Online isolation and purification of four phthalide compounds from Chuanxiong rhizoma using high-speed counter-current chromatography coupled with semi-preparative liquid chromatography

Optimisation of isolation of polyphenols from Malus pumila Mill. Leaves by high-speed countercurrent chromatography using response surface methodology

Considering comprehensive utilization of natural products, isolation and activity determination processes of bioactive compounds are essential. In this study, a combined high-speed countercurrent chromatography (HSCCC) with preparative HPLC method was developed to isolate the five antioxidant polyphenols from 75% ethanol extract of Malus pumila Mill. leaves. The HSCCC conditions were optimized by response surface methodology (RSM) considering two response indexes including retention of stationary phase and analysis time. The optimal HSCCC conditions were flow rate of 2.11 mL/min, revolution speed of 717 rpm, and temperature of 25℃, with a solvent system of ethyl acetate/methanol/water (10:1:10, v/v/v). The unseparated fractions obtained from HSCCC were subjected to preparative HPLC for further isolation. As a result, phloridzin (15.3 mg), isoquercitrin (2.1 mg), quercetin 3-O-xyloside (1.9 mg), quercetin-3-O-arabinoside (4.0 mg), and quercitrin (2.0 mg) were isolated from 200.0 mg extracts. The purities of these compounds were all above 92%. Their chemical structures were identified by mass spectrometer and nuclear magnetic resonance. The five isolated compounds were further investigated for their rat hippocampal neuroprotective effects against hydrogen peroxide-induced oxidative stress. No cytotoxicity was observed in all tested concentrations. While all five compounds except phloridzin showed significantly neurogenic activities and neuroprotective effects, especially at the concentration of 0.5 mg/L. These results demonstrate that RSM is a suitable technique for optimisation of HSCCC and the isolated polyphenols can be used as antioxidants in pharmaceutical and food products.

Structurally diverse phthalides from fibrous roots of Ligusticum chuanxiong Hort. and their biological activities

Falonolide A (1) and B (2), two novel polyyne hybrid phthalides resulting from unprecedented carbon skeleton polymerized by Z-ligustilide and falcarindiol, along with six new related phthalides (3-8), were isolated from Ligusticum chuanxiong Hort. Their structures were elucidated by spectroscopic analysis, computer-assisted structure elucidation (CASE) analysis, DP4+ probability analysis and electronic circular dichroism (ECD) calculations. A plausible biosynthetic pathway for 1-8 was proposed, and the production mechanism of 2 was revealed by density functional theory (DFT) method. Compounds 4 and 6 exhibited significant vasodilatory activity with EC50 of 8.00 ± 0.86 and 6.92 ± 1.02 μM, respectively. Compound 4 also displayed significant inhibitory effect of NO production with EC50 value of 8.82 ± 0.30 μM. Based on the established compounds library, structure-activity relationship analysis of phthalides was explored to provide insights into the drug development of vasodilators and anti-flammatory.

Alkylphthalides with intracellular triglyceride metabolism-promoting activity from the rhizomes of Cnidium officinale Makino

Methanol extract of the Cnidium officinale Makino rhizome, which is used as a crude drug Cnidium Rhizome (Cnidii Rhizoma; "Senkyu" in Japanese) and is listed in the Japanese Pharmacopoeia XVIII, showed intracellular triglyceride metabolism-promoting activity in high glucose-pretreated HepG2 cells. Thirty-five constituents, including two new alkylphthalide glycosides, senkyunosides A (1) and B (2), and a neolignan with a new stereoisomeric structure (3), were isolated in the extract. Their stereostructures were elucidated based on chemical and spectroscopic evidence. Among the isolates, several alkylphthalides, (Z)-3-butylidene-7-methoxyphthalide (9) and senkyunolides G (10), H (14), and I (15), and a polyacetylene falcarindiol (26), were found to show significant activity without any cytotoxicity at 10 μM.

Multi-dimensional preparation of Thymus quinquecostatus Celak. by normal-phase flash chromatography coupled to counter-current chromatography

In this study, a multi-dimensional chromatography system was developed by integrating normal-phase flash chromatography and counter-current chromatography to isolate flavonoids, phenylpropanoids, and thymol from the aerial parts of Thymus quinquecostatus Celak. In the online multi-dimensional switching system, a normal-phase flash chromatograph packed with 1.2 g of dry homogeneous silica gel mixture (containing 600 mg of methanol extract) was connected to counter-current chromatography via a six-port valve. Two two-dimensional separations were performed using n-heptane-ethyl acetate-methanol-water (6:4:6:4, v/v) and ethyl acetate-water solvent systems sequentially to separate the constituents of Thymus quinquecostatus Celak. The upper phase of the former solvent system was utilized as both elution solvent for flash chromatography and the stationary phase for counter-current chromatography, while the lower phase of the latter solvent system containing 10 mM trifluoroacetic acid was employed as elution solvent for flash chromatography and one mobile phase in pH gradient counter-current chromatography. Thymol (7) and xanthomicrol (8), two hydrophobic ingredients, were purified in the initial two-dimensional separation. The subsequent two-dimensional separation yielded six hydrophilic compounds, namely dihydrokaempferol-7-O-D-glucopyranoside (1), lithospermic acid (2), luteolin-7-O-glucuronide (3), rosmarinic acid (4), messerschmidin (5) and apigenin-7-O-D-glucuronide (6). This study represents the first documented use of online multi-dimensional normal-phase flash chromatography coupled to counter-current chromatography for separating constituents from Thymus quinquecostatus Celak.

Levistolide A ameliorates fibrosis in chronic kidney disease via modulating multitarget actions in vitro and in vivo

AIMS

The increasing incidence of chronic kidney disease (CKD) urgently calls for effective nephroprotective agents. Traditional Chinese Medicine Angelica sinensis and its formula are well known for CKD therapy, but the underlying mechanisms and effective substances of reno-protective effects remain unclear. To this end, we isolated eleven ligustilide dimers (1-11) from A. sinensis and examined the molecular mechanism of their nephroprotective effects.

MAIN METHODS

Because of internal RAS playing an important role in CKD, we used renin expression as a target and screened preliminarily for antifibrotic effects of ligustilide dimers (1-11) by constructing a dual luciferase reporter gene in vitro. Furthermore, the reno-protective effects of the ligustilides and their underlying mechanism were investigated in TGF-β1-stimulated HK-2 cells and 5/6 nephrectomy (Nx) mice.

KEY FINDINGS

The ligustilide dimers exhibited anti-fibrotic effects by inhibiting human renin (hREN) promoter activity to decrease renin expression and down-regulate the expression of fibrosis-related factors, including α-SMA, collagen I, and fibronectin in vitro. Levistolide A (LA) and angeolide keto ester (AK) were screened out to identify their ability and underlying mechanism for treating CKD. Experimental validation further indicated that LA or AK treatment inhibited the expression of key molecules in RAS, TGF-β1/Smad, and MAPK pathways to downregulate ECM deposition. Furthermore, LA obviously meliorated renal injury in 5/6 Nx mice through ameliorating oxidant stress, inflammation, apoptosis and renal fibrosis.

SIGNIFICANCE

The experimental results demonstrated that ligustilide dimers were potential nephroprotective agents. LA might be an attractive drug candidate for renin-targeted CKD therapy.

A novel online preparative high-performance liquid chromatography system with the multiple trap columns-valve switch technique for the rapid and efficient isolation of main flavonoids from Epimedium koreanum Nakai

In this work, a new online preparative high-performance liquid chromatography was developed for the fast and efficient separation of complex chemical mixtures from natural products. This system integrates two chromatographic systems into an online automatic separation system using the technique of multiple trap columns with valve switching. The sample was first separated into 18 subfractions in the online preparative high-performance liquid chromatography, and the sample eluents were then diluted and captured online on 18 trap columns by the multiple trap columns technique, respectively. Each subfraction retained on the trap column was transferred online to the separation column for the second separation. Finally, the target compounds were purified by appropriate separation conditions and multiple heart-cutting strategies. Importantly, the system was successfully used to separate 18 high-purity flavonoids from the crude extract of Epimedium koreanum Nakai online in one step. The entire separation time was approximately 20 h, and the structures were characterized by the high-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry and nuclear magnetic resonance. This online preparative high-performance liquid chromatography system represents an efficient and rapid separation system that has the potential for a wide array of applications in the separation of complex chemical components from natural products.

Recent advancements in synthetic methodologies of 3-substituted phthalides and their application in the total synthesis of biologically active natural products

We have provided a critical review that focuses on key developments in the area of 3-substituted phthalides and their role in the development of important biologically active natural products. 3-Substituted phthalides are vital molecules owing to their fascinating biological activity. The scope, isolation, and characterization of various naturally occurring racemic and chiral 3-substituted phthalides have been covered. We have put significant emphasis on recently developed research methodologies for the synthesis of racemic and chiral 3-substituted phthalides. These newer approaches are essential for the development of newer and elegant strategies for the synthesis of phthalide-based or similar molecular architecture with broader substrate scope and higher stereoselectivities. Also, we have discussed the application of 3-substituted phthalides as a precursor for the synthesis of natural products and their analogs.

We have provided contextual information on the chemistry of 3-substituted phthalides and their significance in natural product synthesis.

Separation of six compounds from pigeon pea leaves by elution-extrusion counter-current chromatography

A valid and reliable method was established to separate six compounds from pigeon pea leaves via elution-extrusion counter-current chromatography. A solvent system composed of n-hexane/methanol/formic acid aqueous solution with pH = 3 (10:6:4, v/v) was screened to achieve satisfactory isolation from the ethanol extract of pigeon pea leaves. Four compounds, 9.2 mg of compound 1 (96.8%), 3.2 mg of 2 (88.0%), 6.2 mg of 4 (94.2%) and 25.2 mg of 5 (94.2%), were obtained by conventional elution from 100 mg of the precipitation fraction, respectively. Two compounds, 14.4 mg of 3 (96.3%) and 28.1 mg of 6 (96.6%), with high K values were obtained by the subsequent extrusion procedure. The compounds 1-6 were identified as 3-methoxy-5-(2-phenylethenyl)-phenol, pinostrobin chalcone, pinostrobin, 2-hydroxy-4-methoxy-6-(2-phenylvinyl)-benzoic acid, longistylin C and cajaninstilbene acid by quadrupole time-of-flight mass spectrometry, and 1 H and 13 C NMR spectroscopy. The in vitro antiproliferation activities of compounds 1, 5 and 6 against human hepatoma cell were evaluated and the half-maximum inhibitory concentrations were acquired.

Purified Phlorizin from DocynIa Indica (Wall.) Decne by HSCCC, Compared with Whole Extract, Phlorizin and Non-Phlorizin Fragment Ameliorate Obesity, Insulin Resistance, and Improves Intestinal Barrier Function in High-Fat-Diet-Fed Mice

Natural products generally contain complex and multiple bioactive compounds that are responsible for the effects on health through complicated synergistic and/or suppressive actions. As an important raw material of local ethnic minority tea, ethnomedicines and food supplements in southwestern areas of China, Docynia indica (Wall.) Decne (DID) mainly consists of phlorizin (PHZ), which is the main active component. In this study, the holistic activities and the interactions of components of PHZ, non-phlorizin (NP) in the DID extract (DIDE) were evaluated. A rapid and effective high-speed counter-current chromatography (HSCCC) was performed to knock out PHZ from DIDE and the purity of PHZ was 96.01% determined by HPLC, with a recovery rate of 96.76%. After 13 weeks of treatment course in a high-fat diet (HFD)-induced obese mice model, the results revealed that the DIDE and PHZ significantly decreased weight gain, blood lipid levels, hyperplasia of adipocytes and alleviated inflammation (p < 0.05). Both DIDE and PHZ improves insulin resistance (p < 0.001). Meanwhile, the intestinal barrier function was improved compared to HFD group, through the determination of serum lipopolysaccharides (LPS), glucagon-likepeptide-2 (GLP-2) and hematoxylin-eosin staining of jejunum. Interestingly, after NP treatment, the metabolic syndrome of the HFD-induced obesity appeared to have a similar improvement. All the experiments showed that there is a synergistic weakening phenomenon when PHZ and NP interact with each other in the mixed state. In conclusion, for the PHZ and NP showing a good effect on anti-obesity, anti-inflammation, and intestinal barrier function, DIDE could be a good source of functional food to prevent obesity.

Integrated Metabolomics and Network Pharmacology Approach to Explain Possible Action Mechanisms of Xin-Sheng-Hua Granule for Treating Anemia

As a well-known traditional Chinese medicine (TCM) prescription, Xin-Sheng-Hua Granule (XSHG) has been applied in China for more than 30 years to treat postpartum diseases, especially anemia. However, underlying therapeutic mechanisms of XSHG for anemia were still unclear. In this study, plasma metabolomics profiling with UHPLC-QTOF/MS and multivariate data method was firstly analyzed to discover the potential regulation mechanisms of XSHG on anemia rats induced by bleeding from the orbit. Afterward, the compound-target-pathway network of XSHG was constructed by the use of network pharmacology, thus anemia-relevant signaling pathways were dissected. Finally, the crucial targets in the shared pathways of metabolomics and network pharmacology were experimentally validated by ELISA and Western Blot analysis. The results showed that XSHG could exert excellent effects on anemia probably through regulating coenzyme A biosynthesis, sphingolipids metabolism and HIF-1α pathways, which was reflected by the increased levels of EPOR, F2, COASY, as well as the reduced protein expression of HIF-1α, SPHK1, and S1PR1. Our work successfully explained the polypharmcological mechanisms underlying the efficiency of XSHG on treating anemia, and meanwhile, it probed into the potential treatment strategies for anemia from TCM prescription.

Toward rapid analysis, forecast and discovery of bioactive compounds from herbs by jointly using thin layer chromatography and ratiometric surface-enhanced Raman spectroscopy technique

Conventional isolation and identification of active compounds from herbs have been extensively reported by using various chromatographic and spectroscopic techniques. However, how to quickly discover new bioactive ingredients from natural sources still remains a challenging task due to the interference of their similar structures or matrices. Here, we present a grand approach for rapid analysis, forecast and discovery of bioactive compounds from herbs based on a hyphenated strategy of thin layer chromatography and ratiometric surface-enhanced Raman spectroscopy. The performance of the hyphenated strategy is first evaluated by analyzing four protoberberine alkaloids, berberine (BER), coptisine (COP), palmatine (PAT) and jatrorrhizine (JAT), from a typical herb Coptidis Rhizoma as an example. It has been demonstrated that this coupling method can identify the four compounds by characteristic peaks at 728, 708, 736 and 732 cm^-1, and especially discriminate BER and COP (with similar migration distances) by ratiometric Raman intensity (I₇₀₈/I₇₂₈). The corresponding limits of detection are 0.1, 0.05, 0.1 and 0.5 μM, respectively, which are about 1-2 orders of magnitude lower than those of direct observation method under 254 nm UV lamp. Based on these findings, the proposed method further guides forecast and discovery of unknown compounds from traditional Chinese herb Typhonii Rhizoma. Results infer that two trace alkaloids (BER and COP) from the n-butanol extract of Typhonii Rhizoma are found for the first time. Moreover, in vitro experiments manifest that BER can effectively decrease the viability of human glioma U87 cells by inducing cell cycle arrest in a concentration-dependent manner.

Preparative isolation, quantification and antioxidant activity of dihydrochalcones from Sweet Tea (Lithocarpus polystachyus Rehd.)

Dihydrochalcones are the main active components of Lithocarpus polystachyus Rehd. (Sweet Tea), they are directly related to the sweet tonic beverage and traditional herb. In this work, two runs of preparative high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane/ethyl acetate/ethanol/water (1:4:3:4, v/v) were employed to separate three dihydrochalcones (phloridzin, trilobatin and phloretin) from Sweet Tea. About 6.4mg of phloridzin, 48.4mg of trilobatin, and 4.7mg of phloretin with purities of 96.7%, 98.4% and 98.1% were obtained from 130mg of the crude Sweet Tea extract. Phloridzin, trilobatin, and phloretin had effective radical scavenging activities, with IC50 values of 866.80, 20.16 and 179.47μg/mL, respectively, in a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical method. The contents of phloridzin, trilobatin and phloretin in dried old leaves and tender leaves of tea were in the range of 10.1-18.0, 113.7-128.8, 3.6-4.3mg/g and 9.3-9.8, 82.9-103.1, 1.9-2.5mg/g, respectively. The results indicated that the HPLC had good precision, accuracy and repeatability for the determination of three dihydrochalcones in samples.

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.

Preparative isolation and purification of urolithins from the intestinal metabolites of pomegranate ellagitannins by high-speed counter-current chromatography

Urolithins were separated from the intestinal metabolites of pomegranate ellagitannins by high-speed counter current chromatography in two steps using two solvent systems composed of n-hexane-ethyl acetate-methanol-acetic acid-water (2.5:2:0.25:5, v/v/v/v/v) and n-hexane-ethyl acetate-methanol-acetic acid-water (2.5:0. 8:0.25:5, v/v/v/v/v) for the first time. Each injection of 100mg extract yielded 21mg of pure urolithin A and 10mg of pure urolithin B. High-performance liquid chromatography analyses revealed that the purity of urolithin A and urolihtin B was over 98.5%. The structures of urolithin A and urolitihn B were identified by high resolution-MS, NMR and single crystal x-ray analysis. Urolithins reduced the oxidative stress status in colon cancer by decreasing the intracellular ROS and malondialdehyde levels, and increasing SOD activity in H2O2 treated Caco-2 cells.

High-speed counter-current chromatography coupled online to high performance liquid chromatography-diode array detector-mass spectrometry for purification, analysis and identification of target compounds from natural products

A challenge in coupling high-speed counter-current chromatography (HSCCC) online with high performance liquid chromatography (HPLC) for purity analysis was their time incompatibility. Consequently, HSCCC-HPLC was conducted by either controlling HPLC analysis time and HSCCC flow rate or using stop-and-go scheme. For natural products containing compounds with a wide range of polarities, the former would optimize experimental conditions, while the latter required more time. Here, a novel HSCCC-HPLC-diode array detector-mass spectrometry (HSCCC-HPLC-DAD-MS) was developed for undisrupted purification, analysis and identification of multi-compounds from natural products. Two six-port injection valves and a six-port switching valve were used as interface for collecting key HSCCC effluents alternatively for HPLC-DAD-MS analysis and identification. The ethyl acetate extract of Malus doumeri was performed on the hyphenated system to verify its efficacy. Five main flavonoids, 3-hydroxyphloridzin (1), phloridzin (2), 4',6'-dihydroxyhydrochalcone-2'-O-β-D-glucopyranoside (3, first found in M. doumeri), phloretin (4), and chrysin (5), were purified with purities over 99% by extrusion elution and/or stepwise elution mode in two-step HSCCC, and 25mM ammonium acetate solution was selected instead of water to depress emulsification in the first HSCCC. The online system shortened manipulation time largely compared with off-line analysis procedure and stop-and-go scheme. The results indicated that the present method could serve as a simple, rapid and effective way to achieve target compounds with high purity from natural products.

Gas chromatography-mass spectrometry and high-performance liquid chromotagraphy analysis of the drug absorption characteristics in the buccal mucosa via a circulating device

The aim of the present study was to investigate the characteristics of Su Xiao Jiu Xin dripping pill absorption in the buccal mucosa of healthy volunteers. This pill is a traditional Chinese medicine that is widely used as an emergency treatment for cardiovascular and cerebrovascular diseases. It is sublingually administered and can be absorbed in the buccal mucosa. In the present study, a method was developed to investigate the absorption characteristics in the buccal mucosa of healthy volunteers via a circulating device by gas chromatography-mass spectrometry and high-performance liquid chromatography. The five main efficacy components associated with cardiovascular and cerebrovascular diseases, which are borneol, isoborneol, ligustilide, n-butylphthalide and ferulic acid, were detected and rapidly absorbed. Among these components, four exhibited good absorption, thus confirming that the method developed is efficient for analysis of the absoption characteristics.

Two-dimensional countercurrent chromatography × high performance liquid chromatography for preparative isolation of toad venom

In this work, a new on-line two-dimensional chromatography coupling of flow programming counter-current chromatography and high-performance liquid chromatography (2D CCC×HPLC) was developed for preparative separation of complicated natural products. The CCC column was used as the first dimensional isolation and a preparative ODS column operated in reversed-phase (RP) mode as the second dimension. The CCC was operated at a controlled flow rate to ensure that each fraction eluted within one hour, corresponding to the isolation time of the 2nd dimensional preparative HPLC. The eluent from the 1st dimensional CCC was diluted using a makeup pump and trapped onto holding column, before been eluted and transferred to the 2nd dimensional HPLC. The performance of the holding column was evaluated, in terms of column size, dilution ratio and diameter-height ratio, as well as system pressure, for the solution to the issue of online trapping of low pressure eluent from a CCC column. Satisfactory trapping efficiency and tolerable CCC pressure can be achieved using a commercially available 15mm×30mm i.d. ODS pre-column. The present integrated system was successfully applied in a one-step preparative separation of 12 compounds, from the crude methanol extract of venom of Bufo bufo gargarizans. Compounds 1-12 were isolated in overall yield of 1.0%, 0.8%, 2.0%, 1.3%, 2.0%, 1.5%, 1.9%, 3.6%, 6.1%, 4.8%, 3.5% and 4.1%, with HPLC purity of 99.9%, 99.7%, 90.6%, 99.9%, 77.0%, 99.9%, 90.4%, 99.9%, 52.0%, 99.9%, 99.3%, and 85.0%, respectively. All the results demonstrate that the flow programming CCC×HPLC method is an efficient and convenient way for the separation of compounds from toad venom and it can also be applied to isolate other complex multi-component natural products.