Determination of phenolic acids in plant extracts using CZE with on‐line transient isotachophoretic preconcentration

A novel transient ITP–CZE for preconcentration and determination of seven phenolic acids (caffeic acid, cinnamic acid, p‐coumaric acid, ferulic acid, protocatechuic acid, syringic acid, and vanilic acid) was developed and validated. Effects of several factors such as control of EOF, pH and buffer concentration, addition of organic solvents and CDs, and conditions for sample injection were investigated. Sample self‐stacking was applied by means of induction of transient ITP, which was realized by adding sodium chloride into the sample. The CZE was realized in 200 mM borate buffer ( 9.2) containing 37.5% methanol, 0.001% hexadimethrine bromide, and 15 mM 2‐hydroxypropyl‐β‐CD. Under the optimal conditions for analysis, analytes were separated within 20 min. Linearity was tested for each compound in the concentration range of 0.1–10 μg/mL (R = 0.9906–0.9968) and the detection limits (S/N = 3) ranged from 11 ng/mL (protocatechuic acid) to 31 μg/mL (syringic acid). The validated method was applied to the ethanolic extract of Epilobium parviflorum, Onagraceae. The method of SPE was used for the precleaning of the sample.     

Simultaneous determination of eight Danshen polyphenols in rat plasma and its application to a comparative pharmacokinetic study of DanHong injection and Danshen injection

Polyphenols derived from Danshen are responsible for the therapeutic effects of DanHong injection, a two‐herb combination of Danshen and Honghua. Whether the pharmacokinetics of Danshen polyphenols is changed by coexisting Honghua constituents remains unknown. A sensitive ultra high performance liquid chromatography with tandem mass spectrometry method was developed in this study for simultaneous determination of eight Danshen polyphenols (i.e., protocatechuic aldehyde, protocatechuic acid, tanshinol, salvianolic acid D, rosmarinic acid, salvianolic acid A, lithospermic acid, and salvianolic acid B) in rat plasma and applied to a comparative pharmacokinetic study of DanHong injection and Danshen injection. Liquid chromatography conditions, mass spectrometry parameters, and sample preparation were optimized step by step. The calibration curves showed good linearity (r > 0.99) for all the polyphenols. The mean extraction efficiencies ranged from 62.2 to 88.7% with negligible matrix effects. The intrabatch and interbatch precision at all the quality control levels were less than 15% of the nominal concentrations with accuracy of 88.8–114%, except that precision and accuracy at lower limit of quantitation were 3.2–17.3 and 95.7–119%, respectively. Comparative pharmacokinetic study suggested that the coexisting Honghua constituents might have negligible influences on the pharmacokinetics of Danshen polyphenols from DanHong injection. The bioanalytical method could also be applied to pharmacokinetic studies of other Danshen herbal products.     

Simultaneous determination of six phenolic constituents of Danshen injection in rat plasma by LC-ESI-MS and its application to a pharmacokinetic study

Salvianolic acid A, salvianolic acid B, danshensu, protocatechuic aldehyde, rosmarinic acid and lithospermic acid are the six major active constituents in Danshen injection. In this study, a rapid, sensitive and specific liquid chromatographic-electrospray ionization-mass spectrometry method for the simultaneous quantitative determination of these compounds in rat plasma was developed. After a single step of liquid-liquid extraction with ethyl acetate, they were eluted by a Hypersil C18 column (5 μm, i.d. 4.6 × 200 mm) within 4 min with a mobile phase consisting of acetonitrile and 0.1% formic acid water solution (35:65, v/v). The assay was linear in the concentration range of 0.05-10 μg mL(-1). Absolute recoveries were above 60%. The precisions and accuracies determined within three consecutive days were within acceptable limits. The method was successfully applied to a pharmacokinetic study in rats after an intravenous administration of Danshen injection.     

高效液相色谱二极管阵列检测法同时测定丹参滴注液中四种水溶性成分的含量

建立了高效液相色谱二极管阵列检测(HPLC-DAD)法同时测定丹参滴注液中丹参素、原儿茶醛、迷迭香酸和丹酚酸B四种水溶性成分的含量。采用DiamonsilTMC18色谱柱(250×4.6 mm,5μm),以甲醇和5%冰乙酸为流动相进行梯度洗脱,流速为1.0mL/min,柱温30℃,检测波长为286 nm。在此色谱条件下四种水溶性成分可完全分离。丹参素、原儿茶醛、迷迭香酸和丹酚酸B的线性范围分别为0.2192~1.934μg(r=0.9999),0.03508~0.2456μg(r=1.0000),0.2592~1.814μg(r=1.0000),0.3864~2.705μg(r=0.9999)。平均回收率丹参素为102.6%,相对标准偏差(RSD)为0.55%;原儿茶醛为103.5%,RSD为0.42%;迷迭香酸为99.8%,RSD为0.68%;丹酚酸B为102.8%,RSD为0.49%。该方法简单、快速,四组分分离良好,可用于丹参滴注液的质量控制。     

Simultaneous determination of active ingredients in ethnomedicine Gaultheria leucocarpa var. yunnanensis and its medicinal preparation by capillary electrophoresis with electrochemical detection

A simple and rapid capillary electrophoresis (CE) with electrcochemical detection (ED) method has been established for the simultaneous determination of seven active ingredients in the stems and roots of Gaultheria leucocarpa var. yunnanensis and its medicinal preparation, including (+)-catechin, rutin, gentisic acid, vallinic acid, salicylic acid, quercetin, and protocatechuic acid. The effects of working potential, pH, and concentration of running buffer, separation voltage, and injection time on CE-ED are systematically investigated. Under the optimum conditions, the seven analytes could be completely separated within 23 min in a borax running buffer (pH 8.7). A good linear relationship is obtained over three orders of magnitude with detection limits (signal-to-noise ratio=3) ranging from 5x10(-8) g/mL to 3x10(-7) g/mL for the analytes. The proposed method is successfully used in the analysis of real samples after a relatively simple extraction procedure, and the assay results are satisfactory.     

Combined use of ionic liquid and sulfobutylether‐β‐cyclodextrin as electrolyte additives for separation and determination of camptothecin alkaloids by CZE

This work reported that ionic liquid (IL) ([Bmim] [PF₆]) and sulfobutylether‐β‐CD (SBE‐β‐CD) were used as electrolyte additives for the separation and determination of camptothecin (CPT) alkaloids by CZE. Separation parameters such as the buffer type, pH, and concentration of the running buffer, the concentration of SBE‐β‐CD and IL, temperature, and separation voltage were all investigated in order to achieve the maximum possible resolution. The four analytes were baseline separated within 10 min in capillary at the separation voltage of 15 kV with a running buffer consisting of 20 mM borate buffer, 20 mM IL, and 100 mM SBE‐β‐CD at pH 9.0. Under such conditions, good linearity about two orders of magnitudes of peak areas was achieved for the investigated CPT alkaloids with the correlation coefficients ranging from 0.9946 to 0.9985. For all analytes, detection limits (S/N = 3) and quantitation limits (S/N = 10) range from 0.05 to 0.92 μg/mL and 0.17 to 3.06 μg/mL, respectively. The proposed method has not only been successfully applied to the separation and determination of CPT alkaloids but also showed that IL seemed to be a promising additive in CZE separation.     

Determination of phthalic acid esters in Chinese white spirit using dispersive liquid–liquid microextraction coupled with sweeping β‐cyclodextrin‐modified micellar electrokinetic chromatography

A simple method that consumes low organic solvent is proposed for the analysis of phthalic acid esters in Chinese white spirit using dispersive liquid–liquid microextraction coupled with sweeping‐micellar electrokinetic chromatography. Tetrachloromethane and white‐spirit‐containing ethanol were used as the extraction and dispersing solvents, respectively. The electrophoresis separation buffer was composed of 5 mM β‐cyclodextrin, 50 mM sodium dodecyl sulfate and 25 mM borate buffer (pH 9.2) with 9% acetonitrile, enabling the baseline resolution of the analytes within 13 min. Under the optimum conditions, satisfactory linearities (5–1000 ng/mL, r ≥ 0.9909), good reproducibility (RSD ≤ 6.7% for peak area, and RSD ≤ 2.8% for migration time), low detection limits (0.4–0.8 ng/mL) and acceptable recovery rates (89.6–105.7%) were obtained. The proposed method was successfully applied to 22 Chinese white spirits, and the content of dibutyl phthalate in 55% of the samples exceeded the Specific Migration Limit of 0.3 mg/kg established by the domestic and international regulations.     

Simultaneous determination of trifolirhizin, (–)‐maackiain, (–)‐sophoranone,and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran from Sophora tonkinensis in rat plasma by liquid chromatography with tandem mass spectrometry and its application to a pharmacokinetic study

A new liquid chromatography with tandem mass spectrometry method was developed and validated for the simultaneous determination of trifolirhizin, (–)‐maackiain, (–)‐sophoranone, and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran from Sophora tonkinensis in rat plasma using chlorpropamide as an internal standard. Plasma samples (50 μL) were prepared using a simple deproteinization procedure with 150 μL of acetonitrile containing 100 ng/mL of chlorpropamide. Chromatographic separation was carried out on an Acclaim RSLC120 C₁₈ column (2.1 × 100 mm, 2.2 μm) using a gradient elution consisting of 7.5 mM ammonium acetate and acetonitrile containing 0.1% formic acid (0.4 mL/min flow rate, 7.0 min total run time). The detection and quantitation of all analytes were performed in selected reaction monitoring mode under both positive and negative electrospray ionization. This assay was linear over concentration ranges of 50–5000 ng/mL (trifolirhizin), 25–2500 ng/mL ((–)‐maackiain), 5–250 ng/mL ((–)‐sophoranone), and 1–250 ng/mL 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran) with a lower limit of quantification of 50, 25, 5, and 1 ng/mL for trifolirhizin, (–)‐maackiain, (–)‐sophoranone, and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran, respectively. All the validation data, including the specificity, precision, accuracy, recovery, and stability conformed to the acceptance requirements. The results indicated that the developed method is sufficiently reliable for the pharmacokinetic study of the analytes following oral administration of Sophora tonkinensis extract in rats.     

Separation and determination of corynoxine and corynoxine B using chiral ionic liquid and hydroxypropyl‐β‐cyclodextrin as additives by field‐amplified sample stacking in capillary electrophoresis

A sensitive, fast, and effective method, field‐amplified sample stacking (FASS) in capillary electrophoresis, has been established for the separation and determination of corynoxine and corynoxine B. Hydroxypropyl‐β‐CD (HP‐β‐CD) and tetrabutylammonium‐L‐glutamic acid (TBA‐L‐Glu) were used as additives in the separation system. Electrokinetic injection was chosen to introduce sample from inlet at 10 kV for 50 s after a water plug (0.5 psi, 4 s) was injected to permit FASS. The running buffer (pH 6.1) was composed of 40 mM sodium dihydrogen phosphate solution, 130 mM HP‐β‐CD, and 10 mM TBA‐L‐Glu and the separation voltage was 20 kV. Under the optimum conditions, corynoxine and corynoxine B were successfully enriched and separated within 12 min and the sensitivity was improved approximately by 700–900 folds. Calibration curves were in a good linear relationship within the range of 62.5–5.00 × 10³ ng/mL for both corynoxine and corynoxine B. The limits of detection (S/N = 3) and quantitation (S/N = 10) were 14.9, 45.2 ng/mL for corynoxine and 11.2, 34.5 ng/mL for corynoxine B, respectively. Finally, this method was successfully applied for the determination of corynoxine and corynoxine B in the stems with hooks of Uncaria rhynchophylla and its formulations.     

Simultaneous determination of eight bioactive components of Qishen Yiqi dripping pills in rat plasma using UFLC–MS/MS and its application to a pharmacokinetic study

In this study, a rapid and reliable ultra‐fast liquid chromatography–tandem mass spectrometry method was developed and validated for the simultaneous determination of eight active ingredients, including astragaloside IV, ononin, tanshinol, protocatechualdehyde, protocatechuic acid, salvianolic acid D, rosmarinic acid and ginsenoside Rg₁, in rat plasma. The plasma samples were pretreated by protein precipitation with acetonitrile. Chromatographic separation was performed on a Waters Acquity UPLC® BEH C₁₈ column (1.7 μm particles, 2.1 × 100 mm). The mobile phase consisted of 0.1% aqueous formic acid (A)–acetonitrile with 0.1% formic acid (B) at a flow rate of 0.4 mL/min. Quantification was performed on a triple quadruple tandem mass spectrometry with electrospray ionization by multiple reaction monitoring both in the negative and in the positive ion mode. The lower limit of quantification of tanshinol was 2.0 ng/mL and the others were 5.0 ng/mL. The extraction recoveries, matrix effects, intra‐ and inter‐day precision and accuracy of eight tested components were all within acceptable limits. The validated method was successfully applied to the pharmacokinetic study of the eight active constituents after intragastric administration of three doses (1.0, 3.0, 6.0 g/kg body weight) of Qishen Yiqi Dripping Pills to rats.     

Separation and simultaneous determination of seven bioactive components in Tripterygium wilfordii Hook. F. and Tripterygium preparations by micellar electrokinetic capillary chromatography

A simple, comprehensive, and highly selective MEKC method has been developed for simultaneous analysis of seven bioactive components (triptolide, wilfortrine, wilfordine, wilforgine, wilforine, triptophenolide, and triptonide) in the root extracts of Tripterygium wilfordii Hook. F. (TWHF) and Tripterygium preparations (TPs). Optimal BGE consisted of 10 mM sodium tetraborate, 30 mM SDS, and 30% v/v methanol. The separation voltage was 20 kV and the temperature was 25°C. A DAD was used and the detection wavelength was at 218 nm. Under the optimum conditions, the baseline separation of seven components was achieved in less than 26 min. Excellent precision, good stability, and accuracy were obtained. For all analytes, linear calibrations were established within 10–100 μg/mL. The LOD and LOQ were within 1.2–4.2 μg/mL and 4.0–14 μg/mL, respectively. The developed method was suitable for the determination of key components in TWHF and TPs.     

Simultaneous separation and determination of seven isoflavones in Radix Puerariae by capillary electrophoresis with a dual cyclodextrin system

A simple, comprehensive and efficient capillary electrophoresis method using a dual cyclodextrin system was developed for the simultaneous determination of seven isoflavones (3′‐methoxypuerarin, puerarin, 3′‐hydroxypuerarin, ononin, daidzin, daidzein and genistin). Baseline separations of the seven isoflavones were achieved within 11 min with the running buffer consisting of 35 mm sodium tetraborate, 9.0 mm sulfobutylether‐β‐cyclodextrin and 30 mm α‐cyclodextrin at pH 9.34, and peaks were detected at 254 nm. Other separation parameters included the separation voltage for 15 kV and the working temperature for 25°C. Under the optimum conditions, good linearities were obtained with linear correlation coefficients of seven isoflavones of 0.9978–0.9992. The limits of detection and the limits of quantification were 0.7–2.9 and 2.5–9.5 μg/mL, respectively. Excellent precision and accuracy were obtained. The intraday and interday precision ranged from 0.7 to 2.0% and from 0.8 to 1.9%, respectively. The recoveries of seven analytes were from 97.7 to 103.1%. This method was successfully applied to determine the seven analytes in Radix Puerariae and its preparations.     

Quality evaluation of Guan‐Xin‐Ning injection based on fingerprint analysis and simultaneous separation and determination of seven bioactive constituents by capillary electrophoresis

The purpose of this study was to develop a comprehensive, rapid and practical capillary electrophoresis (CE) method for quality control (QC) of Guan‐Xin‐Ning (GXN) injection based on fingerprint analysis and simultaneous separation and determination of seven constituents. In fingerprint analysis, a capillary zone electrophoresis (CZE) method with a running buffer of 30 mM borate solution (pH 9.3) was established. Meanwhile, ten batches of samples were used to establish the fingerprint electropherogram and 34 common peaks were obtained within 20 min. The RSD of relative migration times (RMT) and relative peak areas (RPA) were less than 5%. In order to further evaluate the quality of GXN injection, a micellar electrokinetic chromatography (MEKC) method was developed for simultaneous separation and determination of bioactive constituents. Seven components reached baseline separation with a running buffer containing 35 mM SDS and 45 mM borate solution (pH 9.3). A good linearity was obtained with correlation coefficients from 0.9906 to 0.9997. The LOD and LOQ ranged from 0.12 to 1.50 μg/mL and from 0.40 to 4.90 μg/mL, respectively. The recoveries ranged between 99.0 and 104.4%. Therefore, it was concluded that the proposed method can be used for full‐scale quality analysis of GXN injection.     

复方丹参片中四种成分的高效液相色谱-电化学检测-紫外检测法分析

建立了电化学检测器与二极管阵列检测器联用的液相色谱(HPLC-ECD-DAD)同时分离和测定复方丹参片中原儿茶酸、原儿茶醛、咖啡酸和丹参酮ⅡA 等4种成分的分析方法。采用Zorbax SB-C18柱(150 mm×4.6 mm i.d.,5.0 μm),以甲醇和0.4%磷酸为流动相(流速1.0 mL/min)进行梯度洗脱;ECD检测电压0.7 V,DAD检测波长270 nm,柱温30 ℃。实验结果表明,原儿茶酸、原儿茶醛、咖啡酸和丹参酮ⅡA质量浓度分别为0.3～9.0 mg/L,1.1～54.0 mg/L,1.1～11.1 mg/L和5.2～52.0 mg/L时与其峰面积呈良好的线性关系(线性相关系数均高于0.999),原儿茶酸、原儿茶醛、咖啡酸和丹参酮ⅡA的平均回收率(n=6)分别为97.8%(相对标准偏差(RSD)为2.15%),98.2%(RSD为2.07%),97.6%(RSD为2.18%)和97.2%(RSD为2.07%)。该法同时利用了ECD和DAD的优点,是一种快速、灵敏、准确的分析方法,可以为复方丹参片的质量控制提供科学依据。     

Simultaneous determination of substrate and product in the process of preparation of valienamine by capillary zone electrophoresis

A simple and rapid CZE method was established for the simultaneous determination of valienamine, acarbose and validamycin A, using a 20‐kV CZE with the detection wavelength of 193 nm and 50 mM phosphoric acid–20 mM Tris (pH 5.3) as a running buffer. The calibration curves of valienamine, acarbose, and validamycin A showed a good linear relationship at a concentration range of 5–1000 μg/mL. The detection limits of valienamine, acarbose, and validamycin A were 0.3, 0.6, and 0.6 μg/mL, respectively, and the average recoveries of each of the above were 99.9, 99.5, and 100.3%. The method has been successfully applied for simultaneous determination of substrate and product in the process of preparation of valienamine.     

High‐speed separation and detection of amino acids in laver using a short capillary electrophoresis system

A high‐speed separation method of capillary MEKC with LIF detection had been developed for separation and determination of amino acids in laver. The CE system comprised a manual slotted‐vial array (SVA) for sample introduction that could improve the separation efficiency by reducing injection volume. Using a capillary with 80 mm effective separation length, the separation conditions for amino acids were optimized. Applied with the separation electric field strength of 300 V/cm, the ten amino acids could be completely separated within 2.5 min with 10 mol/L Na₂HPO₄–NaOH buffer (pH = 11.5) including 30 mmol/L SDS. Theoretical plates for amino acids ranged from 72 000 to 40 000 (corresponding to 1.1–2.0 μm plate heights) and the detection limits were between 25 and 80 nmol/L. Finally, this method was applied to analyze the composition of amino acids in laver and eight known amino acids could be found in the sample. The contents of five amino acids, tyrosine, glutamic acid, glycine, lysine, and aspartic acid that could be completely separated in real sample were determined. The recoveries ranged from 82.3% to 123% that indicated the good reliability for this method in laver sample analysis.     

Determination of Protocatechuic Aldehyde, Danshensu, Salvianolic Acid B and Gallic Acid in Chinese Medicine 'SHUANGDAN' Granule by MEKC

A simple, accurate and effective micellar electrokinetic capillary chromatography (MEKC) method for the separation and determination of protocatechuic aldehyde (PA), danshensu (DSS), salvianolic acid B (SAB) and gallic acid (GA) in Chinese medicine 'SHUANGDAN' granule was developed in this work. The separation was carried out in a 50.0 cm (42.0 cm to the detector) × 75 μm i.d. fused-silica capillary using the optimum buffer solution containing 5.0 mM borate, 15 mM phosphate, 35 mM SDS and 10% (v/v) acetonitrile. The linear relationships between the concentration of the analytes and the corresponding peak areas were investigated, and excellent linear behavior over the investigated concentration ranges was revealed (R²: 0.9985 for PA, 0.9994 for DSS, 0.9989 for SAB and 0.9991 for GA, respectively). The proposed method was successfully applied to the determination of these four active components contained in 'SHUANGDAN' granule. The recoveries of these four components were 97.6–101.2%, 97.6–100.5%, 96.9–101.6% and 97.6–102.9%, respectively.     

Simultaneous Determination of Seven Bioactive Compounds in Chinese Medicine “QI-SHEN-YI-QI” Dropping Pill by LC-UV and LC-ELSD

A high performance liquid chromatography coupled with ultraviolet detection and evaporative light scattering detection (HPLC-UV-ELSD) method was developed for simultaneously determining seven bioactive components, i.e. danshensu, protocatechuic aldehyde, salvianolic acid B, notoginsenoside R₁, ginsenoside Rg₁, ginsenoside Rb₁, and astragaloside IV in “QI-SHEN-YI-QI” dropping pill, a widely used traditional Chinese medicine (TCM) for treating cardiovascular disease. The chromatographic separation was performed on a Zorbax Stable Bond C₁₈ column using gradient elution with acetonitrile and water with acceptable validation results such as linearity and recovery. The recoveries of the seven investigated compounds ranged from 93.3 to 100.2% with RSD values less than 5%. More importantly, this proposed method was successfully used to determine the seven compounds in nine batches of “QI-SHEN-YI-QI” dropping pills, which indicated that the proposed method could be readily utilized as a quality control method for this TCM preparation.     

Multiple on‐line HPLC coupled with biochemical detection methods to evaluate bioactive compounds in Danshen injection

On‐line high performance liquid chromatography (HPLC) coupled with three biochemical detection (BCD) methods was applied to evaluate bioactive components in Danshen injection. On‐line HPLC‐photo‐diode array–fluorescence detection based on the fluorogenic substrate 7‐acetoxy‐1‐methyl quinolinium iodide, was built to search acetylcholinesterase (AChE) inhibitors in Danshen injection. On‐line HPLC coupled with the scavenging assay of 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and 2,2′‐azinobis (3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS) free radicals was developed to screen antioxidants. The three active profiles were obviously different. Radical scavenging profiles revealed seven strong peaks in the chromatographic fingerprint possessing obvious free radical inhibition effects, while some minor peaks exhibited stronger AChE inhibition activities. The main radical scavengers and AChE inhibitors were identified by HPLC‐MS. Several unknown ingredients showing strong AChE inhibition activities needed further identification except protocatechuic aldehydrate, salvianolic acid H or I and lithospermic acid. The on‐line multiple on‐line HPLC‐BCD methods will provide powerful tools in the field of pharmacognosy for fast‐track identification of interesting and/or novel bioactive compounds.