Siming Zhu

Construction of four 3d–4f heterometallic pillar-layered frameworks containing left- and right-handed helical chains and a I− chemosensor

Four new heterometallic coordination complexes, namely, {[Zn4Ln2(imdc)4(SO4)(H2O)8]·4H2O}n [Ln = Nd (1), Sm (2), Eu (3), Gd (4); H3imdc = imidazole-4,5-dicarboxylic acid], were hydrothermally synthesized by the reactions of Ln2O3 with imidazole-4,5-dicarboxylic acid and ZnSO4·7H2O and characterized by single-crystal X-ray diffraction, infrared spectroscopy (IR), elemental analysis (EA), thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD). The single-crystal X-ray diffraction analyses reveal that these polymers are isostructural and possess an interesting 3D pillar-layered architecture with 424·64 topology, in which 2D layers constructed by alternately arranged 1D right-/left-handed helical chains of [Zn2(μ5-imdc)]n bridged via dimeric Eu2 units are pillared by μ2-SO42− and μ3-imdc3− anions. The liquid fluorescence of compounds 1–3 at room temperature shows that these complexes are very good chemosensors for I− ion, and the response of the sensor is based on fluorescence quenching of Zn–Ln MOFs by iodine ions.

Debranching and temperature-cycled crystallization of waxy rice starch and their digestibility.

Slowly digestible starch (SDS) was obtained through debranched waxy rice starch and subsequent crystallization under isothermal and temperature-cycled conditions. Temperature-cycled crystallization of dual 4/-20 °C produced a higher yield of SDS product than isotherm crystallization. Crystal structure of SDS products changed from A-type to a mixture of B and V-type X-ray diffraction patterns. The relative crystallinity was higher in the temperature-cycled samples than that of isotherm. Attenuated total reflectance Fourier transform infrared spectroscopy suggested that the peripheral regions of isothermal storage starch were better organized than temperature-cycles. Temperature cycling induced higher onset temperature for melting of crystals than isothermal storage under a differential scanning calorimeter. The cycled temperature storage induced a greater amount of SDS than the isothermal storage.

Stepwise ethanolic precipitation of sugar beet pectins from the acidic extract

A stepwise ethanol-precipitation (SEP) procedure was developed for the purification of sugar beet pectins (SBP) from a pectin-containing aqueous extract. Five fractions of different chemical and molecular characteristics were produced by stepwise elevating the alcohol concentration of the precipitation medium from 50% to 80% v/v. Comparison of chemical and macromolecular features between the obtained fractions indirectly suggested that the ability of pectin to solubilize in the ethanol-water binary mixture depended greatly on the polymer structure. Fractions rich in neutral sugars were precipitated at relatively high ethanol concentrations, probably due to the enhanced interactions generated between pectin side chains and solvent molecules. Furthermore, the obtained fractions displayed different surface activities. Results obtained in this work indicate that the SEP procedure is more selective with respect to pectin structural features and surface properties than the one-step ethanolic precipitation.

Short communication: Possible mechanism for inhibiting the formation of polymers originated from 5-hydroxymethyl-2-furaldehyde by sulfite groups in the dairy thermal process

5-Hydroxymethyl-2-furaldehyde can undergo polymerization to form high-molecular weight molecules via the Maillard reaction during dairy thermal treatment. In this study, the effect of sulfite group on polymer formation, especially in inhibiting the formation of high-molecular weight polymers has been described. Results showed that the sulfite group significantly inhibited the increase of polymer molecular weight via prevention of the polymerization of 5-hydroxymethyl-2-furaldehyde. The formation of an intermolecular dimer based on the glucose molecule through Schiff base cyclization can lead to a competitive reaction with 1,2-enolization to reduce 5-hydroxymethyl-2-furaldehyde formation, which might be another factor in reducing the formation of high-molecular weight polymers.

Developing precipitation modes for preventing the calcium-oxalate contamination of sugar beet pectins

Effects of precipitation modes on the co-precipitation of insoluble oxalates particles during the purification of sugar beet pectins (SBP) from the extract were investigated. It was observed that soluble oxalate ions formed insoluble oxalate salts with calcium and precipitated with pectins during ethanol precipitation as pH of the medium increased and the solvent changed from water to ethanol-water mixture. Comparison among the employed precipitation methods revealed that both the dialysis-ethanol-precipitation and metal precipitation effectively prevented the calcium-oxalate contamination of SBP. Emulsifying properties of DEPP, EPP and MPP were also studied. It was observed that DEPP performed better than the remainder with respect to emulsifying ability. Based on these results, we concluded that the dialysis-ethanolic-precipitation can be a suitable method for improving the purity as well as emulsifying properties of the resulting pectins.

Characterisation of the turbid particles in the extraction of sugar beet pectins

This paper was aimed at characterising the insoluble substances (IS) responsible for the turbidity of the extract and impurity of the resulting pectins. Results showed that the IS caused a significant increase in the turbidity of the extract. The IS had bi-pyramidal shapes under the SEM observation. The observed XRD peaks for the IS were similar to those of calcium oxalate dihydrate (COD). Moreover, the IS consisted of mainly oxalate and calcium. Results from the present study indicate the IS is COD. The influence of the IS on the purity of pectin was also studied. The presence of the IS in the pectins indicated the IS can precipitate with pectins during the alcohol precipitation, thereby contaminating the resulting pectins.

Antioxidant and antimicrobial activities of essential oil and extracts of Saurauia lantsangensis hu root.

Antioxidant and antimicrobial activities of the essential oil and n-hexane (HEE), chloroform (CHE), ethyl acetate (EAE), and methanol (MEE) extracts, respectively, from the root of Saurauia lantsangensis Hu were investigated. The GC-MS analysis revealed 39 compounds representing 96.41% of the oil containing T-muurolol (13.85%), acetophenone (7.46%), α-cadinol (6.26%), methyl palmitate (5.36%), n-hexadecanoic acid (4.31%), torreyol (3.69%), and isospathulenol (3.48%) as major components. Antioxidant activities determined by three various testing systems, i. e. DPPH radical scavenging, superoxide anion radical scavenging, and reducing power assay, increased in the order: HEE < CHE < oil < MEE < EAE. CHE, EAE, MEE and oil exhibited a promising antimicrobial effect determined as the diameter of zones of inhibition (13.3 - 16.2, 16.5 - 20.4, 13.5 - 16.6, and 16.5 - 22.7 mm), respectively, along with their respective MIC values (500 - 1000, 125 - 500, 250 - 500, and 250 - 500 μg/ml) against Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli), Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus), and a yeast (Hansenula anomala).

28-day repeated dose oral toxicity of human copper-zinc superoxide dismutase from recombinant Pichia pastori in rats.

Human copper/zinc superoxide dismutase from recombinant Pichia pastori (RH-Cu/Zn-SOD) was orally administered, via gavage, to Sprague-Dawley rats at 500, 1,000, and 2,000 mg/kg body weight/day for 28 days. During the 28-day period, animals were examined for evidence of toxicity; there were no deaths, and in-life physical signs were normal. On day 29, the animals were exsanguinated, examined for gross pathology, and tissues were preserved for histopathology. Although statistical differences were noted in some hematology and clinical chemistry, they were of questionable biological significance. The results of the 28-day oral administration demonstrated a lack of toxicity of RH-Cu/Zn-SOD in rats. There were no treatment-related, toxicologically relevant changes in clinical signs, growth, food consumption, hematology, clinical chemistry, organ weights, or pathology. The no observed adverse effect level was greater than 2,000 mg/kg/day for RH-Cu/Zn-SOD in rats.