitro and Lewis lung cancer in vivo. A 75% aqueous ethanol extract of the stem bark of Z. ailanthoides was fractionated with petroleum ether, ethyl acetate and n-butanol. In this paper, the petroleum ether fraction was pre-separated by silica gel column chromatography with a petroleum ether–ethyl acetate gradient. Two fractions were further separated and purified by HPCCC using n-hexane–ethyl acetate–methanol–water (3:1:2:1, v/v) and petroleum–ethyl acetate–methanol–water (8:6:7:7, v/v). Finally, coumarins and lignans including luvangetin, xanthyletin, hinokinin and asarinin were isolated and identified by MS, 1H and 13C NMR. In total, 56 mg of xanthyletin (1), 140 mg of hinokinin (2), 850 mg of luvangetin (3) and 74 mg of asarinin (4) were obtained from approximately 50 g of petroleum ether extract, in 96.0%, 94.0%, 99.0% and 94.0% purity, respectively, as determined by HPLC. The separation method proved to be efficient, especially for those minor components.

Application of counter-current chromatography as a new pretreatment method for the determination of polycyclic aromatic hydrocarbons in environmental water

Co-reporter:Xueli Cao;Chunlei Yang;Hairun Pei;Xinghong Li;Xiaobai Xu;Yoichiro Ito

Journal of Separation Science 2012 Volume 35( Issue 4) pp:596-601

Publication Date(Web):

DOI:10.1002/jssc.201100852

Abstract

Counter-current chromatography (CCC) was investigated as a new sample pretreatment method for the determination of trace polycyclic aromatic hydrocarbons (PAHs) in water environmental samples. The experiment was performed with a non-aqueous binary two-phase solvent system composed of n-heptane and acetonitrile. The CCC column was first filled with the upper stationary phase, and then a large volume of water sample was pumped into the column while the CCC column was rotated at 1600 rpm. Finally, the trace amounts of PAHs extracted and enriched in the stationary phase were eluted out by the lower mobile phase and determined by gas chromatography–flame ionization detector (GC-FID) or gas chromatography–mass spectrometry (GC-MS). The enrichment and cleanup of PAHs can be fulfilled online by this method with high recoveries (84.1–103.2%) and good reproducibility (RSDs: 4.9–12.2%) for 16 EPA PAHs under the optimized CCC pretreatment conditions. This method has been successfully applied to determine PAHs in lake water where 8 PAHs were detected in the concentration of 40.9–89.9 ng/L. The present method is extremely suitable for the preparation of large volume of environmental water sample for the determination of trace amounts of organic pollutants including PAHs as studied in this paper.

Direct screening of G-quadruplex ligands from Kalopanax septemlobus (Thunb.) Koidz extract by high performance liquid chromatography

Co-reporter:Ge Bai, Xueli Cao, Hong Zhang, Junfeng Xiang, Hong Ren, Li Tan, Yalin Tang

Journal of Chromatography A 2011 Volume 1218(Issue 37) pp:6433-6438

Publication Date(Web):16 September 2011

DOI:10.1016/j.chroma.2011.07.028

G-quadruplex DNA structure is considered to be a very attractive target for antitumor drug design due to its unique role in maintaining telomerase activities. Therefore, discovering ligands with high stability of G-quadruplex structure is of great interest. In this paper, high-performance liquid chromatography (HPLC) was used for fast screening of G-quadruplex ligands from the crude extract of Kalopanax septemlobus (Thunb.) Koidz, a traditional Chinese medicine. Four potent G-quadruplex ligands were firstly selected through HPLC by comparing the peak profiles and absorption intensity of the crude sample before and after interaction with G-quadruplex DNA. Then the target compounds were isolated and purified by high-speed countercurrent chromatography (HSCCC) for further confirmation of their stabilities of G-quadruplex by temperature-dependent circular dichroism (CD). Four compounds were isolated and identified as 2,4-dihydroxybenzoic acid (I), chlorogenic acid (II), caffeic acid (III) and 5-feruloylquinic acid (IV) each by MS and NMR. Finally, compound I, II, III were each proved to be potent G-quadruplex ligands by decreasing the peak intensity in HPLC chromatogram after complexation with G-quadruplex, which stabilize G-quadruplex by 7 ± 2 °C, 10 ± 2 °C, and 3 ± 2 °C respectively, based on CD analyses. However, compound IV showed no G-quadruplex stability. The decrease of peak absorption intensity in HPLC chromatogram is the most important signal to find G-quadruplex ligands. This provides a very promising strategy for fast screening G-quadruplex ligands from natural plant extracts.

Development and evaluation of a spiral tube column for counter-current chromatography

Co-reporter:Xueli Cao;Hairun Pei;Liangsheng Huo;Guanghui Hu;Yoichiro Ito

Journal of Separation Science 2011 Volume 34( Issue 19) pp:2611-2617

Publication Date(Web):

DOI:10.1002/jssc.201100205

Abstract

An improved type-J counter-current chromatography (CCC) planet centrifuge with two spiral tube columns (volume 2×15 mL, β value 0.3–0.7, tubing 0.8 mm id) was developed and evaluated for its retention ability of four typical different solvent systems including heptane–methanol (1:1, v/v) (A), hexane–ethyl acetate–methanol–water (1:1:1:1, v/v) (B), n-butanol–acetic acid–water (4:1:5, v/v) (C), PEG1000–K₂HPO₄–water (12.5:12.5:75, w/w) (D) under eight different operation modes. The results indicated that the spiral tube column could significantly increase the retention of four typical solvent systems compared with a traditional multilayer coil column with similar parameters (volume 35 mL, β value 0.3–0.7, tubing 0.8 mm id). The retention of stationary phase (S_f ) for the less polar system (A) and moderately polar solvent system (B) can be increased by about 10%, and for the polar system (C) and aqueous two-phase system (ATPS) (D) by 30–40%. The preliminary applications of this spiral tube column to the separation of small molecular compounds such as moderately polar theaflavins, polar anthocyanins and dipeptides were successful. Acceptable resolution can be obtained between cytochrome c and myoglobin, lysozyme and myoglobin when it was applied on protein separation; however, it still needs to be improved with regard to its column efficiency.

Isolation and purification of series bioactive components from Hypericum perforatum L. by counter-current chromatography

Co-reporter:Xueli Cao, Qiaoe Wang, Yan Li, Ge Bai, Hong Ren, Chunming Xu, Yoichiro Ito

Journal of Chromatography B 2011 Volume 879(7–8) pp:480-488

Publication Date(Web):1 March 2011

DOI:10.1016/j.jchromb.2011.01.007

Counter-current chromatography (CCC) combined with pre-separation by ultrasonic solvent extraction was successively used for the separation of series bioactive compounds from the crude extract of Hypericum perforatum L. The petroleum ether extract was separated by the solvent system of n-heptane–methanol–acetonitrile (1.5:0.5:0.5, v/v) and n-heptane–methanol (1.5:1, v/v) in gradient elution, yielding a phloroglucinol compound, hyperforin with HPLC purity over 98%. The ethyl acetate extract was separated by using the solvent system composed of hexane–ethyl acetate–methanol–water (1:1:1:1 and 1:3:1:3, v/v) in gradient through both reverse phase and normal phase elution mode, yielding a naphthodianthrone compound, hypericin with HPLC purity about 95%. The n-butanol extract was separated with the solvent system composed of n-butanol–ethyl acetate–water (1:4:5 and 1.5:3.5:5, v/v) in elution and back-extrusion mode, yielding two of flavones, rutin and hyperoside, with HPLC purity over 95%. HPLC–MS, reference sample and UV spectrum were selectively used in separation to search for target compounds from HPLC-DAD profiles of different sub-extracts. The structures of isolated compounds were further identified by ESI-MS, 1HNMR and 13CNMR.

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

Co-reporter:Xueli Cao, Cong Wang, Hairun Pei, Baoguo Sun

Journal of Chromatography A 2009 Volume 1216(Issue 19) pp:4268-4274

Publication Date(Web):8 May 2009

DOI:10.1016/j.chroma.2009.01.046

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.