Xujie Li

Bio: Xujie Li is an academic researcher from Central South University. The author has contributed to research in topics: Medicine & Meta-analysis. The author has an hindex of 5, co-authored 5 publications receiving 35 citations.

Separation of α-glucosidase inhibitors from Potentilla kleiniana Wight et Arn using solvent and flow-rate gradient high-speed counter-current chromatography target-guided by ultrafiltration HPLC-MS screening.

Abstract: Introduction Potentilla kleiniana Wight et Arn is widely used as a herbal medicine to treat type 2 diabetes. However, detailed information about its active compounds is lacking. Objective To develop an efficient method for the rapid screening and separation of α-glucosidase inhibitors from Potentilla kleiniana Wight et Arn. Methodology Potential α-glucosidase inhibitors from Potentilla kleiniana Wight et Arn were rapidly screened out through ultrafiltration high-performance liquid chromatography mass spectrometry (HPLC-MS), and then followed by a target-guided high-speed counter-current chromatography (HSCCC) separation using two-phase solvent systems composed of n-hexane/ethyl acetate/methanol/water (1:10:1:10, v/v/v/v and 1:10:5:6, v/v/v/v), and adopting increasing flow-rate from 1.5 to 3.0 mL/min after 200 min. Their structures were identified by ultraviolet (UV), MS, proton nuclear magnetic resonance (1 H-NMR) and carbon-13 (13 C)-NMR, and their α-glucosidase inhibitory activities were assessed by in vitro assay. Results Five α-glucosidase inhibitors including gallic acid (25.7 mg, 98.2%, 1), brevifolincarboxylic acid (9.86 mg, 95.3%, 2), ethyl evifolincarboxylate (13.26 mg, 97.6%, 3), 3,3'-di-O-methylellagic acid-4'-O-β-d-glucopyranoside (16.26 mg, 95.1%, 4), and 3,3'-di-O-methylellagic acid (10.54 mg, 96.8%, 5) were successfully purified from 250 mg n-butanol extract in a single run. Compounds 1, 2, 4 and 5 exhibited stronger α-glucosidase inhibitory activities[half maximal inhibition concentration (IC50 ) values at 173.41 ± 6.35, 323.46 ± 8.08, 44.63 ± 2.50, and 20.73 ± 2.56 μM, respectively] than acarbose (IC50 value at 332.12 ± 5.52 μM, reference compound). Conclusions Notably, compounds 2-5 were reported in the Potentilla kleiniana Wight et Arn for the first time. The results indicated that the proposed method could be applied for the rapid screening and preparative separation of α-glucosidase inhibitors from a complex matrix.

Preparative isolation and purification of 12 main antioxidants from the roots of Polygonum multiflorum Thunb. using high-speed countercurrent chromatography and preparative HPLC guided by 1,1'-diphenyl-2-picrylhydrazyl-HPLC.

Abstract: A hyphenated strategy by off-line coupling of 1,1'-diphenyl-2-picrylhydrazyl-high-performance liquid chromatography, high-speed countercurrent chromatography, and preparative high-performance liquid chromatography was established to screen and separate antioxidants from ethyl acetate fraction of the roots of Polygonum multiflorum. Under the targeted guidance of 1,1'-diphenyl-2-picrylhydrazyl-high-performance liquid chromatography experiment, 12 compounds were identified as potential antioxidants and readily isolated by high-speed counter-current chromatography and preparative high-performance liquid chromatography. Ultraviolet spectroscopy, mass spectrometry, and 1 H NMR spectroscopy were employed to identify their structures, which were assigned as gallic acid (1, 6.2 mg, 98.28%), catechin (2, 8.8 mg, 90.69%), epicatechin (3, 4.1 mg, 96.71%), polydatin (4, 5.3 mg, 94.91%), 2,3,5,4'-tetrahydroxy stilbene-2-Ο-β-D-glucoside (5, 20.2 mg, 95.23%), piceatannol (6, 5.3 mg, 96.85%), rutin (7, 5.4 mg, 97.92%), resveratrol (8, 5.2 mg, 96.94%), isorhapontigenin (9, 11.4 mg, 94.81%), hyperoside (10, 9.7 mg, 98.52%), rhein (11, 4.9 mg, 97.46%), and emodin (12, 8.2 mg, 95.74%). Notably, compounds 6 and 9 were isolated from Polygonum multiflorum for the first time. In addition, antioxidant activity of compounds 1-12 were evaluated, and compounds 1-8 and 10 exhibited stronger antioxidant activity than ascorbic acid (positive control). These results indicated that the proposed method is a highly efficient strategy to screen and isolate antioxidants from complex natural products.

Schiff Base Aggregation-Induced Emission Luminogens for Sensing Applications: A Review.

Abstract: Fluorescence sensing can not only identify a target substrate qualitatively but also achieve the purpose of quantitative detection through the change of the fluorescence signal. It has the advantages of immense sensitivity, rapid response, and excellent selectivity. The proposed aggregation-induced emission (AIE) concept solves the problem of the fluorescence of traditional fluorescent molecules becoming weak or quenched in high concentration or aggregated state conditions. Schiff base fluorescent probes have the advantages of simple synthesis, low toxicity, and easy design. They are often used for the detection of various substances. In this review we cover late developments in Schiff base compounds with AIE characteristics working as fluorescence sensors.

Metal-organic frameworks as effective sensors and scavengers for toxic environmental pollutants

Abstract: Abstract Metal-organic frameworks (MOFs) constructed from a rich library of organic struts and metal ions/clusters represent promising candidates for a wide range of applications. The unique structure, porous nature, easy tunability and processability of these materials make them an outstanding class of materials for tackling serious global problems relating to energy and environment. Among them, environmental pollution is one aspect that has increased at an alarming rate in the past decade or so. With rapid urbanization and industrialization, toxic environmental pollutants are constantly released and accumulated leading to serious contamination in water bodies and thereby having adverse effects on human health. Recent studies have shown that many toxic pollutants, as listed by the World Health Organization and the US Environmental Protection Agency, can be selectively detected, captured, sequestered and removed by MOFs from air and aquatic systems. Most of these sensing/capture processes in MOFs are quantifiable and effective for even a trace amount of the targeted chemical species. The functional sites (ligands and metals) play a critical role in such recognition processes and offer an extensive scope of structural tunability for guest (pollutants, toxic entities) recognition. Whereas on the one hand, the underlying mechanisms governing such sensing and capture are important, it is also crucial to identify MOFs that are best suited for commercial applications for the future. In this review article, we provide an overview of the most recent progress in the sensing, capture and removal of various common toxic pollutants, including neutral and ionic, inorganic and organic species, with brief discussions on the mechanism and efficacy of selected MOFs.