Xiuhua Liu

Antidiabetic activity of silver nanoparticles from green synthesis using Lonicera japonica leaf extract

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.

Naturally occurring Batatasins and their derivatives as α-glucosidase inhibitors

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.

Chemical components and emulsification properties of mucilage from Dioscorea opposita Thunb

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.

Investigation of the interaction of batatasin derivatives with human serum albumin using voltammetric and spectroscopic methods

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.

Hydrogels generated by low-molecular-weight PEGylated luteolin and α-cyclodextrin through self-assembly for 5-fluorouracil delivery

Hydrophobic luteolin (LUT) was conjugated to the oligomeric chain of methoxypoly(ethylene glycol) (mPEG) to form novel amphiphilic mPEG1900–LUT conjugates. Then mPEG1900–LUT, by using its adjacent 3′ and 4′ hydroxyl groups, were assembled with magnetic Fe3O4 particles in an aqueous solution to form mPEG1900–LUT–Fe3O4 conjugates, which formed hybrid Fe3O4 particles. The spectral properties and micellization of the conjugates were studied. Both mPEG1900–LUT and mPEG1900–LUT–Fe3O4 conjugates were able to self-assemble into stable supramolecular hydrogels through α-cyclodextrin (α-CD) in water, and their gelation times and temperatures were determined. The hydrogels displayed typical porous structures, which are suitable for drug delivery. Therefore, 5-fluorouracil (5-FU) was loaded into the formed hydrogels to control its release in vitro. The drug release observations showed that introducing Fe3O4 particles into the hydrogel improved the sustained release effect.

Emulsification properties of polysaccharides from Dioscorea opposita Thunb.

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 34,790Da, 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.

Facile synthesis of mPEG-luteolin-capped silver nanoparticles with antimicrobial activity and cytotoxicity to neuroblastoma SK-N-SH cells

We firstly report a facile route for the green synthesis of mPEG-luteolin-capped silver nanoparticles (mPEG-luteolin-AgNPs) using mPEG-luteolin as both the reducer and stabilizer. The reaction was carried out in a stirred aqueous solution at 50°C without additional poisonous reagents. The prepared mPEG-luteolin-AgNPs was characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), zeta potential and UV-vis (UV-vis) spectrum, respectively. The proportions of mPEG-luteolin capped silver nanoparticles is about 89.9%, and the content of silver is 6.65%. The mPEG-luteolin-AgNPs was evaluated the antimicrobial effects on Staphlococcus aureus, Extended spectrum β-Lactamases Staphlococcus aureus, Escherichia Coli and Extended spectrum β-Lactamases Escherichia Coli using drilling hole method. The results showed that both gram-positive and gram-negative bacteria were killed by the mPEG-luteolin-AgNPs at low concentration. Meanwhile, the cell viability assay demonstrated that mPEG-luteolin-AgNPs had toxic effects on human neuroblastoma SK-N-SH cells.

Molecular spectroscopic insight into the binding of batatasin V isomers to human serum albumin

ABSTRACT Fluorescence, ultraviolet-visible absorption spectroscopy, circular dichroism spectrum, and molecular docking methods were employed to study the interaction mechanisms of batatasin V and its isomer with human serum albumin. The two isomers both bond reactively to the hydrophobic activity in subdomain IIA, with an approximate binding affinity. Thermodynamic parameters and molecular modeling results manifested that hydrogen bonds and van der Waals force were the main contributors to the interaction. The secondary structure of human serum albumin was altered with the obvious decreased amount of α-helix. The results overall suggested similar binding mechanisms of batatasin V isomers with human serum albumin. This work will promote the further study of batatasins for pharmacological function. It could also help to provide some useful information for further drug design based on batatasins.

Determination of chloroacetic acids in water by capillary zone electrophoresis with field-amplified sample injection

ABSTRACT A simple and sensitive method has been developed for the determination of chloroacetic acids and acetic acid in water using capillary zone electrophoresis under modified electroosmotic flow with indirect UV detection. Potassium hydrogen phthalate at pH 5.40 was used as background electrolyte (BGE), and hexadecyltrimethylammonium bromide was used as electroosmotic flow modifier. Field-amplified sample injection (FASI) method was used to enhance the sensitivity. Results showed that the limit of detection for these analytes was enhanced more than 15-fold and the repeatabilities were good with relative standard deviations (RSDs %) of migration time and corrected peak areas being below 0.33%, 4.45% (intra-day) and 0.87%, 9.67% (inter-day), respectively. An off-line liquid–liquid extraction (LLE) process with methyl tert-butyl ether was carried out to detect these compounds in water samples. The dissociation constants of acetic acid and monochloroacetic acid (MCA) were determined with two methods and the results obtained were consistent with the reference values. GRAPHICAL ABSTRACT

Preparation and characterization of D. opposita Thunb polysaccharide-zinc inclusion complex and evaluation of anti-diabetic activities

In the present work, Dioscorea opposita Thunb polysaccharide-zinc (DPS-zinc) inclusion complex was synthesized for the first time and its anti-diabetes activities against Streptozotocin (STZ)-induced diabetic rats were assayed. The detail structural and morphological analysis of as-prepared DPS-zinc complex was done by using different spectroscopic and microscopic methods. The pharmacological study revealed that DPS-zinc presented a potent hypoglycemic effect on STZ-induced diabetic rats, decreased the glucose and insulin levels, reduced malondialdehyde (MDA) contents and increased SOD and T-AOC activities significantly in liver. The levels of T-CHO, TG and LDL-C in serum were dramatically decreased while HDL-C level was increased with the treatment of proposed inclusion complex. In brief, DPS-zinc could be considered as a potential candidate for developing an ingredient of functional foods for zinc supplements with the hypoglycemic action.