Advances in Polyphenol Research: A Journal of Agricultural and Food Chemistry Virtual Issue

Effects of ageing time on the properties of polysaccharide in tangerine peel and its bacterial community

To evaluate the effect of aging time on the quality of tangerine peel (TP) from the perspective of TP polysaccharide (TPP), five polysaccharide samples with different aging times named TPP-0/1/5/10/15 were prepared. Under the conditions of pH 0.5, solid-liquid ratio 1:25 and 80 °C, the TPPs extraction yield ranged from 20.35% to 27.68%. Compared with TPP-0, TPP-1/5/10/15 possesses low molecular weight (Mw) and high methoxy group content. In addition, TPP-15 had the most potent antioxidant activity. And the content of acidic polysaccharides in TPPs was negatively correlated with neutral polysaccharides during aging. Based on the analysis of 16srDNA, the dominant bacteria (Brevundimonas and Pseudomonas) in TP-10 might be critical flora to affect TP quality. This study provided basic information on the relationship between the TPPs and aging time, which could promote a new view to develop TP, and shorten the aging time during TP production.

From Cocoa to Chocolate: Effect of Processing on Flavanols and Methylxanthines and Their Mechanisms of Action

Despite the health benefits associated with the ingestion of the bioactive compounds in cocoa, the high concentrations of polyphenols and methylxanthines in the raw cocoa beans negatively influence the taste, confer the astringency and bitterness, and affect the stability and digestibility of the cocoa products. It is, therefore, necessary to process cocoa beans to develop the characteristic color, taste, and flavor, and reduce the astringency and bitterness, which are desirable in cocoa products. Processing, however, affects the composition and quantities of the bioactive compounds, resulting in the modification of the health-promoting properties of cocoa beans and chocolate. In this advanced review, we sought to better understand the effect of cocoa's transformational process into chocolate on polyphenols and methylxanthine and the mechanism of action of the original flavanols and methylxanthines. More data on the cocoa processing effect on cocoa bioactives are still needed for better understanding the effect of each processing step on the final polyphenolic and methylxanthine composition of chocolate and other cocoa products. Regarding the mechanisms of action, theobromine acts through the modulation of the fatty acid metabolism, mitochondrial function, and energy metabolism pathways, while flavanols mainly act though the protein kinases and antioxidant pathways. Both flavanols and theobromine seem to be involved in the nitric oxide and neurotrophin regulation.

A durable and stable hollow carrier based on metal-phenolic network composed of ZnII and proanthocyanidins/polydopamine

Metal-phenolic networks (MPNs), which are formed by phenolic molecules and metal ions via coordination bonds, are emerging as highly templated functional metal-organic materials. These networks are mostly used in the form of particles for short-term in vivo drug delivery; however, there is a lack of research on durable and stable MPN hollow particles as delivery carriers for in vitro applications. In this study, hollow and yolk-like hybrid cubic MPNs were prepared by etching zeolitic imidazolate framework-8 (ZIF-8) with proanthocyanidins (PCs). Polydopamine (PDA) resulting from the oxidative self-polymerisation of dopamine was deposited on the surface of the fabricated MPN to obtain a PDA coating, which enhanced the mechanical properties of the MPN. The prepared Zn^II-PC/PDA capsules consisted of two layers: a Zn^II-PC layer and a PDA-PDA layer. It showed stability at 25 ℃ for at least 280 days after freeze-drying. Moreover, when loaded with carvacrol, this MPN exhibited an enhanced antibacterial performance. Therefore, this study lays the foundation for the use of MPNs as long-lasting functional carriers.

Polyphenols as Lung Cancer Chemopreventive Agents by Targeting microRNAs

Lung cancer is the second leading cause of cancer-related death worldwide. In recent decades, investigators have found that microRNAs, a group of non-coding RNAs, are abnormally expressed in lung cancer, and play important roles in the initiation and progression of lung cancer. These microRNAs have been used as biomarkers and potential therapeutic targets of lung cancer. Polyphenols are natural and bioactive chemicals that are synthesized by plants, and have promising anticancer effects against several kinds of cancer, including lung cancer. Recent studies identified that polyphenols exert their anticancer effects by regulating the expression levels of microRNAs in lung cancer. Targeting microRNAs using polyphenols may provide a novel strategy for the prevention and treatment of lung cancer. In this review, we reviewed the effects of polyphenols on oncogenic and tumor-suppressive microRNAs in lung cancer. We also reviewed and discussed the potential clinical application of polyphenol-regulated microRNAs in lung cancer treatment.

Polyphenols effect on cerebrovascular health

Polyphenols are a wide group of plant components that include a high number of individual compounds and are present in foods, dietary supplements and drugs. Many of them have shown pharmacological effects, are used in cardiovascular disease prevention, and not as many have been assayed in cancer treatment or co-treatment. In the last few years, however, the research on polyphenols implications in a healthy aging and especially in neurodegeneration and cognition improvement has increased dramatically. Most of the results found in this sense are again related with the capacity of some specific polyphenols to regulate the blood flow, but this time at the cerebral level, and to protect the endothelium at this same level. In this thorough review, we want to concentrate precisely on the effect of polyphenols on the cerebrovascular homeostasis, reviewing the mechanisms that underline this effect and the radiological methods and endogenous biomarkers that are used in human trials aimed at showing the beneficial effect of polyphenols or polyphenols rich foods on neuroprotection and cognition function.

Design of polyphenol-rich diets in clinical trials: A systematic review

Most randomized clinical trials of polyphenols focus on individual foods. Nevertheless, due to their presence in many foods and in order to reflect a real situation, clinical trials based on polyphenol-rich diets are particularly important. This systematic review explores the characteristics of the polyphenol-rich diets used in intervention studies. The bibliography search for English-language scientific papers was performed in the Elsevier Scopus Database and PUBMED in March 2020, and focused on intervention studies with whole polyphenol-rich diets, establishing several exclusion criteria. In studies fulfilling the requirements, information on the design of the polyphenol-rich diet and associated polyphenol intake was extracted and compared. A total of 5 studies were selected. Among them, substantial differences were found in the design of the polyphenol-rich diets, regarding specific instructions and concerning the foods provided. Similarly, although a median daily polyphenol intake of 2,564 mg/day (17,945 mg/week) was obtained from the studies, which corresponds to a nutritional dose, intake values varied widely both for total polyphenols (the difference between studies reached threefold), and for individual polyphenol intake (for hydroxycinnamic acids, a tenfold difference was found between percentile 25 and percentile 75 values). These differences made the comparison of results difficult and may affected the observed health effects. Thus, despite the relevance of studying polyphenol-rich diets as a whole, this systematic review found substantial differences between the studies performed, making direct comparisons difficult.

Acute supplementation with grapes in obese subjects did not affect postprandial metabolism: a randomized, double-blind, crossover clinical trial

PURPOSE

The aim of this study was to determine whether grape polyphenols have a "second-meal effect", modulating glucose and lipid elevations in the postprandial period after two successive meals in subjects with obesity.

METHODS

A randomized, double-blind, placebo-controlled, acute clinical trial was conducted. Twenty-five obese subjects (BMI =  ≥ 30 and < 40 kg/m2) were randomly divided into two groups. At an initial visit, blood was collected in a fasting state and the subjects received breakfast and 46 g of either grape powder (equivalent to 252 g fresh grapes) or placebo, both solved in water. Lunch was provided 5 h later and then blood was collected after 0, 30, 60, 120, 180, 240, 300, 330, 360, and 420 min since arrival. Two weeks later, at a second visit, the subjects received the other powder. The following were determined: glucose, insulin, triglycerides, uric acid, blood count, hemoglobin, viscosity, antioxidant capacity, and satiety perception.

RESULTS

Postprandial increases were observed as expected in, for example, glucose and triglycerides after breakfast and lunch. The grape powder supplementation did not cause any significant modification compared to placebo, in these parameters; nor did it significantly modify plasma antioxidant capacity in the 6 h postprandial period.

DISCUSSION

Single grape powder supplementation did not modify postprandial responses in obese subjects, probably because the polyphenol dose was insufficient to induce such an effect. The result of a combination of grape with other polyphenol-rich products or chronic supplementation with grape powder on postprandial responses remains to be elucidated.

TRIAL REGISTRATION NUMBER

www.clinicaltrials.gov , NCT03741218.

Modifications of Gut Microbiota after Grape Pomace Supplementation in Subjects at Cardiometabolic Risk: A Randomized Cross-Over Controlled Clinical Trial

Polyphenols are dietary bioactive compounds able to induce modifications in the gut microbiota profile, although more clinical studies are needed. With this aim, a randomized cross-over clinical trial was conducted, where 49 subjects at cardiometabolic risk (exhibiting at least two metabolic syndrome factors) were supplemented with a daily dose of 8 g of grape pomace (GP) for 6 weeks, with an equivalent control (CTL) period. The levels of total bacteria and Bacteroidetes, Firmicutes, Lactobacilliales, Bacteroides and Prevotella were estimated in fecal DNA by quantitative real-time PCR (qPCR), while fecal short-chain fatty acids (SCFAs) were assessed by gas chromatography. Several cardiometabolic markers were evaluated in blood samples. GP reduced insulin levels only in half of the participants (responders). GP supplementation did not cause significant modifications in the microbiota profile of the whole group, except for a tendency (p = 0.059) towards a decrease in the proportion of Lactobacilliales, while it increased the proportion of Bacteroides in non-responder subjects. The reduction of insulin levels in subjects at cardiometabolic risk upon GP supplementation appears not to be induced by changes in the major subgroups of gut microbiota. Further studies at the species level may help to elucidate the possible role of microbiota in GP-induced insulinemic status.

Modulating and opposite actions of two aqueous extracts prepared from Cinnamomum cassia L. bark and Quercus ilex L. on the gastrointestinal tract in rats

Cinnamon bark and evergreen oak acorns, natural sources of functional ingredients, are effective for those suffering from diarrhea, constipation and irritable bowel syndrome. This study aimed to evaluate the dissimilar phytochemical composition and the opposite potential actions of Cinnamomum cassia bark (ACCE) and Quercus ilex aqueous extracts (GIAE) on gastrointestinal (GI)-physiological activities and disruptions. An HPLC-PDA/ESI-MS assay was used to identify the distinctive qualitative and quantitative profiles of phenolic compounds. The GI-physiological action of both extracts on gastric emptying (GE) and gastrointestinal transit time (GIT) were evaluated using the phenol-red colorimetric method and a test meal containing charcoal/gum arabic in water. Loperamide (LOP)-induced colonic constipation and delayed emptying of the stomach were used to explore the reverse effects of ACCE/GIAE on GI disorders. HPLC-PDA/ESI-MS showed that the main phenolic compounds detected in ACCE are trans-cinnamic acid, quinic acid, protocatechuic acid and rosmarinic acid, while gallic acid, quinic acid and protocatechuic acid are the major chemical constituents found in GIAE. GIAE at two doses (150 and 300 mg kg-1) exerted a reduction of GE (66.40% and 60.87%, respectively) compared to a control group (70.25%). However, ACCE at the same concentrations induced contradictory actions on GE/GIT in comparison to GIAE and antagonistic synthetic pharmacological drugs in rats. The protective effect of CCAE against constipation induced by LOP in rats was accompanied by a strong antioxidant property related to moderation of intracellular-mediator disorders. An absence of toxic actions was revealed in the case of the hematological profile and biochemical parameters. Hence, in-depth investigations of these nutrients of both extracts may help future researchers to derive the underlying mechanisms and potential molecular targets for the development of physiologically functional foods and future therapies.

Effects of acute intake of grape/pomegranate pomace dietary supplement on glucose metabolism and oxidative stress in adults with abdominal obesity

A controlled acute, cross-over clinical study (NCT02710461) was performed in order to evaluate the effects on glucose metabolism of a grape/pomegranate pomace dietary supplement in subjects with abdominal obesity (aged 40-60, n = 20). A standard 75 g oral glucose tolerance test (OGTT) was administered alone, together with or 10 h after the consumption of 10 g of the dietary supplement, rich in both extractable (0.4 g) and non-extractable (1.4 g) polyphenols. The dietary supplement did not ameliorate glucose or insulin at any sampling time. No improvement in antioxidant capacity was observed in plasma or urine, concordant with no increased urine polyphenol excretion. A tendency towards improved insulin sensitivity was observed when the product was consumed 10 h before glucose solution. These results suggest that a single realistic dose of grape/pomegranate pomace is not able to clearly improve glucose metabolism; chronic intake remains to be evaluated.

Anti-melanogenesis properties of condensed tannins from Vigna angularis seeds with potent antioxidant and DNA damage protection activities

Condensed tannins contained in food are known to have many beneficial impacts on human health. In this study, we attempt to evaluate the structural features, antityrosinase effects, anti-melanogenesis properties, antioxidant activity and DNA damage protection activity of condensed tannins purified from the seeds of Vigna angularis (Willd.) Ohwi et Ohashi. MALDI-TOF MS, ESI-Full-MS, and HPLC-ESI-MS demonstrated that condensed tannins are composed of procyanidins, prodelphinidins and their gallates, among which procyanidins are the dominant components. As reversible and mixed-type inhibitors of tyrosinase, condensed tannins from V. angularis strongly inhibited the monophenolase and odiphenolase activities with IC50 values of 130.0 ± 0.5 and 35.1 ± 2.0 μg mL-1, respectively. What's more, condensed tannins had a good inhibitory effect on cell proliferation, cellular tyrosinase activity, and melanogenesis of B16 mouse melanoma cells. Based on fluorescence quenching analyses, these compounds were determined to be effective quenchers of the enzyme and its substrates. According to molecular docking, the strong interaction between condensed tannins and tyrosinase was mainly driven by hydrogen bonding and hydrophobic force. In addition, condensed tannins showed a powerful antioxidant capacity and DNA damage protection activity. Therefore, condensed tannins from V. angularis have feasible applications in food, medicine, and the cosmetics industry.

A 6-week supplementation with grape pomace to subjects at cardiometabolic risk ameliorates insulin sensitivity, without affecting other metabolic syndrome markers

Grape polyphenols have shown a promising role in the modulation of metabolic syndrome (MetS), mostly in animal models. However, clinical studies are scarce and they usually only consider a fraction of polyphenols, ignoring the non-extractable polyphenols (high molecular weight compounds or associated with macromolecules such as dietary fibre). This study aimed at evaluating the effect of grape pomace, rich in both extractable and non-extractable polyphenols, on markers of MetS. Fifty subjects (22 women) aged 20-65 with at least two MetS factors were randomly assigned to the product (daily dose of 8 g of dried grape pomace) or to the control group in a 6 week crossover design with a 4 week wash-out. Samples were collected at the beginning and at the end of both periods; half of the participants were subjected to an oral glucose tolerance test at the beginning and the end of the supplementation period. Grape pomace supplementation significantly improved fasting insulinaemia (p < 0.01), without affecting other cardiometabolic risk parameters. A tendency towards an improvement in postprandial insulinaemia was observed, particularly in those subjects with higher fasting insulin levels. Therefore, supplementation with grape pomace may be a strategy for improving insulin sensitivity in subjects at high cardiometabolic risk.

Tuning the Mechanical Behavior of Metal-Phenolic Networks through Building Block Composition

Metal-phenolic networks (MPNs) are an emerging class of functional metal-organic materials with a high degree of modularity in terms of the choice of metal ion, phenolic ligand, and assembly method. Although various applications, including drug delivery, imaging, and catalysis, have been studied with MPNs, in the form of films and capsules, the influence of metals and organic building blocks on their mechanical properties is poorly understood. Herein, we demonstrate that the mechanical properties of MPNs can be tuned through choice of the metal ion and/or phenolic ligand. Specifically, the pH of the metal ion solution and/or size of phenolic ligand influence the Young's modulus ( E_Y) of MPNs (higher pHs and smaller ligands lead to higher E_Y). This study systematically investigates the roles of both metal ions and ligands on the mechanical properties of metal-organic materials and provides new insight into engineering the mechanical properties of coordination films.