Ruihong Liang

Pectic-oligosaccharides prepared by dynamic high-pressure microfluidization and their in vitro fermentation properties

Pectic-oligosaccharides (POSs) were prepared from apple pectin by dynamic high-pressure microfluidization (DHPM). Operating under selected conditions (pectin concentration 1.84%, solution temperature 63 °C, DHPM pressure 155MPa and number of cycles 6 passes), 32.92% of the pectin was converted into POS. The resulting POS contains 29.56% galacturonic acid and 58.53% neutral sugars. The prebiotic properties of POS were then evaluated using a fecal batch culture fermentation. The POS increased the number of Bifidobacteria and Lactobacilli, and produced a higher concentration of acetic, lactic, and propionic acid than their parent pectin. Furthermore, POS decreased the number of Bacteroides and Clostridia while their parent pectin increased them. Moreover, the effects of POS on the growth of these bacteria and production of short-chain fatty acids are comparable to those of the most studied prebiotic, fructooligosaccharide. These results indicated that the POS prepared by DHPM has a potential to be an effective prebiotic.

Storage stability and skin permeation of vitamin C liposomes improved by pectin coating

A transdermal drug delivery system was prepared by high methoxyl pectin (HMP) or low methoxyl pectin (LMP) coated vitamin C liposomes. HMP coated vitamin C liposomes (HMP-L) and LMP coated vitamin C liposomes (LMP-L) exhibited an increase in average diameter (from 66.9 nm to 117.3 nm and 129.6 nm, respectively), a decrease in zeta potential (from -2.3 mV to -23.9 mV and -35.5 mV, respectively), and a similar entrapment efficiency (48.3-50.1%). Morphology and FTIR analysis confirmed that pectin was successfully coated on the surface of vitamin C liposomes mainly through the hydrogen bonding interactions. Besides, HMP-L and LMP-L exhibited an obvious improvement in storage stability, with lower aggregation, oxidation of lipid and leakage ratio of vitamin C from liposomes, and LMP-L showed better physicochemical stability than HMP-L. Moreover, skin permeation of vitamin C was improved 1.7-fold for HMP-L and 2.1-fold for LMP-L after 24 h, respectively, compared with vitamin C nanoliposomes. Therefore, this study suggested that pectin coated liposomes, especially the LMP-L, could be a promising transdermal drug delivery system with better storage stability and skin permeation.

Characterization and Bioavailability of Tea Polyphenol Nanoliposome Prepared by Combining an Ethanol Injection Method with Dynamic High-Pressure Microfluidization

Tea polyphenols are major polyphenolic substances found in green tea with various biological activities. To overcome their instability toward oxygen and alkaline environments, tea polyphenol nanoliposome (TPN) was prepared by combining an ethanol injection method with dynamic high-pressure microfluidization. Good physicochemical characterizations (entrapment efficiency = 78.5%, particle size = 66.8 nm, polydispersity index = 0.213, and zeta potential = -6.16 mv) of TPN were observed. Compared with tea polyphenol solution, TPN showed equivalent antioxidant activities, indicated by equal DPPH free radical scavenging and slightly lower ferric reducing activities and lower inhibitions against Staphylococcus aureus , Escerhichia coli , Salmonella typhimurium , and Listeria monocytogenes . In addition, a relatively good sustained release property was observed in TPN, with only 29.8% tea polyphenols released from nanoliposome after 24 h of incubation. Moreover, TPN improved the stability of tea polyphenol in alkaline solution. This study expects to provide theories and practice guides for further applications of TPN.

Improved in vitro digestion stability of (−)-epigallocatechin gallate through nanoliposome encapsulation

(-)-Epigallocatechin gallate (EGCG) is unstable and degraded in near-neutral or alkaline fluids. To overcome its limitation, EGCG nanoliposome (EN) was prepared by an ethanol injection method combined with dynamic high-pressure microfluidization. EN possessed good physicochemical characterizations (high entrapment efficiency=92.1%, small average particle size=71.7nm, low polydispersity index=0.286 and zeta potential=-10.81mv). EN exhibited a relative good sustained release property. Stability of EGCG in simulated intestinal fluid (SIF) was significantly improved by nanoliposome encapsulation. After 1.5h incubating in SIF without or with pancreatin, the residual EGCG of EN was 31.2% and 47.7% respectively, but the residual EGCG in EGCG solution was only 3.4% and 3.5% respectively. The degenerations of in vitro antioxidant activities of EGCG were effectively slowed by nanoliposome encapsulation. This study expects to provide theories and practice guides for further applications of EN.

Pectin Modifications: A Review

In recent years, the interest in studying modification of pectin has increased. A number of hydroxyl and carboxyl groups distributed along the backbone as well as a certain amount of neutral sugars presented as side chains make pectin capable of preparing a broad spectrum of derivatives. By forming pectin derivatives, their properties may be modified and some other new functional properties may be created. This article attempts to review the information about various methods used for pectin modification, including substitution (alkylation, amidation, quaternization, thiolation, sulfation, oxidation, etc.), chain elongation (cross-linking and grafting) and depolymerization (chemical, physical, and enzymatic degradation). Characteristics and applications of some pectin derivatives are also presented. In addition, the safety and regulatory status of pectin and its derivatives were reviewed.

The effect of citric acid on the activity, thermodynamics and conformation of mushroom polyphenoloxidase.

Few reports have focused on the effect of citric acid on thermodynamics and conformation of polyphenoloxidase (PPO). In this study, variations on activity, thermodynamics and conformation of mushroom PPO induced by citric acid (1-60mM) and relationships among these were investigated. It showed that with the increasing concentration of citric acid, the activity of PPO decreased gradually to an inactivity condition; inactivation rate constant (k) of PPO increased and the activation energy (Ea) as well as thermodynamic parameters (ΔG, ΔH, ΔS) decreased, which indicated that the thermosensitivity, stability and number of non-covalent bonds of PPO decreased. The conformation was gradually unfolded, which was reflected in the decrease of α-helix contents, increase of β-sheet and exposure of aromatic amino acid residuals. Moreover, two linear relationships of relative activities, enthalpies (ΔH) against α-helix contents were obtained. It indicated that changes of activity and thermodynamics might correlate to the unfolding of conformation.

Stability and conformational change of methoxypolyethylene glycol modification for native and unfolded trypsin

The effect of succinimidyl carbonates activated methoxypolyethylene glycol (mPEG-SC) on the catalytic properties and conformation of native trypsin and dynamic high-pressure microfluidisation (DHPM) induced unfolded trypsin was studied. The thermal stability of unfolded trypsin was enhanced more significantly than that of native trypsin between 45 and 70°C. The autolysis analysis indicated that modified unfolded trypsin was markedly more resistant to autolysis compared to modified native trypsin between 40 and 180min. Upon mPEG-SC conjugation, the Km value of the enzyme decreased by about 2-fold, and the catalytic efficiency (Kcat/Km) increased by about 3-4-fold. Moreover, the increased thermal stability of unfolded trypsin might be due to the lower surface hydrophobicity and the higher hydrogen bond formation after mPEG-SC modification, which was reflected in the decrease of UV absorbance, the quenching and blue shift of fluorescence spectra, as well as the increase of β-sheet content.

Storage Stability and Antibacterial Activity of Eugenol Nanoliposomes Prepared by an Ethanol Injection-Dynamic High-Pressure Microfluidization Method

Eugenol is a major phenolic component with diverse biological activities. However, it is difficult to formulate into an aqueous solution due to poor water solubility, and this limits its application. In the present study, eugenol nanoliposomes (EN) were prepared by combining the ethanol injection method with the dynamic high-pressure microfluidization method. Good physicochemical characterizations of EN were obtained. The successful encapsulation of eugenol in nanoliposomes was confirmed by Fourier transform infrared spectroscopy. A good storage stability of EN was confirmed by its low variation of average particle diameter and encapsulation efficiency after 8 weeks of storage. No oil drops were found in EN after 8 weeks of storage at 4°C and at room temperature, which suggested that the poor water solubility of eugenol was overcome by nanoliposome encapsulation. Compared with that of eugenol solution, a relatively good sustained release property was observed in EN. The antibacterial activity of EN against four common foodborne pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes) was evaluated in both Luria broth and milk medium.

The effect of high speed shearing on disaggregation and degradation of pectin from creeping fig seeds

The effect of high speed shearing (HSS) on disaggregation and degradation of pectin from creeping fig seeds was investigated. It was found that disaggregation and degradation occurred during the whole shearing process. When pectin solution was sheared at 24,000 rpm for less than 8h, degradation happened but disaggregation was dominant during this period. After 8h, degradation became obvious, however, a small amount of aggregates remained even after 24h treatment, indicating that HSS may not eliminate aggregates efficiently. The presence of aggregates is one of the most probable causes for the inaccurate determination of molecular weight of pectin. A new method was proposed for calculating more accurately the molecular weight based on the change of the reducing sugar content and the variation of molecular weight. Determination of unsaturated uronide and FT-IR spectra analysis indicated that neither β-elimination nor demethoxylation occurred during the HSS, and no new functional group was formed during the HSS process.

Major Polyphenolics in Pineapple Peels and their Antioxidant Interactions

Major polyphenolic compounds in pineapple peels were identified and quantified. The antioxidant capacities of pineapple peel extracts and these polyphenolic compounds were determined using DPPH• scavenging capacity and phosphomolybdenum method. Effects of these polyphenolics’ interactions on their antioxidant capacity were also evaluated. Gallic acid (31.76 mg/100 g dry extracts), catechin (58.51 mg/100 g), epicatechin (50.00 mg/100 g), and ferulic acid (19.50 mg/100 g) were found to be the main polyphenolics in pineapple peels. The IC50 for DPPH• scavenging assay of the extracts was 1.13 mg/ml and total antioxidant capacity was 0.037 g ascorbic acid equivalents/g. The order of DPPH• scavenging capacity of per mole of these polyphenolic compounds present in pineapple peels was gallic acid > epicatechin = catechin > ferulic acid, but it was different when using phosphomolybdenum method the order of which was epicatechin. > catechin > gallic acid = ferulic acid. Results of polyphenolics’ interactions indicated no synergistic effects. In the combinations of ferulic acid-epicatechin and ferulic acid-gallic acid, additive effects were found using both antioxidant activity assays.