Flavonoids regulate tumor-associated macrophages - From structure-activity relationship to clinical potential (Review).

In recent years, the strategy for tumor therapy has changed from focusing on the direct killing effect of different types of therapeutic agents on cancer cells to the new mainstream of multi-mode and -pathway combined interventions in the microenvironment of the developing tumor. Flavonoids, with unique tricyclic structures, have diverse and extensive immunomodulatory and anti-cancer activities in the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) are the most abundant immunosuppressive cells in the TME. The regulation of macrophages to fight cancer is a promising immunotherapeutic strategy. This study covers the most comprehensive cognition of flavonoids in regulating TAMs so far. Far more than a simple list of studies, we try to dig out evidence of crosstalk at the molecular level between flavonoids and TAMs from literature, in order to discuss the most relevant chemical structure and its possible relationship with the multimodal pharmacological activity, as well as systematically build a structure-activity relationship between flavonoids and TAMs. Additionally, we point out the advantages of the macro-control of flavonoids in the TME and discuss the potential clinical implications as well as areas for future research of flavonoids in regulating TAMs. These results will provide hopeful directions for the research of antitumor drugs, while providing new ideas for the pharmaceutical industry to develop more effective forms of flavonoids.

Phytochemicals modulate pancreatic islet ß cell function through glucagon-like peptide-1-related mechanisms.

Glucagon-like peptide-1 (GLP-1) receptor-based therapies have been developed and extensively applied in clinical practice. GLP-1 plays an important role in improving glycemic homeostasis by stimulating insulin biosynthesis and secretion, suppressing glucagon activity, delaying gastric emptying, and reducing appetite and food ingestion. Furthermore, GLP-1 has positive effects on ß-cell function by promoting ß-cell proliferation and neogenesis while simultaneously reducing apoptosis. Here, we summarize possible mechanisms of action of GLP-1 upon pancreatic islets as well as describe phytochemicals that modulate pancreatic islet ß cell function through glucagon-like peptide-1-related mechanisms. Together, this information provides potential lead compound candidates against diabetes that function as GLP-1 receptor-based pharmacotherapy.

Structural requirements of flavonoids for the selective inhibition of α-amylase versus α-glucosidase.

In the present study, 14 structurally unique flavonoids were screened to systematically investigate structural requirements for selectively inhibiting human α-amylase versus α-glucosidase to obtain a slow but complete starch digestion for health benefit. The selective inhibition property of three flavonoids chosen against the two classes of starch digestive enzymes was confirmed through various analytical techniques - in vitro inhibition assay, fluorescence quenching, kinetic study, and molecular modeling. Considering the chemical structure of flavonoids, the double bond between C2 and C3 and OH groups at A5 and B3 are critical for the inhibition of α-amylase allowing flavonoids to lie parallel on the α-amylase catalytic active site, whereas the OH groups at B3 and C3 are important for α-glucosidase inhibition causing B-ring specific entry into the catalytic active site of α-glucosidase. Our findings provide insights into how to apply flavonoids to effectively control digestion rate for improving physiological responses.

The antihypertensive potential of flavonoids from Chinese Herbal Medicine: A review.

With the coming of the era of the aging population, hypertension has become a global health burden to be dealt with. Although there are multiple drugs and procedures to control the symptoms of hypertension, the management of it is still a long-term process, and the side effects of conventional drugs pose a burden on patients. Flavonoids, common compounds found in fruits and vegetables as secondary metabolites, are active components in Chinese Herbal Medicine. The flavonoids are proved to have cardiovascular benefits based on a plethora of animal experiments over the last decade. Thus, the flavonoids or flavonoid-rich plant extracts endowed with anti-hypertension activities and probable mechanisms were reviewed. It has been found that flavonoids may affect blood pressure in various ways. Moreover, despite the substantial evidence of the potential for flavonoids in the control of hypertension, it is not sufficient to support the clinical application of flavonoids as an adjuvant or core drug. So the synergistic effects of flavonoids with other drugs, pharmacokinetic studies, clinical trials and the safety of flavonoids are also incorporated in the discussion. It is believed that more breakthrough studies are needed. Overall, this review may shed some new light on the explicit recognition of the mechanisms of anti-hypertension actions of flavonoids, pointing out the limitations of relevant research at the current stage and the aspects that should be strengthened in future researches.

Myricetin protects mice against MRSA-related lethal pneumonia by targeting ClpP.

Methicillin-resistant Staphylococcus aureus is one of the leading causes of community and nosocomial infections, which has created the urgent need for innovative anti-infective agents to control MRSA-associated infections. A conserved serine protease, caseinolytic peptidase P (ClpP) in Staphylococcus aureus is highly associated with pathogenicity and has been claimed to be a novel antimicrobial target. We aim to search suitable inhibitors of ClpP to attenuate the virulence of MRSA and combat their infections in vivo. Over 500 natural compounds were pre-screened via fluorescence resonance energy transfer using the Suc-LY-AMC substrate. The binding of myricetin to ClpP was determined and the mechanism of action was elucidated by thermal shift assay, surface plasmon resonance, and molecular dynamics simulations. The therapeutic effects of myricetin on S. aureus infection were further investigated using a S. aureus-induced pneumonia model. We revealed that myricetin could effectively block the activity of ClpP without disturbing the growth of the bacteria and the Gln-47 and Met-31 residues were necessary for myricetin binding to ClpP. Importantly, myricetin attenuated the pathogenicity of S. aureus in vivo, while improving the efficacy of the traditional antibiotic oxacillin against MRSA infection and protecting mice from fatal lung infections caused by MRSA. These findings indicate that myricetin has the potential to be applied in the pharmaceutical industry as a promising therapeutic agent.

Anti-browning effect of Rosa roxburghii on apple juice and identification of polyphenol oxidase inhibitors.

Enzymatic browning control of cloudy fruit juice with natural substances has received much attention for improving its nutritional and commercial value. This study explored the anti-browning potential of Rosa roxburghii in apple juice. The anti-browning effects and mechanisms were evaluated by serial measurements of appearance, browning index, polyphenol oxidase (PPO) activity, UPLC-QE-Orbitrap-MS identification, inhibition kinetics and molecular docking. The results showed that Rosa roxburghii juice (0.25%-1.25% w/w) could effectively inhibit browning and PPO activity of apple juice. Ascorbic acid (1.67 g/100 g) as a reducing agent was a main anti-browning factor. Furthermore, seven phenolic compounds in Rosa roxburghii were screened as PPO inhibitors. Representative phenolic inhibitors induced mixed or competitive inhibition of PPO, mainly driven by hydrophobic forces and hydrogen bonds. This work demonstrates that Rosa roxburghii is a promising natural anti-browning ingredient to control the browning of cloudy apple juice due to abundant ascorbic acid and PPO inhibitors.

Flavonoids and hERG channels: Friends or foes?

The cardiac action potential is regulated by several ion channels. Drugs capable to block these channels, in particular the human ether-à-go-go-related gene (hERG) channel, also known as KV11.1 channel, may lead to a potentially lethal ventricular tachyarrhythmia called "Torsades de Pointes". Thus, evaluation of the hERG channel off-target activity of novel chemical entities is nowadays required to safeguard patients as well as to avoid attrition in drug development. Flavonoids, a large class of natural compounds abundantly present in food, beverages, herbal medicines, and dietary food supplements, generally escape this assessment, though consumed in consistent amounts. Continuously growing evidence indicates that these compounds may interact with the hERG channel and block it. The present review, by examining numerous studies, summarizes the state-of-the-art in this field, describing the most significant examples of direct and indirect inhibition of the hERG channel current operated by flavonoids. A description of the molecular interactions between a few of these natural molecules and the Rattus norvegicus channel protein, achieved by an in silico approach, is also presented.

Polyphenols and their applications: An approach in food chemistry and innovation potential.

Polyphenols are compounds naturally present in fruits and vegetables that are gaining more and more attention due to their therapeutic effects and their potential technological applications. In this review, we intend to demonstrate the importance of some phenolic compounds, addressing their biological effects and potential for applications in various industrial fields. The intake of these compounds in appropriate concentrations can present promising effects in the prevention of diseases such as diabetes, obesity, Parkinson's, Alzheimer's, and others. They can also be used to improve the physicochemical properties of starch, in the preservation of foods, as natural dyes, prebiotic ingredients, hydrogels and nanocomplexes. In addition, these compounds have potential for innovation in the most diverse technological fields, including organic fine chemistry, basic materials chemistry, pharmaceuticals, food chemistry, chemical engineering, etc.

Mechanistic studies of inhibition on acrolein by myricetin.

Acrolein (ACR) is an unsaturated aldehyde with high activity and toxicity and is produced in vivo and in food. This study investigated the impact of B-ring structure on the trapping of ACR by flavonols and the trapping mechanism and efficacy of ACR by myricetin. Galangin, kaempferol, quercetin, and myricetin, which possess the same A- and C-ring but different numbers of -OH groups on the B-ring, were selected for this study. Our results suggested that increasing the number of -OH groups on the B-ring can enhance the ACR trapping efficacy of flavonol and myrectin was identified as the most active flavonol. The adducts of myricetin with ACR under different ratios and incubation times were analyzed using LC-MS/MS. We also purified and identified the major mono- and di-ACR-myricetin adducts. Furthermore, myricetin could dose-dependently inhibit the formation of ACR in cookies through the formation of mono- and di-ACR adducts.

The beneficial health effects of flavonoids on the cardiovascular system: Focus on K+ channels.

Substantial experimental evidences support the hypothesis that dietary flavonoid intake has a favourable impact on cardiovascular diseases such as systemic, arterial hypertension and coronary artery diseases, which represent the leading cause of morbidity and mortality worldwide. The biological effects of flavonoids involve complex biochemical interactions with numerous, specific, cellular and molecular targets. K+ channels, fine modulators of both cardiac action potential and vascular cell membrane potential, represent one of these targets. Overexpression, downregulation or dysfunction of these channel proteins are the cause of many cardiovascular diseases. Therefore, it appears of particular interest a detailed analysis of the flavonoid potential, direct/indirect modulation of cardiovascular K+ channels as these natural compounds ingested with the diet, despite extensive gut metabolism, may accumulate at cellular level in the form of the parent aglycones. The present review will portray their effects on cardiovascular K+ channels. Molecular docking was used to strengthen experimental evidences and describe flavonoid-channel interactions at molecular level.

Comparison of three water-soluble polyphosphate tripolyphosphate, phytic acid, and sodium hexametaphosphate as crosslinking agents in chitosan nanoparticle formulation.

Chitosan nanoparticles (CS-NPs) prepared by ionic gelation with tripolyphosphate (TPP) are a promising drug carrier for mucosal administration due to their remarkable mucoadhesivity and biocompatibility. In this work, CS-NPs were obtained by an ionotropic gelation method with polyphosphate crosslinking agents of tripolyphosphate (TPP), phytic acid (PA), and sodium hexametaphosphate (SHMP). The drug encapsulation efficiency, in vitro drug release behavior, mucoadhesivity, and cytotoxicity of the CS-NPs were evaluated. The results demonstrated that the high concentration of H+ ion would impede the formation of CS-TPP-NPs but promote the formation of CS-PA-NPs and CS-SHMP-NPs. The obtained CS-NPs were approximately spherical in shape, biocompatible confirmed by the cytotoxicity test, and bioadhesive particles with a narrow diameter distribution (0.20 ±â€¯0.02 of polydispersity index) less than 200 nm. The encapsulation efficiency of myricetin (MYR) in CS-NPs crosslinked by PA and SHMP (67.3 ±â€¯0.4 % and 62.2 ±â€¯0.2 %) was significantly higher than that in CS-NPs crosslinked by TPP (47.7 ±â€¯0.1 %) (p < 0.05); their drug release rate (43.7 ±â€¯5.1 % and 44.0 ±â€¯3.7 %) was also significantly slower than that of MYR-CS-NPs crosslinked by TPP (103.4 ±â€¯4.0 %) (p < 0.05). Furthermore, a strong mucoadhesiveness of the CS-NPs crosslinked by PA was shown by a fast increase of the turbidity value and a sharp decrease of the zeta potential in the mucin solution test.

Involvement of MdUGT75B1 and MdUGT71B1 in flavonol galactoside/glucoside biosynthesis in apple fruit.

Apple is rich in flavonol glycosides, which are believed to contribute to putative health benefits associated with apple consumption. Glycosylation, catalyzed by uridine diphospho-glycosyltransferases (UGTs), is the last step in flavonol biosynthesis, which confers molecular stability and solubility to the flavonol. In the present study, the involvement of two UGTs, MdUGT75B1 and MdUGT71B1, in flavonol biosynthesis in apple was investigated. The major flavonols are quercetin 3-O-glycosides, and UV-B and blue light treatment significantly enhanced the accumulation of quercetin 3-O-galactoside, quercetin 3-O-glucoside, and kaempferol 3-O-galactoside. Transcript levels of MdUGT75B1 and MdUGT71B1 in fruit subjected to different treatments were correlated well with flavonol accumulation. MdUGT75B1 showed flavonol-specific activity with a preference for UDP-galactose as the sugar donor, while MdUGT71B1 using UDP-glucose exhibited a wider substrate acceptance. Thus, MdUGT75B1 and MdUGT71B1 are key UGTs involved in flavonol biosynthesis and may have important roles in regulating accumulation of these health-promoting bioactive compounds in apple.

Evaluation of astringent taste of green tea through mass spectrometry-based targeted metabolic profiling of polyphenols.

The contributions of many polyphenols other than catechins and flavonols to the astringency of tea are often neglected. Here, the contributions of polyphenols were assessed through targeted metabolic profiling using liquid chromatography-mass spectrometry. A total of 86 polyphenols were identified from 47 green tea samples with varying astringency scores, of which 76 compounds were relatively quantified. A correlation matrix analysis revealed that monohydroxyflavonol and acyl derivatives of polyphenols, except for galloylated catechins, had negative correlations with the other polyphenols. Principal component analysis revealed a distinct separation of monohydroxyflavonol and acyl derivatives of polyphenols from the other polyphenols. The results suggest metabolic differences in terms of hydroxylation, glycosylation, acylation, and condensation reactions of polyphenols between the different tea samples, particularly between the samples obtained in spring and autumn. The correlation analysis showed that metabolic fluxes toward the aforementioned four reactions of polyphenols played unique roles in the astringency of tea infusions.

Characterization of bioactive compounds and antioxidant activity of fruit beers.

Total polyphenols and flavonoids content, phenolics profile by HPLC, and antioxidant activity of ten fruit beer produced adding fruits during the fermentation process were analyzed. The fruits were: cherry, raspberry, peach, apricot, grape, plum, orange and apple. Antioxidant activity, total polyphenols and flavonoids content were considerably higher in most of the fruit beers in respect to conventional, no-fruit beers. Cherries beers exhibit the highest values, followed by grape, plum and orange beers. An enrichment was observed in catechin and quercetin content in all fruit beers examined. Myricetin and resveratrol were also detected in most of the fruit beers. Among phenolic acids, an enrichment in chlorogenic, neochlorogenic, p-coumaric and caffeic acids was measured in most of the fruit beers in respect to conventional beers. Our findings show that fruits addition during the fermentation process considerably increased the antioxidant activity of beer and qualitatively and quantitatively improved its phenolics profile.

A critical review of some fruit trees from the Myrtaceae family as promising sources for food applications with functional claims.

The Myrtaceae family is one of the world's leading commercial fruit tree families. Among the 121 genera belonging to this family, the Syzygium, Eugenia and Campomanesia genera are constituted by a wide variety of fruit species with great potential to be explored economically, besides presenting excellent nutritional value and being considered sources of phytochemicals such as phenolic compounds, carotenoids and volatile compounds. Many of these phytochemicals have been linked to the prevention and management of several chronic and degenerative diseases including cancer, cardiovascular diseases, type 2 diabetes mellitus, obesity, amnesia among other disorders. In this context, this review discusses about the importance of four fruits species representative of Myrtaceae family such as Syzygium cumini, Syzygium malaccense, Eugenia pyriformis and Campomanesia xanthocarpa, focusing on the nutrients and phytochemical constituents as well as demonstrating their biological effects in order to stimulate the cultivation and consumption of these fruits.

Changes in organic acids, polyphenolic and elemental composition of rosé sparkling wines treated with mannoproteins during over-lees aging.

The effect of mannoproteins on the evolution of rosé sparkling wines during over-lees aging was investigated on the basis of the chemical characterization of polyphenols, organic acids, macro- and microelements using a combined analytical approach. Variations on these constituents were assessed using Raman and near-infrared spectroscopy. During the biological aging, caffeic acid, catechin, gallic acid and malvidin-3-O-glucoside were the most abundant polyphenolics in the rosé wines. The phenolic compound tyrosol, a fermentation derivative, was found at concentrations up to 98.07 mg L-1. The addition of mannoproteins significantly affected the concentrations of organic acids and individual polyphenolic compounds, particularly trans-resveratrol, quercetin, catechin, p-coumaric and hydroxybenzoic acids that showed increased concentrations over time. The positive effects of mannoproteins were mainly observed at the end of the biological aging. The mineral composition remained stable, while potassium was the most abundant mineral in all wines. The observed changes involving these constituents may offer new insights on their behavior during wine aging and on the bioactive and nutritional quality of rosé sparkling wines.

Improvement strategies for the oral bioavailability of poorly water-soluble flavonoids: An overview.

Although flavonoid compounds have various pharmacological applications, they generally exhibit low oral bioavailability due to their poor aqueous solubility. To address this problem, numerous promising strategies, such as the use of an absorption enhancer, structural transformation (e.g., prodrugs, glycosylation), and pharmaceutical technologies (e.g., carrier complexes, nanotechnology, cocrystals), have been developed and applied to deliver poorly water-soluble flavonoids. These formulation approaches can effectively improve the oral bioavailability of flavonoids by enhancing their solubility, dissolution rate and permeability; preventing their degradation or metabolism in the gastrointestinal tract; and/or delivering them directly to their physiological targets. This review comprehensively summarizes the viable oral delivery systems for insoluble flavonoids to date and discusses their design principles, potential advantages, possible limitations, and oral delivery efficiency, which will provide some useful clues and references to overcome the absorption barrier of these insoluble flavonoids.

BRS Violeta (BRS Rúbea × IAC 1398-21) grape juice powder produced by foam mat drying. Part I: Effect of drying temperature on phenolic compounds and antioxidant activity.

The BRS Violeta grape presents pulp and skin with high content of phenolic compounds (PCs) and intense purplish color. It was used as raw material for the production of juice and dehydrated products using foam mat drying at 60, 70 and 80 °C and freeze drying (control). HLPC-DAD-ESI-MSn allowed the evaluation of the quantitative and qualitative changes of the main PCs (anthocyanins, flavonols and hydroxycinnamic acid derivatives (HCAD)) present in the grapes during the processing. The use of the steam extraction method to obtain grape juice allowed a greater extraction of flavonols and, mainly derivatives of hydroxycinnamic acids, when compared with anthocyanins. Drying at 70 °C was the most suitable for the preservation of the PCs and, at the same time, for the reduction of the processing time. The powdered products presented considerable concentrations of total PCs (3-5 mg/g) and antioxidant activity (32-79 (DPPH) or 17-27 (FRAP) mg/g).

Wild Brazilian species of Eugenia genera (Myrtaceae) as an innovation hotspot for food and pharmacological purposes.

The Myrtaceae is one of the most common plant families in Brazil, including >1000 species of native fruit spread from North to South, where around 50% of all species are endemic to the Atlantic Rain Forest Biome. Most Brazilian species belong to Eugenia, Campomanesia, Psidium and Myrciaria genera. In general, they are characterized by the presence of leaves opposite, simple, entire, with pellucid glands containing ethereal oils and produces berry-like, fleshy fruits with a wide diversity of beneficial characteristics. Several parts of these plants are widely used in regional folk medicine as an astringent, anti-inflammatory, antihypertensive, to treat gastrointestinal disorders, and so on. Some species have already been studied and most of their metabolic effects are attributed to the presence of polyphenols, carotenoids as well as sesquiterpenes and monoterpenes. In addition, the Myrtaceae family has great economic potential, because of the sensory characteristics which encourages their commercial exploitation plus the presence of phytochemicals which play an important role in managing several degenerative chronic diseases besides representing a hotspot of technological innovation for food, cosmetic and pharmaceutical purposes. In this context, this review discusses about the importance of some Eugenia genera representatives such as Eugenia uniflora, Eugenia stipitata, Eugenia brasiliensis, Eugenia pyriformis and Eugenia dysenterica, emphasizing its profile of bioactive compounds as well as the knowledge of the nutritional and functional fruit potential, providing information for further studies aiming to stimulate the cultivation of Brazilian wild berries, for consumption and new food ingredients.

Attenuation of high glucose induced apoptotic and inflammatory signaling pathways in RIN-m5F pancreatic ß cell lines by Hibiscus rosa sinensis L. petals and its phytoconstituents.

ETHNOPHARMACOLOGICAL RELEVANCE: Hibiscus rosa sinensis petals possess wide range of pharmacological properties, with remarkable nutritional values. Diabetes is one of the most devastating diseases affecting the world today. A few side effects associated with the use of insulin and oral hypoglycemic agents prompted us to search new bioactive principles from antidiabetic plants used in traditional medicine. AIM OF THE STUDY: The anti-diabetic therapeutic potential of the flavonoids rich ethyl acetate fraction of Hibiscus rosa sinensis petals (EHRS) was evaluated. MATERIALS AND METHODS: High glucose (25 mM) induced apoptotic model of diabetes in RIN-m5F pancreatic ß-cells was used for the study. RESULTS: EHRS elevated the release of insulin in pancreatic cells and modulated apoptotic signaling cascades. It significantly reduced NF-κB nuclear translocation, thereby down-regulated the expressions of major inflammatory cytokines and up-regulated expressions of pancreatic ß-cell functional genes such as, foxO-1, Ucn-3, Pdx-1, MafA and Nkx6.1. On comparison with its constituent phytochemicals, superior protective effect shown by EHRS may be due to the additive action of these phytoconstituents. CONCLUSIONS: Results of the present study suggest hibiscus petals as a natural source and functional food of potential therapeutics to protect pancreatic ß-cells in experimental diabetes mellitus.