Jing-Kun Yan

Effect of extraction media on preliminary characterizations and antioxidant activities of Phellinus linteus polysaccharides

Three partially purified polysaccharides were extracted from Phellinus linteus mycelia using hot water, 1% (NH4)2C2O4, and 1.25M NaOH/0.05% NaBH4, and the extracts were named PL-W, PL-A, and, PL-N respectively. PL-N mainly comprised xylose and arabinose with a high molecular weight (Mw) and the highest carbohydrate and uronic acid contents. PL-W and PL-A were mainly composed of glucose with high and low Mw fractions in various ratios. All three polysaccharides existed as compact coils in aqueous solutions and exhibited strong scavenging capacity and antioxidant activities in a concentration-dependent manner. The polysaccharides also had high uronic acid and carbohydrate contents and strong antioxidant activities. The Mws, monosaccharide compositions, and chemical structures of the polysaccharides also affected their antioxidant activities. PL-A and PL-N had better antioxidant activities and could thus be developed as potential natural antioxidant agents for applications in food additives and biomedical industries.

Ultrasonic effects on the degradation kinetics, preliminary characterization and antioxidant activities of polysaccharides from Phellinus linteus mycelia

In this study, a high-molecular-weight polysaccharide PL-N isolated from the alkaline extract of Phellinus linteus mycelia was degraded by ultrasound. Results showed that ultrasound treatment at different ultrasonic intensities decreased the intrinsic viscosity and molecular weight of PL-N, as well as narrowed the molecular weight distribution. A larger reduction in intrinsic viscosity and molecular weight was caused by a higher ultrasonic intensity. The degradation kinetics model was fitted to (1/Mt-1/M0)=k·t, and the reaction rate constant (k) increased with increasing ultrasonic intensity. Ultrasound degradation did not change the primary structure of PL-N, and scanning electron microscopy analysis indicated that the morphology of the original PL-N was different from that of degraded PL-N fractions. Antioxidant activity assays in vitro indicated that the degraded PL-N fraction with low molecular weight had stronger hydroxyl radical scavenging capacity and higher TEAC and FRAP values.

Structural characteristics and antioxidant activities of different families of 4-acetamido-TEMPO-oxidised curdlan

Regioselective oxidation was applied to commercial curdlan for the preparation of its water-soluble derivatives with improved antioxidant activities, using a 4-acetamido-2,2, 6,6-tetramethylpiperidine-1-oxyl radical/NaClO/NaClO2 system at pH 4.8 and 40°C. The structural features, molecular properties, and chain conformations of the oxidised curdlans were determined using Fourier transform (FT) infrared and FT Raman spectroscopy, carbon nuclear magnetic resonance, X-ray diffraction, and size-exclusion chromatography with multi-angle laser-light scattering analyses. The C6 primary hydroxyls of curdlan were successfully oxidised into carboxylate groups with less depolymerization, and no aldehyde groups were formed during oxidation. The crystalline region of curdlan was destroyed after oxidation. The oxidised curdlans formed random coils in aqueous solution, and the chain became more flexible and expanded with increasing carboxylate contents from 2.07mmol/g to 4.87mmol/g. The high polyglucuronic acid derivative (Cur-24) showed the best antioxidant activity in TEAC and FRAP assays, thus it could be explored as novel potential antioxidants for dietary and therapeutic applications.

Structural features and antitumor activity of a novel polysaccharide from alkaline extract of Phellinus linteus mycelia

A novel high molecular weight polysaccharide (PL-N1) was isolated from alkaline extract of the cultured Phellinus linteus mycelia. The weight average molecular weight (Mw) of PL-N1 was estimated at 343,000kDa. PL-N1 comprised arabinose, xylose, glucose, and galactose in the molar ratio of 4.0:6.7:1.3:1.0. The chemical structure of PL-N1 was investigated by FTIR and NMR spectroscopies and methylation analysis. The results showed that the backbone of PL-N1 comprised (1→4)-linked β-D-xylopyranosyl residues, (1→2)-linked α-D-xylopyranosyl residues, (1→4)-linked α-D-glucopyranosyl residues, (1→5)-linked β-D-arabinofuranosyl residues, (1→4)-linked β-D-xylopyranosyl residues which branched at O-2, and (1→4)-linked β-D-galactopyranosyl residues which branched at O-6. The branches consisted of (1→)-linked α-D-arabinofuranosyl residues. Antitumor activity assay in vitro showed that PL-N1 could inhibit the growth of HepG2 cells to a certain extent in a dose-dependent manner. Thus, PL-N1 may be developed as a potential, natural antitumor agent and functional food.

Green synthesis of biocompatible carboxylic curdlan-capped gold nanoparticles and its interaction with protein

This study demonstrates a facile, green strategy for the preparation of gold nanoparticles (AuNPs) from chloroauric acid (HAuCl4) using carboxylic curdlan (Cc) as both reducing and stabilizing agent. The as-prepared AuNPs are characterized by UV-vis spectroscopy, high resolution transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectrometry and Fourier transform infrared spectroscopy. The results indicated that the particle size of the AuNPs changes with variations in the reaction time and concentrations of Cc and HAuCl4. The spherical AuNPs are well dispersed, exhibiting high stability even after six months storage. The carboxylic groups (COO(-)) in the Cc molecules tend to adsorb and stabilize the surface of the AuNPs. The interaction between BSA and the Cc-capped AuNPs was investigated using fluorescence and circular dichroism spectroscopies. The results indicated that the BSA molecules adsorb on the surface of the AuNPs, without significant change in its helical structure even after conjugation with the AuNPs.

Effects of ultrasound on molecular properties, structure, chain conformation and degradation kinetics of carboxylic curdlan

In this study, high-intensity ultrasound (20 kHz), a simple, effective and without any additive method, was used to the degradation of carboxylic curdlan (Cc) produced by 4-acetamido-TEMPO-mediated oxidation. The effects of ultrasound on molecular properties, structure and chain conformations of Cc were investigated by viscometry, size-exclusion chromatography with multiangle laser-light scattering (SEC-MALLS) analysis, as well as FTIR and NMR spectroscopies. The results indicated that the intrinsic viscosity [η] and the weight-average molecular weight (Mw) of Cc decreased obviously after ultrasound, and a uniform and narrow distribution of degradation product was obtained. The z-average radius of gyrations (Rg) firstly increased and then decreased as the sonication time prolonged. Ultrasound destroyed the hydrogen bonds resulting in the transition from compact random coil conformation to more flexible and even shorter extended chains. Ultrasonic treatment could not alter the primary chemical structure of Cc molecules according to the structural analysis by FTIR and NMR spectroscopies. Degradation kinetics based on Schmid model was applied to estimate the degradation rate constant k. It was found that the k value of Cc decreased with increasing the polymer concentration from 0.05 to 0.2% (w/v).

Green synthesis of silver nanoparticles using 4-acetamido-TEMPO-oxidized curdlan

A facile, simple, and eco-friendly method using 4-acetamido-2,2,6,6-tetramethypiperidine-1-oxyl radical-oxidized curdlan (Oc) as both reducing and stabilizing agents was developed for the fabrication of silver nanoparticles (AgNPs) from silver nitrate (AgNO₃). The structure, morphology, and particle size of the as-prepared AgNPs were investigated by ultraviolet-visible spectroscopy, transmission electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, and dynamic laser light scattering. The well-dispersed AgNPs were sphere like with a mean diameter of 15 nm. Their formation was dependent on reaction duration, reaction temperature, Oc concentration, and AgNO₃ concentration. Fourier transform-infrared and Raman spectra demonstrated that the as-prepared AgNPs can readily bind covalently with the carboxylate groups of Oc through the strong monodentate interaction in the reaction medium.

Self-aggregated nanoparticles of carboxylic curdlan-deoxycholic acid conjugates as a carrier of doxorubicin.

In this study, a new non-toxic, biodegradable, biocompatible and water-soluble carboxylic curdlan bearing the dissociable COOH group in 100% purity, which was prepared by 4-acetamido-TEMPO-mediated oxidation, was hydrophobically modified by deoxycholic acid (DOCA) to attain novel amphiphilic curdlan derivatives (CCDs) for the preparation of nano-carriers for antitumor drug doxorubicin (DOX). Under the effect of ultrasonication, the carboxylic curdlan derivatives in water were self-aggregated into spherical nanoparticles with diameters ranging from 214 nm to 380 nm. The critical aggregation concentrations decreased from 0.047 mg/mL to 0.016 mg/mL with increasing DS of DOCA. DOX-loaded CCD nanoparticles were prepared in an aqueous medium with dialysis method. The DOX-CCD nanoparticles exhibited pH- and dose-dependent drug release profiles during in vitro release experiments. Moreover, the drug transport mechanism was Fickian diffusion according to the Ritger-Peppas model. The CCD nanoparticles might be explored as potential carriers for hydrophobic drugs with controlled release and delivery functions.

Ultrasound enhanced production and antioxidant activity of polysaccharides from mycelial fermentation of Phellinus igniarius

In this study, a novel flat-plate ultrasound technology was developed to stimulate polysaccharides production from Phellinus igniarius mycelial fermentation. Three-factor-three-level Box-Behnken design was used to optimize ultrasonic treatment time, duty cycle time and culture time for a high yield of P. igniarius polysaccharides (PIPS). Optimal conditions were found to be ultrasound treatment time 65 min, duty cycle time 25s, and culture time 3.8d that gave a maximum PIPS yield of 1.8002 g/L, which increased ∼ 22.64% compared with the control (without any ultrasound). PIPS mainly contained low-molecular weight (MW) polysaccharides (3.1 kDa, 80%) composed of glucose, rhamnose and mannose in a molar ratio of 11.0:14.0:1.0. PIPS with higher carbohydrate and uronic acid contents exhibited strong antioxidant activities in vitro. Laser scanning confocal microscope (LSCM) observations suggested that ultrasound could change the morphology and structure of P. igniarius mycelium, and accelerate the transfer of nutrients and metabolites.

Three-phase partitioning for efficient extraction and separation of polysaccharides from Corbicula fluminea

Three-phase partitioning (TPP), which is a simple, efficient, and green bioseparation technique, was used to extract and separate polysaccharides from Corbicula fluminea (CFPS). The optimal parameters with a high yield of 9.32% were as follows: mass fraction of (NH4)2SO4, 20.0% (w/v); amount of t-butanol, 9.8mL; temperature, 35.3°C; extraction time, 30min; and pH 6.0. The purified CFPS after TPP consisted of d-glucose, d-glucosamine, and d-mannose in a molar ratio of 57.1: 5.6:1.0 with high purity (86.5%) and different molecular weights (1311.1 and 41.5-92.8kDa). Amino acid analysis, UV-vis absorption and Fourier transform-infrared spectra indicated that the purified CFPS was a proteoglycan with O-glycosidic bonds. Moreover, the purified CFPS possessed strong free-radical scavenging abilities and antioxidant activities in vitro. The obtained Trolox equivalent antioxidant capacity and ferric-reducing ability of plasma values were 95.01μmol Trolox/g sample and 38.30μmol Fe2+/g sample, respectively.