Preparation of flavone di-C-glycoside isomers from Jian-Gu injection (Premna fulva Craib.) using recycling counter-current chromatography

Target-Guided Isolation and Purification of Antioxidants from Urtica laetevirens Maxim. by HSCCC Combined with Online DPPH-HPLC Analysis

Urtica laetevirens Maxim. is used extensively in traditional Chinese medicine (TCM) for its potent antioxidative properties. In this study, three antioxidants were purified from U. laetevirens. using HSCCC guided by online DPPH-HPLC analysis. Firstly, the online DPPH-HPLC analysis was performed to profile out the antioxidant active molecules in U. laetevirens. The ultrasonic-assisted extraction conditions were optimized by response surface methodology and the results showed the targeted antioxidant active molecules could be well enriched under the optimized extraction conditions. Then, the antioxidant active molecules were separated by high-speed countercurrent chromatography ethyl acetate/n-butanol/water (2:3:5, v/v/v) as the solvent system. Finally, the three targets including 16.8 mg of Isovitexin, 9.8 mg of Isoorientin, and 26.7 mg of Apigenin-6,8-di-C-β-d-glucopyranoside were obtained from 100 mg of sample. Their structures were identified by 1H NMR spectroscopy.

Recent Advances on Natural Aryl-C-glycoside Scaffolds: Structure, Bioactivities, and Synthesis-A Comprehensive Review

Aryl-C-glycosides, of both synthetic and natural origin, are of great significance in medicinal chemistry owing to their unique structures and stability towards enzymatic and chemical hydrolysis as compared to O-glycosides. They are well-known antibiotics and potent enzyme inhibitors and possess a wide range of biological activities such as anticancer, antioxidant, antiviral, hypoglycemic effects, and so on. Currently, a number of aryl-C-glycoside drugs are on sale for the treatment of diabetes and related complications. This review summarizes the findings on aryl-C-glycoside scaffolds over the past 20 years, concerning new structures (over 200 molecules), their bioactivities-including anticancer, anti-inflammatory, antioxidant, antivirus, glycation inhibitory activities and other pharmacological effects-as well as their synthesis.

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.

Vicenin 3 ameliorates ECM degradation by regulating the MAPK pathway in SW1353 chondrocytes

Aberrant destruction of the articular extracellular matrix (ECM) has been considered to be one of the pathological features of osteoarthritis (OA) which results in chondrocyte changes and articular cartilage degeneration. The MAPK signaling pathway serves a key role by releasing cartilage-degrading enzymes from OA chondrocytes. However, the use of MAPK inhibitors for OA is hindered by their potential long-term toxicity. Vicenin 3 is one of the major components of the Jian-Gu injection which is effective in the clinical treatment of OA. However, its potential impact on OA remain poorly understood. Therefore, the present study aimed to assess the effects of vicenin 3 on interleukin (IL)-1β-treated SW1353 chondrocytes, which mimic the microenvironment of OA. These chondrocytes were pretreated with vicenin 3 (0, 5 and 20 µM) for 1 h and subsequently stimulated with IL-1β (10 ng/ml) for 24 h. Nitric oxide (NO) production was measured using the Griess reaction, whereas the production of prostaglandin E2 (PGE2), matrix metalloproteinases (MMPs), A disintegrin-like and metalloproteinase with thrombospondin motifs (ADAMTSs), collagen type II and aggrecan were measured using ELISA. The mRNA expression of MMPs and ADAMTSs were measured using reverse transcription-quantitative PCR. The protein expression levels of MAPK were measured using western blotting. Vicenin 3 was found to significantly inhibit IL-1β-induced production of NO and PGE. Increments in the expression levels of MMP-1, MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5 induced by IL-1β, in addition to the IL-1β-induced degradation of collagen type II and aggrecan, were all reversed by vicenin 3 treatment. Furthermore, vicenin 3 suppressed IL-1β-stimulated MAPK activation, an effect that was similar to that exerted by SB203580, a well-known p38 MAPK inhibitor. In conclusion, vicenin 3 may confer therapeutic potential similar to that of the p38 MAPK inhibitor for the treatment of OA.

Preparative separation and purification of Cyclosporin D from fungus Hypoxylon Spp. by improved closed-loop recycling counter-current chromatography

Improved closed-loop recycling counter-current chromatography (CLR CCC) with a two-phase solvent system composed of n-hexane-acetonitrile (1:1, v/v) was developed for separation, purification and preparation of cyclosporin D from the crude extract of fungus Hypoxylon Spp. (sj18). 28 mg cyclosporin D was successfully purified from 300 mg crude extract sample. The purity was 95.2% after five cycles, determined by HPLC. The structure of cyclosporin D was identified and assigned by ¹H NMR, ¹³C NMR and mass spectrometric analyses. In addition, in the study, we show an interesting phenomenon that cyclosporin D can be prepared by the conventional CCC in n-hexane-ethyl acetate-methanol-water solvent system (2.5:1:2.5:1, v/v/v/v), and can also be prepared by the improved closed-loop recycling CCC in n-hexane-acetonitrile solvent system (1:1, v/v), but the efficiency of preparation varies greatly.

Enzymatic basis for stepwise C-glycosylation in the formation of flavonoid di-C-glycosides in sacred lotus (Nelumbo nucifera Gaertn.)

Lotus plumule, the embryo of the seed of the sacred lotus (Nelumbo nucifera), contains a high accumulation of secondary metabolites including flavonoids and possesses important pharmaceutical value. Flavonoid C-glycosides, which accumulate exclusively in lotus plumule, have attracted considerable attention in recent decades due to their unique chemical structure and special bioactivities. As well as mono-C-glycosides, lotus plumule also accumulates various kinds of di-C-glycosides by mechanisms which are as yet unclear. In this study we identified two C-glycosyltransferase (CGT) genes by mining sacred lotus genome data and provide in vitro and in planta evidence that these two enzymes (NnCGT1 and NnCGT2, also designated as UGT708N1 and UGT708N2, respectively) exhibit CGT activity. Recombinant UGT708N1 and UGT708N2 can C-glycosylate 2-hydroxyflavanones and 2-hydroxynaringenin C-glucoside, forming flavone mono-C-glycosides and di-C-glycosides, respectively, after dehydration. In addition, the above reactions were successfully catalysed by cell-free extracts from tobacco leaves transiently expressing NnCGT1 or NnCGT2. Finally, enzyme assays using cell-free extracts of lotus plumule suggested that flavone di-C-glycosides (vicenin-1, vicenin-3, schaftoside and isoschaftoside) are biosynthesized through sequentially C-glucosylating and C-arabinosylating/C-xylosylating 2-hydroxynaringenin. Taken together, our results provide novel insights into the biosynthesis of flavonoid di-C-glycosides by proposing a new biosynthetic pathway for flavone C-glycosides in N. nucifera and identifying a novel uridine diphosphate-glycosyltransferase (UGT708N2) that specifically catalyses the second glycsosylation, C-arabinosylating and C-xylosylating 2-hydroxynaringenin C-glucoside.

Chromatographic behavior of six lanthanides on a centrifugal mixer-settler extractor cascade

This work furthers the development of counter-current chromatography as an industrial separation process method. It was demonstrated that the industrial counter-current chromatography methods, in particular, for the separation groups of rare earth metals, can be implemented in a modified cascade of centrifugal mixer-settler extractors. The retention behavior of rare earth elements (samarium, europium, gadolinium, terbium, dysprosium and yttrium) on the pilot chromatographic unit consisting of 70 serially connected centrifugal mixer-settler extractors was experimentally studied under isocratic elution conditions using the mixture of 30 vol.% Cyanex^Ⓡ572 + 10 vol.% tributylphosphate in a hydrocarbon diluent as the stationary phase and aqueous nitric acid as the mobile phase. Theoretical analysis of experimental studies showed an acceptable agreement between the assumptions of the theory and experimental results.

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.

Optimization Studies on the Extraction of Flavone Di-C-glycosides from Premna fulva Craib by Deep Eutectic Solvents

Deep eutectic solvents (DESs) are emerging as new extraction solvents for the extraction of bioactive compounds from natural plants. In this work, a total of thirteen choline chloride-based DESs were synthesized and evaluated for the simultaneous extraction of five bioactive flavone di-C-glycosides from Premna fulva Craib. DES-F, which was composed of choline chloride and 1,3-propanediol, showed the best extraction efficiency for the flavone di-C-glycosides, exceeding that of the conventional industrial solvent (40% ethanol). Subsequently, the extraction parameters for ultrasonic-assisted extraction (liquid-solid ratio, water content (%) in the selected DES, and extraction time) were optimized using response surface methodology. Furthermore, the microstructural alterations in the samples after extraction were evaluated using scanning electron microscopy. In addition, we further verified the recovery of flavone di-C-glycosides from the DESs using macroporous resins and evaluated the reusability of the DESs as solvents. The results indicated that DES-F was an efficient and sustainable solvent for the extraction of bioactive flavone di-C-glycosides from Premna fulva Craib. Therefore, this novel strategy may represent a sustainable approach for the extraction of bioactive products and could make phytochemistry more attractive and environmentally friendly.

The 10th international conference on countercurrent chromatography held at Technische Universität Braunschweig, Braunschweig, Germany, August 1-3, 2018

The 10th International Countercurrent Chromatography Conference (CCC 2018) was held at Technische Universität Braunschweig, Germany, from August 1st-3rd, 2018. The presentations in the scientific program demonstrated the progress in the field of countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC) in recent years and numerous applications have impressively proven the potential of this all-liquid separation technique not only for academic research but also for industry. Special highlights of the conference were the celebration of the 90th birthday of Dr. Yoichiro Ito, the pioneer of countercurrent chromatography, as well as the foundation of an international "Society of Partition and Countercurrent Chromatography (SPCC)".