Flavonoids, phenolic acids, carotenoids and antioxidant activity of fresh eating citrus fruits, using the coupled in vitro digestion and human intestinal HepG2 cells model

Efficacy and molecular mechanisms of hesperidin in mitigating Alzheimer's disease: A systematic review

Hesperidin, a flavonoid glycoside, is a natural phenolic compound that has broad biological effects. Increasing evidence suggests that hesperidin inhibits the occurrence and development of neurodegenerative diseases, including Alzheimer's disease (AD). This article reviews the neuropharmacological mechanisms of hesperidin in the prevention and treatment of AD through in vitro and in vivo studies. A systematic review of preclinical studies was conducted using PubMed, Web of Science, Scopus, and Google Scholar (up to July 1, 2024). The neuroprotective potential of hesperidin was mediated through mechanisms such as inhibition of β-amyloid (Aβ) aggregation, enhancement of endogenous antioxidant defense functions, reduction of neuroinflammation and apoptosis, improvement of mitochondrial dysfunction, regulation of autophagy, and promotion of neurogenesis. Despite various preclinical studies on the role of hesperidin in AD, its exact effects on humans remain unclear. Few clinical trials have indicated that dietary supplements rich in hesperidin can improve cerebral blood flow, cognition, and memory performance. The neuroprotective effect of hesperidin may be exerted via regulating different molecular pathways, including the RAGE/NF-κB, Akt/Nrf2, and AMPK/BDNF/CREB pathways. However, further clinical trials are needed to confirm the neuroprotective effects of this natural flavonoid compound and to assess its safety.

Fates of bioactive compounds and antioxidant activities of red pitaya pulp upon in vitro gastrointestinal digestion

Health benefit effects of bioactive compounds depend on their bioavailabilities, which could vary according to factors including food matrix and digestion environment. To understand the "bioaccessible" health benefit of red pitay pulp, the INFOGEST static in vitro simulation of gastrointestinal (GI) digestion model and targeted metabolomics method were applied to unravel the fates of bioactive compounds in the whole food of red pitaya pulp during GI digestion. The antioxidant activity as one of the health benefit indices was also assessed to compare the changes in bioactive properties of red pitaya pulp. Results showed that, after GI digestion, total phenolic and flavonoid content increased by 84% and 4.55 folds, respectively. But total betacyanin content decreased. All the detected phenolic acids increased during the GI process, and lots of new phenolic compounds were produced. The overall chemical antioxidant capacity of red pitaya pulp increased after GI digestion. Correlation analysis results indicated that flavonoids and ferulic acid were probably the primary sources of the antioxidant capacity of the red pitaya pulp and its digests. Moreover, the cytoprotective effects against H2O2-induced oxidative damage varied among gastric cell, enterocyte and hepatocyte. The GI digests of red pitaya pulp could better alleviate the H2O2-induced oxidative stress in cells by preventing the increase of reactive oxygen species (ROS), inhibiting the production of malondialdehyde (MDA), increasing the production of glutathione (GSH), and promoting the activities of catalase (CAT) and superoxide dismutase (SOD). These findings can be used as a basis for future studies in the design and production of functional ingredients/foods.

Quality Change of Citri Reticulatae Pericarpium (Pericarps of Citrus reticulata 'Chachi') During Storage and Its Sex-Based In Vitro Digestive Performance

Citri Reticulatae Pericarpium (CRP), particularly including the pericarp of Citrus reticulata 'Chachi' (GCP), has been widely used as a food, a dietary supplement, and traditional Chinese medicine. Despite the widespread use of traditional foods, there is limited evidence regarding the precise relationships between storage conditions, aging duration, and the digestive performance of CRP. In this study, the aim was to investigate the impact of the storage conditions on the quality of aged GCP during shelf life and to evaluate the subsequent digestive performance of corresponding GCP decoctions. Respiration in GCP was monitored by measuring oxygen (O2), carbon dioxide (CO2), and methane (CH4) gases throughout the storage simulation, with O2 and CO2 validated as prospective safety measures. Five flavonoids (hesperidin, didymin, nobiletin, tangeretin, and 3,5,6,7,8,3',4'-heptamethoxyflavone) were determined as quality indicators, and their contents were significantly affected by the duration of the storage simulation and the aging periods of GCP. Our study also found that temperature and humidity significantly affected the volatile organic compounds (VOCs) emission from GCP. Eighteen compounds were proposed to show potential as descriptive measures of aging periods while eight compounds were proposed as potential indicators to discriminate among the spoilage level. Furthermore, the bioaccessibility of hesperidin ranged from ~30% to ~50% and was not significantly affected by the GCP's aging time nor the consumer's sex (p < 0.05). This study presents evidence for the future control of the quality of GCP and its digestive performance in males and females.

In Vitro Comparative Analysis of the Effect and Structure-Based Influencing Factors of Flavonols on Lipid Accumulation

Flavonols represented by quercetin have been widely reported to have biological activities of regulating lipid metabolism. However, the differences in flavonols with different structures in lipid-lowering activity and the influencing factors remain unclear. In this study, the stability, transmembrane uptake ratio, and lipid metabolism regulation activities of 12 flavonol compounds in the 3T3-L1 cell model were systematically compared. The results showed that kaempferide had the highest cellular uptake ratio and the most potent inhibitory effect on adipogenesis at a dosing concentration of 20 μM, followed by isorhamnetin and kaempferol. They inhibited TG accumulation by more than 65% and downregulated the expression of PPARγ and SREBP1c by more than 60%. The other four aglycones, including quercetin, did not exhibit significant activity due to the structural instability in the cell culture medium. Meanwhile, five quercetin glucosides were quite stable but showed a low uptake ratio that no obvious activity was observed. Correlation analysis also showed that for 11 compounds except galangin, the activity was positively correlated with the cellular uptake ratio (p < 0.05, r = 0.6349). These findings may provide a valuable idea and insight for exploring the structure-based activity of flavonoids at the cellular level.

Unlocking Nature's Potential: A Comparative Study of Bioactive Compounds Extracted from Tropical Microalgae

To promote the use of marine microalgae for nutraceuticals, we aimed to characterize extracts of Nannochloropsis oculata, Porphyridium cruentum, and Skeletonema costatum, all of which harbor numerous bioactive substances. Chlorophylls and carotenoids were identified as the primary pigments in N. oculata and S. costatum extracts. Furthermore, the total phenolic and total flavonoid contents in the three microalgae ranged 20.32-21.96 mg GAE/g and 0.3-2.1 mg QE/g, respectively. Notably, the extract of N. oculata exhibited the most significant radical scavenging activity in both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays, with flavonoids and pigments identified as the main contributors to antioxidant activities. Our results revealed variations in metabolite profiles among the microalgal extracts: N. oculata extract (43 types), P. cruentum (13 types), and S. costatum (21 types). Hexadecanamide emerged as the major metabolite detected in all microalgae. Collectively, the results of the present study may open new avenues of microalgae for various applications.

Effect of hydrocolloid concentration in low-calorie orange jellies on preservation of bioactive compounds and antioxidant capacity

The purpose of this paper was to avaliate of the concentration of hydrocolloids (low methoxyl pectin [LMP], guar gum [GG], and carrageenan gum [CG]) in low-calorie orange jellies in order to maximize the amount of bioactive compounds and antioxidant capacity, and to study the influence on degradation these compounds. A mixture design with seven tests was used to analyze the total phenolic compounds, ascorbic acid (vitamin C) and antioxidant capacity (ABTS, DPPH and β-carotene/linoleic acid methods). The results were analyzed by response surface methodology and the Scott-Knott mean test at a significance level of 5% (p ≤ 0.05). In general, the regions containing 0.5% GG and 0.5% GC had higher levels of the variables under study, and this combination preserved the bioactive compounds and antioxidant activity of jellies in relation to that of orange juice.

Integrated metabolomics and network pharmacology to reveal antioxidant mechanisms and potential pharmacological ingredients of citrus herbs

The benefits of citrus herbs are strongly associated with their secondary metabolites. In the study, we conducted widely-targeted metabolomics and ultra-high performance liquid chromatography (UPLC) to compare the variability of ingredients in four citrus herbs. In total, we discovered 1126 secondary metabolites, primarily comprising flavonoids, phenolic acids, lignans and coumarins, and alkaloids. Differential metabolites of citrus herbs were searched by multivariate statistical analysis. Notably, Citri Reticulatae Pericarpium contained higher levels of flavonoids, while Zhique and Huajuhong demonstrated a greater abundance of coumarins. Among the flavonoids determined by UPLC, Guangchenpi demonstrated significantly elevated levels of polymethoxyflavones (tangeretin and nobiletin) compared to other citrus herbs. Additionally, we determined their antioxidant capacity (Chenpi > Guangchenpi > Huajuhong > Zhique) using in vitro assays. Finally, we utilized network pharmacology to explore the antioxidant mechanisms and potential pharmacological ingredients, providing a basis for future preventive and therapeutic applications of these metabolites.

Gluten-Free Bread Enriched with Artichoke Leaf Extract In Vitro Exerted Antioxidant and Anti-Inflammatory Properties

Due to its high nutritional value and broad beneficial effects, the artichoke plant (Cynara cardunculus L.) is an excellent healthy food candidate. Additionally, the artichoke by-products are usually discarded even though they still contain a huge concentration of dietary fibers, phenolic acids, and other micronutrients. The present work aimed to characterize a laboratory-made gluten-free bread (B) using rice flour supplemented with a powdered extract from artichoke leaves (AEs). The AE, accounting for the 5% of titratable chlorogenic acid, was added to the experimental gluten-free bread. Accounting for different combinations, four different bread batches were prepared. To evaluate the differences, a gluten-free type-II sourdough (tII-SD) was added in two doughs (SB and SB-AE), while the related controls (YB and YB-AE) did not contain the tII-SD. Profiling the digested bread samples, SB showed the lowest glycemic index, while SB-AE showed the highest antioxidant properties. The digested samples were also fermented in fecal batches containing viable cells from fecal microbiota samples obtained from healthy donors. Based on plate counts, no clear tendencies emerged concerning the analyzed microbial patterns; by contrast, when profiling volatile organic compounds, significant differences were observed in SB-AE, exhibiting the highest scores of hydrocinnamic and cyclohexanecarboxylic acids. The fecal fermented supernatants were recovered and assayed for healthy properties on human keratinocyte cell lines against oxidative stress and for effectiveness in modulating the expression of proinflammatory cytokines in Caco-2 cells. While the first assay emphasized the contribution of AE to protect against stressor agents, the latter enlightened how the combination of SB with AE decreased the cellular TNF-α and IL1-β expression. In conclusion, this preliminary study suggests that the combination of AE with sourdough biotechnology could be a promising tool to increase the nutritional and healthy features of gluten-free bread.

Stability and antioxidant activity of phenolic compounds during in vitro digestion

The impact of phenolic compounds on the human body depended on the type, content, bioavailability, and antioxidant activity. After digestion, different phenolic compounds had different changes of bioavailability and antioxidant activity, which needed to be considered in the application. In this experiment, the structural stability and antioxidant activity of 27 phenolic compounds (phenolic acids, flavonols, flavonoids, and flavanones) were investigated during the in vitro simulated digestion. This experiment eliminated the influence of food matrix, provide a basis for regularity for the changes of phenolic substances in different materials. Results showed that the bioaccessibility of phenolic compounds with different structures varied, and there was a conformational relationship between the structure and stability. After oral digestion, most of the phenolic compounds underwent degradation and the cellular antioxidant activity (CAA) values decreased to a large extent (p < 0.05). After gastric digestion, the content (p > 0.05) and CAA values (p < 0.05) of most phenolic compounds increased. However, after intestinal digestion, the phenolic compounds were degraded to a greater extent, and different structures of phenolic compounds had different changes in CAA values (p < 0.05). In general, the CAA values of most phenolic compounds after in vitro digestion were lower than the initial value. The 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ehylbenzthiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) values of phenolic acids and flavonols decreased after in vitro simulated digestion (p < 0.05), while the values of DPPH, ABTS, and FRAP of most flavonoids (p < 0.05) increased. The increased oxygen radical absorption capacity (ORAC) values were found in most phenolic acids, flavonols, and flavonoids (p < 0.05), and most flavanones showed unremarkable changes in ORAC values (p > 0.05). In general, the changing trend of chemical-based antioxidant activity was consistent with the content of phenolic compounds.

Red-fleshed apple flavonoid extract alleviates CCl4-induced liver injury in mice

In recent years, the global incidence of liver damage has increased. Despite the many known health benefits of red-fleshed apple flavonoids, their potential liver-protective effects have not yet been investigated. In this study, we analyzed the composition of red-fleshed apple flavonoid extract (RAFE) by high-performance liquid chromatography (HPLC). We then induced liver damage in mice with carbon tetrachloride (CCl4) and performed interventions with RAFE to analyze its effect on liver damage, using bifendate as a positive control. The results showed that catechin was the most abundant flavonoid in 'XJ4' RAFE (49.346 mg/100 g). In liver-injured mice, the liver coefficients converged to normal levels following RAFE intervention. Moreover, RAFE significantly reduced the enzymatic activity levels of glutamic oxaloacetic transaminase (ALT), glutamic alanine transaminase (AST), and alkaline phosphatase (ALP) in mouse serum. Furthermore, RAFE significantly increased the content or enzyme activity level of total glutathione, total antioxidant capacity, and superoxide dismutase, and significantly decreased the content of malondialdehyde in the liver of mice. In parallel, we performed histopathological observations of mouse livers for each group. The results showed that RAFE restored the pathological changes caused by CCl4 around the central hepatic vein in mice and resulted in tightly bound hepatocytes. The recovery effect of RAFE was dose-dependent in the liver tissue. Regarding intestinal microorganisms, we found that RAFE restored the microbial diversity in liver-injured mice, with a similar microbial composition in the RAFE intervention group and normal group. RAFE reduced the ratio of Firmicutes to Bacteroidetes, increased the levels of probiotic bacteria, such as Lactobacillus acidophilus, and Clostridium, and reduced the levels of harmful bacteria, such as Erysipelothrix Rosenbach. Therefore, RAFE ameliorated CCl4-induced liver damage by modulating the abundance and composition of intestinal microorganisms in mice. In conclusion, RAFE alleviated CCl4-induced liver damage in mice, with H-RAFE (5 mg kg-1) significantly improving liver damage in mice but M-RAFE (1 mg kg-1) significantly improving the imbalance of intestinal microorganisms in mice. Our research suggests that RAFE could be employed for the adjuvant treatment and prevention of liver damage, and may have important applications in food and medicine.

In Vitro Bioaccessibility of Bioactive Compounds of Freeze-Dried Orange Juice Co-Product Formulated with Gum Arabic and Modified Starch

The large amount of waste generated by the orange juice industry has sparked the interest of many researchers in incorporating recycling systems and following a much more sustainable circular economy model. This work proposes the valorization of the co-product generated in the orange juice extraction industry after freeze-drying for its subsequent reuse as a natural ingredient in the food industry. In addition, the possible protective effect of gum Arabic and corn starch esterified with octenyl succinic groups, in proportions optimised in previous studies 0.25 and 0.45 g/g orange co-product dry solutes, on the main bioactive compounds of orange peel during the freeze-drying process has been studied. The samples were characterised for their content of vitamin C (ascorbic and dehydroascorbic acids), flavonoids (hesperidin and narirutin), total phenols and total carotenoids, as well as their antioxidant capacity (DPPH and FRAP assays). In addition, samples were digested, mimicking the human enzymatic oral gastro-intestinal digestion process, and the bioaccessibility of the bioactive compounds was evaluated. It was observed that the addition of both biopolymers improved the stability of the hydrophilic compounds during freeze-drying. This conservative effect was more remarkable for higher biopolymer concentrations. However, no protective effect on carotenoid compounds was observed. This trend was reflected in the antioxidant activity of the different samples. In addition, the incorporation of biopolymers improved the bioaccessibility of the bioactive compounds studied. In conclusion, the results supported the feasibility of the freeze-dried orange juice co-product as a natural, sustainable source of health-promoting compounds.

The profiles of durian (Durio zibethinus Murr.) shell phenolics and their antioxidant effects on H2O2-treated HepG2 cells as well as the metabolites and organ distribution in rats

Durian is a nutritious tropical fruit with potent antioxidant, anti-inflammatory, antibacterial and anti-cancer effects. However, the durian shell was mainly discarded as waste, while there were few studies on the characterization of its phenolic profiles, antioxidant activities, and in vivo metabolites. In the present study, a total of 17 compounds were identified in durian shell extract (DSE) by using an ultra-high-performance liquid chromatography coupled with linear ion trap quadrupole Orbitrap mass spectrometry (UHPLC-LTQ-Orbitrap-MS/MS), while 33 metabolites were found in rats' plasma, urine and organ. Moreover, DSE could effectively reduce H₂O₂-induced oxidative damage in HepG2 cells, reduce the expression of Reactive Oxygen Species (ROS), Malondialdehyde (MDA) and Lactate Dehydrogenase (LDH) and inhibit apoptosis by regulating the expression of Bcl-2-Associated X (BAX), B-Cell Lymphoma 2 (BCL-2), Caspase-3 and Caspase-9 genes and proteins related to mitochondrial pathway apoptosis. This is the first comprehensive report on Durian shell phenolics, their metabolic profiles and underlying mechanisms of the in vitro antioxidant activities.

Encapsulation of Formosa Papaya (Carica papaya L.) Seed Extract: Physicochemical Characteristics of Particles, and Study of Stability and Release of Encapsulated Phenolic Compounds

Papaya seeds are a promising source of phenolic compounds, but these are unstable, and the papaya extract has a bitter taste. This study aimed to encapsulate papaya seed extracts at different maturation levels, and to characterize the obtained microparticles for their physicochemical properties, chemical stability and release of bioactives. Extracts of papaya (unripe and ripe) seeds were spray-dried using concentrations of 0, 15 and 30% of maltodextrin and inlet air temperatures of 130 and 150 °C. The powders were analyzed for yield, moisture, Aw, hygroscopicity, dispersibility, color parameters, morphology, mean diameter, total phenolics, antioxidant activity, stability during storage and release of phenolics in simulated gastrointestinal fluids. Powders produced with maltodextrin showed better results regarding particle diameter, hygroscopicity, dispersibility, and phenolic stability during storage. All powders showed antioxidant action and significant values of total phenolic compounds. Samples without maltodextrin underwent caking. Drying temperatures had little influence on the characteristics of the powders. Encapsulated phenolic compounds were released in large amounts in the intestinal phase (86.6–100%). Powders produced with unripe seeds, 15% of maltodextrin and an inlet air temperature of 130 °C showed the best results. Thus, encapsulation was efficient, and encapsulated papaya seed extract has potential for food application as a natural additive.

The Effect of Vibratory Grinding Time on Moisture Sorption, Particle Size Distribution, and Phenolic Bioaccessibility of Carob Powder

Carob pod powder, an excellent source of health-promoting substances, has found its use in a wide range of food products. Grinding conditions affect the physical and chemical properties of the powder, but their influence on the bioaccessibility of phenolic compounds in carob pod powder has not yet been determined. The carob pods were ground for 30-180 s in a vibratory grinder. The median values (D₅₀) of particle size decreased after 60 s of grinding (87.9 μm), then increased to 135.1 μm. Lightness showed a negative correlation with D₅₀ and a_w, while the values of redness and yellowness decreased with the reduction in particle size and water activity. The smaller the value of D₅₀, the higher the equilibrium moisture content of carob powder. Phenolic acids (vanillic, ferulic, cinnamic) and flavonoids (luteolin, naringenin, apigenin) were found in all samples of carob powder. The grinding time influenced their content in carob powder, with maximum values at 180 s. Similar observations were made when assessing antioxidant capacity. The in vitro digestion process only improved the bioaccessibility of catechin content in all samples. However, the bioaccessibility of the phenolic compounds and the total phenolic and flavonoid contents decreased with the increase in grinding time. Our findings revealed that the grinding of carob pods for 180 s improved the extractability of phenolics; however, their bioaccessibility was reduced. It is sufficient to ground the carob pod for 30 s, ensuring good availability of nutraceuticals and lower energy cost for grinding.

Review of factors affecting citrus polyphenol bioavailability and their importance in designing in vitro, animal, and intervention studies

Evidence from in vitro, animal, and human studies links citrus fruit consumption with several health-promoting effects. However, many in vitro studies disregard bioavailability data, a key factor determining responses in humans. Citrus (poly)phenol metabolism and bioavailability follow specific pathways that vary widely among individuals and are affected by several intrinsic (age, sex, gut microbiota, metabolic state, genetic polymorphisms) and extrinsic (food matrix, co-consumed food, (poly)phenol solubility, dose, food processing, lifestyle) factors. The gut microbiota is crucial to both absorption of citrus (poly)phenols and the production of catabolites, and absorption of both takes place mostly in the colon. Citrus (poly)phenol absorption can reach up to 100% in some individuals when the sum of the gut microbiota products are taken into account. This review emphasizes the importance of understanding citrus (poly)phenol absorption, metabolism, and bioavailability using evidence primarily derived from human studies in designing in vitro, animal, and further human clinical studies.

Isoflavone consumption reduces inflammation through modulation of phenylalanine and lipid metabolism

INTRODUCTION

Phytoestrogens found in soy, fruits, peanuts, and other legumes, have been identified as metabolites capable of providing beneficial effects in multiple pathological conditions due to their ability to mimic endogenous estrogen. Interestingly, the health-promoting effects of some phytoestrogens, such as isoflavones, are dependent on the presence of specific gut bacteria. Specifically, gut bacteria can metabolize isoflavones into equol, which has a higher affinity for endogenous estrogen receptors compared to dietary isoflavones. We have previously shown that patients with multiple sclerosis (MS), a neuroinflammatory disease, lack gut bacteria that are able to metabolize phytoestrogen. Further, we have validated the importance of both isoflavones and phytoestrogen-metabolizing gut bacteria in disease protection utilizing an animal model of MS. Specifically, we have shown that an isoflavone-rich diet can protect from neuroinflammatory diseases, and that protection was dependent on the ability of gut bacteria to metabolize isoflavones into equol. Additionally, mice on a diet with isoflavones showed an anti-inflammatory response compared to the mice on a diet lacking isoflavones. However, it is unknown how isoflavones and/or equol mediates their protective effects, especially their effects on host metabolite levels.

OBJECTIVES

In this study, we utilized untargeted metabolomics to identify metabolites found in plasma that were modulated by the presence of dietary isoflavones.

RESULTS

We found that the consumption of isoflavones increased anti-inflammatory monounsaturated fatty acids and beneficial polyunsaturated fatty acids while reducing pro-inflammatory glycerophospholipids, sphingolipids, phenylalanine metabolism, and arachidonic acid derivatives.

CONCLUSION

Isoflavone consumption alters the systemic metabolic landscape through concurrent increases in monounsaturated fatty acids and beneficial polyunsaturated fatty acids plus reduction in pro-inflammatory metabolites and pathways. This highlights a potential mechanism by which an isoflavone diet may modulate immune-mediated disease.

The flavonoid profiles in the pulp of different pomelo (Citrus grandis L. Osbeck) and grapefruit (Citrus paradisi Mcfad) cultivars and their in vitro bioactivity

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Fourteen flavonoid compounds were detected in pomelo and grapefruit pulp.

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The flavonoid profiles in pomelo and grapefruit pulp had varietal difference.

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Flavonoids of pomelo and grapefruit showed strong cellular antioxidant activity.

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Flavonoids of pomelo and grapefruit are good inhibitors of pancreatic lipase.

Previous results indicated that the flavonoid profiles might have varietal differences in pomelo, but detailed information is unknown. We previously isolated 4 new flavonoids, cigranoside C, D, E, F, in Citrus grandis Shatianyu pulp. However, their distribution in different pomelo cultivars remains to be explored. Therefore, the flavonoid profiles and in vitro bioactivity of the pulp from 5 pomelo and 1 grapefruit cultivars commonly consumed in China were investigated. Fourteen flavonoids were identified, cigranoside C, D, E were detected in these pomelo and grapefruit. Naringin and cigranoside C were the major flavonoids in grapefruit, Guanximiyu-W, Guanximiyu-R and Liangpingyu, while melitidin and rhoifolin was the predominant flavonoid in Shatianyu and Yuhuanyu, respectively. Pomelo and grapefruit showed strong antioxidant activity, and were potent inhibitors of pancreatic lipase with IC₅₀ values of 11.4–72.6 mg fruit/mL except Shatianyu. Thus, pomelo and grapefruit are natural antioxidants and possess anti-obesity potential.

A review of in vitro methods to evaluate the bioaccessibility of phenolic compounds in tropical fruits

International guidelines strongly advise about the frequent and varied intake of plant in diet. In this scenario, the consumption of fruits is closely related to health benefits due to the abundant presence of bioactive substances. Accordingly, the production of tropical fruits has stood out worldwide, reaching records since the past decade. However, to ensure that phenolic substances are indeed used by the body, they need to be accessible for absorption. For this purpose, several methods are used to assess the phenomenon of bioaccessibility. We provide information on i) in vitro methods for the evaluation of the bioaccessibility of phenolic compounds in tropical fruits, including their derivatives and by-products; ii) a study performed using a semi-dynamic in vitro digestion model; iii) simulated digestion with a dialysis membrane step, polyphenol transport/uptake using cell culture, and in vitro colonic fermentation process. Although standardized static and semi-dynamic in vitro digestion methods already exist, few studies use these protocols to assess the bioaccessibility of polyphenols in tropical fruits. To guarantee that in vitro digestion assays reproduce consistent results compared to in vivo reference methods, it is essential to universalize standardized methods that allow the comparison between results, enabling the validation of in vitro digestion methods.

Contribution of the diverse experimental models to unravelling the biological scope of dietary (poly)phenols

The health benefits associated with (poly)phenols need to be supported by robust and insightful information on their biological effects. The use of in vitro, ex vivo, and in vivo models is crucial to demonstrate functionalities in specific targets. In this regard, bioaccessibility, bioavailability, and tissue/organ distribution need to be fully understood and established. In addition, the structure-function relationships, concerning both descriptive and mechanistic information, between specific compounds and therapeutic objectives, need to be supported by results obtained from in vivo studies. Nevertheless, these studies are not always possible or have some limitations, particularly concerning the mechanistic information explaining the health benefits provided that should be covered with complementary experimental models. Based on these premises, this review aims to overview the contribution of the separate experimental approaches to gain insights into the bioaccessibility, bioavailability, and bioactivity of (poly)phenols. To achieve this objective, recent evidence available on the linkage of healthy/functional foods with the incidence of non-communicable pathologies is presented. The different experimental approaches provide complementary information that allows advances to be applied to the knowledge gained on the functional properties and mechanistic facts responsible for the health attributions of polyphenols. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Garambullo (Myrtillocactus geometrizans): effect of in vitro gastrointestinal digestion on the bioaccessibility and antioxidant capacity of phytochemicals

Garambullo (Myrtillocactus geometrizans), endemic fruit from Mexico, contains several bioactive compounds (phenolic compounds, betalains, antioxidant fiber), highlighting it as a good functional food. In this research, the impact of the in vitro gastrointestinal digestion on phytochemical bioaccessibility from garambullo and its antioxidant capacity are studied. The fruit contained previously unidentified phytochemicals in the polar and non-polar extracts (acetone and hexane). The bioaccessibility decreased in the mouth and stomach for flavanones (up to 11.9 and 8.9%, respectively), isoflavones (up to 20.0 and 9.2%, respectively), flavonols (up to 15.2 and 15.7%, respectively), hydroxycinnamic acids (up to 21.7 and 13.1%, respectively), and betalains (up to 10.5 and 4.2%, respectively); hydroxybenzoic acids were increased (up to 752.8 and 552.6%, respectively), while tocopherols increased in the mouth (127.7%) and decreased in the stomach (up to 90.3%). In the intestinal phase, the digestible fraction showed low phytochemicals bioaccessibility, and some compounds were recovered in the non-digestible fraction. The antioxidant capacity decreased in different compartments of the gastrointestinal tract, being higher in the mouth (872.9, 883.6, 385.2, and 631.2 μmol TE per g dw by ABTS, DPPH, ORAC, and FRAP, respectively) and stomach (836.2, 942.1, 289.0, and 494.9 μmol TE per g dw ABTS, DPPH, ORAC, and FRAP, respectively). The results indicate that digestion positively or negatively affects compounds' bioaccessibility depending on their structural family, and the antioxidant capacity decreases but remains higher than other functional foods.

Effects of edible whole citrus fruits on endogenous antioxidant enzymes of HepG2 cells

The effects of eating fresh citrus fruits including two varieties of mandarins, one of sweet oranges, one of grapefruit, two of pomelo, and one of kumquat cultivated in China on endogenous antioxidant enzymes were investigated by in vitro digestion and HepG2 cells. The correlations between enzyme activity and cell uptake of phytochemicals, and cellular antioxidant capacities were analyzed. The results showed that most of fresh citrus fruits increased the endogenous antioxidant activity. Bairoumiyou, Hongroumiyou, Ponkan, and Jinju after digestion significantly increased the activity of catalase (CAT) (P &lt; 0.05). Hongroumiyou, Bairoumiyou, Ponkan navel orange, and Jinju after digestion significantly increased glutathione peroxidases (GPxs) activity (P &lt; 0.05), while Huyou and Satsuma could not increase the activity of GPxs after digestion. Thioredoxin oxidoreductase (TrxR) activity was improved significantly by most of the digested whole citrus fruits except Ponkan (P &lt; 0.05) and the one added whole citrus fruits had higher increase than added citrus fruits extracts. The results indicated that edible whole citrus fruits had similar effects as extracts on enzymes.

Assessment of Lemon Juice Starter Addition on Secondary Fermented Soy Sauce

Soy sauce is one of the most popular ingredients for delicious cuisines across the world, and it is made via various fermentation processes using wheat and soybeans. The purpose of this study was to add a lemon juice starter into secondary fermentation soy sauce to produce a new flavor of soy sauce to meet current health awareness and innovation market trends. The results showed that the lactic acid bacteria of the A group (soy sauce/starter culture ratio of 3:1) gradually decreased from 9.89 to 8.32 log CFU/mL by the seventh day, and then to 5.39 log CFU/mL by the 30th day, while they were not detected by the 60th day. Meanwhile, those of the B group (soy sauce/starter culture ratio of 1:1) showed a decrease from 10.39 to 8.58 log CFU/mL by the seventh day, and then to 5.39 log CFU/mL by the 30th day and 4.43 log CFU/mL by the 60th day, while they were not detected by the 90th day. As for yeast, the A group showed a decrease from 10.83 to 9.29 log CFU/mL (or 10.25 to 9.27 log CFU/mL for the B group) by the seventh day. Yeasts were not detected after 30 days in either the A or B group. The acidity and salinity of the lemon-flavored sauce was maintained after secondary fermentation. Sensory evaluation showed that the soy sauce with a lemon juice starter was accepted by consumers and obtained a better result than commercial soy sauce. In conclusion, secondary fermentation with starters contributes to the flavor quality of sauce products. Fruit juice is adjustable in terms of the acidity and salinity of the soy sauce and produces good flavor after secondary fermentation whenever it acts as a starter. The fact that customers favored the innovative lemon-flavored soy sauce indicates that this study is on the right trend.

Digestive recovery of polyphenols, antioxidant activity, and anti-inflammatory activity of selected edible flowers from the family Fabaceae

Edible flowers are regaining popularity as therapeutic agents, due to their phytochemical composition. The present study assessed the recovery of phenolics along with the antioxidant and anti-inflammatory properties of seven edible flowers of the Fabaceae family after being subjected to simulated gastrointestinal conditions and dialysis. The total phenolic content of all the flowers decreased after the gastric phase, whereas the total flavonoid content increased. The total anthocyanin content of four flower species decreased after the intestinal phase of digestion. Cassia auriculata expressed the highest hydrogen peroxide and nitric oxide scavenging activities in the dialyzed fraction. Bauhinia racemose had the highest activity in the inhibition of heat-induced hemolysis of red blood cells after dialysis (4.43 ± 01.5%). In general, the results suggest a reduction in the phenolic contents after gastrointestinal digestion and dialysis; however, phenolics, flavonoids and anthocyanins were sufficiently available to be absorbed with the dialysis to exert antioxidant and anti-inflammatory activities. PRACTICAL APPLICATION: The presence of various phenolic compounds in edible flowers has attracted the attention of consumers as well as the food industry, due to their potential to be incorporated in functional foods and drugs. However, the availability of phenolics after digestion is an important measure to get a realistic view of the health effects exerted upon the consumption of these edible flowers. The present study provides new information on the antioxidant and anti-inflammatory potential of selected edible flowers before and after in vitro digestion. This would be more useful for nutritionists, policymakers and consumers to effectively utilize edible flowers by understanding the changes undergone by the phenolic compounds upon digestion.

Different Effects of Vitamin C-Based Supplements on the Advance of Linseed Oil Component Oxidation and Lipolysis during In Vitro Gastrointestinal Digestion

Although widely consumed, dietary supplements based on Vitamin C contain high doses of this compound, whose impact on lipid oxidation during digestion needs to be addressed. Therefore, the effect of seven commercial supplements and of pure l-ascorbic acid and ascorbyl palmitate on linseed oil during in vitro gastrointestinal digestion was tackled. The advance of lipid oxidation was studied through the generation of oxidation compounds, the degradation of polyunsaturated fatty acyl chains and of gamma-tocopherol, by employing Proton Nuclear Magnetic Resonance. Supplements containing exclusively l-ascorbic acid enhanced the advance of linseed oil oxidation during digestion. This was evidenced by increased formation of linolenic-derived conjugated hydroxy-dienes and alkanals and by the generation of conjugated keto-dienes and reactive alpha,beta-unsaturated aldehydes, such as 4,5-epoxy-2-alkenals; moreover, gamma-tocopherol was completely degraded. Conversely, supplements composed of mixtures of ascorbic acid/salt with citric acid and carotenes, and of ascorbyl palmitate, protected linseed oil against oxidation and reduced gamma-tocopherol degradation. The study through Solid Phase Microextraction-Gas Chromatography/Mass Spectrometry of the volatile compounds of the digests corroborated these findings. Furthermore, a decreased lipid bioaccessibility was noticed in the presence of the highest dose of l-ascorbic acid. Both the chemical form of Vitamin C and the presence of other ingredients in dietary supplements have shown to be of great relevance regarding oxidation and hydrolysis reactions occurring during lipid digestion.

Citrus polyphenols and risk of type 2 diabetes: Evidence from mechanistic studies

Citrus fruits are a rich source of (poly)phenols, a group of dietary bioactive compounds that protect against developing type 2 diabetes. Our review critically evaluates how experimental in vitro and animal models have elucidated some of the underlying mechanisms on how citrus (poly)phenols affect the markers of type 2 diabetes. According to animal studies, the beneficial effects derived from consuming citrus compounds appear to be related to long-term effects, rather than acute. There are some notable effects from citrus (poly)phenol metabolites on post-absorptive processes, such as modulation of hepatic glucose metabolism and insulin sensitivity in target tissues, but with a more modest effect on digestion and sugar absorption within the gut. Experimental studies on cells and other systems in vitro have indicated some of the possible mechanisms involved, but ∼70% of the studies utilized unrealistically high concentrations and forms of the compounds, compromising physiological relevance. Future studies should discuss the relevance of concentration used in in vitro experiments, relative to the proposed site of action, and also examine the role of catabolites produced by the gut microbiota. Finally, it is important to examine the relationship between the gut microbiota and bioavailability on the action of citrus (poly)phenols.

A Concise Review of Current In Vitro Chemical and Cell-Based Antioxidant Assay Methods

Antioxidants remain interesting molecules of choice for suppression of the toxic effects of free radicals in foods and human systems. The current practice involves the use of mainly synthetic molecules as potent antioxidant agents. However, due to the potential negative impact on human health, there is an intensive effort within the research community to develop natural alternatives with similar antioxidant efficacy but without the negative side effects of synthetic molecules. Still, the successful development of new molecules depends on the use of reliable chemical or cell culture assays to screen antioxidant properties. Chemical antioxidant assays include the determination of scavenging ability against free radicals such as DPPH, superoxide anion radicals, hydroxyl radicals, hydrogen peroxide, and nitric oxide. Other antioxidant tests include the ability of compounds to bind and sequester prooxidant metal cations, reduce ferric iron, and attenuate the rate of lipid oxidation. Ex vivo tests utilize cell cultures to confirm entry of the molecules into cells and the ability to quench synthetic intracellular free radicals or to stimulate the increased biosynthesis of endogenous antioxidants. In order to assist researchers in their choice of antioxidant evaluation methods, this review presents background scientific information on some of the most commonly used antioxidant assays with a comparative discussion of the relevance of published literature data to food science and human nutrition applications.

Phenolic acid metabolites of polyphenols act as inductors for hormesis in C. elegans

INTRODUCTION

Aging represents a major risk factors for metabolic diseases, such as diabetes, obesity, or neurodegeneration. Polyphenols and their metabolites, especially simple phenolic acids, gained growing attention as a preventive strategy against age-related, non-communicable diseases, due to their hormetic potential. Using Caenorhabditis elegans (C. elegans) we investigate the effect of protocatechuic, gallic, and vanillic acid on mitochondrial function, health parameters, and the induction of potential hormetic pathways.

METHODS

Lifespan, heat-stress resistance and chemotaxis of C. elegans strain P X 627, a specific model for aging, were assessed in 2-day and 10-day old nematodes. Mitochondrial membrane potential (ΔΨm) and ATP generation were measured. mRNA expression levels of longevity and energy metabolism-related genes were determined using qRT-PCR.

RESULTS

All phenolic acids were able to significantly increase the nematodes lifespan, heat-stress resistance and chemotaxis at micromolar concentrations. While ΔΨm was only affected by age, vanillic acid (VA) significantly decreased ATP concentrations in aged nematodes. Longevity pathways, were activated by all phenolic acids, while VA also induced glycolytic activity and response to cold.

CONCLUSION

While life- and health span parameters are positively affected by the investigated phenolic acids, the concentrations applied were unable to affect mitochondrial performance. Therefore we suggest a hormetic mode of action, especially by activation of the sirtuin-pathway.

In Vitro Bioaccessibility of Bioactive Compounds from Citrus Pomaces and Orange Pomace Biscuits

The present investigation aimed to provide novel information on the chemical composition and in vitro bioaccessibility of bioactive compounds from raw citrus pomaces (mandarin varieties Clemenule and Ortanique and orange varieties Navel and Valencia). The effects of the baking process on their bioaccessibility was also assessed. Samples of pomaces and biscuits containing them as an ingredient were digested, mimicking the human enzymatic oral gastrointestinal digestion process, and the composition of the digests were analyzed. UHPLC-MS/MS results of the citrus pomaces flavonoid composition showed nobiletin, hesperidin/neohesperidin, tangeretin, heptamethoxyflavone, tetramethylscutellarein, and naringin/narirutin. The analysis of the digests indicated the bioaccessibility of compounds possessing antioxidant [6.6–11.0 mg GAE/g digest, 65.5–97.1 µmol Trolox Equivalents (TE)/g digest, and 135.5–214.8 µmol TE/g digest for total phenol content (TPC), ABTS, and ORAC-FL methods, respectively; significant reduction (p < 0.05) in Reactive Oxygen Species (ROS) formation under tert-butyl hydroperoxide (1 mM)-induced conditions in IEC-6 and CCD-18Co cells when pre-treated with concentrations 5–25 µg/mL of the digests], anti-inflammatory [significant reduction (p < 0.05) in nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW264.7 macrophages], and antidiabetic (IC₅₀ 3.97–11.42 mg/mL and 58.04–105.68 mg/mL for α-glucosidase and α-amylase inhibition capacities) properties in the citrus pomaces under study. In addition, orange pomace biscuits with the nutrition claims “no-added sugars” and “source of fiber”, as well as those with good sensory quality (6.9–6.7, scale 1–9) and potential health promoting properties, were obtained. In conclusion, the results supported the feasibility of citrus pomace as a natural sustainable source of health-promoting compounds such as flavonoids. Unfractionated orange pomace may be employed as a functional food ingredient for reducing the risk of pathophysiological processes linked to oxidative stress, inflammation, and carbohydrate metabolism, such as diabetes, among others.

Digestibility, bioactivity and prebiotic potential of phenolics released from whole gold kiwifruit and pomace by in vitro gastrointestinal digestion and colonic fermentation

The aim of this study was to evaluate the release of phenolics, biological activity variation and prebiotic potential of whole gold kiwifruit and pomace by in vitro digestion and colonic fermentation. The released phenolics of whole kiwifruit and pomace after digestion were 99.53 and 101.04 mg GAE per 100 g FW, respectively. Six compounds were quantified, and catechin, gallic and caffeic acid were mainly released in the oral phase, protocatechuic acid in the gastric phase, and coumaric and hydroxybenzoic acid during fermentation. The whole kiwifruit possessed higher antioxidant activity than the pomace, while both showed decreases during the whole digestion and fermentation process. After S-intestine digestion, the α-glucosidase inhibitory activities of pomace and whole kiwifruit were 1.33 and 3.11 mg acarbose per g FW, respectively. The fermentation of the whole kiwifruit and pomace caused reduction of the pH and variation of the gut microbiota diversity. Compared with whole kiwifruit, the pomace showed stronger modulative effects on the ratio of Firmicutes/Bacteroidetes. These findings provide scientific evidence for the utilization of pomace and whole gold kiwifruit.

Determination of etoxazole in different parts of citrus fruit and its potential dietary exposure risk assessment

In this study, the profile of etoxazole in whole citrus, peel and pulp samples collected from Chongqing, Guangdong and Anhui provinces was monitored and their dietary risk to human had also been assessed. The final residual levels and distributions of etoxazole in citrus samples were detected by using an ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). The results showed that final concentrations of etoxazole in whole citrus, peel, and pulp were ranged at 0.012-0.174, 0.010-0.637, and 0.010-0.011 mg kg^-1, respectively. The assessment of dietary risk suggested that chronic dietary risk of etoxazole in whole fruit and peel were 0.010-0.197% and 0.035-0.951%, respectively. Our findings indicated that the chronic risk of daily consumption of citrus fruit is acceptable at recommended dosage.

Simulated gastrointestinal digestion of Brazilian açaí seeds affects the content of flavan-3-ol derivatives, and their antioxidant and anti-inflammatory activities

Açaí seeds (Euterpe oleracea Mart.) are the major residue generated during industrial extraction of açaí fruit pulp - a popular and typical Amazon fruit rich in bioactive compounds and nutrients. In this study, we investigated the bioaccessibility of an açaí seed extract using an in vitro simulated gastrointestinal digestion model. Catechin, epicatechin and procyanidins B1 and B2 were identified and quantified in the açaí seed extract and monitored by HPLC-DAD through the digestion phases. Bioaccessibility of these flavan-3-ols and deactivation of reactive oxygen species decreased after the intestinal phase, except for peroxyl radical (ROO^●). RAW 264.7 macrophages treated either with the digested or undigested açaí seed extract showed reduced NF-κB activation and TNF-α levels, even following gastrointestinal digestion. Thus, the ROO^● scavenging capacity and anti-inflammatory activity of the extract were found to be still remarkable after digestion, suggesting that açaí seeds could be explored as a source of bioactive compounds for functional foods, cosmetic or pharmaceutical purposes.

Neohesperidin attenuates obesity by altering the composition of the gut microbiota in high-fat diet-fed mice

Obesity and related metabolic disorders are associated with intestinal microbiota dysbiosis, disrupted intestinal barrier, and chronic inflammation. Neohesperidin (Neo), a natural polyphenol abundant in citrus fruits, is known for its preventative and therapeutic effects on numerous diseases. Here, we report that Neo administration attenuates weight gain, low-grade inflammation, and insulin resistance in mice fed high-fat diet (HFD). Also, Neo administration substantially restores gut barrier damage, metabolic endotoxemia, and systemic inflammation. Sequencing of 16S rRNA genes in fecal samples revealed that Neo administration reverses HFD-induced intestinal microbiota dysbiosis: an increase in the diversity of gut microbiota and alteration in the composition of intestinal microbiota (particularly in the relative abundances of Bacteroidetes and Firmicutes). Furthermore, systemic antibiotic treatment abolishes the beneficial effects of Neo in body weight control, suggesting that the effect of Neo on obesity attenuation largely depends on the gut microbiota. More importantly, we demonstrate that the impact of Neo on the regulation of obesity could be transferred from Neo-treated mice to HFD-fed mice via fecal microbiota transplantation. Collectively, our data highlight the efficacy of Neo as a prebiotic agent for attenuating obesity, implying a potential mechanism for gut microbiota mediated the beneficial effect of Neo.

Polyphenols as Possible Agents for Pancreatic Diseases

Pancreatic cancer (PC) is very aggressive and it is estimated that it kills nearly 50% of patients within the first six months. The lack of symptoms specific to this disease prevents early diagnosis and treatment. Today, gemcitabine alone or in combination with other cytostatic agents such as cisplatin (Cis), 5-fluorouracil (5-FU), irinotecan, capecitabine, or oxaliplatin (Oxa) is used in conventional therapy. Outgoing literature provides data on the use of polyphenols, biologically active compounds, in the treatment of pancreatic cancer and the prevention of acute pancreatitis. Therefore, the first part of this review gives a brief overview of the state of pancreatic disease as well as the procedures for its treatment. The second part provides a detailed overview of the research regarding the anticancer effects of both pure polyphenols and their plant extracts. The results regarding the antiproliferative, antimetastatic, as well as inhibitory effects of polyphenols against PC cell lines as well as the prevention of acute pancreatitis are presented in detail. Finally, particular emphasis is given to the polyphenolic profiles of apples, berries, cherries, sour cherries, and grapes, given the fact that these fruits are rich in polyphenols and anthocyanins. Polyphenolic profiles, the content of individual polyphenols, and their relationships are discussed. Based on this, significant data can be obtained regarding the amount of fruit that should be consumed daily to achieve a therapeutic effect.

Phenolic profiles, antioxidant, antiproliferative, and hypoglycemic activities of Ehretia macrophyla Wall. (EMW) fruit

Phenolic profiles, antioxidant, antiproliferative, and hypoglycemic activities of the whole Ehretia macrophylla Wall. (EMW) fruit were investigated in the present study. Catechin (CE), o-methoxy benzoic acid (o-MBA), and rosmarinic acid (RA) were the predominant phenolics in free extract, while CE, vanillic acid (VA), and o-MBA were for bound extract. These extracts exhibited potential antioxidant capacity measured by peroxyl radical scavenging capacity (PSC), oxygen radical absorbance capacity (ORAC), and cellular antioxidant activity (CAA) assays. This fruit also possessed dose-dependently antiproliferative activity, and this may be due to the synergistic and additive effects of individual phenolics. Furthermore, EMW fruit showed favorable hypoglycemic activity via inhibition of activities of α-glucosidase and α-amylase, enhancement of glucose consumption, glycogen accumulation, and glycogen synthase 2 (GYS2) activity, and downregulation of activities of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK). Therefore, EMW fruit has the potential as an ingredient of functional foods to improve human health and shows promising applications with additional health and economical benefits. PRACTICAL APPLICATION: EMW fruit is a plant-based food rich in natural phenolic compounds, which suggesting its potential bioactivities for humans such as antioxidant, antiproliferative, and hypoglycemic activities. Our findings would provide a logical strategy to promote the comprehensive utilization of phenolics in EMW fruit with both health and economical benefits.

Hepatoprotective and Anti-Oxidative Effects of Total Flavonoids From Qu Zhi Qiao (Fruit of Citrus Paradisi cv.Changshanhuyou) on Nonalcoholic Steatohepatitis In Vivo and In Vitro Through Nrf2-ARE Signaling Pathway

Nonalcoholic steatohepatitis (NASH) is a liver disease defined as the dynamic condition of hepatocellular injury during the progress of nonalcoholic fatty liver disease (NAFLD). Total flavonoids from the dry and immature fruits of Citrus Paradisi cv.Changshanhuyou (accepted species name: Citrus × aurantium L) (Qu Zhi Qiao, QZQ) are purified and named TFCH. This study was purposed to investigate and analyze the effect of TFCH on NASH model through Nuclear factor erythroid 2-related factor 2 (Nrf2)- antioxidant response elements pathway in vivo and in vitro. In vivo study was performed using male C57BL/6 mice fed with high fat diet 16 weeks for NASH model. After 7-week modeling, mice in TFCH-treated group were daily treated with intragastric administration of TFCH at 25 mg/kg, 50 mg/kg, 200 mg/kg, respectively, for successive 8 weeks. Histopathological and immunohistochemical analyses were conducted for evaluating severity of NASH-mice model and the effect of TFCH treatment. In vitro experiment was performed by using human LX-2 cells and cultured with Free fatty acid (FFA) (Oleic acid: palmitic: l: 0.5 mmol/L) for 24 h and then treated with TFCH at different concentrations (0, 25, 50, 100, 200 mg/ml) for 6 h,12 h, and 24 h. Anti-apoptosis effect of TFCH on LX-2 cells cultured with FFA was revealed by the CCK-8 assay. Lipid parameters and oxidative stress markers were measured in vivo and in vitro, results showed that TFCH dose-dependently and greatly increased the antioxidant ability and reduced the oxidative damage in NASH model. The protein expression of Nrf2 and the downstream target genes in mice liver and human LX-2 cells were tested by Western blot analysis to investigate the possible molecular mechanisms of TFCH. Our results indicated that TFCH up-regulated protein expression of these genes and have the significant influence in activating the Nrf2-ARE signaling pathway. This study shows Nrf2-ARE signaling pathway may provide novel therapeutic opportunities for NASH therapy in the future.

Valorization of byproducts from tropical fruits: Extraction methodologies, applications, environmental, and economic assessment: A review (Part 1: General overview of the byproducts, traditional biorefinery practices, and possible applications)

Tropical fruits represent one of the most important crops in the world. The continuously growing global market for the main tropical fruits is currently estimated at 84 million tons, of which approximately half is lost or wasted throughout the whole processing chain. Developing novel processes for the conversion of these byproducts into value-added products could provide a viable way to manage this waste problem, aiming at the same time to create a sustainable economic growth within a bio-economy perspective. Given the ever-increasing concern about sustainability, complete valorization through a bio-refinery approach, that is, zero waste concept, as well as the use of green techniques is therefore of utmost importance. This paper aims to report the status on the valorization of tropical fruit byproducts within a bio-refinery frame, via the application of traditional methodologies, and with specific attention to the extraction of phenolics and carotenoids as bioactive compounds. The different types of byproducts, and their content of bioactives is reviewed, with a special emphasis on the lesser-known tropical fruits. Moreover, the bioactivity of the different types of extracts and their possible application as a resource for different sectors (food, pharmaceutical, and environmental sciences) is discussed. Consequently, this review presents the concepts of tropical fruit biorefineries, and the potential applications of the isolated fractions.

Assessment of the Phenolic Profiles, Hypoglycemic Activity, and Molecular Mechanism of Different Highland Barley (Hordeum vulgare L.) Varieties

The phenolic profiles, hypoglycemic activity, and molecular mechanism of the effect on type 2 diabetes mellitus (T2DM) of four highland barley varieties were investigated in the present study. The fundamental phenolics in highland barley were ferulic acid, naringin, and catechin, which mainly existed in bound form. These varieties showed favorable hypoglycemic activity via inhibition of α-glucosidase and α-amylase activities, enhancement of glucose consumption, glycogen accumulation and glycogen synthase 2 (GYS2) activity, and down-regulation of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK) activities. Specifically, ZQ320 variety exhibited the strongest hypoglycemic activity compared to the other varieties. Highland barley phenolics could inhibit gluconeogenesis and motivate glycogen synthesis via down-regulating the gene expression of G6Pase, PEPCK, and glycogen synthase kinase 3β (GSK3β), while activating the expression of insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3 kinase (PI3K), serine/threonine kinase (Akt), GYS2, and glucose transporter type 4 (GLUT4). Therefore, phenolics from highland barley could be served as suitable candidates for therapeutic agent in T2DM to improve human health.

The Bioprotective Effects of Polyphenols on Metabolic Syndrome against Oxidative Stress: Evidences and Perspectives

Polyphenols are the general designation of various kinds of phytochemicals, mainly classified as flavonoids and nonflavonoids. Polyphenolic compounds have been confirmed to exhibit numerous bioactivities and potential health benefits both in vivo and in vitro. Dietary polyphenols have been shown to significantly alleviate several manifestations of metabolic syndrome, namely, central obesity, hypertension, dyslipidemia, and high blood sugar. This review is aimed at discussing the bioprotective effects and related molecular mechanisms of polyphenols, mainly by increasing antioxidant capacity or oxygen scavenging capacity. Polyphenols can exert their antioxidative activity by balancing the organic oxidoreductase enzyme system, regulating antioxidant responsive signaling pathways, and restoring mitochondrial function. These data are helpful for providing new insights into the potential biological effects of polyphenolic compounds and the development of future antioxidant therapeutics.

Antioxidant and Photoprotective Activity of Apigenin and its Potassium Salt Derivative in Human Keratinocytes and Absorption in Caco-2 Cell Monolayers

Ultraviolet (UV) radiation, especially types A (UVA) and B (UVB), is one of the main causes of skin disorders, including photoaging and skin cancer. Ultraviolent radiation causes oxidative stress, inflammation, p53 induction, DNA damage, mutagenesis, and oxidation of various molecules such as lipids and proteins. In recent decades, the use of polyphenols as molecules with an antioxidant and anti-inflammatory capacity has increased. However, some of these compounds are poorly soluble, and information regarding their absorption and bioavailability is scarce. The main objective of this study was to compare the intestinal absorption and biological activity of apigenin and its more soluble potassium salt (apigenin-K) in terms of antioxidant and photoprotective capacity. Photoprotective effects against UVA and UVB radiation were studied in human keratinocytes, and antioxidant capacity was determined by different methods, including trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) assays. Finally, the intestinal absorption of both apigenins was determined using an in vitro Caco-2 cell model. Apigenin showed a slightly higher antioxidant capacity in antioxidant activity assays when compared with apigenin-K. However, no significant differences were obtained for their photoprotective capacities against UVA or UVB. Results indicated that both apigenins protected cell viability in approximately 50% at 5 J/m² of UVA and 90% at 500 J/m² of UVB radiation. Regarding intestinal absorption, both apigenins showed similar apparent permeabilities (P_app), 1.81 × 10^-5 cm/s and 1.78 × 10^-5 cm/s, respectively. Taken together, these results suggest that both apigenins may be interesting candidates for the development of oral (nutraceutical) and topical photoprotective ingredients against UVA and UVB-induced skin damage, but the increased water solubility of apigenin-K makes it the best candidate for further development.