Fabrication of a bio-based polymer adsorbent and its application for extraction and determination of glycosides from Huangqi Liuyi decoction.

Huangqi Liuyi Decoction, a famous classical Chinese prescription, shows significant curative effect on diabetes and its complications, in which calycosin-7-glucoside, liquiritin and glycyrrhizic acid are the main components that playing these mentioned pharmacological activity, under the synergistic action of various other ingredients in the decoction. However, there are significant differences in the content of active compounds in Chinese medicinal materials, which mainly due to origin, picking seasons, and processing methods. Hence, the accurate content of the glycosides is the prerequisite for ensuring the pharmacological efficacy. Aiming at establishing an efficient extraction and determination method for accurate quantitative analysis of calycosin-7-glucoside, liquiritin and glycyrrhizic acid in Huangqi Liuyi Decoction, an on line solid-phase extraction-high-performance liquid chromatography method was developed, using a homemade bio-based monolithic adsorbent. The bio-based adsorbent was prepared in a stainless steel tube, using bio-monomers of methyleugenol and S-allyl-L-cysteine, which effectively reduced the dependence of the polymer field on non-renewable fossil resources and reduced carbon emissions. Furthermore, the prepared adsorbent owned abundant chemical groups, which can produce interactions of hydrogen bond, dipole-dipole, π-π and hydrophobic force with the target glycosides, thus improving the specific recognition ability of the adsorbent. The experiments were carried out on an LC-3000 HPLC instrument with a six-way valve. Methodology validation indicates that the recovery is in the range of 97.0%-103.4% with the RSD in the range of 1.6%-4.0%, due to the specific selectivity of the bio-based monolithic adsorbent for these three glycosides, and good matrix-removal ability for Huangqi Liuyi decoction. The limit of detection is 0.17, 0.50 and 0.33 µg/mL for calycosin-7-glucoside, liquiritin and glycyrrhizic acid, respectively, and the limit of quantitation is 0.50, 1.50 and 1.00 µg/mL, respectively, with the linear range of 2-200 µg/mL for calycosin-7-glucoside, and 5-500 µg/mL for liquiritin and glycyrrhizic acid. The present work provided a simple and efficient method for the extraction and determination of glycosides in complex medicinal plants.

Preparation of a novel MOF-POPM and its application in online purification and enrichment of oleanolic acid in medicinal plants.

In present work, a method for enrichment, purification, and content determination of oleanolic acid (OA) in medicinal plants was established based on on-line solid phase extraction (SPE). A metal organic frameworks-porous organic polymer monolith (MOF-POPM) was prepared with functionalized UiO-66-(OH)2 as monomer and was used as SPE column for online enrichment and purification of OA. The ratio of adsorbent, enriching and eluting solvent, mobile phase pH, and flow rate had been systematically investigated. Under the optimum conditions, the linear range of OA was 0.59-2500 µg/mL with r = 0.9996. The limit of detection (LOD) was 0.18 µg/mL and the limit of quantification (LOQ) was 0.59 µg/mL. The intra-day relative standard deviations (RSDs) and inter-day RSDs of retention time and peak area were less than 0.3% and 1.3%, respectively. The average recoveries of OA in medicinal plants samples ranged from 87.7 to 104.6%. The results demonstrated that the online system was reliable and accurate for enrichment, purification, and content determination of OA in medicinal plants.

Establishment and application of characteristic degradation fingerprint for the quality control of Compound Banlangen Granules polysaccharides.

Compound Chinese medicine preparation is a complex multi-component system. The traditional methods such as physicochemical identification and quantification of several main index components cannot provide adequate quality evaluation for Compound Banlangen Granules. The objective of this work was to establish a characteristic degradation fingerprint of Compound Banlangen Granules polysaccharides, and the reference fingerprint was obtained from the model samples prepared using prescription medicinal herbs from different origins. The partial degradation products of Compound Banlangen Granules polysaccharides were profiled by capillary zone electrophoresis, and the quality difference of polysaccharides of these preparations was compared by cluster analysis and principal component analysis. It was found that the contents and the characteristic degradation fingerprints of the polysaccharides from 25 batches of Compound Banlangen Granules of 17 manufacturers were significantly different. The quality of Compound Banlangen Granules polysaccharides was evaluated by the characteristic degradation fingerprint tool with satisfactory results. The present method provides a reference for the quality control strategy development of polysaccharides in other compound Chinese medicine preparations.

Separation and purification of glycosides from medicinal plants based on strong polar separation medium with online closed-loop mode.

Natural glycosides widely distributed in medicinal plants are valuable sources of therapeutic agents, showing various pharmacological effects. The separation and purification of natural glycosides are meaningful for their pharmacological research, which face with great challenges due to the complex of medicinal plants samples. In this work, two kinds of functional monolithic separation mediums A and S were fabricated and fully applied in the online extraction, separation and purification of active glycoside components from medicinal plants with a simple-procedure closed-loop mode. Chrysophanol glucoside and physcion glucoside were detected and separated from Rhei Radix et Rhizoma using separation medium A as a solid-phase extraction adsorbent. Rhapontin was isolated and purified from Rheum hotaoense C. Y. Cheng et Kao using separation medium S as the stationary phase of high-performance liquid chromatography. Compared to the reported literatures, high yield of 5.68, 1.20 and 4.76 mg g-1 of these three products were obtained with high purity. These two online closed-loop mode methods were carried out using high-performance liquid chromatography system, in which the sample injection, isolation and purification procedures are all online mode, and reduced loss compared to offline extraction and purification procedures, thus achieving high recovery and high purity.

Fabrication and characterization of a composite monolithic guard column for the analysis of active components contained in medicinal plants using high-performance liquid chromatography.

A composite monolithic column was prepared via polymerization in a 10-mm-long tube, using a porphyrin-based covalent organic framework (COF) as the co-monomer. The fabricated monolith exhibit good permeability, relatively uniform porous structure and high specific surface area, which was used as a guard column prior to an analytical column for the analysis of active components in medicinal plants with HPLC. Ten kinds of medicinal plants were used as the samples, in which sixteen target components were separated and analyzed, as well as the fingerprints of herb and herb couple. Compared to a generally used commercial VAST silica gel-C18 guard column, the homemade guard column shows good permeability with fast mass transfer, short analytical time and strong reusability with more than 100 injections, thus indicating the present monolith is an outstanding guard column prior to the C18 analytical column for the analysis of multiple active components in various medicinal plants.

Preparation of poly(ionic liquid@MOF) composite monolithic column and its application in the online enrichment and purification of tectochrysin in medicinal plants.

Herein, a poly(ionic liquid@MOF) composite monolithic column was prepared via in situ radical polymerization using ionic liquid (1-allyl-3-methylimidazolium hexafluorophosphate) and MOF (derivatized UIO66-2COOH) as copolymer monomers. The composite monolithic column was characterized via scanning electron microscopy (SEM), nitrogen adsorption-desorption isotherms and mercury intrusion porosimetry. Subsequently, the composite monolithic column combined with high performance liquid chromatography (HPLC) was used as a solid-phase extraction (SPE) absorbent for online purification and enrichment of tectochrysin in medicinal plants. The results indicated that the addition of the ionic liquid and MOF not only increased the surface area but also increased the adsorption capacity of the monolith for tectochrysin. The method showed good linearity in the concentration range of 0.01-500 µg mL-1. The calibration equation was y = 2154.6x - 8.3785 and the limit of detection (LOD, S/N = 3) and the limit of quantification (LOQ, S/N = 10) were 3.33 ng mL-1 and 10 ng mL-1, respectively. The relative standard deviation (RSD) of the intra-day and inter-day precision was less than 2.62%, the RSD of inter-column was less than 3.16%, and the recoveries ranged from 100.58% to 105.00%. Thus, results showed that this method is simple, accurate and convenient for the online enrichment and purification of tectochrysin from medicinal plants.

Extraction and determination of tussilagone from Farfarae Flos with online solid-phase extraction-high-performance liquid chromatography using a homemade monolithic cartridge doped with porous organic cage material.

A solid-phase extraction cartridge was fabricated using diallyl isophthalate as the monomer with the addition of porous organic cage material via in situ free-radical polymerization in a stainless-steel column. The resulting monolithic adsorbent exhibited a relatively uniform porous structure, a high specific surface area of 113.98 m2 /g, and multiple functional chemical groups according to the characterization results. An online solid-phase extraction-high-performance liquid chromatography procedure was fabricated to extract and determine tussilagone from Farfarae Flos. The results show that the complex sample matrices can be removed in the solid-phase extraction procedure. Simultaneously, tussilagone can remain, which can be subsequently switched to an octadecylsilane bonded analytical column. The methodological validation showed that the correlation coefficient was 0.9999 with a linear range of 0.6-200.0 µg/mL, the limit of detection was 0.2 µg/mL, the limit of quantification was 0.6 µg/mL, accuracy was 100.3-100.6%, and relative standard deviation of precision was ≤1.9%. The present monolithic cartridge exhibits good reusability of not more than 100 times. The real sample of Farfarae Flos was determined with a tussilagone content of 0.74 mg/g.

On-line enrichment and determination of aristolochic acid in medicinal plants using a MOF-based composite monolith as adsorbent.

In this study, modified UiO-66-NH2 and N-methylolacrylamide (NMA) were used as common monomers to prepare a metal organic framework (MOF)-based composite monolith through in-situ polymerization, which was used as a new adsorbent to purify and enrich aristolochic acid-I (AA-I) in medicinal plants. The MOF-based composite monolithic column was characterized by nitrogen adsorption-desorption isotherm, mercury intrusion porosimetry and scanning electron microscopy (SEM). The adsorption ability of MOF-based composite monolith for AA-I was compared with that of the polymer monolith without MOF added. The results proved that the addition of UiO-66-NH2 can increase both the specific surface area and the permeability of the monolith. Moreover, the adsorption amount of AA-I on the monolith improved. This proposed on-line solid phase extraction (SPE) method showed good linear relationship in the range 0.044 ~ 400 µg/mL with r = 0.9994; the limit of detection (LOD) was 13.08 ng/mL and the limit of quantification (LOQ) was 44.00 ng/mL; the intra-day and inter-day accuracies were less than 0.97%; the inter-column accuracies was less than 6.11%; the recovery was in the range of 91.11%~106.48%. The method was found to be easy, accurate and convenient for on-line enrichment and purification of AA-I in medicinal plants.

Ionic liquid-organic-functionalized ordered mesoporous silica-integrated dispersive solid-phase extraction for determination of plant growth regulators in fresh Panax ginseng.

The massive accumulation of plant growth regulators (PGRs) in Panax ginseng causes serious harm to human health. A new analytical method for the simultaneous determination of multiple PGRs in 19 types of fresh Panax ginseng is developed by a new designed wool cluster-inspired ionic liquid-functionalized ordered mesoporous silica-integrated dispersive solid-phase extraction coupled to high performance liquid chromatography (IL-WFOMS-I-DSPE-HPLC). The proposed method combines the advantages of the multiple adsorption mechanisms, high mass transfer rate and large adsorption capacity of the synthesized IL-WFOMS adsorbent with the safe, convenient operation of the new designed I-DSPE method. Under optimized conditions, the recoveries at three spike levels were in a range of 77.6-98.3% for 3-indole acetic acid (IAA), 3-indole propionic acid (IPA), 3-indole butyric acid (IBA), and 1-naphthaleneacetic acid (NAA) with the relative standard deviations (RSD) ≤8.6%, n = 3. This method exhibits the advantages of safety, convenience, reliability, and has great potential for simultaneous determination of multiple trace PGRs in complex sample matrices.

Fabrication of a cycloalkyl-monolith for on-line solid-phase extraction and determination of four polyphyllins in plasma.

A cycloalkyl-based polymer monolithic column for solid-phase extraction was prepared via radical polymerization using cyclohexyl methacrylate as the monomer. The preparative conditions such as crosslinker/monomer ratio and the amount of the porogens were optimized and the resulting monoliths were characterized by scanning electron microscopy and nitrogen adsorption-desorption method. On-line solid-phase extraction-high-performance liquid chromatography was performed to quantitatively analyse polyphyllin I, II, VI and VII contained in herbal medicine of paridis rhizome in mouse plasma using the homemade optimized monolithic SPE column combined with a C18 column, in which water was used to remove the plasma matrix while the polyphyllins in the mouse plasma were eluted by acetonitrile-water (42:58, V/V). Results obtained from the method validation show that the present method is feasible for the quantitative analysis of the four polyphyllins in plasma. The developed method was further applied for the real mouse plasma sample. These results show that the homemade cycloalkyl-based polymer monolithic SPE column has good ability for clean-up of the interfering bio-matrix and simultaneously extracting the four polyphyllins from mouse plasma. Furthermore, the present method is a promising method for quantitative determination of saponins compounds from complex bio-samples with the advantages of simple and efficient.

Simple quantitative analytical methods for the determination of alkaloids from medicinal and edible plant foods using a homemade chromatographic monolithic column.

A polymer-based chromatographic monolithic column was prepared via in-situ radical polymerization using tetrahydrofurfuryl methacrylate as the monomer. The homemade column was used for the separation and quantitative analysis of alkaloids, including piperine from Piper longum (fruit of Piper longum Linn.) and pepper (fruit of Piper nigrum L.), hydroxy-α-sanshool, and hydroxy-γ-sanshool from zanthoxylum (fruit of Zanthoxylum bungeanum Maxim), as well as caffeine from Wuyi rock tea. The chromatographic fractions were identified by mass spectrometry. Single factor test and orthogonal test were both carried out to optimize the extraction conditions. The method validation indicated that the accuracy represented by spiked recovery ranged in 98.89%-102.06%, the correlation coefficients in 0.99986-0.99999. These results show that the prepared monolithic column can be successfully used to quantitatively analyse alkaloids from the real medicinal and edible plant foods with reversed-phase mechanism, which can avoid the long analytical time using traditional packed C18 column. The present method is a simple, and inexpensive method for quantitatively analysing alkaloids from medicinal and edible plant foods, exhibiting good specificity and durability.

A metal organic framework polymer monolithic column as a novel adsorbent for on-line solid phase extraction and determination of ursolic acid in Chinese herbal medicine.

A metal organic framework (MOF)-polymer monolithic column was prepared by redox initiation using modified MOF and N-methylolacrylamide (NMA) as co-monomers. The obtained monolithic column was characterized by scanning electron microscopy (SEM) and nitrogen adsorption-desorption isotherm measurement. It was used as a solid phase extraction (SPE) absorbent for the online enrichment of ursolic acid (UA) by high performance liquid chromatography. The adsorption amount of UA on the monolith was compared with that of silica gel-C18 adsorbent and the monolith without MOF material. The MOF-polymer monolithic column showed high selectivity and good permeability. Under the optimum conditions for extraction and determination, the calibration equation was y = 79.854× + 0.1939; the linear range was 0.001-0.9 mg/mL; the linear regression coefficient was 0.9993; the limit of detection (LOD) and the limit of quantification (LOQ) were 0.17 µg/mL and 0.57 µg/mL, respectively; the inter-day and intra-day accuracies were <6.44%; the recovery was in the range of 86.52-105.26%. The MOF-polymer monolithic column was successfully used as SPE column for enrichment and determination of UA in Chinese herbal medicine.

A novel poly (NMA-co-DEA-co-EDMA) monolithic column as a sorbent for online solid-phase extraction and its application in the determination of ß-sitosterol in plant oil samples.

A novel monolithic column was prepared by in-situ free radical polymerization using N-methylolacrylamide (NMA) and N,N-diethylacrylamide (DEA) as co-monomers. The monolith was characterized by scanning electron microscopy (SEM) and its nitrogen adsorption-desorption isotherm, and it was used as a solid phase extraction (SPE) absorbent for the online enrichment of ß-sitosterol by high performance liquid chromatography. The optimized method had good linearity, and the linear regression coefficient was 0.998. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.006 mg/mL and 0.02 mg/mL, respectively. The interday and intraday accuracies were less than 7.28%. The spiked recoveries of ß-sitosterol in the six plant oil were 90.96-103.56%. The maximum amount of ß-sitosterol adsorbed on the monolithic column was 12.69 mg/g, and the enrichment factor of ß-sitosterol was 78. The results showed that the monolith could be used as an online SPE absorbent for the determination of ß-sitosterol in plant oil samples.

Graphene oxide-based composite monolith as new sorbent for the on-line solid phase extraction and high performance liquid chromatography determination of ß-sitosterol in food samples.

A composite monolithic column was prepared by redox initiation method for the on-line purification and enrichment of ß-sitosterol, in which graphene oxide (GO) was embedded. The obtained monolithic column was characterized by scanning electron microscopy (SEM) and nitrogen adsorption-desorption isotherm measurement, which indicated that the monolith possessed characteristics of porous structure and high permeability. Under the optimum conditions for extraction and determination, the calibration equation was y = 47.92 × -0.1391; the linear range was 0.008-1.0 mg mL-1; the linear regression coefficient was 0.998; the limit of detection (LOD) is 2.4 µg mL-1; the limit of quantitation (LOQ) was 8 µg mL-1; precisions for intra-day and inter-day assays presented as relative standard deviations were less than 4.3% and 6.8%, respectively. Under the selective conditions, the enrichment factor of the method was 119. The recovery was in the range of 80.40-98.00%. Moreover, the adsorption amount of the monolith was compared with silica gel-C18 adsorbent and the monolith without graphene oxide being embedded. The polymerization monolithic column showed high selectivity and good permeability, and it was successfully used as on-line solid-phase extraction (SPE) column for determination of ß-sitosterol in edible oil.