Chemical characterization and DPP-IV inhibitory activity evaluation of tripeptides from Gynura divaricata (L.) DC.

ETHNOPHARMACOLOGICAL RELEVANCE: Gynura divaricata (L.) DC. (GD), a herbal medicine, has been used for the prevention and treatment of hyperglycemia in China. However, hypoglycemic ingredients within GD have not yet been well studied. AIM OF THE STUDY: The aim of this study was to explore undiscovered compounds with dipeptidyl peptidase IV (DPP-IV) inhibitory activity within GD. MATERIALS AND METHODS: A four-step strategy was developed to explore undiscovered DPP-IV inhibitors within GD. First, the components were preliminarily characterized using UHPLC-HRMS combined with a library search. Second, preliminarily characterized compounds were searched for potential bioactivity. Third, a mixture of these preliminarily characterized compounds was isolated and thoroughly characterized based on fragmentation patterns associated with molecular networking. Fourth, the activities of these compounds were verified using DPP-IV inhibitory assay and molecular docking. RESULTS: Diprotin A, a tripeptide inhibitor against DPP-IV, was identified. Thereafter, a mixture of twenty-five diprotin A analogs was isolated and characterized, which exhibited IC50 of 0.40 mg/mL for DPP-IV. Molecular docking results also confirmed the interactions between the tripeptide analogs and DPP-IV mainly via H-bonds and hydrophobic interactions. CONCLUSIONS: This is the first report of DPP-IV inhibitors within GD. These findings demonstrate that the extract of GD might be beneficial for the treatment of type 2 diabetes mellitus, and is expected to promote further development and utilization of GD in herbal medicine.

Sustainable and Green Synthesis of Waste-Biomass-Derived Carbon Dots for Parallel and Semi-Quantitative Visual Detection of Cr(VI) and Fe3.

Carbon dot (CD)-based multi-mode sensing has drawn much attention owing to its wider application range and higher availability compared with single-mode sensing. Herein, a simple and green methodology to construct a CD-based dual-mode fluorescent sensor from the waste biomass of flowers of wintersweet (FW-CDs) for parallel and semi-quantitative visual detection of Cr(VI) and Fe3+ was firstly reported. The FW-CD fluorescent probe had a high sensitivity to Cr(VI) and Fe3+ with wide ranges of linearity from 0.1 to 60 µM and 0.05 to 100 µM along with low detection limits (LOD) of 0.07 µM and 0.15 µM, respectively. Accordingly, the FW-CD-based dual-mode sensor had an excellent parallel sensing capacity toward Cr(VI) and Fe3+ with high selectivity and strong anti-interference capability by co-using dual-functional integration and dual-masking strategies. The developed parallel sensing platform was successfully applied to Cr(VI) and Fe3+ quantitative detection in real samples with high precision and good recovery. More importantly, a novel FW-CD-based fluorescent hydrogel sensor was fabricated and first applied in the parallel and semi-quantitative visual detection of Cr(VI) and ferrous ions in industrial effluent and iron supplements, further demonstrating the significant advantage of parallel and visual sensing strategies.

[Methods and techniques of capillary electrophoresis for drug screening].

Capillary electrophoresis (CE) shows enormous potential for application in new drug research and development. Because of the aqueous medium employed as the running buffer in CE, drug screening can be carried out in an environment similar to that in physiological testing media. Drug screening methods based on CE are different from other instrumental measurements in vitro. CE can not only sustain the biological activity of the screened molecules and ligands, but also help evaluate the interactions between the receptors and the ligands. Based on these interactions, some important pharmacological parameters related to drug screening, such as the association constant Kb, bonding rate constant Kon, and dissociation rate constant Koff, can be determined by CE. Thus, CE is an effective tool for simulating and predicting the entire interaction process between receptors and drugs in vivo. In this review, the history of CE for drug screening is revisited. The theories, common methods for drug screening by CE, and some application examples and related technologies are reviewed. The methods of drug screening by means of affinity CE and kinetic CE are introduced. Some selected studies on different ligands at the molecular and cellular level are reported, along with examples several types of drugs. Techniques based on a combination of CE with mass spectrometry and chemiluminescence are reviewed, with focus on the screening of candidate drugs and active compounds from traditional Chinese medicine. The application prospect of drug screening by CE combined with a DNA-encoded compound library is introduced. This paper discusses the core of the fraction collection step in CE and emphasizes the significance of combining CE with systematic evolution of ligands by exponential enrichment. In conclusion, various optional methods for CE drug screening would pave the way for new concepts related to drug screening and evaluation in the future.

Extraction and determination of bioactive flavonoids from Abelmoschus manihot (Linn.) Medicus flowers using deep eutectic solvents coupled with high-performance liquid chromatography.

A highly efficient and ecofriendly extraction method using deep eutectic solvents was developed to extract bioactive flavonoids from Abelmoschus manihot (Linn.) Medicus flowers. First, a series of deep eutectic solvents using choline chloride as hydrogen bond acceptor with different hydrogen bond donors was successfully synthesized. Then, the types of deep eutectic solvents and the extraction conditions for bioactive flavonoids (hyperoside, isoquercitrin, and myricetin) were optimized based on the flavonoids extraction efficiencies. The optimized deep eutectic solvent for hyperoside and isoquercitrin extraction was composed of choline chloride and acetic acid with a molar ratio of 1:2. The optimized deep eutectic solvent for myricetin extraction was composed of one mole of choline chloride and two moles of methacrylic acid. The optimal extraction conditions were set as: solid to solvent ratio, 35:1 (mg/mL); extraction time, 30 min; extraction temperature, 30°C. Qualitative and quantitative analysis were performed using ultra high performance liquid chromatography with tandem mass spectrometry and high-performance liquid chromatography. And the extraction efficiencies of hyperoside, isoquercitrin, and myricetin under optimal extraction conditions were calculated as 11.57, 5.64, and 1.11 mg/g, much higher than those extracted by traditional extraction solvents. Therefore, the prepared deep eutectic solvents can be selected as alternative solvent to extract bioactive flavonoids.

Novel dual functional monomers based molecularly imprinted polymers for selective extraction of myricetin from herbal medicines.

Herein, novel dual functional monomers based molecularly imprinted polymers (MIPs) were successfully prepared and used to extract myricetin from Carthamus tinctorius L., also named safflower (family, Compositae) and the flower of Abelmoschus manihot (Linn.) Medicus (family, Malvaceae). The polymers were prepared using myricetin as template, 4-vinylpyridine (4-VP) and glycidyl methacrylate (GMA) as dual functional monomers, ethylene glycol dimethyl acrylate (EGDMA) as cross-linker and methanol-acetonitrile (1:2, v/v) as solvent, respectively. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were applied to characterize the polymers. Further, the adsorption and selectivity experiments of MIPs were evaluated. The results revealed that MIPs showed high adsorption ability and selectivity toward myricetin. Finally, MIPs were employed as adsorbents for solid phase extraction (SPE) of myricetin from safflower and the flowers of A. manihot (Linn.) Medicus. Further analysis was conducted by using high performance liquid chromatography-diode array detection (HPLC-DAD). The recovery of mrricetin in safflower and in the flowers of A. manihot ranged from 79.82% to 83.91%, 81.50% to 84.32%, respectively. These results indicated that MIPs can be applied to the extraction and separation of myricetin from various complex matrixes.

Preparation and evaluation of a reversed-phase/hydrophilic interaction/ion-exchange mixed-mode chromatographic stationary phase functionalized with dopamine-based dendrimers.

In this work, a novel dendritic stationary phase was synthesized by the repeated grafting of 1,4-butanediol diglycidyl ether (BDDE) and dopamine (DA) on the surface of silica for performing mixed-mode high-performance liquid chromatography (MHPLC). Elemental analysis (EA), thermogravimetric analysis (TGA) and Fourier transform infrared spectrometry (FT-IR) showed the successful preparation of the dendritic stationary phase. The prepared stationary phase showed the retention mechanisms of reversed-phase liquid chromatography (RPLC), hydrophilic interaction chromatography (HILIC) and ion-exchange chromatography (IEC) under different mobile phase conditions. In detail, alkylbenzenes, polycyclic aromatic hydrocarbons (PAHs) and hydrophobic positional isomers were separated successfully in the RPLC mode. The baseline separation of nucleobases, nucleosides and flavonoids was achieved under HILIC mode, respectively. Meanwhile, some acidic and basic analytes were used to evaluate the IEC mode. The effects of different chromatographic conditions, such as acetonitrile content, salt concentration and pH in the mobile phase, on the different chromatographic modes were also investigated. In addition, the application of the mixed-mode dendritic stationary phase was demonstrated by the analysis of traditional Chinese medicine (TCM), including Carthamus tinctorius L. and Abelmoschus manihot (Linn.) Medicus. Interestingly, the stationary phase also has the ability for the capture and separation of boric acids. These meaningful applications confirmed that the mixed-mode dendritic stationary phase can be potentially applied in the analysis of complex samples.

Molecularly imprinted polymers for the selective extraction of tiliroside from the flowers of Edgeworthia gardneri (wall.) Meisn.

Nano-sized molecularly imprinted polymers for tiliroside were successfully prepared by a precipitation polymerization method. Acrylamide, ethylene glycol dimethacrylate, azobisisobutyronitrile, and acetonitrile/dimethyl sulfoxide were used as functional monomer, cross-linker, initiator, and porogen, respectively. The structural features and morphological characterization of tiliroside-imprinted polymers were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The adsorption experiments indicated that the tiliroside-imprinted polymers exhibited high selective recognition property to tiliroside. Scatchard analysis indicated that the homogeneous-binding sites were formed in the polymers. The selectivity test revealed that the adsorption capacity and selectivity of polymers to tiliroside was significantly higher than that of rutin, astragalin, and kaempferol. Finally, the tiliroside-imprinted polymers were employed as adsorbents in solid-phase extraction for the extraction of tiliroside from the ethyl acetate extract of the flowers of Edgeworthia gardneri (wall.) Meisn. The results demonstrated that the extraction recoveries of tiliroside ranged from 69.3 to 73.5% by using tiliroside-imprinted polymers coupled with solid-phase extraction method. These results indicated that the tiliroside-based molecularly imprinted solid-phase extraction method was proven to be an effective technique for the separation and enrichment of tiliroside from natural medicines.