Effect of Storage Conditions on Phenolic Profiles and Antioxidant Activity of Litchi Pericarp.

Changes of phenolic profiles and antioxidant activity of litchi pericarp during storage at 4 °C for seven days and at room temperature (RT) for 72 h were evaluated in this study. The contents of total phenolic and procyanidin decreased by 20.2% and 24.2% at 4 °C and by 37.8% and 47.8% at RT, respectively. Interestingly, the corresponding reductions of anthocyanins were 41.3% and 73%, respectively. Four phenolic compounds, including epicatechin, procyanidin A2, procyanidin B2, and quercetin-3-O-rutinoside-7-O-α-l-rhamnosidase were detected in litchi pericarp. Their contents after storage at 4 °C and at RT were decreased by 22.1⁻49.7% and 27.6⁻48.7%, respectively. The oxygen radical absorbance capacity (ORAC) and cellular antioxidant activity (CAA) of litchi pericarp decreased by 17.6% and 58.7% at 4 °C, and by 23.4% and 66.0% at RT, respectively. The results indicated that storage at 4 °C preserved more phenolics and retained higher antioxidant activity in litchi pericarp compared to storage at RT, suggesting that storage at 4 °C should be considered as a more effective method for slowing down the degradation of litchi pericarp phenolics.

A Comparison of the Chemical Composition, In Vitro Bioaccessibility and Antioxidant Activity of Phenolic Compounds from Rice Bran and Its Dietary Fibres.

The composition, in vitro bioaccessibility and antioxidant activities of the phenolic compounds in defatted rice bran (DRB) and its soluble and insoluble dietary fibres were systematically evaluated in this study. The total phenolic content of insoluble dietary fibre from DRB (IDFDRB) was much higher than that of the soluble dietary fibre from DRB (SDFDRB) but was 10% lower than that of DRB. Bound phenolics accounted for more than 90% of the total phenolics in IDFDRB, whereas they accounted for 34.2% and 40.5% of the total phenolics in DRB and SDFDRB, respectively. Additionally, the phenolic profiles and antioxidant activities were significantly different in DRB, SDFDRB and IDFDRB. The phenolic compounds in IDFDRB were much less bioaccessibility than those in DRB and SDFDRB due to the higher proportion of bound phenolics in IDFDRB. Considering that bound phenolics could be released from food matrices by bacterial enzymes in the large intestine and go on to exert significant beneficial health effects in vivo, further studies on IDFDRB are needed to investigate the release of the phenolics from IDFDRB via gut microbiota and the related health benefits.

Effects of UV/H2O2 degradation and step gradient ethanol precipitation on Sargassum fusiforme polysaccharides: Physicochemical characterization and protective effects against intestinal epithelial injury.

In this study, the degraded purified fraction from Sargassum fusiforme polysaccharides (SFP), named DSFP, was produced by the treatment of ultraviolet/hydrogen peroxide (UV/H2O2) degradation and step gradient ethanol precipitation. Results showed that the treatment significantly reduced the molecular weight of polysaccharides, from 282.83 kDa to 18.54 kDa, and influenced their surface morphology and roughness. SFP and DSFP were typical sulfated polysaccharides, mainly composed of fucose, galacturonic acid, glucuronic acid, galactose, and mannose. Both SFP and DSFP increased cell migration during intestinal epithelial wound healing and stimulated the cell cycle progression by promoting the transition from G0/G1 to S phase in the rat intestine epithelium cells (IEC-6). But DSFP had a stronger positive effect on wound healing and cell migration than SFP. It reinforced the intestinal barrier function and attenuated lipopolysaccharides-induced intestinal inflammation. DSFP significantly downregulated the expression of Toll-like receptor 4, tumor necrosis factor-α, interleukin-6, interleukin-1ß, and inducible nitric oxide synthase by 53.14%, 92.41%, 66.01%, 68.24%, and 78.09%, respectively, and upregulated that of interleukin-10 by 2.48 folds when compared to the model. Therefore, the treatment (UV/H2O2 degradation and step gradient ethanol precipitation) could effectively improve the protective effects against intestinal epithelial injury.

Structure determination, bitterness evaluation and hepatic gluconeogenesis inhibitory activity of triterpenoids from the Momordica charantia fruit.

Triterpenoids are hypoglycemic substances and flavor components of Momordica charantia L., whether their bitterness correlated with hypoglycemic potential remain unknown. Thus, triterpenoids in M. charantia were isolated by phytochemical methods and identified by spectroscopic analysis. The bitterness levels and hypoglycaemic activity of isolated triterpenoids were evaluated by electronic tongue and hepatic gluconeogenesis assay. Eighteen triterpenoids including two new ones, Momordicoside Y and Z, were identified. Among the six identified bitter triterpenoids, karaviloside III, goyaglycoside C, and momordicoside F2 were bitterer than caffeine (P < 0.05), with caffeine equivalent (CE) values of 289.19, 4.32, and 41.24 mg CE/mg, respectively. Momordicoside Y, charantoside C, momordicoside F1, and momordicoside G could inhibit hepatic gluconeogenesis by 23.9%, 36.2%, 33.4%, 34.4% at 40 µM, respectively. These four compounds could interact with active site of phosphoenolpyruvate carboxykinase in molecular docking simulation. No correlation was observed between hepatic gluconeogenesis inhibitory activity and bitterness of triterpenoids.

Effects of different extraction methods on contents, profiles, and antioxidant abilities of free and bound phenolics of Sargassum polycystum from the South China Sea.

Total phenolic content (TPC), phenolic profiles, and antioxidant activity of free and bound extracts of Sargassum polycystum, obtained by different extraction solvents and hydrolysis methods, were investigated. Aqueous acetone afforded the highest free TPC and antioxidant ability, followed by aqueous ethanol and aqueous methanol. Twelve free phenolic compounds were identified by ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS), including two hydroxycinnamic acids, seven flavonoids, one stilbene, and two phlorotannins. Three to nine different free phenolic compounds were extracted by these solvents with different compositions, including nine by 70% acetone and eight by 70% methanol, 70% ethanol, and 50% ethanol. The highest total content of free phenolic compounds determined by high-performance liquid chromatography-diode array detection was obtained from 70% ethanol. Alkaline hydrolysis afforded higher bound TPC (274.27 mg GAE/100 g DW) and antioxidant ability than acid hydrolysis. Five bound phenolic compounds were characterized by UHPLC-MS and five were released from alkaline hydrolysis, whereas two were released from acid hydrolysis. Total content of bound phenolic compounds released by alkaline hydrolysis was 14.68-fold higher than that by acid hydrolysis. The free and bound TPC, phenolic profiles, and antioxidant activities depended on the extraction solvent used. These results indicate that S. polycystum is a potentially useful antioxidant source and contribute to the development of seaweed-based functional foods. PRACTICAL APPLICATION: Phenolics are usually divided into free and bound forms based on their extractability and interaction with cell wall components. The nutritional effects of bound phenolics in algae have long been neglected. These topics contribute to the development of seaweed-based functional foods.

Hydrolyzed Bound Phenolics from Rice Bran Alleviate Hyperlipidemia and Improve Gut Microbiota Dysbiosis in High-Fat-Diet Fed Mice.

It has been confirmed the lipid-lowering effect of rice bran free phenolics, but it is unknown whether rice bran bound phenolics, the phenolic profile of which differs from the free ones, have a similar effect. Thus, the hypolipidemic effect and potential mechanism of hydrolyzed bound phenolics (HBP) from rice bran was investigated in this study. The results showed that HBP supplementation significantly improved serum lipid profiles of high-fat-diet fed mice. HBP inhibited the activation of nuclear receptors liver X receptor-α (LXRα), sterol regulatory element binding protein 1c (SREBP-1c), and peroxisome proliferators-activated receptors-γ (PPARγ), and, therefore, changed the expressions of their downstream genes, including LDLR, CD36, ACC1, FAS, and DGAT2 in the liver. Moreover, HBP supplementation reversed the high-fat-diet induced gut microbiota dysbiosis. These findings suggest that HBP might alleviate the hyperlipidemia via inhibiting the hepatic de novolipogenesis, regulating the uptake of cholesterol and fatty acid in the liver and their absorption in the gut. The attenuation of microbiota dysbiosis might contribute to the above effects.

Rice bran-modified wheat gluten nanoparticles effectively stabilized pickering emulsion: An interfacial antioxidant inhibiting lipid oxidation.

This study investigated the fabrication of Pickering emulsion stabilized by rice bran-modified wheat gluten nanoparticle (RGNP) and evaluated the effect of rice bran-modification on lipid oxidation of emulsified soybean oil, with native wheat gluten nanoparticle (CGNP) as the control. Compared with CGNP, RGNP exhibited stronger antioxidant activities due to high content of polyphenols. RGNP were roughly spherical (mean size of about 250 nm) with balanced wettability (104.6 ± 2.3°) and had excellent colloidal thermal stability. When used at a concentration of 1.5 wt%, both CGNP and RGNP could stabilize Pickering emulsions at varying oil volume fractions (0.20-0.85). For high internal phase emulsions, nanoparticles adsorbed at an oil-water interface forming an interconnected network structure, depressing the oxidation of soybean oil. RGNP as an interfacial antioxidant further improved the Pickering emulsion' oxidative stability. This work may expand the application of wheat gluten as an antioxidant solid particle in Pickering emulsion.

Influence of UV/H2O2 treatment on polysaccharides from Sargassum fusiforme: Physicochemical properties and RAW 264.7 cells responses.

There are few studies on seaweed polysaccharides with UV/H2O2 treatment, so the aim of this study was to evaluate the effects of UV/H2O2 treatment on physicochemical properties and RAW 264.7 cells responses of polysaccharides from Sargassum fusiforme (PSF). Results showed that the contents of reducing sugar and sulfate in PSF with UV/H2O2 treatment for 2 h increased by 202.86% and 31.77%, respectively, and the contents of total sugar, protein and uronic acid decreased by 14.29%, 57.11% and 43.18% compared with those of original polysaccharides. In addition, UV/H2O2 treatment did not change the monosaccharide types of original polysaccharides, but it could change its monosaccharide composition and surface morphology. Besides, polysaccharides after UV/H2O2 treatment for 0.5-2 h had lower toxicity than original polysaccharides in RAW 264.7 cells. Typically, PSF with UV/H2O2 treatment for 2 h (PSF-T2) could effectively inhibit pro-inflammatory molecules production (including NO, IL-1ß, IL-6 and TNF-α), and down-regulate related genes expression (including Tlr4, Irak, Il-1ß, Il-6, Il-12 and Tnf-α). Therefore, UV/H2O2 treatment is a potential way to prepare polysaccharide with better anti-inflammatory activity.

The possible mechanism of the protective effect of a sulfated polysaccharide from Gracilaria Lemaneiformis against colitis induced by dextran sulfate sodium in mice.

This study aimed to investigate the possible mechanism of the protective effect of a sulfated polysaccharide (SP) from Gracilaria Lemaneiformis against colitis induced by dextran sulfate sodium (DSS). Balb/c mice were gavaged with SP for four weeks, then colon tissue, cecal contents and feces were collected for further analysis. Results showed that SP was effective for inhibiting colon shortening and oedema forming. It could alleviate colonic inflammation via down-regulating the expression of tumor necrosis factor-α (TNF-α), interleukin (IL-6, IL-1ß). Besides, it enhanced the intestinal barrier by up-regulating the expression of tight junction proteins Claudin-1 and Zonula occludens-1 (ZO-1) as well as Mucin (MUC-2). The increased expression of short chain fatty acid (SCFA) receptors including G protein-coupled receptor (GPR43, GPR109A) and olfactory receptor (Olfr78), and SCFA production in feces indicated that most of SCFA were absorbed in colon, which could play positive roles in ameliorating colitis. Furthermore, the results of gut microbiota showed that Enterorhabdus, Desulfovibrio, Alistipes, Bacteroides acidifaciens had closest correlations with the strongest protective effects against colitis. Therefore, SP could alleviate DSS-induced colitis via enhancing intestinal barrier, reducing inflammation, activating SCFA receptors and regulating gut microbiota. It could be developed as functional foods which is good for gut health.

In vitro fermentation characteristics of polysaccharide from Sargassum fusiforme and its modulation effects on gut microbiota.

In this study, polysaccharides from Sargassum fusiforme (SFP) were obtained by cellulase assisted hot water extraction. The chemical composition, structural characteristics, and in vitro fermentation properties of SFP were investigated. Results showed that the contents of total carbohydrate, protein, uronic acid and sulfate in SFP were 83.25%, 1.42%, 12.80% and 7.81%, respectively. It mainly consisted of fucose glucose and galactose, with molecular weight of 255.83 kDa. UV spectrum, FTIR, SEM and AFM results showed that SFP was a typical sulfate polysaccharide with relative smooth surface and regular shape. After in vitro fermentation for 24 h, the pH value of fermentation medium declined significantly (p < 0.05), utilization of carbohydrate was 53.17%. The contents of total SCFAs increased by 10.77 times. Moreover, SFP fermentation could change obviously the microbiota composition. It significantly increased the abundance of Faecalibacterium (increased by 49.07% compared with the Blank24 group), Phascolarctobacterium (increased by 88.06%), Bifidobacterium (increased by 139.13%), Ruminococcaceae_UCG-014 (increased by 177.78%), and Lactobacillus (increased by 400.00%), decreased the abundance of Prevotella_9 (decreased by 34.54%) and Blautia (decreased by 40.79%) at genus level. These results showed that SFP could be utilized by microbiota in human feces, and may have the potential to improve intestinal health.

Structural characteristics and anti-inflammatory activity of UV/H2O2-treated algal sulfated polysaccharide from Gracilaria lemaneiformis.

The study aimed to study the effects on structural characteristics and anti-inflammatory activities of algal sulfated polysaccharides isolated from Gracilaria lemaneiformis (GLP) after a combined treatment of UV irradiation (average irradiance of 6500 mJ/cm2) and H2O2 (50 mmol/L) for various time periods up to 60 min. After a 30-min treatment, the molecular weight and particle size of GLP was decreased by 15 and 2.6 fold, respectively with small but significant decrease in the contents of total sugars, uronic acids and proteins. There seemed to have no starch and the presence of longer side chains of branches in the GLP samples before and after UV/H2O2 treatment based on the I2-KI assay. Scanning electron microscope and atomic force microscope analysis confirmed that the UV/H2O2 treatment could modify the surface morphology of GLP. GLP treated for 5 min possessed the strongest in vitro anti-inflammatory activity by inhibiting the production of nitric oxide, tumor necrosis factor-α and interleukin-6 by 60.49%, 62.81% and 36.29%, respectively in IEC-6 cells when compared to the model. Therefore, UV/H2O2 treatment had the potential to enhance the anti-inflammatory activity of algal sulfated polysaccharides.

Structural characteristic of a sulfated polysaccharide from Gracilaria Lemaneiformis and its lipid metabolism regulation effect.

A sulfated polysaccharide extracted from Gracilaria lemaneiformis (GLP) with a prominent effect in regulating lipid metabolism was isolated. The molecular weight was 31.5 kDa and it was composed mainly of galactose, glucose and xylose. Fourier-transform infrared (FT-IR) spectrum and nuclear magnetic resonance (NMR) analysis suggested that GLP was composed of the following repeating unit: [3-ß-Gal-4(OSO3)-1→4-α-3,6-anhydrogal-2(OSO3)-1→]. GLP could significantly decrease serum total cholesterol, triglyceride and free fatty acid levels and lower alanine aminotransferase and aspartate aminotransferase activities in high-fat-diet mice. Additionally, GLP could keep the body weight and attenuate accumulation of fat surrounding the liver and epididymis induced by high-fat diet. Results of RT-PCR indicated that GLP might regulate lipid metabolism and accelerate free fatty acid oxidation by up-regulating the expression of the PPARα, ACS and CPT1a gene. The present study suggests that GLP may be potentially useful for regulating lipid metabolism.

Co-culture submerged fermentation by lactobacillus and yeast more effectively improved the profiles and bioaccessibility of phenolics in extruded brown rice than single-culture fermentation.

This study aims to investigate the effects of fermentation on the phenolic components and their bioaccessibility in extruded brown rice (EBR). The saccharified solution of EBR (SS-EBR) depicted higher phenolics when fermented by single or co-culture of Lactobacillusplantarum, Lactobacillus fermentum and Saccharomyces cerevisiae for 24 h at 37 °C. The co-culture fermented SS-EBR more significantly enhanced free, conjugated and bound phenolics and flavonoids with total increment of 93.3% and 61.3%, respectively. Fermentation changed the contents and compositions of phenolics in each fraction with more than 10-fold increase in vanillic acid and quercetin contents. Ferulic, p-cumaric and chlorogenic acids were increased by 83.5%, 52.2% and 113.4%, respectively, while kaempferol and cinnamic acid were found only in fermented SS-EBR. Fermentation also improved the oxygen radical absorption capacity (ORAC) and the bioaccessible phenolics in SS-EBR. Hence, the co-culture fermented SS-EBR, can be utilized as a functional supplement to provide more bioaccessible antioxidants.

Phytochemical Profile, Bioactivity, and Prebiotic Potential of Bound Phenolics Released from Rice Bran Dietary Fiber during in Vitro Gastrointestinal Digestion and Colonic Fermentation.

Whole-grain dietary fiber is rich in bound-form phenolics, and the biological activity of this special structural feature has attracted increasing attention. In this study, rice bran dietary fiber (RBDF) was subjected to in vitro gastrointestinal digestion and colonic fermentation to investigate the liberation of bound phenolics and their potential activities. Bound phenolics were released at a higher ratio during colonic fermentation (27.57%) than gastrointestinal digestion (2.68%). Nine phenolic compounds were detected from the fermentation supernatants. The released phenolics showed radical scavenging activity (DPPH and ABTS assays) and α-glucosidase inhibitory activity (IC50 = 19.11 µg GAE/mL). Compared with phenolics-removed RBDF (PR-RBDF), RBDF had a significantly stronger prebiotic effect on the microbes associated with diabetes (Lactobacillus spp., Akkermansia muciniphila, and Faecalibacterium prausnitzii). These findings indicate that bound phenolics may act as important functional components that could contribute to the health benefits of whole-grain dietary fiber.

Physicochemical properties and prebiotic activities of polysaccharides from longan pulp based on different extraction techniques.

Longan pulp polysaccharides were extracted with hot water (LP-H), superfine grinding (LP-S) and superfine grinding-assisted enzymatic treatments (LP-SE). The yields, physicochemical properties and prebiotic activities of polysaccharides were investigated. Compared with LP-H and LP-S, the yield, sugar content, solubility, arabinose and mannose percentage of LP-SE increased while its apparent viscosity, particle size, Mw and glucose percentage declined. Three LPs contained similar glycosidic linkage of →3)-α-l-Araf-(1→, →3,6)-ß-d-Galp-(1→ and α-l-Rhap(l→, while they each contained specific glycosidic linkage of →4)-ß-d-Glcp(l→, →4)-ß-d-Galp-(1→ and →5)-α-l-Araf-(1→ in LP-H, LP-S and LP-SE, respectively. Moreover, LP-SE exhibited stronger stimulation than LP-H and LP-S on the proliferation of Lactobacillus plantarum, Lactobacillus bulgaricus, Lactobacillus fermentum and Leuconostoc mesenteroides. The results indicated three extraction methods had some effect on chemical composition and structure of polysaccharide. LP-SE extracted by superfine grinding-assisted enzymatic treatment exhibited the highest prebiotic activities, which have a great potential in applying in functional food and medical industry.

Physicochemical and biological properties of longan pulp polysaccharides modified by Lactobacillus fermentum fermentation.

Longan polysaccharides are valuable compounds with many biological activities. Lactobacillus fermentum was selected to ferment longan pulp and the polysaccharides from unfermented and fermented longan pulp (denoted as LP and LP-F, respectively) were isolated. Their physicochemical, immunomodulatory and prebiotic activities were investigated. The results revealed that LP-F, the molecular weight of which was lower than that of LP, contained less neutral sugar, uronic acid and glucose but more arabinose, galactose, rhamnose and mannose. Compared with LP, LP-F had better solubility, lower apparent viscosity and particle size. LP-F exhibited stronger stimulation on macrophages secretion of NO and IL-6, as well as better proliferation of Leuconostoc mesenteroides and Lactobacillus casei. In summary, fermentation treatment could change the physicochemical properties and enhance the bioactivity of polysaccharides from longan pulp.

Lychee (Litchi chinensis Sonn.) Pulp Phenolic Extract Provides Protection against Alcoholic Liver Injury in Mice by Alleviating Intestinal Microbiota Dysbiosis, Intestinal Barrier Dysfunction, and Liver Inflammation.

Liver injury is the most common consequence of alcohol abuse, which is promoted by the inflammatory response triggered by gut-derived endotoxins produced as a consequence of intestinal microbiota dysbiosis and barrier dysfunction. The aim of this study was to investigate whether modulation of intestinal microbiota and barrier function, and liver inflammation contributes to the hepatoprotective effect of lychee pulp phenolic extract (LPPE) in alcohol-fed mice. Mice were treated with an ethanol-containing liquid diet alone or in combination with LPPE for 8 weeks. LPPE supplementation alleviated ethanol-induced liver injury and downregulated key markers of inflammation. Moreover, LPPE supplementation reversed the ethanol-induced alteration of intestinal microbiota composition and increased the expression of intestinal tight junction proteins, mucus protecting proteins, and antimicrobial proteins. Furthermore, in addition to decreasing serum endotoxin level, LPPE supplementation suppressed CD14 and toll-like receptor 4 expression, and repressed the activation of nuclear factor-κB p65 in the liver. These data suggest that intestinal microbiota dysbiosis, intestinal barrier dysfunction, and liver inflammation are improved by LPPE, and therefore, the intake of LPPE or Litchi pulp may be an effective strategy to alleviate the susceptibility to alcohol-induced hepatic diseases.

Lychee (Litchi chinensis Sonn.) Pulp Phenolic Extract Confers a Protective Activity against Alcoholic Liver Disease in Mice by Alleviating Mitochondrial Dysfunction.

Mitochondria play an important role in the initiation and development of alcoholic liver disease (ALD). Our previous studies found lychee pulp phenolic extract (LPPE) exerted protective effect against ALD partly by inhibiting fatty acid ß-oxidation, and phenolic-rich lychee pulp extract improved restraint stress-induced liver injury by inhibiting mitochondrial dysfunction. The aim of this study was to investigate whether LPPE exerted protective effect against ALD via modulating mitochondrial function. The mice were treated with an ethanol-containing liquid diet alone or in combination with LPPE for 8 weeks. LPPE supplementation significantly alleviated hepatic steatosis, suppressed serum aspartate aminotransferase activity, and decreased triglyceride levels in serum and liver. On the basis of lipid peroxidation and antioxidant enzyme analyses, LPPE supplementation inhibited serum and hepatic oxidative stress. Moreover, LPPE supplementation significantly suppressed mitochondrial 8-hydroxy-2'-deoxyguanosine level, and increased mitochondrial membrane potential, mitochondrial DNA content, activities of mitochondrial complexes I and IV, and hepatic ATP level. Furthermore, LPPE supplementation significantly inhibited cytoplasmic cytochrome c level and caspase-3 activity, repressed Bax expression and Bax/Bcl-2 ratio, and increased Bcl-2 expression in liver. In summary, LPPE exerts beneficial effects against alcoholic liver injury by alleviating mitochondrial dysfunction.

Dynamic changes in the free and bound phenolic compounds and antioxidant activity of brown rice at different germination stages.

Germinated brown rice is a good source of the phenolics associated with antioxidant effects. Germination significantly increased by 63.2% and 23.6% the total phenolic and flavonoid contents, respectively. The percentage contribution of bound phenolics to total was 42.3% before and decreased slightly to 37.6% after germination. The percentage contribution of bound flavonoids to total, 51.1%, was the same before and after germination. The change in the amounts of free and bound forms indicated that transformations could occur during the germination process. Six individual phenolics were detected by HPLC. The levels of ferulic, coumaric, syringic, and caffeic acid significantly increased. The ratio of bound ferric reducing antioxidant power to total was basically constant, while germination increased the ratio of bound oxygen radical absorbance capacity to total. This indicated that the increase of bound phenolics exerts beneficial health effects throughout the digestive tract after absorption and may reduce mutations.