LC-Q-TOF-MS/MS detection of food flavonoids: principle, methodology, and applications.

Flavonoids have been attracting increasing research interest because of their multiple health promoting effects. However, many flavonoids with similar structures are present in foods, often at low concentrations, which increases the difficulty of their separation and identification. Liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (LC-Q-TOF-MS/MS) has become one of the most widely used techniques for flavonoid detection. LC-Q-TOF-MS/MS can achieve highly efficient separation by LC; it also provides structural information regarding flavonoids by Q-TOF-MS/MS. This review presents a comprehensive summary of the scientific principles and detailed methodologies (e.g., qualitative determination, quantitative determination, and data processing) of LC-Q-TOF-MS/MS specifically for food flavonoids. It also discusses the recent applications of LC-Q-TOF-MS/MS in determination of flavonoid types and contents in agricultural products, changes in their structures and contents during food processing, and metabolism in vivo after consumption. Moreover, it proposes necessary technological improvements and potential applications. This review would facilitate the scientific understanding of theory and technique of LC-Q-TOF-MS/MS for flavonoid detection, and promote its applications in food and health industry.

Nutrients and bioactives in citrus fruits: Different citrus varieties, fruit parts, and growth stages.

Citrus fruits are consumed in large quantities worldwide due to their attractive aromas and taste, as well as their high nutritional values and various health-promoting effects, which are due to their abundance of nutrients and bioactives. In addition to water, carbohydrates, vitamins, minerals, and dietary fibers are important nutrients in citrus, providing them with high nutritional values. Citrus fruits are also rich in various bioactives such as flavonoids, essential oils, carotenoids, limonoids, and synephrines, which protect from various ailments, including cancer and inflammatory, digestive, and cardiovascular diseases. The composition and content of nutrients and bioactives differ significantly among citrus varieties, fruit parts, and growth stages. To better understand the nutrient and bioactive profiles of citrus fruits and provide guidance for the utilization of high-value citrus resources, this review systematically summarizes the nutrients and bioactives in citrus fruit, including their contents, structural characteristics, and potential health benefits. We also explore the composition variation in different citrus varieties, fruits parts, and growth stages, as well as their health-promoting effects and applications.

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.

Carotenoid fates in plant foods: Chemical changes from farm to table and nutrition.

Carotenoids in plant foods are sources of pro-vitamin A and nutrients with several health benefits, including antioxidant and anticancer activities. However, humans cannot synthesize carotenoids de novo and must obtain them from the diet, typically via plant foods. We review the chemical changes of carotenoids in plant foods from farm to table and nutrition, including nutrient release and degradation during processing and metabolism in vivo. We also describe the influencing factors and proposals corresponding to enhancing the release, retention and utilization of carotenoids, thus benefiting human health. Processing methods influence the release and degradation of carotenoids, and nonthermal processing may optimize processing effects. The carotenoid profile, food matrix, and body status influence the digestion, absorption, and biotransformation of carotenoids in vivo; food design (diet and carotenoid delivery systems) can increase the bioavailability levels of carotenoids in the human body. In this review, the dynamic fate of carotenoids in plant foods is summarized systematically and deeply, focusing on changes in their chemical structure; identifying critical control points and influencing factors to facilitate carotenoid regulation; and suggesting multi-dimensional strategies based on the current state of food processing industries to achieve health benefits for consumers.

Using the Intrinsic Fluorescence of DNA to Characterize Aptamer Binding.

The reliable, readily accessible and label-free measurement of aptamer binding remains a challenge in the field. Recent reports have shown large changes in the intrinsic fluorescence of DNA upon the formation of G-quadruplex and i-motif structures. In this work, we examined whether DNA intrinsic fluorescence can be used for studying aptamer binding. First, DNA hybridization resulted in a drop in the fluorescence, which was observed for A30/T30 and a 24-mer random DNA sequence. Next, a series of DNA aptamers were studied. Cortisol and Hg2+ induced fluorescence increases for their respective aptamers. For the cortisol aptamer, the length of the terminal stem needs to be short to produce a fluorescence change. However, caffeine and adenosine failed to produce a fluorescence change, regardless of the stem length. Overall, using the intrinsic fluorescence of DNA may be a reliable and accessible method to study a limited number of aptamers that can produce fluorescence changes.

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.

Biosynthesis of citrus flavonoids and their health effects.

Citrus-derived flavonoids play important roles in the regulation of physiological conditions of citrus plants, including color changes of flower and fruit, flavor development, and anti-stress physiology. Moreover, citrus flavonoids possess multiple health-promoting effects in humans, and they are important ingredients for nutraceuticals and functional foods. The biosynthesis of flavonoids in citrus plants is of special significance because it determines the chemical structures and bioaccumulation of these bioactive compounds in the plants, which consequently influences their physiological functions in both citrus plants and human body. This review systematically summarizes: 1) the biosynthesis pathway of citrus-derived flavonoids, 2) the biosynthesis location and distribution of flavonoids in citrus plants, 3) the factors affecting flavonoid biosynthesis, 4) the biological significance of flavonoid biosynthesis in citrus plants, and 5) the health-promoting properties of citrus-derived flavonoids. The collation of this information provides scientific guidance for the development of healthy citrus foods and other health-promoting products containing citrus flavonoids.

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.

Adaptive Structured Pickering Emulsions and Porous Materials Based on Cellulose Nanocrystal Surfactants.

Taking advantage of the formation and assembly of cellulose nanocrystal surfactants (CNCSs) at the water-oil interface, where polar cellulose nanocrystals (CNCs) and end-functionalized polymer chains interact, the preparation and stability of emulsions prepared with CNCSs were investigated. The packing density of CNCSs at the interface can be adjusted by tuning parameters such as pH, ionic strength, and concentration/molecular weight of the end-functionalized polymer ligands. Stable non-spherical emulsions are obtained during homogenization, as a result of the interfacial jamming of CNCSs, with pH-triggered reconfigurability. Porous materials are prepared by freeze-drying creamed, CNCS-stabilized emulsions. The cells of the porous materials have a controlled pore size and shape that are commensurate with the droplets in the emulsion and are responsive to pH. The behavior of the adaptive, reconfigurable supracolloidal system is coupled to its internal and surrounding environment.

Synergistic chemopreventive effects of nobiletin and atorvastatin on colon carcinogenesis.

Different cancer chemopreventive agents may act synergistically and their combination may produce enhanced protective effects against carcinogenesis than each individual agent alone. Herein, we investigated the chemopreventive effects of nobiletin (NBT, a citrus polymethoxyflavone) and atorvastatin (ATST, a lipid-lowering drug) in colon cancer cells/macrophages and an azoxymethane (AOM)-induced colon carcinogenesis rat model. The results demonstrated that co-treatments of NBT/ATST produced enhanced growth inhibitory and anti-inflammatory effects on the colon cancer cells and macrophages, respectively. Isobologram analysis confirmed that these interactions between NBT and ATST were synergistic. NBT/ATST co-treatment also synergistically induced extensive cell cycle arrest and apoptosis in colon cancer cells. Oral administration of NBT (0.1%, w/w in diet) or ATST (0.04%, w/w in diet) significantly decreased colonic tumor incidence and multiplicity in AOM-treated rats. Most importantly, co-treatment of NBT/ATST at their half doses (0.05% NBT + 0.02% ATST, w/w in diet) resulted in even stronger inhibitory effects on colonic tumor incidence and multiplicity than did NBT or ATST alone at higher doses. Statistical analysis confirmed that the enhanced chemopreventive activities against colon carcinogenesis in rats by the NBT/ATST combination were highly synergistic. Our results further demonstrated that NBT/ATST co-treatment profoundly modulated key cellular signaling regulators associated with inflammation, cell proliferation, cell cycle progression, apoptosis, angiogenesis and metastasis in the colon of AOM-treated rats. In conclusion, for the first time, our results demonstrated a strong synergy in inhibiting colon carcinogenesis produced by the co-treatment of NBT and ATST, which provided a scientific basis for using NBT in combination with ATST for colon cancer chemoprevention in humans.

Effect of different drying technologies on drying characteristics and quality of red pepper (Capsicum frutescens L.): a comparative study.

BACKGROUND: Hot air drying and sun drying are traditional drying technologies widely used in the drying of agricultural products for a long time, but usually recognized as time-consuming or producing lower-quality products. Infrared drying is a rather effective drying technology that has advantages over traditional drying technologies. Thus, in order to investigate the application of infrared drying in the dehydration of red pepper, the drying characteristics and quality of infrared-dried red pepper were compared with those of sun-dried and hot air-dried red pepper. RESULTS: The infrared drying technology significantly enhanced the drying rate when compared with hot air drying and sun drying. Temperature was the most important factor affecting the moisture transfer during the process of infrared drying as well as hot air drying. Effective moisture diffusivity (Deff ) values of infrared drying ranged from 1.58 × 10(-9) to 3.78 × 10(-9) m(2) s(-1) . The Ea values of infrared drying and hot air drying were 42.67 and 44.48 kJ mol(-1) respectively. Infrared drying and hot air drying produced color loss to a similar extent. Relatively higher crispness values were observed for infrared-dried samples. CONCLUSION: Sun drying produced dried red pepper with the best color when compared with hot air drying and infrared drying. Meanwhile, infrared drying markedly improved the drying rate at the same drying temperature level of hot air drying, and the products obtained had relatively better quality with higher crispness values. © 2015 Society of Chemical Industry.

In situ SERS detection of emulsifiers at lipid interfaces using label-free amphiphilic gold nanoparticles.

Herein, we fabricated amphiphilic gold nanoparticles (GNPs) that can self-assemble at oil-water interfaces. We applied those GNPs for in situ SERS detection of emulsifier molecules within the interfacial region of oil in water (O/W) emulsion systems.

Fabrication of lipophilic gold nanoparticles for studying lipids by surface enhanced Raman spectroscopy (SERS).

A simple fabrication method for preparing lipophilic gold nanoparticles (AuNPs) suitable for use as substrates in surface-enhanced Raman scattering (SERS) applications of lipids was developed. The AuNPs were shown to be dispersible within lipid phases, where they greatly increased the SERS signals of lipids.

Surface-Enhanced Raman Spectroscopy for the Chemical Analysis of Food.

Surface-enhanced Raman spectroscopy (SERS) is an emerging and promising technique for the chemical analysis of food. The use of metallic nanosubstrates improves the sensitivity and capacity of conventional Raman spectroscopy greatly. This paper comprehensively reviews the development and applications of SERS in the chemical analysis of food, mainly focusing on food additives and chemical contaminants. The progress of SERS development and their applications in chemical analysis of food, from detection and characterization of target analytes in simple solvents to complex food matrices, is summarized. The advantages and limitations of different SERS substrates and methodologies are discussed. As most of the current SERS research on chemical analysis of food is still in an early stage, there are still several hurdles for further advancing SERS techniques into real-world applications for complex food products. This review includes our perspectives on the future trends of the SERS technique in the field of food analysis.

Structure characterization and gelling properties of RG-I-enriched pectins extracted from citrus peels using four different methods.

To facilitate the application of rhamnogalacturonan-I (RG-I)-enriched pectins (RGPs) as novel, healthy, and gelling food additives, this study compared the structural characteristics and gelling properties of RGPs extracted from citrus peel via four methods (alkali: AK, high-temperature/pressure: TP, citric acid: CA, and enzyme-assisted: EA extractions). AK and CA yielded pectins with the highest RG-I proportions (54.8 % and 51.9 %, respectively) by disrupting the homogalacturonan region; TP and EA increased the RG-I proportions by ~10 %. Among the four methods, AK induced the lowest degree of esterification (DE) (6.7 %) and longer side chains that form strong entanglement, contributing to its highest gel hardness. The relatively low DE (18.5 %) of CA RGP facilitated stable gel formation. Notably, its highly branched RG-I region afforded more intramolecular hydrophobic interactions, making a more highly cross-linked gel network of better gel resilience. In contrast, TP induced the highest DE (57 %) and curved molecular chains; it inhibited Ca2+ binding, entanglement, and intramolecular hydrophobic interactions, and thus no gel formed. EA RGP was associated with the lowest molecular size, rendering it more difficult for Ca2+ to form links, which resulted no gel. These findings offer insights into the relationship among the extraction methods, molecular structures, and gelling properties of RGPs.

Strain specificity of lactobacilli with promoted colonization by galactooligosaccharides administration in protecting intestinal barriers during Salmonella infection.

INTRODUCTION: Galactooligosaccharides (GOS) are lactogenic prebiotics that exert health benefits by stimulating the growth of different Lactobacillus strains in the gastrointestinal (GI) tract. OBJECTIVES: This study aimed to investigate the mechanism of action of different GOS-enriched lactobacilli in intestinal health. METHODS: Piglets and mice were supplemented with GOS to identify specific enrichment of Lactobacillus. The protective effects of individual GOS-enriched lactobacilli were investigated in Salmonella-infected mice. Macrophage depletion and transcriptome analysis were further performed to assess the involvement of macrophages and the underlying mechanisms of individual lactobacilli. An in vitro cell co-culture system was also used to evaluate the anti-adhesive and anti-invasive activities of lactobacilli against Salmonella in epithelial cells. RESULTS: GOS markedly increased the relative abundance of three lactobacilli including L. delbrueckii, L. johnsonii, and L. reuteri in both piglets and mice. Supplementation with GOS further alleviated Salmonella infection in mice. L. delbrueckii (ATCC®BAA 365™), but not L. johnsonii or L. reuteri, enhanced propionate production in the intestinal tract and ameliorated Salmonella-induced intestinal inflammation and barrier dysfunction by suppressing the JAK2-STAT3 signaling and M1 macrophage polarization. L. johnsonii (BNCC 186110), on the other hand, inhibited Salmonella adhesion and invasion of epithelial cells through competitive exclusion. However, L. reuteri (BNCC 186135) failed to protect mice against Salmonella infection. CONCLUSION: GOS-enriched lactobacilli show a differential role in protecting against Salmonella-induced intestinal barrier dysfunction and inflammation. Our results provide novel insights into the mechanism of action of GOS and individual Lactobacillus strains in the control and prevention of intestinal inflammatory disorders.

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.

Antimicrobial ergosteroids and pyrrole derivatives from halotolerant Aspergillus flocculosus PT05-1 cultured in a hypersaline medium.

In order to obtain more structurally novel and bioactive lead compounds for subsequent drug discovery, we have shifted the focus of our study from traditional microbial resources to 'extremophiles'. In this study, a halotolerant fungus Aspergillus flocculosus PT05-1 was isolated from the sediment of Putian saltern of Fujian Province of China in a hypersaline medium. Two new compounds, (22R,23S)-epoxy-3ß,11α,14ß,16ß-tetrahydroxyergosta-5,7-dien-12-one (1) and 6-(1H-pyrrol-2-yl)hexa-1,3,5-trienyl-4-methoxy-2H-pyran-2-one (5) (existed as a pair of epimers with the configuration of 1E,3Z,5E and 1E,3E,5E separately), along with nine known compounds were isolated and identified from the fermentation broth of A. flocculosus PT05-1 grown at a 10 % saline medium. New ergosteroid 1 together with 7-nor-ergosterolide (2) and 3ß-hydroxyergosta-8,24(28)-dien-7-one (3) showed cytotoxicity against HL-60 and BEL-7402 cells with IC50 values of 12-18 µM, and antimicrobial activity against Enterobacter aerogenes, Pseudomonas aeruginosa, and Candida albicans with MIC values of 1.6-15 µM, respectively. New compound 5 exhibited antibacterial effect on E. aerogenes with MIC value of 3.7 µM. This study also showed great prospects in developing medicinal resources from extremophiles.

Semi-quantification of surface-enhanced Raman scattering using a handheld Raman spectrometer: a feasibility study.

The feasibility of utilizing a handheld Raman spectrometer for surface-enhanced Raman scattering detection was evaluated on the pesticide ferbam. A layman's "answer box" was established for semi-quantifying the risk level of ferbam. This study advanced the application of a handheld Raman spectrometer to on-site evaluation of trace amounts of analytes.

Comparison of the peroxidase activities of iron oxide nanozyme with DNAzyme and horseradish peroxidase.

Peroxidase-based assays are the most extensively used in bioanalytical sensors because of their simple colorimetric readout and high sensitivity owing to enzymatic signal amplification. To improve the stability, modification, and cost of protein-based enzymes, such as horseradish peroxidase (HRP), various enzyme mimics, such as DNAzymes and nanozymes, have emerged over the last few decades. In this study, we compared the peroxidase activities of HRP, a G-quadruplex (G4)-hemin DNAzyme, and Fe3O4 nanozymes in terms of activity and stability under different conditions. The reactions were much slower at pH 7 than at pH 4. At pH 4, the turnover rate of HRP (375 s-1) was faster than that of G4 DNAzyme (0.14 s-1) and Fe3O4 (6.1 × 10-4 s-1, calculated by surface Fe concentration). When normalized to mass concentrations, the trend was the same. Through observation of the reaction for a long time of 2 h, the changes in the color and UV-vis spectra were also different for these catalysts, indicating different reaction mechanisms among these catalysts. Moreover, different buffers and nanozyme sizes were found to influence the activity of the catalysts. Fe3O4 showed the highest stability compared to HRP and G4 DNAzyme after a catalytic reaction or incubation with H2O2 for a few hours. This study helps to understand the properties of catalysts and the development of novel catalysts with enzyme-mimicking activities for application in various fields.