Entrapping curcumin in the hydrophobic reservoir of rice proteins toward stable antioxidant nanoparticles.

Loading hydrophobic phytochemicals by protein particles is challenged by either insufficient loading capacity or colloidal instability. In this study, hydrosoluble curcumin-loaded nanoparticles were prepared using hydrophobic rice proteins (RPs). The fabrication was facilitated by dissolving curcumin and RPs at pH 12.0 before neutralizing the basicity. The formation of nanoparticles was studied by fluorescence and infrared spectroscopy, and the microstructures were studied by transmission electron microscopy. The results showed the entrapping of curcumin inside the hydrophobic reservoir formed by the acid-induced refolding of RPs. Due to promoted burial of the hydrophobic moieties, the curcumin-loaded RP-nanoparticles displayed excellent colloidal stability during the 28-day storage. Bearing 144.41 mg/g protein of curcumin, the nanoparticles demonstrated prominent antioxidant properties, with the DPPH scavenging capacity increased by up to 88.62% compared to the free curcumin. This study harnessed hydrophobic attractions as a tool for management of the protein-phytochemical interactions, overcoming colloidal instabilities of both individual components.

Synthesis of Rice Husk-Based MCM-41 for Removal of Aflatoxin B1 from Peanut Oil.

Edible oils, especially peanut oil, usually contain aflatoxin B1 (AFB1) at extremely high concentrations. This study focused on the synthesis of rice husk-based mesoporous silica (MCM-41) for the removal of AFB1 from peanut oil. MCM-41 was characterized by X-ray diffraction, N2 physisorption, and transmission electron microscope. MCM-41 was shown to have ordered channels with high specific surface area (1246 m2/g), pore volume (1.75 cm3/g), and pore diameter (3.11 nm). Under the optimal concentration of 1.0 mg/mL of the adsorbent dose, the adsorption behavior of MCM-41, natural montmorillonite (MONT), and commercial activated carbon (CA) for AFB1 were compared. The adsorption of AFB1 in peanut oil onto the three adsorbents was slower compared to that of AFB1 in an aqueous solution. In addition, the pseudo-second-order kinetic model better fit the adsorption kinetics of AFB1, while the adsorption mechanism followed the Langmuir adsorption isotherm on the three adsorbents. The calculated maximum adsorbed amounts of AFB1 on MONT, MCM-41, and CA were 199.41, 215.93, and 248.93 ng/mg, respectively. These results suggested that MCM-41 without modification could meet market demand and could be considered a good candidate for the removal of AFB1 from peanut oil. This study provides insights that could prove to be of economic and practical value.

Complexation of rice glutelin fibrils with cyanidin-3-O-glucoside at acidic condition: Thermal stability, binding mechanism and structural characterization.

The complexation of rice glutelin fibrils (RGFs) with cyanidin-3-O-glucoside (C3G) at acidic condition was investigated. The RGFs at pH 3.5 had a greatest protective effect on the thermal stability of C3G. The binding of C3G for RGFs was exothermic and driven by hydrophobic and electrostatic interactions. The RGFs exhibited a stronger binding interaction with C3G than rice glutelin (RG), resulting from the exposure of hydrophobic groups and positive charges on the fibrils surface, and thus RGFs exhibited better protective effect on C3G. The interaction with C3G resulted in the rearrangement of polypeptide chain, thereby reducing the ß-sheet content. The larger aggregates were observed in RG/RGFs-C3G complexes due to protein-polyphenols aggregation. It was noteworthy that the pre-formed RGFs were restructured into entangled aggregates due to the interaction. This study proposed a novel protein fibril to protect anthocyanins, expanding the application of anthocyanins as stable and functional ingredients in acidic food systems.

Rice peptide nanoparticle as a bifunctional food-grade Pickering stabilizer prepared by ultrasonication: Structural characteristics, antioxidant activity, and emulsifying properties.

In this study, a novel food-grade Pickering stabilizer was fabricated from insoluble rice peptide aggregates that are considered undesirable and formed during the hydrolysis of rice protein using ultrasonication. The results confirmed that ultrasonication was effective in fabricating rice peptide nanoparticles (RPNs) with a spherical appearance, and the particle size was reduced with ultrasonic time, reaching a minimum size of 357.8 nm in 30 min. Moreover, ultrasonic treatment could improve the antioxidant activity of RPNs by promoting the DPPH scavenging (3.5-fold increase) and Fe2+ chelating activity (3.8-fold increase). Notably, the bioactive RPNs could form stable Pickering emulsions that possess both physical and oxidative stability during storage, which might be due to the antioxidative physical barrier formed by RPNs. These findings suggest a new approach for the effective utilization of insoluble aggregates produced during protein hydrolysis as well as provide a novel bifunctional Pickering stabilizer with intrinsic antioxidant properties.

Hydrophilic co-assemblies of two hydrophobic biomolecules improving the bioavailability of silybin.

Benefitting from the versatility and biocompatibility of food sourced materials, the construction of hybrid structures via their molecular interplay generates novel platforms with unexpected properties. In this work, two hydrophobic biomolecules were co-assembled into water-soluble amphiphiles at pH 7 by a facile pH-cycle approach. Wheat gluten proteins (WPs) and shellac were dissolved together at pH 12 followed by a one-step adjustment to pH 7, yielding nanospheres with a protein recovery over 90%. Structural characterization evidenced that shellac stiffened the protein backbones that were resistant against thermodynamically-favored folding. The reactions were proven to be initiated between the protein secondary structures and shellac, forming a relatively unfolded three-dimensional conformation during the acid-induced co-assembly. Silybin was employed as a hydrophobic bioactive model and was entrapped following the same procedure as the hybrid assembly, with a maximum loading of 102 mg g-1 hybrid. The bioavailability of silybin loaded in shellac-WP co-assemblies was improved as assessed by cell proliferation assays, due to the improved dispersity and cell internalization of the co-assemblies. The preparation method based on a simple pH manipulation may be applied to encapsulate various hydrophobic bioactive compounds, apart from the silybin explored in this study.

Preservation of hydrogen peroxide-induced oxidative damage in HepG-2 cells by rice protein hydrolysates pretreated with electron beams.

In this paper, electron beam irradiated rice protein hydrolysates (ERPHs) were assessed for their ability to prevent hydrogen peroxide-induced oxidative stress in human HepG-2 cells. The related mechanism was also studied by analyzing the structural changes. Cytotoxicity experiments showed that rice protein hydrolysates pretreated with electron beam irradiation (EBI) were not toxic to cells if appropriate concentrations were applied. Cell viability markedly increased when the cells were treated with ERPHs before H2O2 induction. Furthermore, the ERPHs effectively suppressed H2O2-induced ROS production and lipid peroxidation and increased the protein expression levels of the intracellular antioxidant enzymes SOD, GSH-Px and CAT in H2O2-stressed HepG-2 cells. Consequently, the loss of mitochondrial membrane potential and cell apoptosis was alleviated. Circular dichroism analysis showed that pretreatment of rice protein with EBI significantly changed the secondary structure (the conversion of α-helices to random coils), which is beneficial to the improvement of its antioxidative activity. ERPHs exhibited stronger antioxidative effects than those without irradiation, possibly because of the difference in molecular weight distribution and amino acid composition. These findings indicate an efficient way to produce peptides with better antioxidant activity.

Absorption Rates and Mechanisms of Avenanthramides in a Caco-2 Cell Model and Their Antioxidant Activity during Absorption.

Avenanthramides (AVNs) are a unique kind of polyphenols that were only detected in the oats and have been demonstrated to exhibit strong antioxidant activities but low bioavailability. The purpose of the present research was to evaluate the absorption rates and mechanisms of AVNs (AVN 2c, AVN 2f, and AVN 2p) using a human colon adenocarcinoma cell line (Caco-2) cell model and clarify the influence of the absorption process on the antioxidant capacities of AVNs. Furthermore, the absorption rates and antioxidant activities of ferulic acid and caffeic acid were compared with those of AVNs. Results showed that the apparent absorption rates (Papp) of AVN 2c, AVN 2f, and AVN 2p were 0.65 ± 0.05 × 10-6, 1.18 ± 0.16 × 10-6, and 1.44 ± 0.09 × 10-6 cm/s, respectively, which were significantly lower than those of caffeic acid (3.76 ± 0.31 × 10-6 cm/s) and ferulic acid (1.69 ± 0.13 × 10-5 cm/s). Moreover, the metabolites (caffeic acid, ferulic acid, and AVN 2f) of AVNs after absorption were detected and quantified by high-performance liquid chromatography-mass spectrometry. Before absorption, although the antioxidant capacities of AVNs were significantly stronger than those of ferulic acid and caffeic acid, there was an opposite result after absorption. In addition, AVNs transported the Caco-2 monolayer by paracellular diffusion and were affected by monoamine oxidase and efflux transporters (P-gp, MRP2) during absorption. The co-administration of quercetin could significantly improve the absorption rates of AVNs.

Effect of high energy electron beam on proteolysis and antioxidant activity of rice proteins.

This research focused on the effects of electron beam irradiation (EBI) on the hydrolysis and antioxidant activity of rice proteins (RPs). The RPs were treated with 0, 5, 10, 20 and 30 kGy doses of EBI. The results showed that EBI pretreatment improved significantly (P < 0.05) the degree of hydrolysis, increasing the DH value by more than 15.09% at a dose of 30 kGy. In addition, radical scavenging results showed that EBI treatment had effects on antioxidant activity and could increase the DPPH and ABTS+ radical scavenging activity of rice protein hydrolysates (RPHs) by 32.06% and 79.11%, respectively (30 kGy). The CAA test also confirmed that EBI pretreatment could effectively improve the ability of RPHs to remove intracellular free radicals. Scanning electron microscopy indicated that EBI treatment destroyed microstructures and resulted in cracks and fragments of RPs. Circular dichroism analysis showed that EBI affected the secondary structure of RPs by destroying the α-helix structure. Changes in the UV visible spectra indicated unfolding of RPs by EBI. Amino acid and molecular weight distribution analysis revealed that EBI pretreatment could increase the ratio of antioxidant-related amino acids and produce smaller peptides. Therefore, EBI pretreatment is an efficient method to promote protein proteolysis due to its effect on the molecular conformation as well as on protein microstructure. Moreover, EBI treatment applied before enzymatic hydrolysis has the potential to prepare hydrolysates with high bioactivity.

Co-folding of hydrophobic rice proteins and shellac in hydrophilic binary microstructures for cellular uptake of apigenin.

Developing food structures that combine material properties from two or three components is intriguing as well as challenging. This study reports a simple technique for co-solvation of two hydrophobic biopolymers in a neutral aqueous solution. The process suspended rice proteins (RPs) and shellac at pH 12 with a one-step adjustment to pH 7. Results from scanning electron microscopy, polyacrylamide gel electrophoresis, and fluorescence studies showed that shellac-RP complexes (SRPs) nucleated through hydrophobic attractions between the two biopolymers. As a result, the refolding of the backbones of RPs was resisted, leading to formation of spherical SRPs with less compactness and larger sizes than untreated RPs. The nanoscale spheres were induced with Ca2+ to structural transition to ribbons or networks. The tunable structures were used to entrap and deliver apigenin for improved, controllable cellular uptake in a HepG-2 cell model compared with free apigenin.

Effects of Milk Proteins on the Bioaccessibility and Antioxidant Activity of Oat Phenolics During In Vitro Digestion.

This study investigated the effects of milk solution or milk proteins (casein and whey protein) on the bioaccessibility and antioxidant activity of oat phenolics during in vitro gastric and pancreatic digestion. During digestion, most of oat phenolics were partially degraded by alkaline pH of pancreatic fluid (pH 7.5). For phenolic acids, both milk solution and milk protein only had a slight influence on their bioaccessibility, while exhibited a significant effect on antioxidant activity of oat phenolic extracts and bioaccessibility of avenanthramides (AVs), a kind of bioactive phenols exclusively found in oats. The antioxidant activity and bioaccessibility of AVs were decreased by adding milk and casein, while significantly improved when mixed with milk whey protein. Remarkably, the bioaccessibility of AV 2c, which had the highest antioxidant activity among all phenolic compounds detected in oats, increased above 360% after intestinal digestion by mixing with whey protein. This result suggested the possibility of protecting AVs against digestive alteration and oxidation by milk whey protein. PRACTICAL APPLICATION: In recent years, oats are often consumed with milk under different conditions of preparation, and there have been many oat milk products manufactured by food companies all over the world. The results of this paper showed that the adding of milk may reduce the absorption and antioxidant activity of phenolic compounds from oat. However, the antioxidant activity and bioaccessibility of oat phenolics were significantly increased when mixed with milk whey protein, suggesting that oats could be consumed with milk whey protein to improve their functional properties.

Coordination of Fe(II) to Eugenol to Engineer Self-Assembled Emulsions by Rice Proteins for Iron Fortification.

Fortification of ferrous irons (FeII ) is challenging due to fast oxidation. In this paper, we report that the coordination of FeII to eugenol can effectively inhibit the oxidation of FeII . The coordination was studied by UV-Vis spectra, nuclear magnetic resonance, Raman spectra, and so on, showing that it took less than 1 hr for FeII to be fully oxidized in water, whereas more than 10 days in eugenol. In addition, by gently mixing FeII coordinated eugenol and modified rice protein (MRP) solutions at ambient temperature, core-shell structures <200 nm were spontaneously formed, which can be utilized as protective and delivery systems for the organic ferrous irons. Based on the simulated digestion of MRPs, the FeII loaded emulsions may be delivered into intestinal tract beyond 2-hr oral administration. The results highlight the effectiveness of fortification of ferrous irons via polyphenol coordination combined with self-emulsification, advancing the future oral fortification of ferrous irons towards a feasible approach. PRACTICAL APPLICATION: The coordination of metal ions with food polyphenols can provide the functional food with excellent redox stability. The FeII loaded eugenol emulsified by MRPs can be used as a straightforward protocol for the development of functional ingredients for iron fortification in food industry.

Impact of binding interaction characteristics on physicochemical, structural, and rheological properties of waxy rice flour.

Impact of covalent and non-covalent binding interactions on physicochemical, structural, and rheological properties of waxy rice flour were investigated using several typical types of chemicals. Dynamic rheometer was used to investigate the viscoelastic properties and resistance to deformation or shearing. Both hydrogen bonds and hydrophobic interactions were necessary for waxy rice flour to form a material with stable structure matrix. Besides this, X-ray diffraction pattern and pasting property measurements showed that the relative crystallinity and pasting viscosity values of waxy rice flour exposed to SDS and l-cysteine treatments increased whereas those of urea decreased compared with the control. Addition of acid, alkali, and NaCl might result in electrostatic forces, ion interactions, and indirectly change hydrogen bonds and hydrophobic interactions between starch and protein, which played a synthetic role on property changes of waxy rice flour.

Phenolic contents, cellular antioxidant activity and antiproliferative capacity of different varieties of oats.

The objectives of this research were to determine the phenolic contents, oxygen radical absorbance capacities (ORAC), cellular antioxidant activities (CAA), and antiproliferative capacities of nine oat varieties and four brans in China. Of all varieties, Longyan 3 and Beiyan 1 exhibited the highest total avenanthramides (146.94±7.31 and 120.95±6.66µg/g, respectively) and ORAC values (21.03±0.56 and 21.18±1.45µM Trolox/g, respectively), while Shaotong exhibited the highest total phenolic acids (143.52±9.42µg/g) and CAA values (33.38±1.74µM quercetin/100g). The EC50 of antiproliferative capacities ranged from 167.31±6.42 to 233.42±21.31mg/mL, with the lowest in Beixiao 8 while the highest in Jinyan 8. ORAC values correlated with avenanthramides while CAA values correlated with phenolic acids. Moreover, phenolic contents, antioxidant properties, and antiproliferative capacities of oat brans was higher than that of corresponding whole oats in most cases.

Isolation of a novel calcium-binding peptide from wheat germ protein hydrolysates and the prediction for its mechanism of combination.

To isolate a novel peptide with specific calcium-binding capacity, wheat germ protein was hydrolyzed. The hydrolysates were purified using ultrafiltration, anion-exchange chromatography, gel filtration chromatography, and reversed-phase high performance liquid chromatography. The amino acid sequence of the purified peptide was determined and confirmed to be FVDVT (Phe-Val-Asp-Val-Thr). The calcium-binding capacity of FVDVT reached 89.94±0.75%, increased by 86.37% compared to the hydrolysates. The chelating mechanism between FVDVT and calcium was further investigated by Ultraviolet-Visible absorption spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and 1H nuclear magnetic resonances spectroscopy. The results indicated that the oxygen atoms of the carboxy group and the nitrogen atoms of the amido group provided major binding sites. In addition, aspartic acid and threonine show considerable capacity for incorporating with calcium by donating electron pairs. This study provides a feasible approach to isolate calcium-binding peptides and to clarify the possible binding mechanism of calcium and peptide.

In vivo toxicity assessment of deoxynivalenol-contaminated wheat after ozone degradation.

The effect of ozone on deoxynivalenol (DON) detoxification was investigated. Ozone treatment could significantly reduce the levels of DON in wheat; 53% of DON in wheat was decomposed with 90 mg l-1 of ozone at a flow rate of 15 l min-1 for 4 h. The safety of DON-contaminated wheats (DCWs) untreated/treated by ozone was also evaluated. Institute of Cancer Research (ICR) mice were divided into a standard diet group and five experimental diet groups for a 51-day orally administration experiment. In the experiment, no remarkable changes in the general appearance of the mice were observed, and all the mice survived until the scheduled necropsy. The results of sub-chronic toxicity indicated that mice fed on DCWs alone had significantly decreased in body weight gain, thymus and spleen weights, ratios of liver, thymus and spleen to body weight, blood indices (red blood cell, haemoglobin, white blood cell), and pro-inflammatory cytokines (interleukin-6 (IL-6), tumour necrosis factor alpha (TNF-α)), while showing a significant increase in alanine aminotransferase, aspartate aminotransferase, blood creatinine and blood urea nitrogen levels. Histopathological examination indicate that DON elicited some degree of toxicity on the liver, kidney and thymus tissue. Mice fed on DCWs treated by ozone mitigated the adverse effects compared with mice fed on DCWs. All the results suggested that the deleterious effects of DON could be highly reduced by ozone, and ozone itself shows minor toxic effects on animals in this process.

Antitumor activities and immunomodulatory of rice bran polysaccharides and its sulfates in vitro.

Polysaccharides purified from rice bran show antitumor activity against tumor cells, yet the mechanism of this action remains poorly understood. To address this issue, our study evaluated the effect of rice bran polysaccharides on mouse melanoma cell line B16, and Raw264.7 macrophages. Rice bran polysaccharides (RBP) failed to inhibit B16 cell growth in vitro. However, Raw264.7 macrophages treated by RBP enhancement of cytotoxic effects. The cytotoxicity was confirmed by the stimulation of nitric oxide (NO) production and tumor necrosis factor-α (TNF-α) secretion on Raw264.7 macrophages in a dose-dependent manner. RBP2, a fraction of RBP, notably enhanced the inhibition of B16 cells and boosted the immunepotentiation effect compared with RBP. To further enhance the inhibition of B16 cell growth, sulfated polysaccharides (SRBP) was derived using the chlorosulfonic acid-pyridine method. SRBP2 was found to suppress B16 cell growth, reduce B16 cell survival and stimulate NO and TNF-α production. However, SRBP2 displayed a cytotoxic effect on Raw264.7 macrophages. These results suggest that the antitumor activity of RBP and RBP2 is mediated mainly through the activation of macrophages. SRBP2 exerts its antitumor activity by inducing apoptosis in tumor cells and the secretion of NO and TNF-α.

Protective effects of rice dreg protein hydrolysates against hydrogen peroxide-induced oxidative stress in HepG-2 cells.

In this paper, the effects of rice dreg protein hydrolysates (RDPHs) obtained by various proteases on hydrogen peroxide-induced oxidative stress in HepG-2 cells were investigated. Cell cytotoxicity was evaluated through the aspects of cell viability, ROS level, antioxidant enzyme activity, and production of malondialdehyde (MDA). Cell apoptosis was assessed by flow cytometry. Molecular weight distribution was analyzed by gel permeation chromatography, and amino acid composition was measured using an automatic amino acid analyzer. The survival of cells and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were significantly increased through the pre-incubation of HepG-2 cells with RDPHs before H2O2 exposure. Additionally, these pretreatments also resulted in a reduction in ROS and MDA levels. As a result, apoptosis and loss of mitochondrial membrane potential of the HepG-2 cells were alleviated. Furthermore, the protective effects of protein hydrolysates obtained by various proteases were noticeably distinct, in which RDPHs prepared by alkaline protease showed higher antioxidant activities. The difference in the protective effects might be attributed to the specific peptide or amino acid composition. Therefore, enzymatic hydrolysis with different enzymes studied here could attenuate H2O2-induced cell damage, and the type of protease greatly influenced the anti-oxidative activity. Particularly, optimum use of Alcalase could produce peptides with higher antioxidant activity.

Calcium-binding capacity of wheat germ protein hydrolysate and characterization of Peptide-calcium complex.

This study investigates the ability of various wheat germ protein hydrolysates (WGPHs) to bind calcium and characterizes the peptide-calcium complexes. We demonstrate that the amount of Ca bound depended greatly on the type of enzyme, degree of hydrolysis (DH), amino acid composition, and molecular mass distribution of different hydrolysates. The maximum level of Ca bound (67.5 mg·g(-1)) occurred when Alcalase was used to hydrolyze wheat germ protein at a DH of 21.5%. Peptide fragments exhibiting high calcium-binding capacity had molecular mass <2000 Da. The calcium-binding peptides mainly consisted of Glu, Arg, Asp, and Gly, and the level of Ca bound was related to the hydrophobic amino acid content in WGPHs. UV-visible and Fourier transform infrared spectra demonstrate that amino nitrogen atoms and oxygen atoms on the carboxyl group were involved in complexation. Therefore, wheat germ protein is a promising protein source for the production of calcium-binding peptides and could be utilized as a bioactive ingredient for nutraceutical food production.

The interaction between tea polyphenols and rice starch during gelatinization.

The interaction between tea polyphenols (TPLs) and rice starch (RS) during gelatinization has been studied. In the RVA analysis, TPLs-fortified RS exhibited no clearly defined peak viscosity and hot paste viscosity. After excluding other factors, irregular viscosity changes were attributed to the strong interactions between RS and TPLs during pasting/gelatinization. Subsequently, the coupling constants of samples A (the gelatinized sample of the blend of 16% TPLs and RS) and B (the blend of 16% TPLs and gelatinized RS sample) in (1)H-NMR measurements were found to be the difference. Sample A had two coupling constants, (26h)J(HH) = 82.08, 100.77 Hz and (6h)J(HH) = 35.57 Hz, whereas Sample B had one larger coupling constant, (9h)J(HH) = 140.24 Hz. This implied that these two samples differed in H-H interaction and interaction strength of sample A may be stronger than that of sample B. More important is, sample A had clearly broadened O-H stretching and frequency red-shifts of C-O-H bending as compared with sample B in quantitative FT-IR analysis. The overall results indicate that TPLs and RS can have hydrogen bonding interaction during gelatinization.

Characterization and anti-tumor activities of sulfated polysaccharide SRBPS2a obtained from defatted rice bran.

A novel chemically sulfated polysaccharide SRBPS2a with potent anti-tumor activity was derived from defatted rice bran by chlorosulfonic acid-pyridine (CSA-Pyr) method. The average molecular weight of SRBPS2a was 3.5 x 10(5) Da and the degree of sulfation (DS) was 1.29. The Fourier-transform infrared spectra (FT-IR) and 13C NMR spectroscopy analysis revealed that SRBPS2a was mainly consist of beta-(1-->3)-D-galactopyranosyl residues, the sulfate substitution site was on C-2 and C-4 while the side chains were cut off during the sulfated reaction. Furthermore, SRBPS2a exhibited evident growth inhibition on mouse mammary tumor EMT-6 cells both in vitro and in vivo.