Dioscorea opposita Thunb, commonly known as “yam” that has a long dietary therapy history for diabetes, is widely consumed as a botanical dietary supplement and widely cultivated in China. In this work, a method for rapid screening of α-glucosidase inhibitors from Dioscorea opposita Thunb peel extract was developed using α-glucosidase functionalized magnetic nanoparticles (αG-MNPs) as a solid phase extraction absorbent in combination with high performance liquid chromatography-mass spectrometry (HPLC-MS). Two α-glucosidase inhibitors were selectively extracted and identified as batatasin I and 2,4-dimethoxy-6,7-dihydroxyphenanthrene. Their α-glucosidase inhibitory activities (IC50 = 2.55 mM and 0.40 mM, respectively) were significantly higher than that of acarbose (as control). Taking advantage of the specificity in enzyme binding and the convenience of magnetic separation, this method has great potential for rapid and fast screening of α-glucosidase inhibitors from complex natural resources.

In this work we report the green synthesis of silver nanoparticles (AgNPs) using the aqueous leaf extract of Lonicera japonica. A color change from pale yellow to brown was observed during the synthesis process. Ultraviolet-visible (UV-vis) studies show an absorption band at 435 nm due to surface plasmon resonance of the AgNPs, further characterized using the average size and stability of the AgNPs, which were 53 nm and −35.6 mV as determined by a zeta sizer. The spherical, hexagonal shape and the face centered cubic crystalline structure of metallic silver were confirmed by high resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). The functional group of biomolecules present in the AgNPs was characterized by Fourier transform infrared spectra (FTIR). The synthesized AgNPs exhibited strong antioxidant activity. The antidiabetic ability of AgNPs was shown by the effective inhibition against carbohydrate digestive enzymes such as α-amylase and α-glucosidase with IC50 values of 54.56 and 37.86 μg mL−1, respectively. The inhibition of the kinetic mechanism was analyzed with LB and Dixon plots. AgNPs were identified to be reversible noncompetitive inhibitors and Ki values of 25.9 and 24.6 μg were found for key enzymes of diabetes (α-amylase and α-glucosidase). We conclude that the results suggest that the AgNPs were found to show remarkable potential antidiabetic activity against the key enzymes of diabetes and were found to be an appropriate nanomedicine for nanobiomedical applications.

Applying voltammetric, spectroscopic, and molecular docking technology, the binding properties of batatasin derivatives with HSA were systematically estimated. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) results showed that the common irreversible oxidation peaks of these compounds at 0.50–0.60 V were an adsorption process with equal numbers of electrons and protons. These compounds could interact with HSA and form non-electroactive complexes, at a binding ratio of 1:1. Comparing their association constants with HSA, 2-hydroxy-3,5-dimethoxy-bibenzyl was the strongest, following by demethyl batatasin IV, 2,3-dihydroxy-bibenzyl and 2-(1-phenethyl)phenol which were basically comparable. The equal fluorescent emission point proved further that these compounds interacted with HSA indeed and new complexes generated. The compounds caused a large reduction of α-helix structure in HSA and extension of its peptide chain which were proved by UV-Vis and CD spectrometric results. Molecular docking results directly demonstrated that the compounds bound near Trp-214 in subdomain IIA mainly through hydrogen bonds.

Batatasins are endogenous plant hormones found in yams and other related plant species. These plants are widely consumed as botanical dietary supplements in many parts of the world. This study investigated the inhibitory effects and mechanisms of Batatasin I, III, IV, V against α-glucosidase regarding their antidiabetic activities. The results revealed that Batatasin I, III, IV inhibited α-glucosidase in a reversible and noncompetitive manner, with IC50 values of 2.55, 1.89 and 2.52 mM respectively, while Batatasin V completely abolished its inhibitory activity even at the highest concentrations tested. Furthermore, a class of Batatasin-derived compounds with different substitution patterns was synthesized and subjected to the assay to clarify the structure–activity relationships, which suggested that the hydroxyl at the C-2′ position may play a significant role in improving the inhibitory activities. Their probable binding modes and the specificity of the binding sites were studied using molecule docking simulation. It was concluded that Batatasins, especially Batatasin III and IV, are promising α-glucosidase inhibitors, which therefore could be used as functional food to alleviate postprandial hyperglycemia and as potential candidates for the development of antidiabetic agents.

Based on the quenching of the fluorescence intensity of quantum dots, the interaction of CdSe/ZnS quantum dots with four flavonoid compounds, including quercetin, rutin, luteolin, and 5,7,3′,4′-tetrahydroxy-flavanone, and their mechanism were studied. A fluorescence method with a detection limit of 0.14 mg L−1 for the determination of quercetin at concentrations between 0.576 and 184 mg L−1 was proposed according to its quenching effect on the QDs. The quercetin samples were determined by this method with satisfactory results. The study indicated that CdSe/ZnS QDs could be a potential excellent fluorescence probe to detect flavonoids.

•A composite consisting of graphene nanoplatelets (GNPs) and titanate nanotubes (TNTs) were synthesized.•The composite was characterized by XRD, TEM, FT-IR and impedance.•Horseradish peroxidase (HRP) biosensors were developed using the composite, GNPs and TNTs as immobilization material respectively.•Direct electron transfer of HRP was achieved on the composite biosensor.•The composite HRP biosensor shows superiority over the other two in electrochemical and analytical performance.A novel nanocomposite consisting of graphene nanoplatelets (GNPs) and titanate nanotubes (TNTs) have been synthesized successfully utilizing the hydrothermal method. The GNP–TNT composite was characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and electrochemical impedance spectroscopy. The voltammetric characterization of GNP–TNT composite, pure GNPs and pure TNTs modified horseradish peroxidase (HRP) biosensors were conducted to select the most suitable electrode immobilization material for enzyme biosensors. The GNPs was firstly eliminated owing to its extremely high background charging current, distinct electrochemical interference from its surface functional groups and low signal to noise ratio. Next, the direct electron transfer of HRP on electrode and the catalytic current of HRP towards H2O2 was increased around 45% and 72% respectively on GNP–TNT composite modified electrodes compared with those on pure TNTs modified electrodes. GNP–TNT composite modified HRP biosensor also exhibited superiority over pure TNTs modified HRP biosensor in the analytical performance. The precision and stability study provided additional evidence for the feasibility of using GNP–TNT composite as electrode modification material.

A copper monolayer was formed on a gold electrode surface via underpotential deposition (UPD) method to construct a Cu UPD|DTBP–Protein G immunosensor for the sensitive detection of 17β-estradiol. Copper UPD monolayer can minimize the non-specific adsorption of biological molecules on the immunosensor surface and enhance the binding efficiency between immunosensor surface and thiolated Protein G. The crosslinker DTBP (Dimethyl 3,3′-dithiobispropionimidate·2HCl) has strong ability to immobilize Protein G molecules on the electrode surface and the immobilized Protein G provides an orientation-controlled binding of antibodies. A monolayer of propanethiol was firstly self-assembled on the gold electrode surface, and a copper monolayer was deposited via UPD on the propanethiol modified electrode. Propanethiol monolayer helps to stabilize the copper monolayer by pushing the formation and stripping potentials of the copper UPD monolayer outside the potential range in which copper monolayer can be damaged easily by oxygen in air. A droplet DTBP–Protein G was then applied on the modified electrode surface followed by the immobilization of estradiol antibody. Finally, a competitive immunoassay was conducted between estradiol–BSA (bovine serum albumin) conjugate and free estradiol for the limited binding sites of estradiol antibody. Square wave voltammetry (SWV) was employed to monitor the electrochemical reduction current of ferrocenemethanol and the SWV current decreased with the increase of estradiol–BSA conjugate concentration at the immunosensor surface. Calibration of immunosensors in waste water samples spiked with 17β-estradiol yielded a linear response up to ∼2200 pg mL−1, a sensitivity of 3.20 μA/pg mL−1 and a detection limit of 12 pg mL−1. The favorable characteristics of the immunosensors such as high selectivity, sensitivity and low detection limit can be attributed to the Cu UPD|DTBP–Protein G scaffold.Highlights► Copper monolayer was formed on gold electrode via underpotential deposition (UPD). ► Copper UPD monolayer minimized non-specific adsorption of biomacromolecules. ► Propanethiol enhanced stability of copper UPD monolayer on gold electrode surface. ► Protein G was thiolated by DTBP to improve binding of antibody on immunosensor. ► SWV was used to monitor conductivity change on immunosensor surface.

The inhibitory activities of crude extracts and purified constituents from the fresh tuberous rhizomes of Chinese Yam (Dioscorea opposita Thunb.), which is commonly called Huai Shan Yao in Chinese, were evaluated against yeast α-glucosidase in order to search for the active principals for treatment of diabetes. Bioassay-guiding isolation gave four compounds: trans-N-p-coumaroyltyramine (1) (IC50 = 0.40 μM), 1,7-bis(4-hydroxyphenyl)heptane-3,5-diol (2) (IC50 = 0.38 mM), 6-hydroxy-2,4,7-trimethoxyphenanthrene (3) (IC50 = 0.77 mM) as α-glucosidase inhibitors, and cis-N-p-coumaroyltyramine (4), an isomer of compound 1, which showed no inhibitory activity against α-glucosidase. Furthermore, the separation and purification of compound 3 from Chinese Yam (Huai Shan Yao) was conducted by high-speed counter-current chromatography (HSCCC) using hexane–ethyl acetate–methanol–water (1:1:1:1, v/v/v/v). Compound 1, 2 and 4 were isolated from or detected in the Dioscoreaceae family for the first time.

Two new phenolic compounds were isolated from whole plant of Artemisia sphaerocephala. The structures were elucidated on the basis of spectroscopic methods as 4-(1-hydroxylethyl)-phenol-1-O-β-d-glucopyranoside and 4-O-acetophenone-β-d-glucopyranosyl-(1-3)-β-d-glucopyranoside.

•Graded alcohol precipitation was used to extract Dioscorea opposita polysaccharides.•Monosaccharides, amino acid content and molecular weight were measured.•Study the rheology of polysaccharides at different concentrations, temperatures and pH.•Arginine contributes to the seminal emissions, NO relaxation and hormones release.•Polysaccharide samples showed pseudoplastic properties and “gel-like” behaviour.This study investigated the chemical components and rheological properties of polysaccharides from Dioscorea opposita Thunb. Graded alcohol precipitation was used to extract Dioscorea opposita polysaccharide samples (S1, S2, S3 and S4). The monosaccharides, amino acid content and molecular weight of each sample were measured and compared. The rheological properties of the polysaccharide samples at different concentrations, temperatures and pH values were studied. The rheological properties of S1, S2 and S3 exhibited pseudoplastic properties and “gel-like” behaviour. The viscosity of S1 was improved with rising temperatures, especially temperatures higher than 80 °C, which may be caused by the starch gelatinisation. The acidic and basic environments may break the structures of S3 and S4. However, the extreme conditions improved the viscosity of S1. This work was a basic investigation of the Dioscorea opposita polysaccharides, contributing to the function of yam products and applications of natural thickeners in the food industry.

•Molecular weights of Dioscorea opposita polysaccharides were in different ranges.•The synergistic effect on emulsification properties of polysaccharides with gum arabic.•Sample 2 and 3 showed emulsifying properties with medium-chain-triglycerides.•Sample 2, gum arabic and triglycerides (1:1:1) presented the best emulsification.This study investigated the emulsification properties of polysaccharides from Dioscorea opposita Thunb. Graded alcohol precipitation was used to extract Dioscorea opposita polysaccharides fractions (4 samples) in different ranges of molecular weight. Sample 3 contained more glucose and protein (80.13% and 0.34%, respectively), and molecular weight was approximately 34,790 Da, distributing narrowly. The droplet sizes and stabilities of emulsions made of gum arabic (GA) and polysaccharide samples at different concentrations and ratios were measured, specifically the emulsions of GA and medium-chain-triglycerides (MCT); polysaccharides and MCT; and polysaccharides, GA and MCT (1:1:1). The results indicated that sample 2 and 3 had emulsifying properties, and the emulsions made with sample 2, GA and MCT (1:1:1) presented the best emulsification properties. Therefore, polysaccharides of Dioscorea opposita could be utilised as a natural emulsifier that can be improved synergistically with other emulsifiers, such as gum arabic.

•Mucilage from Dioscorea opposita shows high emulsification.•Change in pH does not affect the emulsion stability of mucilage.•Mucilage from industrial waste serves as a sustainable resource for natural emulsifier.The properties of mucilage obtained from Dioscorea opposita, generated during industrial manufacturing were investigated in this study. Characteristics such as monosaccharide content, amino acid content, molecular weight, and structural features were measured, whereas morphology was observed using a scanning/transmission electron microscope. Additionally, emulsification properties at different concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) and under acidic and basic pH (5.0 and 9.0) conditions were studied. The results showed that emulsions prepared from mucilage and medium-chain triglycerides presented more effective emulsifying functions and higher stability, especially at low concentrations. Both, acidic and basic conditions improved the overall emulsification properties, which suggested that the isoelectric point of amino acids may be involved in the emulsification properties. The results of this study show that mucilage from Dioscorea opposita can be considered as a sustainable resource of a natural emulsifier obtained from industrial waste.

Based on the quenching of the fluorescence intensity of quantum dots, the interaction of CdSe/ZnS quantum dots with four flavonoid compounds, including quercetin, rutin, luteolin, and 5,7,3′,4′-tetrahydroxy-flavanone, and their mechanism were studied. A fluorescence method with a detection limit of 0.14 mg L−1 for the determination of quercetin at concentrations between 0.576 and 184 mg L−1 was proposed according to its quenching effect on the QDs. The quercetin samples were determined by this method with satisfactory results. The study indicated that CdSe/ZnS QDs could be a potential excellent fluorescence probe to detect flavonoids.