Separation of anthraquinone compounds from the seed of Cassia obtusifolia L. using recycling counter-current chromatography

Modeling of analytical, preparative and industrial scale counter-current chromatography separations

Analytical, preparative and industrial scale counter-current chromatography (CCC) processes differ in the volumes of the loaded solution of components to be separated and in the design of the equipment. Preliminary mathematical modeling is necessary for selection of the optimal design and operation mode of these CCC separations. This study aims to compare simulations of CCC separations at different scales, using an exact description based on the model of equilibrium cells and a much simpler approximate solution based on the Gaussian distribution. Equations for modeling CCC separations of different scales and examples of simulation these separations are presented. It is shown that the discrepancy between the two simulations increases with an increase in the volume of the loaded solution of the components and a decrease in the number of equilibrium cells of a CCC device. In analytical and preparative separations, which are based on complex centrifugal devices, and relatively small sample volumes are injected, approximate equations can be used to simulate various options of CCC separation. In industrial-scale CCC separations, large volumes of the solution of components may be loaded, and as we have proposed previously, these separations can be based on a cascade of mixer-settler extractors. In this case, a more accurate mathematical description based on the cell model equations should be used for modeling.

Physcion prevents induction of optic nerve injury in rats via inhibition of the JAK2/STAT3 pathway

Optic nerve injury is a type of neurodegenerative disease. Physcion is an anthraquinone that exerts a protective role against various diseases. However, its function in regulating optic nerve injury remains largely unknown. An in vitro model of optic nerve injury was established in HAPI cells treated with IFN-β. Functional assays were used to detect HAPI cell viability and apoptosis. The levels of inflammation and the expression levels of oxidative stress-related genes were measured in HAPI cells. In addition, western blot analysis was used to detect the expression levels of Janus kinase 2 (JAK2)/STAT3-linked genes in HAPI cells. Treatment of the cells with physcion prevented cells against IFN-β-induced neuronal injury. Physcion restrained IFN-β-induced inflammatory response and oxidative stress in HAPI cells. In addition, it improved IFN-β-induced injury in HAPI cells by suppressing the JAK2/STAT3 pathway. In conclusion, the present study revealed that physcion improved optic nerve injury in vitro by inhibiting the JAK2/STAT3 pathway. Physcion may be a promising therapeutic target for the treatment of this disease.

Intermittent sample loading technique as a tool for obtaining high- concentration elution bands in recycling liquid-liquid chromatography: Theoretical study of periodic and semi-continuous separation processes

To improve the efficiency of countercurrent chromatography (CCC) separations, we have previously proposed a new sample loading method called intermittent sample loading (ISL), in which continuous sample feed alternates with short periods of "clean" mobile phase feed to the CCC device. In semi-continuous separation processes, during sample feed periods, the sample is loaded in separate batches, each consisting of a series of intermittent sample loads. It was shown that the application of the intermittent sample loading method in the conventional isocratic CCC separations significantly increased process productivity and the concentration of compounds in the separated fractions. In this study, to further improve the CCC separations with intermittent sample loading, we discuss the application of the ISL method in the processes of close-loop recycling counter-current chromatography (CLR CCC). The advantage of the ISL CLR CCC over the ISL CCC is higher resolution and lower solvent consumption. Equations are presented that allow the simulation of periodic and semi-continuous ISL CLR CCC separations and the selection of optimal operational conditions for these separation processes. It is shown that the use of ISL technique in CLR CCC separations makes it possible to produce fractions of compounds with a much higher concentration than when using the conventional single sample loading method.

Online extraction and enrichment coupling with high-speed counter-current chromatography for effective and target isolation of antitumor anthraquinones from seeds of Cassia obtusifolia

Traditional bioassay-guided investigation of bioactive compounds from natural products comprises critical steps, such as extraction, repeated column separation, and activity assay. Thus, the development of facile, rapid, and efficient technology is critically important. Here, a HepG2 cell-based extraction method was first developed to rapidly screen potential antitumor compounds from the seeds ofCassia obtusifolia. Then, an online extraction and enrichment-high-speed counter-current chromatography (HSCCC) strategy was fabricated to facilely and efficiently isolate target antitumor compounds, which included direct extraction from solid C. obtusifolia, removal of polar interferences, enrichment of target compounds, and preparative isolation by HSCCC using flow rate stepwise increasing mode. After further purification by Sephadex LH-20 column, five antitumor anthraquinones, aurantio-obtusin, 1-desmethylaurantio-obtusin, chryso-obtusin, obtusin, and questin, were obtained for structural characterization and bioassay verification. The results may not only provide new perspectives for facile and rapid investigation of bioactive compounds from complex natural products, but also offer a scientific basis for the potential applications of C. obtusifolia.

A simple and highly efficient counter-current chromatography method for the isolation of concentrated fractions of compounds based on the sequential sample loading technique: Comparative theoretical study of conventional multiple and intermittent sample loading counter-current chromatography separations

A new modification of the conventional multiple sample loading (MSL) mode - sequential sample loading (SSL) - is suggested to enhance further the performance of the counter-current chromatography (CCC) separation processes. The sequential sample loading technique is simple and easy to implement: the continuous sample solution supply to a CCC column is alternated (interrupted) with short periods of the "pure" mobile phase supply. Periodic (batch) and continuous SSL CCC separations can be designed and implemented. In continuous processes, the sample solution loading is carried out in the form of separate series, consisting of a number of sequential sample solution loads. In this work, the modeling of the conventional multiple sample loading and the sequential sample loading counter-current chromatography is used to compare the two operating modes considered. Equations for the calculation of band profiles, the recovery yield and the purity are given. Equations are also derived permitting the calculation of the optimum operating parameters of the separation processes. It is shown that the use of sequential sample loading makes it possible to produce fractions of purified compounds with a much higher concentration than in the original sample solution. The simulations of the conventional multiple sample loading and the sequential sample loading counter-current chromatography separations are presented in "Mathcad" software.

Development of a Specific Mini-Barcode From Plastome and its Application for Qualitative and Quantitative Identification of Processed Herbal Products Using DNA Metabarcoding Technique: A Case Study on Senna

Herbal products play an important role globally in the pharmaceutical and healthcare industries. However, some specific groups of herbal products are easily adulterated by confused materials on the market, which seriously reduces the products’ quality. Universal conventional DNA barcodes would function poorly since the processed herbal products generally suffer from varying degrees of DNA degradation and DNA mixing during processing or manufacturing. For quality control purposes, an accurate and effective method should be provided for species identification of these herbal products. Here, we provided a strategy of developing the specific mini-barcode using Senna as an example, and by coupling with the metabarcoding technique, it realized the qualitative and quantitative identification of processed herbal products. The plastomes of Senna obtusifolia (L.) H.S.Irwin & Barneby and Senna occidentalis (L.) Link were newly assembled, and the hypervariable coding-regions were identified by comparing their genomes. Then, the specific mini-barcodes were developed based on the identified hypervariable regions. Finally, we applied the DNA metabarcoding technique to the developed mini-barcodes. Results showed that the lengths of plastomes of S. obtusifolia and S. occidentalis were 162,426 and 159,993 bp, respectively. Four hypervariable coding-regions ycf1, rpl23, petL, and matK were identified. Two specific mini-barcodes were successfully developed from matK, and the mini-barcode of primer 647F-847R was proved to be able to qualitatively and quantitatively identify these two processed Senna seeds. Overall, our study established a valuable way to develop the specific mini-barcode, which may provide a new idea for the quality control of processed herbal products.

Analytical, Preparative, and Industrial-Scale Separation of Substances by Methods of Countercurrent Liquid-Liquid Chromatography

Countercurrent liquid-liquid chromatographic techniques (CCC), similar to solvent extraction, are based on the different distribution of compounds between two immiscible liquids and have been most widely used in natural product separations. Due to its high load capacity, low solvent consumption, the diversity of separation methods, and easy scale-up, CCC provides an attractive tool to obtain pure compounds in the analytical, preparative, and industrial-scale separations. This review focuses on the steady-state and non-steady-state CCC separations ranging from conventional CCC to more novel methods such as different modifications of dual mode, closed-loop recycling, and closed-loop recycling dual modes. The design and modeling of various embodiments of CCC separation processes have been described.

Operating mode and parameter selection in liquid-liquid chromatography

The presence of a liquid stationary phase in liquid-liquid chromatography (LLC) allows for high versatility of operation as well as adaptability to different sample types and separation tasks. LLC, also known as countercurrent chromatography (CCC) or centrifugal partition chromatography (CPC), offers the user a variety of operating modes, many of which have no direct equivalent in conventional preparative liquid-solid chromatography. These operating modes have the potential to greatly improve LLC separation performance compared to the standard "classical" isocratic batch injection mode, and they often require minimal to no addition of equipment to the standard set-up. However, reports of the use of alternative LLC operating modes make up only a fraction of the literature. This is likely due, at least in part, to the lack of clear guidelines and methods for operating mode and parameter selection, leaving alternative process options to be avoided and underutilized. This review seeks to remedy this by providing a thorough overview of the available LLC operating modes, identifying the key characteristics, advantages and disadvantages, and areas of application of each. Additionally, the equations and short-cut models aiding in operating mode and parameter selection are presented and critiqued, and their notation is unified for clarity. By rendering LLC and its alternative operating modes more accessible to current and prospective users, it is hoped to help expand the application of this technology and support the achievement of its full potential.

Modeling of closed-loop recycling dual-mode counter-current chromatography based on non-ideal recycling model

Closed-loop recycling dual-mode counter-current chromatography (CLR DM CCC) includes two separation stages: 1 - closed-loop recycling separation of solutes with mobile x-phase (CLR CCC); 2 - separation of solutes with the mobile y-phase in the opposite flow direction. Previous analysis of CLR DM CCC separations has been limited to the ideal recycling model, which neglects extra-column dispersion. In this study, the analysis of CLR CCC separations is based on the non-ideal recycling model, which takes into account the extra-column dispersion caused by the recycling system. This is of great practical importance, since by selecting the optimal parameters of the recycling system the separation can be significantly improved. Comparative analysis of CLR CCC and CLR DM CCC separations has shown that at low separations factors compounds with low partition coefficients can be separated by CLR CCC using recycling systems with a long recycling line; the separation of compounds with high partition coefficients and the separation of complex mixtures can be performed by CLR DM CCC. Simple equations for simulation and design of CLR DM CCC separations are developed. Several variants of the implementation of this separation method are discussed; examples of simulation are presented in "Mathcad" program.

Physiological, transcriptional, and metabolic alterations in spaceflight-subjected Senna obtusifolia

Senna obtusifolia is a widely used medicinal herb in Asian countries. To select elite cultivars, S. obtusifolia seeds were carried by "ShenZhou Ⅷ" recoverable satellite to space. Three spaceflight-subjected lines (SP-lines), namely QC10, QC29, QC46, and their ground control line (GC-line) were cultivated on the ground. Previous studies demonstrated that biological traits and secondary metabolites are different between SP-lines and GC-line. Here, we combined physiological, transcriptional, and metabolic studies to compare the differences between SP-lines and GC-line. The results showed that activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and monodehydroascorbate reductase (MDHAR) were dramatically increased in SP-lines as compared to that of GC-line. Transcript levels of SOD, POD, CAT, APX, and MDHAR were significantly up-regulated in SP-lines. Malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) contents decreased in SP-lines. Seed yields of QC29 and QC46 were considerably higher than that of GC-line. Besides, QC29 had significantly higher aurantio-obtusin content. Pearson correlation coefficient analysis revealed positive relationships between POD and aurantio-obtusin, as well as APX and aurantio-obtusin. In conclusion, SP-lines have higher antioxidant gene expression level and antioxidant enzyme activity as compared to that of GC-line. With higher seed yield and aurantio-obtusin content, QC29 can be used to breed elite S. obtusifolia cultivars. This study provides a new insight in SP-lines and paves the way to breed elite S. obtusifolia cultivars in the future.

Industrial countercurrent chromatography separations based on a cascade of centrifugal mixer-settler extractors

In hydrometallurgy, traditional extraction technologies, in particular, for isolation and purification of rare-earth metals include a number of processing steps using up to hundreds of mixer-settler extractors. These technologies could be greatly simplified by using the methods of countercurrent chromatography (CCC) separation. However, the current CCC equipment cannot process large volumes of feed material formed during the industrial production of these metals. In this paper, the cascade of centrifugal mixer-settler extractors assembled as a multi-stage unit is suggested for industrial application of CCC and discussed.

Identification of seeds based on molecular markers and secondary metabolites in Senna obtusifolia and Senna occidentalis

BACKGROUND

Senna obtusifolia and Senna occidentalis (Leguminosae), whose seeds have similar appearance and chemical constituents, are easily confused in using their seeds. To elucidate the similarities and differences between S. obtusifolia seeds and S. occidentalis seeds, three molecular markers and high performance liquid chromatography (HPLC) were employed to evaluate the seeds characteristics of these two medicinal herbs.

RESULTS

The results showed that selected 3 ISSR and 7 SCoT primers could distinguish S. obtusifolia seeds from S. occidentalis seeds based on the specific band and UPGMA dendrogram. ITS2 sequence indicated that the intra-specific similarity of 20 S. obtusifolia and 16 S. occidentalis was 99.79 and 100.0%, respectively, while the inter-specific similarity between S . obtusifolia and S. occidentalis was 89.58%. Although phylogenetic analysis revealed that these two species had a close relationship, they were assigned to different branches. HPLC fingerprint results showed that seeds of S. obtusifolia and S. occidentalis shared some secondary metabolites, but aurantio-obtusin was not detected in S. occidentalis seeds which could differentiate S. obtusifolia seeds from S. occidentalis seeds.

CONCLUSIONS

The present study not only compared the seeds characters of S. obtusifolia and S. occidentalis from molecular and secondary metabolites levels, but also provided a convenient method to identify S. obtusifolia seeds and S. occidentalis seeds effectively.

Countercurrent Separation of Natural Products: An Update

This work assesses the current instrumentation, method development, and applications in countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC), collectively referred to as countercurrent separation (CCS). The article provides a critical review of the CCS literature from 2007 since our last review (J. Nat. Prod. 2008, 71, 1489-1508), with a special emphasis on the applications of CCS in natural products research. The current state of CCS is reviewed in regard to three continuing topics (instrumentation, solvent system development, theory) and three new topics (optimization of parameters, workflow, bioactivity applications). The goals of this review are to deliver the necessary background with references for an up-to-date perspective of CCS, to point out its potential for the natural product scientist, and thereby to induce new applications in natural product chemistry, metabolome, and drug discovery research involving organisms from terrestrial and marine sources.

Modeling of closed-loop recycling liquid-liquid chromatography: Analytical solutions and model analysis

In closed-loop recycling (CLR) chromatography, the effluent from the outlet of a column is directly returned into the column through the sample feed line and continuously recycled until the required separation is reached. To select optimal operating conditions for the separation of a given feed mixture, an appropriate mathematical description of the process is required. This work is concerned with the analysis of models for the CLR separations. Due to the effect of counteracting mechanisms on separation of solutes, analytical solutions of the models could be helpful to understand and optimize chromatographic processes. The objective of this work was to develop analytical expressions to describe the CLR counter-current (liquid-liquid) chromatography (CCC). The equilibrium dispersion and cell models were used to describe the transport and separation of solutes inside a CLR CCC column. The Laplace transformation is applied to solve the model equations. Several possible CLR chromatography methods for the binary and complex mixture separations are simulated.