Lijuan Mei

Optimization of polysaccharides from Lycium ruthenicum fruit using RSM and its anti-oxidant activity

Dynamic microwave-assisted extraction (DMAE) technique was employed for the extraction of polysaccharides from Lycium ruthenicum (LRP). The extracting parameters were optimized by using three-variable-three-level Box-Behnken design and response surface methodology (RSM) based on the single-factor experiments. RSM analysis indicated good correspondence between experimental and predicted values. The optimum extraction parameters for the yield of polysaccharide were ratio of water to raw material 31.5 mL/g, extracting time 25.8 min and microwave power 544.0 W. Polysaccharide was analyzed by chemical methods and Fourier-transform infrared (FT-IR). The antioxidant activities of LRP were investigated including scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydrogen peroxide and free radicals of superoxide anion in vitro. The results of antioxidant activity exhibited LRP had the potential to be explored as novel natural antioxidant for using in functional foods or medicine.

Separation and purification of five phenylpropanoid glycosides from Lamiophlomis rotata (Benth.) Kudo by a macroporous resin column combined with high‐speed counter‐current chromatography

Five phenylethanoid glycosides (PhGs), forsythoside B, verbascoside, alyssonoside, isoverbascoside, and leucosceptoside B, were isolated and purified from Lamiophlomis rotata (Benth.) Kudo by high-speed counter-current chromatography (HSCCC) combined with macroporous resin (MR) column separation. In the present study, the two-phase solvent system composed of ethyl acetate/n-butanol/water (13:3:10, v/v/v) was used for HSCCC separation. A total of 27 mg of forsythoside B, 41 mg of verbascoside, 29 mg of alyssonoside, 23 mg of isoverbascoside, and 13 mg of leucosceptoside B with purities of 97.7, 99.2, 99.5, 99.3, and 97.3%, respectively, were obtained in a one-step separation within 4 h from 150 mg of crude extract. The recoveries of the five PhGs after MR-HSCCC separation were 74.5, 76.5, 72.5, 76.4, and 77.0%, respectively. The chemical structures of all five compounds were identified by (1) H and (13) C NMR spectroscopy.

Two-dimensional hydrophilic interaction chromatography × reversed-phase liquid chromatography for the preparative isolation of potential anti-hepatitis phenylpropanoids from Salvia prattii.

Traditional Tibetan medicine is important for discovery of drug precursors. However, knowledge of the chemical composition of traditional Tibetan medicines is very limited due to the lack of appropriate chromatographic purification methods. In the present work, Salvia prattii was taken as an example, and an off-line hydrophilic interaction liquid chromatography/reversed-phase liquid chromatography preparative method was developed for the purification of phenylpropanoids with high purity from a crude sample of Salvia prattii. Based on the separation results of four different chromatographic stationary phases, the first-dimensional preparation was performed on an XAmide preparative column with the crude sample concentration of 62.0 mg/mL, and five main fractions were obtained from the 12.4 g crude sample with a recovery of 54.8%. An XCharge C18 preparative column was applied in the second-dimensional preparation to further isolate the phenylpropanoids from the redissolved first-dimensional fractions with concentration of approximately 50.0 mg/mL. The purities of the phenylpropanoids isolated from the crude sample of Salvia prattii were higher than 98%, indicating that the method was efficient for the purification of phenylpropanoids with high purity from Salvia prattii. Additionally, this method showed great potential in the preparation of phenylpropanoids and can serve as a good example for the purification of phenylpropanoids from other plant materials.

Two-dimensional chromatography based on on-line HPLC-DPPH bioactivity-guided assay for the preparative isolation of analogue antioxidant compound from Arenaria kansuensis.

Traditional Tibetan medicine is important for discovery of drug precursors. However, information about the chemical composition of traditional Tibetan medicine is very limited due to the lack of appropriate chromatographic purification methods. In the present work, A. kansuensis was taken as an example and a novel two-dimensional reversed-phase/hydrophilic interaction liquid chromatography(HILIC) method based on on-line HPLC-DPPH bioactivity-guided assay was developed for the purification of analogue antioxidant compounds with high purity from the extract of A. kansuensis. Based on the separation results of many different chromatographic stationary phases, the first-dimensional (1D) preparation was carried on a RP-C18HCE prep column, and 2 antioxidant fractions were obtained from the 800mg crude sample with a recovery of 56.7%. A HILIC-XAmide prep column was selected for the second-dimensional (2D) preparation. Finally, a novel antioxidant β-carboline Alkaloids (Glusodichotomine AK) and 4 known compounds (Tricin, Homoeriodictyol, Luteolin, Glucodichotomine B) were purified from A. kansuensis. The purity of the compounds isolated from the crude extract was >98%, which indicated that the method built in this work was efficient to manufacture single analogue antioxidant compounds of high purity from the extract of A. kansuensis. Additionally, this method showed great potential in the preparation of analogue structure antioxidant compounds and can serve as a good example for the purification of analogue structure antioxidant carboline alkaloids and flavonoids from other plant materials.

Isolation and identification of antioxidant and α-glucosidase inhibitory compounds from fruit juice of Nitraria tangutorum

Nitraria tangutorum Bor., having edible berries, is valued for reputed health benefits in Qinghai-Tibet plateau. The phytochemical research on the fruit juice of N. tangutorum led to the isolation of twenty-six compounds including five new compounds, tangutorids A-D (1, 2, 3a, and 3b), and (3E,5E)-7-O-β-glucosyl-4-(2-methoxy-2-oxoethyl)hepta-3,5-dienoic acid (15). The structures of these compounds were elucidated through comprehensive spectroscopic analyses. Tangutorids A-F were the first examples of glucose-derived β-carbolines from natural products. The biogenetic pathways of 1-8 were proposed to involve Pictet-Spengler reactions and described starting from the co-isolated tryptophan (10) and corresponding aldehydes. All isolates were evaluated for their antioxidant and α-glucosidase inhibitory activities. Compounds 21, 22, and 24 showed antioxidant activity with SC50 values ranging from 12.2±1.9 to 30.4±2.7μg/mL, and compound 1 showed strong α-glucosidase inhibitory effect with IC50 value of 63.3±4.6μg/mL.

Isolation and Identification of Saponins from the Natural Pasturage Asterothamnus centrali-asiaticus Employing Preparative Two-Dimensional Reversed-Phase Liquid Chromatography/Hydrophilic Interaction Chromatography

Asterothamnus centrali-asiaticus, a kind of characteristic shrub abundant in grassland and desert areas, has been used as forage fodder for camels and goats in Central Asia, and this plant also plays a critical role in the maintenance of desert grassland ecosystems as a result of its tolerance to poor soils and sand burial. However, its chemical composition has been rarely reported. In this study, phytochemical investigation of this pasturage was performed and three new triterpenoid saponins (1-3) were isolated together with nine known triterpenoid saponins (4-12) using preparative two-dimensional reversed-phase liquid chromatography/hydrophilic interaction chromatography (2D RPLC/HILIC). Their structures were elucidated via diverse spectroscopic analyses, including infrared (IR) spectrometry, high-resolution electrospray ionization mass spectrometry (HR-ESIMS), and one-dimensional (1D) and 2D nuclear magnetic resonance (NMR). All isolated triterpenoid saponins (1-12) were reported from this genus for the first time, and they were further evaluated for their cytotoxicity against four cancer cell lines (A549, HepG2, MGC-803, and MFC), which indicated that compound 11 showed potent cytotoxicity against the HepG2 cell line, with an IC50 value of 6.85 μg/mL.

Anti-inflammatory bioactive equivalence of combinatorial components β-carboline alkaloids identified in Arenaria kansuensis by two-dimensional chromatography and solid-phase extraction coupled with liquid–liquid extraction enrichment technology

Bioactive equivalent combinatorial components play a critical role in herbal medicines. However, how to discover and enrich them efficiently is a question for herbal pharmaceuticals researchers. In our work, a novel two-dimensional reversed-phase/hydrophilic interaction high-performance liquid chromatography method was established to perform real-time components trapping and combining for preparation and isolation of coeluting components. Arenaria kansuensis was taken as an example, and solid-phase extraction coupled with liquid-liquid extraction as a simple and efficient method for enriching trace components, reversed phase column coupled with hydrophilic interaction liquid chromatography XAmide column as two-dimensional chromatography technology for isolation and preparation of coeluting constituents, enzyme-linked immune-sorbent assay as bio-guided assay, and anti-inflammatory bioactivity evaluation for bioactive constituents. A combination of 12 β-carboline alkaloids was identified as anti-inflammatory bioactive equivalent combinatorial components from A. kansuensis, which accounts for 1.9% w/w of original A. kansuensis. This work answers the key question of which are real anti-inflammatory components from A. kansuensis and provides a fast and efficient approach for discovering and enriching trace β-carboline alkaloids from herbal medicines for the first time. More importantly, the discovery of bioactive equivalent combinatorial components could improve the quality control of herbal products and inspire a herbal medicine based on combinatorial therapeutics.

Highly efficient TfOH-catalyzed head-to-tail dimerization of vinylarenes

ABSTRACT A convenient and efficient TfOH-catalyzed head-to-tail dimerization of vinylarenes has been realized under mild conditions. The present protocol provides an attractive approach to a diverse range of higher olefins in good to excellent yields. GRAPHICAL ABSTRACT

A new isocoumarin from the aerial parts of Aconitum gymnandrum.

Abstract A new isocoumarin, along with 10 known compounds, was isolated from the aerial parts of Aconitum gymnandrum. Their structures were elucidated by spectroscopic methods including extensive 1D and 2D NMR techniques. Among the known compounds, compound 11 was obtained as a natural product for the first time, which was previously reported as a synthetic product. In addition, compounds 1–5, 7 and 9 were tested for their cytotoxicity against four human cancer cell lines. The results showed that compounds 3, 4 and 7 displayed cytotoxicity against lung cancer A549 and gastric cancer MGC80, respectively, whereas 5 and 9 showed selective cytotoxicity against hepatocellular carcinoma HepG2.

The influence of organic sample solvents on the separation efficiency of basic compounds under strong cation exchange mode.

This study investigated the influence of organic sample solvents on separation efficiency of basic compounds under strong cation exchange (SCX) mode. The mixtures of acidic aqueous solution and organic solvent such as acetonitrile, ethanol, methanol and dimethyl sulfoxide (DMSO) were tested as sample solvents. For later-eluting analytes, the increase of sample solvent elution strength was responsible for the decrease of separation efficiency. Thus, sample solvents with weak elution strength could provide high separation efficiencies. For earlier-eluting analytes, the retention of organic sample solvents was the main factor affecting separation efficiency. Weakly retained solvents could provide high separation efficiency. In addition, an optimized approach was proposed to reduce the effect of organic sample solvent, in which low ionic solvent was employed as initial mobile phase in the gradient. At last, the analysis of impurities in hydrophobic drug berberine was performed. The results showed that using acidic aqueous methanol as sample solvents could provide high separation efficiency and good resolution (R>1.5).