Huilan Yue

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.

Separation and purification of water-soluble iridoid glucosides by high speed counter-current chromatography combined with macroporous resin column separation

Four iridoid glucosides, shanzhiside methyl ester, phloyoside II, chlorotuberside, and penstemonoside, were isolated and purified from an herbal medicinal plant for the first time by high-speed counter-current chromatography (HSCCC) using a two-phase solvent system composed of ethyl acetate-n-butanol-water (5:14:12, v/v/v). A total of 37mg of shanzhiside methyl ester, 29mg of phloyoside II, 27mg of chlorotuberside, and 21mg of penstemonoside with the purity of 99.2%, 98.5%, 97.3%, and 99.3%, respectively, were obtained in one-step separation within 4h from 150mg of crude extract. To the best of our knowledge, this is the first report of separation and purification of iridoid glucosides from natural sources by HSCCC. The chemical structures of all the four compounds were identified by ESI-MS, (1)H NMR, and (13)C NMR.

Metal-free Oxidative Coupling of Aromatic Alkenes with Thiols Leading to (E)-Vinyl Sulfones

A facile I2O5-mediated direct oxidative coupling of aromatic alkenes with thiols toward vinyl sulfones has been developed under metal-free conditions. This methodology provides a convenient and efficient approach to various (E)-vinyl sulfones from readily available starting materials with excellent regioselectivity. The present oxidative coupling reaction, not only expands the scope of functionalization of alkenes with thiols, but also makes it a practical and powerful complement to traditional methods for the synthesis of (E)-vinyl sulfones.

Visible-light-enabled spirocyclization of alkynes leading to 3-sulfonyl and 3-sulfenyl azaspiro[4,5]trienones

A mild and convenient visible-light-induced method has been developed for the construction of 3-sulfonyl and 3-sulfenyl azaspiro[4,5]trienones through metal-free difunctionalization of alkynes with sulfinic acids or thiols at room temperature. The present protocol simply utilizes visible light as the safe and eco-friendly energy source, and inexpensive and non-toxic organic dyes (Eosin Y and Na2-Eosin Y) as photocatalysts providing various sulfur-containing azaspiro[4,5]trienones in moderate to good yields.

Preparative Isolation and Purification of Three Stilbene Glycosides from the Tibetan Medicinal Plant Rheum tanguticum Maxim. Ex Balf. by High-speed Counter-current Chromatography

INTRODUCTION Stilbene glycosides are the primary constituents of Rheum tanguticum Maxim. ex Balf., to which different bioactivities has been attributed, including: anti-HIV, anti-oxidant, anti-tumour, anti-malarial, and anti-allergy activity. However, effective methods for the isolation and purification of stilbene glycosides, such as trans-rhapontin, cis-rhapontin and trans-desoxyrhaponticin, from this herb are not currently available. OBJECTIVE To develop an efficient method for the preparative isolation and purification of three stilbene glycosides from Rheum tanguticum Maxim. ex Balf. via high-speed counter-current chromatography (HSCCC). METHODS A solvent system composed of chloroform:n-butanol:methanol:water (4:1:3:2, v/v/v/v) was developed for the separation. The upper phase was used as the stationary phase, and the lower phase was used as the mobile phase. The flow rate was 1.8 mL/min. The apparatus was controlled at 800 rpm and 25 °C, and the effluent was monitored at 280 nm. Chemical constituents were analysed by high-performance liquid chromatography (HPLC), and their structures were identified by ¹H- and ¹³C-NMR. RESULTS Under the optimised conditions, 25.5 mg trans-rhapontin, 16.0 mg cis-rhapontin and 20.5 mg trans-desoxyrhaponticin were separated from 80 mg crude sample; the isolates had purities of 99.6, 97.2 and 99.2%, respectively. CONCLUSION A simple and efficient HSCCC method has been optimised for the preparative separation of stilbene glycosides from Rheum tanguticum Maxim. ex Balf.

Separation of Four Phenylpropanoid Glycosides from a Chinese Herb by HSCCC

Four phenylpropanoid glycosides (PPGs), such as echinacoside, wiedemannioside C, forsythoside B and verbascoside, were isolated and purified from the Tibetan medicinal herb Pedicularis longiflora Rudolph. var. tubiformis (Klotz) Tsoong by high-speed counter-current chromatography (HSCCC) combined with macroporous resin (MR) column separation for the first time. In the present study, the two-phase solvent system composed of ethyl acetate-n-butanol-water (10 : 6:15, v/v/v) was used for HSCCC separation. A total of 3.5 mg of echinacoside, 12.6 mg of wiedemannioside C, 22.7 mg of forsythoside B and 48.7 mg of verbascoside with the purity of 93.6, 97.9, 97.8 and 98.1%, respectively, were obtained from 120 mg of crude sample. The HSCCC fractions were analyzed by HPLC, and the chemical structures were identified by (1)H NMR and (13)C NMR. The results demonstrate that MR coupled with HSCCC is a powerful technique for separation of PPGs from natural products.

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

Erythritol Attenuates Postprandial Blood Glucose by Inhibiting α-Glucosidase

Diabetes mellitus (DM) is a serious metabolic disorder, where impaired postprandial blood glucose regulation often leads to severe health complications. The natural chemical erythritol is a C4 polyol approved by the U.S. Food and Drug Administration for use as a sweetener. Here, we examined a potential role for erythritol in the control of postprandial blood glucose levels in DM. An anti-postprandial hyperglycemia effect upon erythritol administration (500 mg kg-1) was demonstrated in alloxan-induced DM model mice by monitoring changes in blood glucose after intragastric administration of drugs and starch. We also found that erythritol most likely exerts its anti-postprandial hyperglycemic activities by inhibiting α-glucosidase in a competitive manner. This was supported by enzyme activity assays and molecular modeling experiments. In the latter experiments, it was possible to successfully dock erythritol into the catalytic pocket of α-glucosidase, with the resultant interaction likely driven by electrostatic interactions involving Asp215, Asp69, and Arg446 residues. This study suggests that erythritol may not only serve as a glucose substitute but also be a useful agent in the treatment of DM to help manage postprandial blood glucose levels.

Visible-Light-Enabled Construction of Thiocarbamates from Isocyanides, Thiols, and Water at Room Temperature

A convenient visible-light-induced method for the synthesis of thiocarbamates from isocyanides, thiols, and water has been developed under mild reaction conditions. The present protocol offers a cost-effective and operationally straightforward approach to the various thiocarbamates in moderate to good yields by simple use of cheap Rose Bengal as the photocatalyst and water as the reaction reagent as well as an environmentally benign cosolvent.

SEMI-PREPARATIVE SEPARATION AND PURIFICATION OF THREE FLAVONOIDS FROM PEDICULARIS LONGIFLORA VAR. TUBIFORMIS (KLOTZSCH) P. C. TSOONG BY HSCCC

An effective high–speed counter–current chromatography (HSCCC) method was established for semi-preparative isolation and purification of bioactive chemical constituents from the Tibetan medicinal plant Pedicularis longiflora var. tubiformis (Klotzsch) P. C. Tsoong. With a two-phase solvent system composed of chloroform–methanol–water (8:4:5, v/v), 40 mg of extract was separated to yield luteolin (12.5 mg), apigenin (9.6 mg), and chrysoeriol (4.8 mg), with purities of 99.3, 98.2, and 98.6%, respectively, as determined by high-performance liquid chromatography (HPLC). The chemical structures of these three components were identified by 1H NMR and 13C NMR.