Two‐dimensional strong cation exchange/positively charged reversed‐phase liquid chromatography for alkaloid analysis and purification

Peak tailing and nonalkaloid coelution usually hinder alkaloid purification. In this study, a 2DLC, strong cation exchange (SCX) coupled with positively charged RP (PGRP) LC, was developed to overcome these problems. Ten compounds including basic and nonbasic compounds were analyzed. Nonbasic compounds, which are coeluted with basic compounds on RP or PGRP columns, were weakly retained on the SCX column. In addition, a symmetrical peak shape (tailing factors <1.2) of basic compounds can be obtained in the current system. Compared to two other 2D systems, the current system provided the highest orthogonality (R² = 0.045). Furthermore, the SCX coupled with PGRP system was applied for alkaloid purification from a traditional Chinese medicine. Nineteen alkaloids were obtained and one of them was identified as a novel compound. The overall results demonstrate that the proposed system is a powerful tool for alkaloid purification.     

Nutritional Composition,Efficacy, and Processing of Vigna angularis (Adzuki Bean) for the Human Diet: An Overview

Adzuki beans are grown in several countries around the world and are widely popular in Asia, where they are often prepared in various food forms. Adzuki beans are rich in starch, and their proteins contain a balanced variety of amino acids with high lysine content, making up for the lack of protein content of cereals in the daily diet. Therefore, the research on adzuki beans and the development of their products have broad prospects for development. The starch, protein, fat, polysaccharide, and polyphenol contents and compositions of adzuki beans vary greatly among different varieties. The processing characteristic components of adzuki beans, such as starch, isolated protein, and heated flavor, are reported with a view to further promote the processing and development of adzuki bean foods. In addition to favorable edibility, the human health benefits of adzuki beans include antioxidant, antibacterial, and anti-inflammatory properties. Furtherly, adzuki beans and extracts have positive effects on the prevention and treatment of diseases, including diabetes, diabetes-induced kidney disease or kidney damage, obesity, and high-fat-induced cognitive decline. This also makes a case for the dual use of adzuki beans for food and medicine and contributes to the promotion of adzuki beans as a healthy, edible legume.     

Systematic evaluation and optimization of high‐performance liquid chromatography separation of polyoxins

The chromatographic behavior of a kind of nucleoside peptides, polyoxins, was investigated in this study. Molecular simulation technique was used to elucidate the temperature‐dependent peak sharpening of polyoxins. There was a relatively small energy barrier between the global minimum conformer and the local minimum conformer of polyoxin A and the high temperature helped to quickly cross the energy barrier and accelerate the conformational transformation for getting the global minimum, so that stationary phase could not identify these two conformations and presented a sharp peak. Two kinds of mixed‐mode columns, strong cation exchange or strong anion exchange ligands bonded with C18 (C18SCX and C18SAX) were used to improve separation selectivity of four polyoxins (A, K, F, H). The electrostatic attraction was necessary to increase the retention to ensure that the alkyl chain can give better play to its hydrophobic effect. Therefore, four polyoxins were well separated on C18SCX at pH 2 and they were also well separated on C18SAX at pH 7. In the small‐scale purification of polyoxins, the sample loading of the C18SCX was five times than that of the C18SAX and the purity of the collected four polyoxins was all over 90%.     

Synthesis,chromatographic evaluation and hydrophilic interaction/reversed-phase mixed-mode behavior of a “Click β-cyclodextrin” stationary phase

A native β-cyclodextrin (β-CD) stationary phase was prepared by covalently bonding β-CD on silica particles via Huisgen [3 + 2] dipolar cycloaddition between the organic azide and terminal alkyne, the so-called Click chemistry. The resulting β-CD bonded silica (Click β-CD) was characterized by FT-IR, solid state ¹³C cross polarization/magic-angle spinning (CP/MAS) NMR and elemental analyses, which proved the successful immobilization of β-CD on the silica support with Click chemistry. The retentive properties of Click β-CD were investigated under hydrophilic interaction liquid chromatography (HILIC) mode in different mobile phase conditions with a set of polar compounds including nucleosides, organic acids and alkaloids. The effects of water content, concentration of the salt and pH of the buffer solution on the retention time were studied and the results demonstrated the typical retention behavior of HILIC on Click β-CD. Separation of very polar components, such as nucleosides and oligosaccharides, and chiral separation under HILIC mode were successfully achieved. In addition, Click β-CD was chromatographically evaluated with a set of flavone glycosides. The retention curves depending on the mobile phase of acetonitrile content were “U” curves, which is an indication of HILIC/RPLC mixed-mode retention behavior. The difference of the separation selectivity between HILIC and RPLC was described as orthogonality by using geometric approach and the orthogonality reached 69.4%. The mixed-mode HPLC properties and excellent orthogonality demonstrated the flexibility in HPLC methods development and great potential in two-dimensional liquid chromatography separation.     

Use of an Orthogonal System, RP-LC–HILIC, for Evaluation of Purity

The reliability of evaluation of compound purity depends on the analytical method selected. A suitable analytical method, including the modes of separation and detection, can provide reliable information about compound purity. Effective separation is the key to achieving precise results. In this work we developed a novel method, based on an orthogonal system, RP-LC-hydrophilic interaction liquid chromatography, for evaluating the purity of compounds isolated by preparative reversed-phase liquid chromatography. Because of its good orthogonality, good separation and more accurate assessment of compound purity could be achieved.     

Purification of flavonoids and triterpene saponins from the licorice extract using preparative HPLC under RP and HILIC mode

A four‐channel preparative HPLC was employed to isolate and purify compounds from licorice extract. Two separation modes, RP and hydrophilic interaction LC (HILIC), were used in preparative HPLC. HILIC mode was adopted to resolve the purification of the compounds with similar hydrophobicity, which were co‐eluted under RP mode. Using the two separation modes during the purification process, fifteen compounds were isolated from licorice extract. The results indicated that preparative HPLC performed under HILIC mode is an efficient method for the isolation and purification of compounds from natural products.     

Purification of alkaloids from Corydalis yanhusuo W. T. Wang using preparative 2‐D HPLC

Two‐dimensional preparative multi‐channel parallel high performance liquid chromatography was successfully applied for the first time to isolate and purify alkaloids from Corydalis yanhusuo. The experiments were performed in off‐line mode using the same preparative chromatographic column with pH 3.5 in the first and pH 10.0 in the second separation dimension. In the preparative process, UV‐triggered fraction collection was used in the first dimension while UV and MS‐triggered collection were used in the second dimension for reasons of sensitivity and complementarity. Two pure compounds and nine fractions were obtained in the first dimension. Then two representative fractions were further purified in the second dimension and six pure compounds were obtained. The results demonstrated that this procedure is an effective approach for the preparative isolation and purification of alkaloids from Corydalis yanhusuo. Based on the different pH values of the mobile phase in this method, it is also suitable for the preparative isolation and purification of other compounds from TCMs which are sensitive to the pH of the solutions. Moreover, this method will be a promising tool for the purification of low content compounds from natural products.     

反相高效液相色谱与紫外光谱对硝基苯类化合物的联合定性

结合高效液相色谱和紫外光谱各自的优点和信息，建立了有机化合物的高效液相色谱和紫外光谱联合定性方法。在高效液相色谱中，二极管阵列检测器实时在线地提供样品组分的紫外光谱，由此建立紫外光谱谱图库，并发展了谱图库检索算法，同时测定了硝基苯类化合物的反相色谱用热力学参数ａ、ｃ值。结果表明，该法是可行的，满足定性所需的精度。     

Characterization of phthalides in Ligusticum chuanxiong by liquid chromatographic-atmospheric pressure chemical ionization-mass spectrometry

High-performance liquid chromatography (HPLC) with diode-array detection interfaced to atmospheric pressure chemical ionization (APCI)-mass spectrometry (MS) is applied to analyze phthalides from Chuanxiong (the rhizome of Ligusticum chuanxiong). This herb material, containing plenty of phthalide compositions, is selected as the analytical target in this paper for its hematological activity. Some of the phthalides are not stable and are difficult to analyze by gas chromatography-MS. Under optimized LC-MS-MS conditions, six phthalides in the methanol extract of Chuanxiong are unambiguously identified, and characteristic fragments are obtained using homemade reference standards. Ten other phthalides in the extract are confirmed by means of LC-APCI-MS with positive-negative ion mode and collision-induced dissociation in combination with UV spectrophotometry. The results show that LC-MS-MS is a method of choice for fast detection and detailed structural analysis of such mixtures in the crude extract of Chuanxiong.