Structural characteristics and gelling properties of citrus pectins after chemical and enzymatic modifications: Conformation plays a vital role in Ca2+-induced gelation.

Due to the excellent health benefits of rhamnogalacturonan I (RG-I)-enriched pectin, there has been increasing research interest in its gelling properties. To elucidate its structure-gelation relationship, chemical modifications were used to obtain RG-I-enriched pectin (P11). Then, enzymatic modification was performed to obtain debranched pectins GP11 and AP11, respectively. The effects of RG-I side chains on structural characteristics (especially spatial conformation) and gelling properties were investigated. Among the low-methoxylated pectins (LMPs), AP11, with a loose conformation (Dmax 52 nm) showed the poorest gelling, followed by GP11. In addition to primary structure, spatial conformation (Dmax and Rg) also showed strong correlations (r2 > 0.8) with gelation. We speculate that compact conformation may shorten distance between pectin chains and reduces steric hindrance, contributing to formation of strong gel network. This is particularly important in LMPs with abundant side chains. The results provide novel insights into relationship between spatial conformation and gelling properties of RG-I-enriched pectin.

Caseinate-reinforced pectin hydrogels: Efficient encapsulation, desirable release, and chemical stabilization of (-)-epigallocatechin.

(-)-Epigallocatechin (EGC) has good health benefits, but its chemical stability is low. Pectin hydrogels have potential for the encapsulation and delivery of EGC, but they are limited by porous networks and poor mechanical properties. In this study, protein (whey protein isolate and caseinate)-reinforced pectin hydrogel beads (HBPEC-WPI and HBPEC-CAS) were developed to overcome these limitations. The results showed that HBPEC-CAS was a superior delivery system for EGC. HBPEC-CAS had a compact network structure, mainly because of the hydrogen bonds that formed between caseinate and pectin. Moreover, the EGC encapsulation efficiency of HBPEC-CAS (2.4%) reached 92.23 %; HBPEC-CAS (2.4%) could also delay the release of EGC in an aqueous environment, while ensuring its sufficient release in a simulated gastrointestinal environment. Notably, EGC was chemically stabilized in HBPEC-CAS (2.4%) during a 6-day storage period at 37 °C through the inhibition of its epimerization, oxidation, dimerization, and trimerization. The numerous hydroxyl groups in EGC readily interacted with the exposed amino acid residues in caseinate and created more protective sites. This study developed a strategy for protein-reinforced pectin hydrogel development and approaches for the protection of tea polyphenols; the findings offer useful insights for the tea-based food and beverage industry.

Research advances of in vivo biological fate of food bioactives delivered by colloidal systems.

Food bioactives exhibit various health-promoting effects and are widely used in functional foods to maintain human health. After oral intake, bioactives undergo complex biological processes before reaching the target organs to exert their biological effects. However, several factors may reduce their bioavailability. Colloidal systems have attracted special attention due to their great potential to improve bioavailability and bioefficiency. Herein, we focus on the importance of in vivo studies of the biological fates of bioactives delivered by colloidal systems. Increasing evidence demonstrates that the construction, composition, and physicochemical properties of the delivery systems significantly influence the in vivo biological fates of bioactives. These results demonstrate the great potential to control the in vivo behavior of food bioactives by designing specific delivery systems. We also compare in vivo and in vitro models used for biological studies of the fate of food bioactives delivered by colloidal systems. Meanwhile, the significance of the gut microbiota, targeted delivery, and personalized nutrition should be carefully considered. This review provides new insight for further studies of food bioactives delivered by colloidal systems, as well as scientific guidance for the reasonable design of personalized nutrition.

Hypolipidemic activity and safety evaluation of a rhamnan-type sulfated polysaccharide-chromium (III) complex.

BACKGROUND: Hyperlipidaemia is a chronic disorder characterized by imbalance of energy metabolism and high blood lipid level. The rhamnan-type sulfated polysaccharide is an excellent metal-ion chelating ligands. In this study, hypolipidemic activity and safety evaluation of a rhamnan-type sulfated polysaccharide-chromium (III) complex (RSPC) were studied. METHODS: Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the structure of RSPC. The effects of the RSPC on lipid metabolism in hyperlipidemic mice were evaluated by lipid contents, histopathological observation, immunofluorescent analysis, and adipocytokine levels. Moreover, sub-acute toxicity evaluation of RSPC was carried out on ICR mice. RESULTS: SEM and AFM further demonstrated formation of the polysaccharide-chromium (III) complex and revealed the intertwined network of RSPC. The RSPC significantly (p < 0.05) regulated lipid levels in the mice. The RSPC inhibited over-growth of adipocytes and reduced inflammatory infiltration induced by hyperlipidemia. The RSPC promoted differentiation of white adipose tissue into beige adipocytes and increased expression of uncoupling protein 1 (UCP1), thereby eliminating fat accumulation. Moreover, RSPC (5 mg/kg for mice; equivalent to 924 µg/d for adults) promoted secretion of adiponectin and suppressed resistin, leptin, and tumor necrosis factor alpha. Sub-acute toxicity evaluation showed that 1500 mg/kg of RSPC exhibited no apparent adverse effects on the mice. CONCLUSION: These results indicated that RSPC could be safely used to prevent hyperlipidemia and inflammation and may provide a new idea for the prevention of hyperlipidaemia and the related metabolic disorders.

Orange Pectin with Compact Conformation Effectively Alleviates Acute Colitis in Mice.

A comprehensive understanding of the relationships between the structure and function is critical for the targeted preparation of functional pectins. In this study, we compared the alleviating effects of five orange pectins (200 mg/kg) extracted using acid (P2), alkali (P10), cellulase (C), acid + cellulase (P2 + C), and alkali + cellulase (P10 + C) on dextran sodium sulfate-induced acute colitis. The physiological and histopathological indicators revealed that the alleviating effects were most significant for P10 + C, followed by P10, P2 + C, P2, and C. P10 + C increased the diversity and relative abundance of Akkermansia, leading to increased generation of colonic short-chain fatty acids as well as mRNA and protein expressions of GPR43, GPR109A, claudin-1, ZO-1, and occludin. Therefore, proinflammatory cytokines were decreased, and anti-inflammatory cytokines were increased. A compact conformation of P10 + C contributed to the alleviation effects on acute colitis. Alkali + cellulase-extracted orange pectin with a compact conformation has potential as adjuvant treatment for intestinal inflammation.

Hypolipidemic effect of chromium-modified enzymatic product of sulfated rhamnose polysaccharide from Enteromorpha prolifera in type 2 diabetic mice.

Sulfated rhamnose polysaccharide (SRP) derived from Enteromorpha prolifera is a metal-ion chelating agent that could potentially be used to treat diabetes. The aim of our study was to determine the effect of a variant of SRP on DIABETES. First, we synthesized and characterized SRPE-3 chromium(III) [SRPE-3-Cr(III)] complex using an enzymatic method. The maximum chelation rate was 18.2% under optimal chelating conditions of pH 6.0, time 4 h, and temperature 60 °C. Fourier transform infrared spectroscopy results showed important sites for Cr(III)-binding were O-H and C=O groups. We then studied the hypolipidemic effects of SRPE-3-Cr(III) on type 2 diabetes mellitus (T2DM) induced by a high-fat, high-sucrose diet (HFSD). Decreased blood glucose content, body fat ratio, serum TG, TC, LDL-C, and increased serum HDL-C were observed after treatment with SRPE-3-Cr(III). In addition, SRPE-3-Cr(III) significantly reduced leptin, resistin, and TNF-α levels, and increased adiponectin contents relative to T2DM. Histopathology results also showed that SRPE-3-Cr(III) could alleviate the HFSD-lesioned tissues. SRPE-3-Cr(III) also improved lipid metabolism via a reduction in aspartate aminotransferase, alanine aminotransferase, fatty acid synthase, and acetyl-CoA carboxylase activities in the liver. SRPE-3-Cr(III) at low doses exhibited better lipid-lowering activities, hence, could be considered to be a novel compound to treat hyperlipidemia and also act as an anti-diabetic agent.

Effects of High-Pressure Homogenization on Pectin Structure and Cloud Stability of Not-From-Concentrate Orange Juice.

Not-from-concentrate (NFC) juice is popular with consumers due to its similarity to fresh fruit juice in taste, flavor, and beneficial nutrients. As a commonly used technology in fruit juice production, high-pressure homogenization (HPH) can enhance the commercial value of juice by improving the color, flavor, taste, and nutrient contents. In this study, the effects of HPH on the pectin structural properties and stability of NFC orange juice were investigated. The correlations between HPH-induced changes in the structure of pectin and the stability of orange juice were revealed. Compared with non-homogenized orange juice, HPH increased the galacturonic acid (GalA) content and the linearity of pectin, while decreasing the molecular weight (Mw), pectin branching, and rhamnogalacturonan (RG) contribution, and cracks and pores of different sizes formed on the surface of pectin, implying depolymerization. Meanwhile, with increasing pressure and number homogenization of passes, HPH effectively improved the stability of NFC orange juice. HPH can effectively prevent the stratification of orange juice, thereby promoting consumer acceptance and endowing a higher commercial value. The improvement of the stability of NFC orange juice by HPH was related to the structural properties of pectin. Turbidity was significantly (P < 0.01) positively correlated with GalA and pectin linearity, but was significantly (P < 0.01) negatively correlated with Mw, RG contribution, and pectin branching. Modification of pectin structure can improve the stability of NFC orange juice. In this work, the relationship between the pectin structure and stability of NFC orange juice is elucidated, providing a path toward improving consumer acceptance and enhancing the palatability and nutritional and functional qualities of orange juice. Manufacturers can use this relationship to modify pectin directionally and produce high-quality NFC orange juice beverages.

In-vivo biotransformation of citrus functional components and their effects on health.

Citrus, one of the most popular fruits worldwide, contains various functional components, including flavonoids, dietary fibers (DFs), essential oils (EOs), synephrines, limonoids, and carotenoids. The functional components of citrus attract special attention due to their health-promoting effects. Food components undergo complex biotransformation by host itself and the gut microbiota after oral intake, which alters their bioaccessibility, bioavailability, and bioactivity in the host body. To better understand the health effects of citrus fruits, it is important to understand the in-vivo biotransformation of citrus functional components. We reviewed the biotransformation of citrus functional components (flavonoids, DFs, EOs, synephrines, limonoids, and carotenoids) in the body from their intake to excretion. In addition, we described the importance of biotransformation in terms of health effects. This review would facilitate mechanistic understanding of the health-promoting effect of citrus and its functional components, and also provide guidance for the development of health-promoting foods based on citrus and its functional components.

Naringin Alleviates Atherosclerosis in ApoE-/- Mice by Regulating Cholesterol Metabolism Involved in Gut Microbiota Remodeling.

Naringin, a major flavonoid in citrus, has potential for preventing atherosclerosis. The presence in the colon of a large amount of naringin after oral intake might affect the gut microbiota. We investigated the role of gut microbiota remodeling in the alleviation of atherosclerosis by naringin. Naringin significantly alleviated atherosclerosis and lowered the serum and liver cholesterol levels by 24.04 and 28.37% in ApoE-/- mice fed with a high-fat diet. Nontarget metabolomics showed that naringin modulated the hepatic levels of cholesterol derivatives and bile acids. Naringin increased the excretion of bile acids and neutral sterols by 1.6- and 4.3-fold, respectively. The main potential pathway by which naringin alleviated atherosclerosis was the gut microbiota-liver-cholesterol axis. Naringin modulated the abundances of bile salt hydrolase- and 7α-dehydroxylase-producing bacteria, promoting bile acid synthesis from cholesterol by upregulating CYP7A1 via suppression of the FXR/FGF15 pathway. In addition, naringin facilitated reverse cholesterol transport by downregulating PCSK9/IDOL. The results provide insight into the atherosclerosis-alleviation mechanisms of citrus flavonoids and a scientific basis for the development of functional foods containing citrus flavonoids.

Effect of mesoscopic structure of citrus pectin on its emulsifying properties: Compactness is more important than size.

We previously explored citrus oil emulsion stabilized by citrus pectin. In this report, we characterized key parameters of the citrus pectin mesoscopic structure and their effect on emulsifying capacity, and explored the underlying mechanism by determining the interfacial properties, emulsifying ability, and micromorphology. To generate different mesoscopic structure, citrus pectins were hydrolyzed or regulated by pH and NaCl. Hydrolysis decreased the size of citrus pectin mesoscopic structure with constant compactness, leading to superior interfacial properties but inferior emulsifying ability. In contrast, pH and NaCl regulation decreased the mesoscopic structure size and increased the compactness, and pH- and NaCl-regulated citrus pectin formed a compact absorbed layer at the interface to resist droplet coalescence/flocculation during homogenization. Our results support the importance of compactness of the citrus pectin mesoscopic structure on emulsifying capacity. This study increased our understanding on the relationship between the mesoscopic structures of polysaccharide emulsifier and emulsifying ability.

The structure-property relationships of acid- and alkali-extracted grapefruit peel pectins.

Structure and properties of pectin can be affected by extraction methods. In this study, grapefruit peel pectins extracted by HCl (at pH 1 [P1], 2 [P2], and 3 [P3]) and NaOH (at pH 9 [P9], 10 [P10], and 11 [P11]) were prepared and characterized. Atomic force microscopy (AFM) provided direct evidence of complex nano-structural patterns of pectins and revealed cross-linked networks of P10 and P11. Small-angle X-ray scattering (SAXS) demonstrated that P1, P2, and P3 possessed a relatively extended conformation, whereas P9, P10, and P11 displayed a three-dimensional structure and folded conformation. The compact and extended conformations of P3 contributed to its high viscosity in solution and the stability of the formed emulsion (75%). Porous surface and larger three-dimensional nanostructure (Dmax: 23 nm) of P10 facilitated its ion-binding capacity. Our results provide valuable insight into relationship between extraction methods and structure-properties of pectin, facilitating design of functional pectins.

Efficiency of four different dietary preparation methods in extracting functional compounds from dried tangerine peel.

Dried tangerine peel (DTP) is an excellent plant resource that has been used as ingredients for both food and traditional Chinese medicine. In this study, the efficiency of four different dietary preparation methods (i.e. soaking, boiling, steaming, and ethanol extraction) in extraction of functional compounds (i.e. flavonoids and essential oil constituents) from DTP was evaluated systematically for the first time. To conduct a comprehensive evaluation of the extraction of the functional compounds, a synthetic evaluation model based on a weighting method was established. The optimum conditions of each dietary preparation method (e.g., time, temperature, solid-liquid ratio, etc.) were determined by response surface methodology. Ethanol extraction showed the best extraction efficiency, followed by soaking, boiling, and steaming. Additionally, different DTP extracts were shown to be clearly distinguished by electronic eye and electronic tongue. This research provides essential findings for the effective dietary instruction of DTP consumption.

Hypoglycemic activity and mechanism of the sulfated rhamnose polysaccharides chromium(III) complex in type 2 diabetic mice.

The sulfated rhamnose polysaccharides found in Enteromorpha prolifera belong to a class of unique polyanionic polysaccharides with high chelation capacity. In this study, a complex of sulfated rhamnose polysaccharides with chromium(III) (SRPC) was synthesized, and its effect on type 2 diabetes mellitus (T2DM) in mice fed a high-fat, high-sucrose diet was investigated. The molecular weight of SRPC is 4.57 kDa, and its chromium content is 28 µg/mg. Results indicated that mice treated by oral administration of SRPC (10 mg/kg and 30 mg/kg body mass per day) for 11 weeks showed significantly improved oral glucose tolerance, decreased body mass gain, reduced serum insulin levels, and increased tissue glycogen content relative to T2DM mice (p < 0.01). SRPC treatment improved glucose metabolism via activation of the IR/IRS-2/PI3K/PKB/GSK-3ß signaling pathway (which is related to glycogen synthesis) and enhanced glucose transport through insulin signaling cascade-induced GLUT4 translocation. Because of its effectiveness and stability, SRPC could be used as a therapeutic agent for blood glucose control and a promising nutraceutical for T2DM treatment.

Characterization and Hypoglycemic Activity of a Rhamnan-Type Sulfated Polysaccharide Derivative.

Polysaccharide chromium (III) derivatives are gaining increasing attention in improving type 2 diabetes. In this study, the sulfated polysaccharide from Enteromorpha prolifera (SPE) with 4.8 kDa was prepared by specific enzymatic hydrolysis. The obtained SPE was used to prepare a rhamnan-type sulfated polysaccharide derivative (SPED). Results indicated that O-H, C=O, and S=O were effectively involved in the chelation of SPED (chromium content 20.26%). Acute (half lethal dose > 2.38 g/kg) and sub-acute toxicity showed that SPED had no damaging effects on mice. Anti-diabetic experiment demonstrated that SPED improved glucose metabolism. Moreover, SPED promoted the PI3K/PKB/GSK-3ß signaling pathway by regulating mRNA expression of insulin receptors (IR), insulin receptor substrate 2 (IRS-2), phosphatidylinositol 3 kinase (PI3K), protein kinase B (PKB), and glycogen synthase kinase 3ß (GSK-3ß). In conclusion, the SPED might represent a novel marine-derived candidate against hyperglycemia, which may undergo further pharmaceutical development as a hypoglycemic agent.

Dietary Fibers from Fruits and Vegetables and Their Health Benefits via Modulation of Gut Microbiota.

Dietary fibers (DFs) regulate host health through various mechanisms related to their dietary sources, specific physicochemical structures, fermentability, and physiological properties in the gut. Considering the numerous types and sources of DFs and their different physicochemical and physiological properties, it is challenging yet important to establish the key mechanisms for the beneficial health effects of DFs. In this review, the types and structures of DFs from different fruits and vegetables were summarized and the effects of different processing methods on DF properties were discussed. Moreover, the impacts of DFs on gut microbial ecology, host physiology, and health were described. Understanding the complex interaction between different DFs and gut microbiota is vital for personalized nutrition. It is also important to comprehend factors influencing gut microbiota and strategies to regulate the microbiota, thereby augmenting beneficial health responses. The exploration of molecular mechanism linking DFs, gut microbiota, and host physiology may allow for the identification of effective targets to fight against major chronic diseases.

Directional preparation of anticoagulant-active sulfated polysaccharides from Enteromorpha prolifera using artificial neural networks.

The sulfated polysaccharides from Enteromorpha prolifera (PE) are a potential source of anticoagulant agents. In this study, the PE was degraded by specific degradase and five hydrolysis products with different molecular weights were prepared. The product of 206 kDa is a kind of high rhamnose-containing polysaccharide with sulfate ester (34.29%). It could effectively prolong the activated partial thromboplastin time (APTT), which indicated inhibition of the intrinsic coagulation pathway. The artificial neural network (ANN) was built to realize the directional preparation of anticoagulant-active polysaccharides. Based on monitoring glucose concentration on-line, a visualization system of enzymatic hydrolysis was developed to simplify the operation of ANN. The model could be further applied to predict molecular weights of polysaccharides that possess diverse biological activities.

A novel low molecular weight Enteromorpha polysaccharide-iron (III) complex and its effect on rats with iron deficiency anemia (IDA).

Iron deficiency anemia (IDA) is a common nutritional disease that affects normal erythropoiesis. Traditional iron supplements usually cause gastrointestinal irritation. In this study, a novel low-molecular-weight polysaccharide from Enteromorpha prolifera (LPE) was prepared by oxidation degradation, and LPE-iron (III) complex was synthesized and characterized. The molecular weight of LPE-iron (III) complex was 21.25kDa, and iron content was 25%. The therapeutic effects of LPE-iron (III) complex on IDA were investigated in rats. The hematological indices and organ coefficients of the rats were analyzed. Results showed a dose-dependent relationship, and a prior intragastric administration of LPE-iron (III) complex (2mg Fe/kg body weight) exhibited considerable effect when compared with the positive control. Therefore, LPE-iron (III) complex could be exploited as a new iron fortifier.

Characterization of high yield exopolysaccharide produced by Phyllobacterium sp. 921F exhibiting moisture preserving properties.

A new strain bacteria was isolated and named as Phyllobacterium sp. 921F, due to its high production capacity of exopolysaccharide (EPS). Characterization of physico-chemical properties of the EPS and optimization for high production were conducted to aim at industrial applications. The optimum pH and temperature were 7.0 and 30°C, respectively. The following scale-up fermentation was carried out in 30L bioreactor and amounts of EPS (21.9g/L) were produced. The EPS with a molecular mass of 1082kDa was composed of glucose, galactose, and pyruvate. The EPS solution behaved as Newtonian at low concentrations (≤0.3%) and as shear thinning at higher concentration (e.g, 1%). The moisture retention ability of the EPS was found to be superior to hyaluronic acid. Results suggest that Phyllobacterium sp. 921F is a good candidate for large-scale production of the EPS which might be utilized in food and cosmetics industries.

Optimization study on the hydrogen peroxide pretreatment and production of bioethanol from seaweed Ulva prolifera biomass.

The seaweed Ulva prolifera, distributed in inter-tidal zones worldwide, contains a large percentage of cellulosic materials. The technical feasibility of using U. prolifera residue (UPR) obtained after extraction of polysaccharides as a renewable energy resource was investigated. An environment-friendly and economical pretreatment process was conducted using hydrogen peroxide. The hydrogen peroxide pretreatment improved the efficiency of enzymatic hydrolysis. The resulting yield of reducing sugar reached a maximum of 0.42g/g UPR under the optimal pretreatment condition (hydrogen peroxide 0.2%, 50°C, pH 4.0, 12h). The rate of conversion of reducing sugar in the concentrated hydrolysates to bioethanol reached 31.4% by Saccharomyces cerevisiae fermentation, which corresponds to 61.7% of the theoretical maximum yield. Compared with other reported traditional processes on Ulva biomass, the reducing sugar and bioethanol yield are substantially higher. Thus, hydrogen peroxide pretreatment is an effective enhancement of the process of bioethanol production from the seaweed U. prolifera.