Preparative purification of salidroside from Rhodiola rosea by two‐step adsorption chromatography on resins

Salidroside is an effective adaptogenic drug extracted from Rhodiola species. In the present study, a simple and efficient method for preparative separation and purification of salidroside from the Chinese medicinal plant Rhodiola rosesa was developed by adsorption chromatography on macroporous resins. The static adsorption isotherms and kinetics of some resins have been determined and compared for preparative separation of salidroside. According to our results, HPD‐200 resin is the most appropriate medium for the separation of salidroside and its adsorption data fit the Langmuir isotherm well. Dynamic adsorption and desorption were carried out in glass columns packed with HPD‐200 to optimize the separation process. After two adsorption and desorption runs, a product with a salidroside content of 92.21% and an overall recovery of 48.82% was achieved. In addition, pure lamellar crystals of salidroside with a purity of 99.00% could be obtained from this product. Its molecular weight was determined by an ESI‐MS method. The simple purification scheme avoids toxic organic solvents used in silica gel and high‐speed counter‐current chromatographic separation processes and thus increases the safety of the process and can be helpful for large‐scale salidroside production from Rhodiola rosea or other plant extracts.     

Development of an analytical strategy to identify and classify the global chemical constituents of Ziziphi Spinosae Semen by using UHPLC with quadrupole time‐of‐flight mass spectrometry combined with multiple data‐processing approaches

According to traditional Chinese medical theory, Ziziphi Spinosae Semen needs to be stir‐fried before clinical application for its sedative‐hypnotic effect enhancement. A rapid and comprehensive analysis strategy of ultra high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry and multiple data analysis platforms was developed for the efficient and sensitive identification of components in crude and parched Ziziphi Spinosae Semen to explore the composition changes that happen during the stir‐frying process. Both positive and negative ion modes were applied for mass spectrometry detection, and 40 components were identified from crude and parched Ziziphi Spinosae Semen, respectively. Principal component analysis and t‐test were applied to find differences between crude and parched Ziziphi Spinosae Semen. As a result, Ziziphi Spinosae Semen samples could be clearly divided into two groups according to their processing methods, and 19 key markers that contributed to the classification significantly (P < 0.05) were found. This kind of change in contents of components might be responsible for the recommended clinical application of parched Ziziphi Spinosae Semen.     

Highly selective separation and purification of chicoric acid from Echinacea purpurea by quality control methods in macroporous adsorption resin column chromatography

Chicoric acid is the main phenolic active ingredient in Echinacea purpurea (Asteraceae), best known for its immune‐enhancing ability, as well as used as a herbal medicine. To achieve further utilization of medicinal ingredients from E. purpurea, an efficient preparative separation of chicoric acid was developed based on macroporous adsorption resin chromatography. The separation characteristics of several different typical macroporous adsorption resins were evaluated by adsorption/desorption column experiments, and HPD100 was revealed as the optimal one, which exhibited that the adsorbents fitted well to the pseudo‐second‐order kinetics model and Langmuir isotherm model, and the optimal process parameters were obtained. The breakthrough curves could be predicted and end‐point could be determined early. Besides, the optimal elution conditions of chicoric acid can be achieved using the quality control methods. As a result, the purity of chicoric acid was increased 15.8‐fold (from 4 to 63%) after the treatment with HPD100. The process of the enrichment and separation of chicoric acid is considerate, because of its high efficiency and simple operation. The established separation and purification method of chicoric acid is expected to be valuable for further utilization of E. purpurea according to product application in pharmaceutical fields in the future.     

Enrichment and purification of madecassoside and asiaticoside from Centella asiatica extracts with macroporous resins

In present study, the performance and separation characteristics of five macroporous resins for the enrichment and purification of asiaticoside and madecassoside from Centella asiatica extracts have been evaluated. The adsorption and desorption properties of total triterpene saponins (80% purity) on macroporous resins including HPD100, HPD300, X-5, AB-8 and D101 have been compared. According to our results, HPD100 offered higher adsorption and desorption capacities and higher adsorption speed for asiaticoside and madecassoside than other resins. Column packed with HPD100 resin was used to perform dynamic adsorption and desorption tests to optimize the separation process of asiaticoside and madecassoside from C. asiatica extracts. After the treatment with gradient elution on HPD100 resin, the content of madecassoside in the product increased from 3.9 to 39.7%, and the recovery yield was 70.4%; for asiaticoside the content increased from 2.0 to 21.5%, and the recovery yield was 72.0%. The results showed that HPD100 resin revealed a good ability to separate madecassoside and asiaticoside, and the method can be referenced for the separation of other triterpene saponins from herbal raw materials.     

Separation of epimeric aromatic acid (−)‐menthol esters by countercurrent chromatography using hydroxypropyl‐β‐cyclodextrin as an additive

The separation of ten epimeric aromatic acid (−)‐menthol esters by countercurrent chromatography with hydroxypropyl‐β‐cyclodextrin as the mobile phase additive was investigated, and methods for the analysis of all the epimeric esters by reversed‐phase high‐performance liquid chromatography were established. A biphasic solvent system composed of n‐hexane/20–70% methanol containing 50 mmol/L of hydroxypropyl‐β‐cyclodextrin (1:1, v/v) was selected, which provided high separation factors for five of the epimeric esters, and successful separations by countercurrent chromatography were achieved. The complete separation of five pairs of epimeric ester was obtained with the purity being over 98% for each peak fractions, as determined by high‐performance liquid chromatography. The recovery of each analyte from the eluted fractions reached around 80–88%.     

Separation of isorhamnetin 3‐sulphate and astragalin from Flaveria bidentis (L.) Kuntze using macroporous resin and followed by high‐speed countercurrent chromatography

D4020 resin offered the best dynamic adsorption and desorption capacity for total flavonoids based on the research results from ten kinds of macroporous resin. A column packed with D4020 resin was used to optimize the separation of total flavonoids from Flaveria bidentis (L.) Kuntze extracts. The content of flavonoids in the product was increased from 4.3 to 30.1% with a recovery yield of 90%. After the treatment with gradient elution on D4020 resin, the contents of isorhamnetin 3‐sulfate and astragalin were increased from 0.49 to 8.70% with a recovery yield of 74.1% and 1.16 to 30.8%, with a recovery yield of 92.2%, respectively. Further purification was carried out by one‐run high‐speed countercurrent chromatography yielding 4.5 mg of isorhamnetin 3‐sulfate at a high purity of 96.48% and yielding 24.4 mg of astragalin at a high purity of over 98.46%.     

Development of a method to screen and isolate bioactive constituents from Stellera chamaejasme by ultrafiltration and liquid chromatography combined with semi‐preparative high‐performance liquid chromatography and high‐speed counter current chromatography

A simple and efficient method based on ultrafiltration with liquid chromatography and mass spectrometry was used for the rapid screening and identification of ligands in the extracts of Stellera chamaejasme. The bound ligands, i.e. daphnoretin, isopimpinellin, chamaechromone, neochamaejasmin A, and chamaejasmine (purity of 96.8, 90.75, 91.41, 93.98, and 98.91%, respectively), were separated by semi‐preparative high‐performance liquid chromatography combined with high‐speed counter‐current chromatography. To the best of our knowledge, this is the first study to report the detection of potent lipoxidase and lactate dehydrogenase inhibitors in Stellera chamaejasme extracts. The results demonstrate that our method of ultrafiltration with liquid chromatography and mass spectrometry combined with mixed chromatography can be used to screen and confirm the bioactivity of all isolated compounds. This method also eliminates the need for separation of inactive compounds, thereby improving efficiency when studying bioactive substances. For some complex mixtures, neither semi‐preparative high‐performance liquid chromatography nor high‐speed counter‐current chromatography can purify all the target active compounds with high purity in a one‐step separation. The combination of the two methods allow for efficient purification of target bioactive compounds with different polarities and physicochemical properties based on their complementary properties.     

Two‐dimensional hydrophilic interaction chromatography × reversed‐phase liquid chromatography for the preparative isolation of potential anti‐hepatitis phenylpropanoids from Salvia prattii

Traditional Tibetan medicine is important for discovery of drug precursors. However, knowledge of the chemical composition of traditional Tibetan medicines is very limited due to the lack of appropriate chromatographic purification methods. In the present work, Salvia prattii was taken as an example, and an off‐line hydrophilic interaction liquid chromatography/reversed‐phase liquid chromatography preparative method was developed for the purification of phenylpropanoids with high purity from a crude sample of Salvia prattii. Based on the separation results of four different chromatographic stationary phases, the first‐dimensional preparation was performed on an XAmide preparative column with the crude sample concentration of 62.0 mg/mL, and five main fractions were obtained from the 12.4 g crude sample with a recovery of 54.8%. An XCharge C₁₈ preparative column was applied in the second‐dimensional preparation to further isolate the phenylpropanoids from the redissolved first‐dimensional fractions with concentration of approximately 50.0 mg/mL. The purities of the phenylpropanoids isolated from the crude sample of Salvia prattii were higher than 98%, indicating that the method was efficient for the purification of phenylpropanoids with high purity from Salvia prattii. Additionally, this method showed great potential in the preparation of phenylpropanoids and can serve as a good example for the purification of phenylpropanoids from other plant materials.     

Preparative separation and enrichment of four taxoids from Taxus chinensis needles extracts by macroporous resin column chromatography

An environment‐friendly method was established for the preparative separation and enrichment of four taxoids, namely 10‐deacetylbaccatin III (10‐DAB III), 7‐xylosyl‐10‐deacetyltaxol (7‐xyl‐10‐DAT), cephalomannine and paclitaxel from Taxus chinensis needles extracts. Characteristics of seven widely used macroporous resins for four taxoids were compared, AB‐8 resin offered better adsorption and desorption capacities than others. AB‐8 resin column chromatography was used to study the desorption process for four taxoids. The optimum parameters for desorption were 30% ethanol 5 RV for removing impurities, following 15 RV for 10‐DAB III, after the desorption of impurities with 35% ethanol 10 RV, 45% ethanol 30 RV for 7‐xyl‐10‐DAT, then 65% ethanol 10 RV for cephalomannine and paclitaxel, the flow rate was 6 RV/h. After separation on AB‐8 resin column chromatography, the contents of 10‐DAB III, 7‐xyl‐10‐DAT, cephalomannine and paclitaxel in the product reached 4.58, 13.17, 1.36 and 3.08%, respectively, which were 7.63‐, 3.68‐, 6.18‐ and 6.55‐fold to those in T. chinensis needles extracts. The recovery yields were 94.96, 77.32, 88.09 and 95.25%. In general, the AB‐8 resin column chromatography has the advantages of lower cost, high efficiency and simple procedure. Therefore, it may provide scientific references for the preparative separation and enrichment of taxoids from other T. species.     

Combined chromatographic strategy based on macroporous resin,high‐speed counter‐current chromatography and preparative HPLC for systematic separation of seven antioxidants from the fruit of Terminalia billerica

In the present study, combined chromatographic strategy based on macroporous resin, high‐speed counter‐current chromatography and preparative high‐performance liquid chromatography for systematic separation of antioxidants from crude samples guided by high‐performance liquid chromatography with 1,1‐diphenyl‐2‐picrylhydrazyl has been successfully established. Based on this strategy, seven antioxidants including isorugosin A, _β‐1,2,3,6‐tetragalloyl‐D ‐glucose, chebulinic acid, 1,2,3,4,6‐penta‐O‐galloyl‐_β‐D‐glucose, chebulagic acid, ethyl gallate, and gallic acid were obtained from the fruit of Terminalia billerica. First, high‐performance liquid chromatography with 1,1‐diphenyl‐2‐picrylhydrazyl experiment showed the presence of seven main antioxidants in the crude extract of the fruit of Terminalia billerica. Then, a macroporous resin column chromatography method was developed for the enrichment of these seven antioxidants. Finally, an efficient method based on high‐speed counter‐current chromatography and preparative high‐performance liquid chromatography was developed for the separation of these antioxidants. In the selection of solvent systems, it was found that acetic acid could be a good regulator for modifying the partition coefficient values of tannins. The present study provides a reference for systematic separation of antioxidants from crude samples. Considering the general existence of antioxidants in crude samples, this combined chromatographic strategy might lead to broader application prospects.     

Separation and purification of two taxanes and one xylosyl‐containing taxane from Taxus wallichiana Zucc.: A comparison between high‐speed countercurrent chromatography and reversed‐phase flash chromatography

10‐Deacetylbaccatin III, an important semisynthetic precursor of paclitaxel and docetaxel, can be extracted from Taxus wallichiana Zucc. A process for the isolation and purification of 10‐deacetylbaccatin III ( 1 ), baccatin III ( 2 ), and 7β‐xylosyl‐10‐deacetyltaxol ( 3 ) from the leaves and branches of Taxus wallichiana Zucc. via macroporous resin column chromatography combined with high‐speed countercurrent chromatography or reversed‐phase flash chromatography was developed in this study. After fractionation by macroporous resin column chromatography, 80% methanol fraction was selected based on high‐performance liquid chromatography and liquid chromatography with mass spectrometry qualitative analysis. A solvent system composed of n‐hexane, ethyl acetate, methanol, and water (1.6:2.5:1.6:2.5, v/v/v/v) was used for the high‐speed countercurrent chromatography separation at a flow rate of 2.5 mL/min. The reversed‐phase flash chromatography separation was performed using methanol/water as the mobile phase at a flow rate of 3 mL/min. The high‐speed countercurrent chromatography separation produced compounds 1 (10.2 mg, 94.4%), 2 (2.1 mg, 98.0%), and 3 (4.6 mg, 98.8%) from 100 mg of sample within 110 min, while the reversed‐phase flash chromatography separation purified compounds 1 (9.8 mg, 95.6%) and 3 (4.9 mg, 97.9%) from 100 mg of sample within 120 min.     

Preparative enantioseparation of loxoprofen precursor by recycling countercurrent chromatography with hydroxypropyl‐β‐cyclodextrin as a chiral selector

Recycling countercurrent chromatography was successfully applied to the resolution of 2‐(4‐bromomethylphenyl)propionic acid, a key synthetic intermediate for synthesis of nonsteroidal anti‐inflammatory drug loxoprofen, using hydroxypropyl‐β‐cyclodextrin as chiral selector. The two‐phase solvent system composed of n‐hexane/n‐butyl acetate/0.1 mol/L citrate buffer solution with pH 2.4 (8:2:10, v/v/v) was selected. Influence factors for the enantioseparation were optimized, including type of substituted β‐cyclodextrin, concentration of hydroxypropyl‐β‐cyclodextrin, separation temperature, and pH of aqueous phase. Under optimized separation conditions, 50 mg of 2‐(4‐bromomethylphenyl)propionic acid was enantioseparated using preparative recycling countercurrent chromatography. Technical details for recycling elution mode were discussed. The purities of both the S and R enantiomers were over 99.0% as determined by high‐performance liquid chromatography. The enantiomeric excess of the S and R enantiomers reached 98.0%. The recovery of the enantiomers from eluted fractions was 40.8–65.6%, yielding 16.4 mg of the S enantiomer and 10.2 mg of the R enantiomer. At the same time, we attempted to enantioseparate the anti‐inflammatory drug loxoprofen by countercurrent chromatography and high‐performance liquid chromatography using a chiral mobile phase additive. However, no successful enantioseparation was achieved so far.     

Enrichment of total steroidal saponins from the extracts of Trillium tschonoskii Maxim by macroporous resin and the simultaneous determination of eight steroidal saponins in the final product by HPLC

An effective and simple method was established for the separation and enrichment of steroidal saponins from Trillium tschonoskii Maxim. The adsorption and desorption properties of seven macroporous resins were investigated. Among the tested resins, AB‐8 resin showed the best adsorption and desorption capacities. The adsorption of steroidal saponins on AB‐8 at 25°C was quite consistent with both the Freundlich isotherm model and the pseudo‐second‐order kinetics model. By optimizing the dynamic adsorption and desorption parameters, the content of steroidal saponins increased from 5.20% in the crude extracts to 51.93% in the final product, with a recovery yield of 86.67%. Furthermore, by scale‐up separation, the concentration and recovery of total steroidal saponins were 43.8 and 85.5%, respectively, which suggested that AB‐8 resin had great industrial and pharmaceutical potential because of its high efficiency and cost‐effectiveness. In addition, a high‐performance liquid chromatography method for the simultaneous determination of eight steroidal saponins was established for the first time, which was employed to qualitatively and quantitatively analyze the final product. Based on the methodological validation results, the high‐performance liquid chromatography method can be widely applied to the quality control of steroidal saponins from Trillium tschonoskii Maxim due to its excellent accuracy, stability, and repeatability.     

Efficient separation of high‐purity compounds from Oxytropis falcata using two‐dimensional preparative chromatography

The separation of high‐purity compounds from traditional Tibetan medicines plays an important role in investigating their bioactivity. Nevertheless, it is often quite difficult to isolate compounds with high purity because of the complexity of traditional Tibetan medicines. In this work, an offline two‐dimensional reversed‐phase preparative method was successfully developed for the separation of high‐purity compounds from Oxytropis falcata . Based on the analysis results, an ODS C18 prep column was used for first‐dimensional preparation, and 14.8 g of the crude sample was separated into five fractions with a recovery of 74.6%. Then, an XAqua C18 prep column was used to isolate high‐purity compounds in the second‐dimensional preparation because its separation selectivity is different with the ODS C18 stationary phase. As a result, eight compounds in the crude sample were isolated in more than 98% purity. This is the first report of trans‐cinnamic acid ( 1 ) and trifolirhizin ( 2 ) from Oxytropis falcata . This method has the potential to be an efficient separation method of high‐purity compounds from Oxytropis falcata and it shows great promise for the separation of high‐purity compounds from complex samples.     

Validation of an analytical method using UPLC–MS/MS to quantify four bioactive components in rat plasma and its application to pharmacokinetic study of traditional and dispensing granules decoction of Ziziphi Spinosae Semen

A rapid and sensitive UPLC–MS/MS method was established for the simultaneous quantification of 6′′′-feruloylspinosin, spinosin, jujuboside A, and jujuboside B in rat plasma after the oral administration of traditional and dispensing granules (DG) decoction of Ziziphi Spinosae Semen (ZSS). The four components were separated using 0.1% formic acid and acetonitrile as a mobile phase by gradient elution at a flow rate of 0.3 mL/min equipped with a C₁₈ column (2.1 × 50 mm, 1.7 μm particle size, Acquity BEH C₁₈). The mass spectrometer was operated under multiple reaction monitoring mode. An aliquot of 100 μL rat plasma was deproteinized by 300 μL methanol. The supernatant was injected into the UPLC–MS/MS system for analysis. The calibration curves displayed good linearity. The intra-day and inter-day precisions (RSD) were less than 7.3%. The accuracies ranged from −1.3 to 6.1%. The extraction recoveries ranged from 95.8 to 101.9%, and the matrix effects were satisfactory. For DG, half-life values (t_1/2) of 6′′′-feruloylspinosin and C_max of jujuboside A were elevated remarkably. MRT_0–t of jujuboside B was significantly increased. No significant variation was observed for the pharmacokinetic parameters of spinosin. The results could provide a scientific basis for the clinical application of traditional and DG decoction of ZSS.     

Ionic‐liquid‐based ultrasound‐assisted extraction of isoflavones from Belamcanda chinensis and subsequent screening and isolation of potential α‐glucosidase inhibitors by ultrafiltration and semipreparative high‐performance liquid chromatography

The separation of a compound of interest from its structurally similar homologues to produce high‐purity natural products is a challenging problem. This work proposes a novel method for the separation of iristectorigenin A from its structurally similar homologues by ionic‐liquid‐based ultrasound‐assisted extraction and the subsequent screening and isolation of potential α‐glucosidase inhibitors via ultrafiltration and semipreparative high‐performance liquid chromatography. Ionic‐liquid‐based ultrasound‐assisted extraction was successfully applied to the extraction of tectorigenin, iristectorigenin A, irigenin, and irisflorentin from Belamcanda chinensis . The optimum conditions for the efficient extraction of isoflavones were determined as 1.0 M 1‐ethyl‐3‐methylimidazolium tetrafluoroborate with extraction time of 30 min and a solvent to solid ratio of 30 mL/g. Ultrafiltration with liquid chromatography and mass spectrometry was applied to screen and identify α‐glucosidase inhibitors from B. chinensis , followed by the application of semipreparative high‐performance liquid chromatography to separate and isolate the active constituents. Four major compounds including tectorigenin, iristectorigenin A, irigenin, and irisflorentin were screened and identified as α‐glucosidase inhibitors, and then the four active compounds abovementioned were subsequently isolated by semipreparative high‐performance liquid chromatography (99.89, 88.97, 99.79, and 99.97% purity, respectively). The results demonstrate that ionic liquid extraction can be successfully applied to the extraction of isoflavones from B. chinensis .     

Separation and purification of intermediates for the preparation of naproxen from synthetic mixtures by countercurrent chromatography

Three key intermediates in the preparation of the nonsteroidal anti‐inflammatory drug naproxen were successfully separated and purified with high purity from synthetic mixtures by countercurrent chromatography with a selected biphasic solvent system. The biphasic solvent system composed of n‐hexane/ethyl acetate/methanol/water (9:1:9:1, v/v/v/v) was selected according to partition performance of the three components using thin‐layer chromatography. Fifty milligrams of the synthetic mixture after the three‐step reaction was injected into a preparative countercurrent chromatography separation column and yielded 3.5, 14.0, and 8.0 mg of three key intermediates with 95.0, 99.0, and 98.0% purity, and the recovery of each component was 65.2, 71.2, and 69.6%, respectively. The results indicated that countercurrent chromatography is an efficient alternative and economical method for the separation and purification of intermediate components from synthetic mixtures.     

Combined application of chromatographic techniques for the separation of phenolic compounds from Stenoloma chusanum Ching

High‐speed countercurrent chromatography combined with preparative high‐performance liquid chromatography was successfully used to separate seven phenolic compounds from Stenoloma chusanum Ching. A biphasic solvent system composed of hexane/ethyl acetate/methanol/water (1:2:1:2, v/v) was used for the first step high‐speed countercurrent chromatography separation in elution–extrusion mode. A mobile phase composed of acetonitrile (18%) and pure water (82%) was used for further preparative high‐performance liquid chromatography purification. In total, the combined separation yielded seven compounds, including 3,4‐dihydroxy benzoic acid, 3,4‐dihydroxy benzaldehyde, esculetin, caffeic acid, syringic acid, luteolin, and apigenin, at a purity of over 90%. Esculetin was separated from Stenoloma chusanum Ching for the first time. The results suggest that the proposed combination method is a useful strategy for separating compounds from complex samples.     

Separation of four flavonol glycosides from Solanum rostratum Dunal using aqueous two‐phase flotation followed by preparative high‐performance liquid chromatography

Aqueous two‐phase flotation followed by preparative high‐performance liquid chromatography was used to separate four flavonol glycosides from Solanum rostratum Dunal. In the aqueous two‐phase flotation section, the effects of sublation solvent, solution pH, (NH₄)₂SO₄ concentration in aqueous solution, cosolvent, N₂ flow rate, flotation time, and volumes of the polyethylene glycol phase on the recovery were investigated in detail, and the optimal conditions were selected: 50 wt% polyethylene glycol 1000 ethanol solvent as the flotation solvent, pH 4, 350 g/L of (NH₄)₂SO₄ concentration in aqueous phase, 40 mL/min of N₂ flow rate, 30 min of flotation time, 10.0 mL of flotation solvent volume, and two times. After aqueous two‐phase flotation concentration, the flotation products were purified by preparative high‐performance liquid chromatography. The purities of the final products A and B were 98.1 and 99.0%. Product B was the mixture of three compounds based on the analysis of high‐performance liquid chromatography at the temperature of 10°C, while product A was hyperoside after the identification by nuclear magnetic resonance. Astragalin, 3’‐O‐methylquercetin 3‐O‐β‐d ‐galactopyranoside, and 3’‐O‐methylquercetin 3‐O‐β‐d ‐glucopyranoside were obtained with the purity of 93.8, 97.1, and 99.2%, respectively, after the further separation of product B using preparative high‐performance liquid chromatography.     

Purification of flavonoids from licorice using an off‐line preparative two‐dimensional normal‐phase liquid chromatography/reversed‐phase liquid chromatography method

An orthogonal (71.9%) off‐line preparative two‐dimensional normal‐phase liquid chromatography/reversed‐phase liquid chromatography method coupled with effective sample pretreatment was developed for separation and purification of flavonoids from licorice. Most of the nonflavonoids were firstly removed using a self‐made Click TE‐Cys (60 μm) solid‐phase extraction. In the first dimension, an industrial grade preparative chromatography was employed to purify the crude flavonoids. Click TE‐Cys (10 μm) was selected as the stationary phase that provided an excellent separation with high reproducibility. Ethyl acetate/ethanol was selected as the mobile phase owing to their excellent solubility for flavonoids. Flavonoids co‐eluted in the first dimension were selected for further purification using reversed‐phase liquid chromatography. Multiple compounds could be isolated from one normal‐phase fraction and some compounds with bad resolution in one‐dimensional liquid chromatography could be prepared in this two‐dimensional system owing to the orthogonal separation. Moreover, this two‐dimensional liquid chromatography method was beneficial for the preparation of relatively trace flavonoid compounds, which were enriched in the first dimension and further purified in the second dimension. Totally, 24 flavonoid compounds with high purity were obtained. The results demonstrated that the off‐line two‐dimensional liquid chromatography method was effective for the preparative separation and purification of flavonoids from licorice.