Young apple polyphenols postpone starch digestion in vitro and in vivo

Assessment of polyphenols in purple and red rice bran: Phenolic profiles, antioxidant activities, and mechanism of inhibition against amylolytic enzymes

Pigmented Thai rice varieties, including purple (Riceberry) and red (Hommali), are gaining popularity due to their health benefits as a source of polyphenols that may exert a hypoglycemic effect through specific inhibition of amylolytic enzymes. This study determined the free phenolic extract from purple rice bran (PFE) to exhibit notably greater content of phytochemical compounds than did phenolic extracts from red rice bran, whether free (RFE) or bound fractions. This phytochemical content correlated with increased antioxidant activity and strong inhibition capacity against amylolytic enzymes, suppressing the conversion of carbohydrates into glucose. Several polyphenol compounds were identified in pigmented rice bran extracts, including benzoic acid, chlorogenic acid, ferulic acid, apigenin, and rutin; among these, flavonoids exhibited greater effect on inhibition capacity. Mechanistically, PFE was found to act as a competitive and uncompetitive inhibitor of α-amylase and α-glucosidase respectively, while RFE showed respective uncompetitive and competitive inhibitory modes.

Characterization of Eurotium cristatum Fermented Thinned Young Apple and Mechanisms Underlying Its Alleviating Impacts on Experimental Colitis

A hundred million tons of young apples are thinned and discarded in the orchard per year, aiming to increase the yield and quality of apples. We fermented thinned young apples using a potential probiotic fungus, Eurotium cristatum, which notably disrupted the microstructure of raw samples, as characterized by the scanning electron microscope. Fermentation substantially altered the metabolite profiles of samples, which are predicted to alleviate colitis via regulating inflammatory response and response to lipopolysaccharide by using network pharmacology analysis. In vivo, oral gavage of water extracts of E. cristatum fermented young apples (E.YAP) effectively alleviated DSS-induced colitis, restored the histopathology damage, reduced the levels of inflammatory cytokines, and promoted colonic expressions of tight junction proteins. Moreover, E.YAP ameliorated gut dysbacteriosis by increasing abundances of Lactobacillus,Blautia, Muribaculaceae, and Prevotellaceae_UCG-001 while inhibiting Turicibacter, Alistipes, and Desulfovibrio. Importantly, E.YAP increased colonic bile acids, such as CA, TCA, DCA, TUDCA, and LCA, thereby alleviating colitis via PXR/NF-κB signaling. Furthermore, a synbiotic combination with Limosilactobacillus reuteri WX-94, a probiotic strain isolated from feces of healthy individuals with anti-inflammatory properties, augmented anticolitis capacities of E.YAP. Our findings demonstrate that E.YAP could be a novel, potent, food-based anti-inflammatory prebiotic for relieving inflammatory injuries.

The Behavior of Phenolic Compounds from Apples during Simulated Gastrointestinal Digestion with Focus on Chlorogenic Acid

The fate of phenolic compounds during digestion is important for their bioactive effects in the digestive tract. The aim was to study the various phenolic compounds occurring in the peel and flesh of apples in in vitro simulated gastrointestinal digestion, focusing on the behavior of chlorogenic acids. Additionally, the behavior of individual chlorogenic acids (chlorogenic, neochlorogenic, and cryptochlorogenic) was studied in models of simulated salivary, gastric, and intestinal fluid electrolyte solutions (SSF, SGF, SIF). At the end of the intestinal phase of the digestion of peel and flesh, the amount of recovered dihydrochalcones and flavonols increased or was similar to the amount in the gastric phase, which showed their stability. Anthocyanins and flavan-3-ols decreased, which suggests their biotransformation. Chlorogenic acid isomerized into neochlorogenic and cryptochlorogenic acid: chlorogenic acid from the peel into 22% and 41% of the isomers in the salivary and intestinal phases, respectively; chlorogenic acid from the flesh into 12% of the isomers in the intestinal phase. Similarly, chlorogenic acid isomerized in model solutions (20% and 26% of the isomers in SSF and SIF, respectively). Neochlorogenic and cryptochlorogenic acid isomerized in SSF and SIF into other two forms. They were all stable in SGF. For bioactive effects in the digestive tract, the biotransformation of chlorogenic acids should be considered.

Phenolic Compounds from Apples: From Natural Fruits to the Beneficial Effects in the Digestive System

Conditions in the gastrointestinal tract and microbial metabolism lead to biotransformation of parent, native phenolic compounds from apples into different chemical forms. The aim of this work was to review current knowledge about the forms of phenolic compounds from apples in the gastrointestinal tract and to connect it to their potential beneficial effects, including the mitigation of health problems of the digestive tract. Phenolic compounds from apples are found in the gastrointestinal tract in a variety of forms: native (flavan-3-ols, phenolic acids, flavonols, dihydrochalcones, and anthocyanins), degradation products, various metabolites, and catabolites. Native forms can show beneficial effects in the stomach and small intestine and during the beginning phase of digestion in the colon. Different products of degradation and phase II metabolites can be found in the small intestine and colon, while catabolites might be important for bioactivities in the colon. Most studies connect beneficial effects for different described health problems to the whole apple or to the amount of all phenolic compounds from apples. This expresses the influence of all native polyphenols from apples on beneficial effects. However, further studies of the peculiar compounds resulting from native phenols and their effects on the various parts of the digestive tract could provide a better understanding of the specific derivatives with bioactivity in humans.

Polyphenolic profile, processing impact, and bioaccessibility of apple fermented products

Health-promoting foods have become increasingly popular due to intensified consumer interest and awareness of illnesses. There is a global market for apple fruits, which are affordable, nutritious, tasty, and produced in large quantities for direct consumption as well as food processing to make derived products. The food matrix of apples is suitable for fermentation, besides containing a high amount of phenolics and polyphenols. Fermentation of apples is one of the most common methods of preserving apple fruit and its byproducts. With different fermentation techniques, apple fruit can be used to make a wide range of products, such as fermented apple juice, cider, liqueurs, apple cider, apple vinegar and fermented apple solids, because it is not only a low-cost and simple method of processing the fruit, but it can also sometimes increase the bioavailability of nutrients and the levels of components that can improve health and sensory quality. To understand the health benefits of food products and how the fermentation process impacts polyphenols, it is also crucial to observe the effects of digestion on polyphenol bioaccessibility. Polyphenolic profile changes can be observed via both in vitro and in vivo digestion methods; however, in vitro digestion methods have the advantage of observing every step of gastrointestinal track effects and have less cost as well. In this review, the polyphenolic profile, processing impact, and bioaccessibility of apple-fermented products is assessed, with most available studies showing polyphenol profiles and bioaccessibility in apple varieties and fermented apple products.

Lowering glycemic levels via gastrointestinal tract factors: the roles of dietary fiber, polyphenols, and their combination

Dietary fiber (DF) and polyphenols (DP) are typical blood sugar-lowering components, and both play distinct yet interconnected roles in exerting their blood sugar-lowering effects. We comprehensively summarized the single and combined effects of DF and DP on blood glucose homeostasis through regulating the relevant factors in the upper gastrointestinal tract (UGT) and lower gastrointestinal tract (LGT). In the UGT, DF slowed down glucose metabolism by enhancing digesta viscosity and hindering enzyme-substrate interaction. DP primarily targeted enzymes and substrates. When combined, DP enhanced the adsorption capacity of DF for glucose. DF weakened DP's inhibitory effect on enzymes. Both DF and DP disrupted glucose intestinal uptake via physical or genomic modulation, but the co-consumption of DF and DP demonstrated a lower inhibitory effect on glucose uptake than DP alone. In the LGT, DF and DP showed synergistic or antagonistic effects on gut microbiota. Remarkably, whole foods exhibited potent prebiotic effects due to their compound-rich matrix, potentially enhancing glucose homeostasis and expanding dietary options for glucose regulation research.

Effect of (poly)phenol-rich 'Daux Belan' apple supplementation on diet-induced obesity and glucose intolerance in C57BL/6NCrl mice

Obesity is a state of metabolic dysfunction that can lead to dyslipidemia and impaired glucose homeostasis. Apple polyphenols have been shown to ameliorate dyslipidemia/metabolic dysfunction in humans. The influence of apple (poly)phenols on energy metabolism in high-fat (HF) diet-induced obese mice remains controversial. This study examined the effect of dietary supplementation of (poly)phenol-rich 'Daux Belan' apple (DB; 6.2 mg gallic acid equivalence (GAE)/mouse/day; 0.15% (poly)phenol) in the form of freeze-dried powder on glucose and lipid metabolism in male HF-fed C57BL/6NCrl mice, in comparison to low-(poly)phenol-containing 'Zestar' apple (Z; 0.4 mg GAE/mouse/day). Obesity, glucose intolerance, hypertriglyceridemia, and hepatic lipid vacuolation were induced by HF feeding while circulating cholesterol levels remained unchanged. DB apple supplementation did not protect against HF-induced body weight gain, hyperglycemia, hepatic triglyceride level elevation, and hepatic lipid vacuolation at the tested dosage. Future studies should be conducted with increased DB dosage and employ apple (poly)phenols supplemented in the form of extracts or sugar-free powder.

Purple red rice bran anthocyanins reduce the digestibility of rice starch by forming V-type inclusion complexes

Purple red rice bran, a by-product of the rice polishing process, contained abundant anthocyanins. However, most of them were discarded resulting in a waste of resources. This study investigated the effects of purple red rice bran anthocyanin extracts (PRRBAE) on the physicochemical properties and digestive properties of rice starch and its mechanism of action. Infrared spectroscopy and X-ray diffraction indicated that PRRBAE could interact with rice starch through non-covalent bonds to form intrahelical V-type complexes. The DPPH and ABTS⁺ assays showed that PRRBAE could confer better antioxidant activity on rice starch. In addition, the PRRBAE could increase the resistant starch content and decrease the enzyme activities by changing the tertiary and secondary structure of starch-digesting enzymes. Further, molecular docking suggested that aromatic amino acids play a key role in the interaction of starch-digesting enzymes with PRRBAE. These findings will contribute to a better understanding of the mechanism of PRRBAE reducing starch digestibility, and to the development of high value-added products and low glycemic index (GI) foods.

Protective Effect of Apple Polyphenols on H₂O₂-Induced Oxidative Stress Damage in Human Colon Adenocarcinoma Caco-2 Cells

Apple is an important dietary agent for human and apple polyphenols (AP) are the main secondary metabolites of apples. In this study, the protective effects of AP on hydrogen peroxide (H₂O₂)-induced oxidative stress damage in human colon adenocarcinoma Caco-2 cells were investigated by cell viability, oxidative stress change as well as cell apoptosis. Pre-adding AP could significantly increase the survival rate of H₂O₂-treated Caco-2 cells. Besides, the activities of antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GSH-PX) and catalase (CAT) were elevated. While the malondialdehyde (MDA) content which is the major oxidant products of polyunsaturated fatty acids (PUFA) reduced after AP treatment. In addition, AP also suppressed the emergence of DNA fragment and decreased the expression of apoptosis-related protein Caspase-3. These results demonstrated that AP could ameliorate H₂O₂-induced oxidative stress damage in Caco-2 cells, which could serve as a reference for further studies of apple natural active products and deep study of the anti-oxidative stress mechanism.

Apple polyphenols delay postharvest senescence and quality deterioration of 'Jinshayou' pummelo fruit during storage

INTRODUCTION

Apple polyphenols (AP), derived from the peel of mature-green apples, are widely used as natural plant-derived preservatives in the postharvest preservation of numerous horticultural products.

METHODS

The goal of this research was to investigate how AP (at 0.5% and 1.0%) influences senescence-related physiological parameters and antioxidant capacity of 'Jinshayou' pummelo fruits stored at 20°C for 90 d.

RESULTS

The treating pummelo fruit with AP could effectively retard the loss of green color and internal nutritional quality, resulting in higher levels of total soluble solid (TSS) content, titratable acidity (TA) content and pericarp firmness, thus maintaining the overall quality. Concurrently, AP treatment promoted the increases in ascorbic acid, reduced glutathione, total phenols (TP) and total flavonoids (TF) contents, increased the scavenging rates of 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and hydroxyl radical (•OH), and enhanced the activities of superoxide dismutase (SOD), catalase, peroxidase, ascorbate peroxidase (APX), and glutathione reductase (GR) as well as their encoding genes expression (CmSOD, CmCAT, CmPOD, CmAPX, and CmGR), reducing the increases in electrolyte leakage, malondialdehyde content and hydrogen peroxide level, resulting in lower fruit decay rate and weight loss rate. The storage quality of 'Jinshayou' pummelo fruit was found to be maintained best with a 1.0% AP concentration.

CONCLUSION

AP treatment can be regarded as a promising and effective preservative of delaying quality deterioration and improving antioxidant capacity of 'Jinshayou' pummelo fruit during storage at room temperature.

Polyphenol-Modified Starches and Their Applications in the Food Industry: Recent Updates and Future Directions

Health problems associated with excess calories, such as diabetes and obesity, have become serious public issues worldwide. Innovative methods are needed to reduce food caloric impact without negatively affecting sensory properties. The interaction between starch and phenolic compounds has presented a positive impact on health and has been applied to various aspects of food. In particular, an interaction between polyphenols and starch is widely found in food systems and may endow foods with several unique properties and functional effects. This review summarizes knowledge of the interaction between polyphenols and starch accumulated over the past decade. It discusses changes in the physicochemical properties, in vitro digestibility, prebiotic properties, and antioxidant activity of the starch-polyphenol complex. It also reviews innovative methods of obtaining the complexes and their applications in the food industry. For a brief description, phenolic compounds interact with starch through covalent or non-covalent bonds. The smoothness of starch granules disappears after complexation, while the crystalline structure either remains unchanged or forms a new structure and/or V-type complex. Polyphenols influence starch swelling power, solubility, pasting, and thermal properties; however, research remains limited regarding their effects on oil absorption and freeze-thaw stability. The interaction between starch and polyphenolic compounds could promote health and nutritional value by reducing starch digestion rate and enhancing bioavailability; as such, this review might provide a theoretical basis for the development of novel functional foods for the prevention and control of hyperglycemia. Further establishing a comprehensive understanding of starch-polyphenol complexes could improve their application in the food industry.

Physicochemical, Pasting, and Thermal Properties of Native Corn Starch-Mung Bean Protein Isolate Composites

Starch is widely used in food and non-food industries because of its unique characteristics. However, native starch shows some weaknesses that restrict its applications. Recently, some studies have demonstrated the benefits of using protein to overcome these limitations. Therefore, the aim of the present study was to investigate the effect of mung bean protein isolate (MBPI) (2%, 4%, 6%, and 8%) on the physicochemical, pasting, and thermal properties of native corn starch (NCS), as a novel starch-protein composite. Higher swelling power (SP), water absorbance capacity (WAC), and solubility values of NCS were observed with increasing MBPI concentration. Additionally, by the addition of MBPI, the rapid visco analyzer (RVA) showed a reduction in pasting temperature (77.98 to 76.53 °C), final viscosity (5762 to 4875 cP), and setback (3063 to 2400 cP), while the peak viscosity (4691 to 5648 cP) and breakdown (1992 to 3173 cP) increased. The thermal properties of NCS/MBPI gels investigated by differential scanning calorimetry (DSC) showed higher onset, peak, and conclusion temperatures (69.69 to 72.21 °C, 73.45 to 76.72 °C, and 77.75 to 82.26 °C, respectively), but lower gelatinization enthalpy (10.85 to 8.79 J/g) by increasing MBPI concentration. Fourier transform infrared spectroscopy (FT-IR) indicated that the addition of MBPI decreased the amount of hydrogen bonds within starch. Furthermore, after three cycles of freeze-thaw shocks, the syneresis of NCS-MBPI composites decreased from 38.18 to 22.01%. These results indicated that the MBPI could improve the physicochemical properties of NCS, especially its syneresis and retrogradation characteristics.

Therapeutic potential of non-starch polysaccharides on type 2 diabetes: from hypoglycemic mechanism to clinical trials

Non-starch polysaccharides (NSPs) have been reported to exert therapeutic potential on managing type 2 diabetes mellitus (T2DM). Various mechanisms have been proposed; however, several studies have not considered the correlations between the anti-T2DM activity of NSPs and their molecular structure. Moreover, the current understanding of the role of NSPs in T2DM treatment is mainly based on in vitro and in vivo data, and more human clinical trials are required to verify the actual efficacy in treating T2DM. The related anti-T2DM mechanisms of NSPs, including regulating insulin action, promoting glucose metabolism and regulating postprandial blood glucose level, anti-inflammatory and regulating gut microbiota (GM), are reviewed. The structure-function relationships are summarized, and the relationships between NSPs structure and anti-T2DM activity from clinical trials are highlighted. The development of anti-T2DM medication or dietary supplements of NSPs could be promoted with an in-depth understanding of the multiple regulatory effects in the treatment/intervention of T2DM.

Research progress of anthocyanin prebiotic activity: A review

BACKGROUND

Anthocyanins are a kind of flavonoids and natural water-soluble pigments, which endow fruits, vegetables, and plants with multiple colors. They are important source of new products with prebiotic activity. However, there is no systematic review documenting prebiotic activity of anthocyanins and their structural analogues. This study aims to fill this gap in literature.

PURPOSE

The objective of this review is to summarize and evaluate the prebiotic activity of anthocyanin's, and discuss the physical and molecular modification methods to improve their biological activities.

STUDY DESIGN AND METHODS

In this review, the databases (PubMed, Google Scholar, Web of Science, Researchgate and Elsevier) were searched profoundly with keywords (anthocyanin's, prebiotics, probiotics, physical embedding and molecular modification).

RESULTS

A total of 34 articles were considered for reviewing. These studies approved that anthocyanins play an important role in promoting the proliferation of probiotics, inhibiting the growth of harmful bacteria and improving the intestinal environment. In addition, physical embedding and molecular modification have also been proved to be effective methods to improve the prebiotic activity of anthocyanins. Anthocyanins could promote the production of short chain fatty acids, accelerate self degradation and improve microbial related enzyme activities to promote the proliferation of probiotics. They inhibited the growth of harmful bacteria by inhibiting the expression of harmful bacteria genes, interfering with the role of metabolism related enzymes and affecting respiratory metabolism. They promoted the formation of a complete intestinal barrier and regulated the intestinal environment to keep the body healthy. Physical embedding, including microencapsulation and colloidal embedding, greatly improved the stability of anthocyanins. On the other hand, molecular modification, especially enzymatic modification, significantly improved the biological activities (antioxidant, prebiotic activity and so on) of anthocyanins.

CONCLUSION

All these research results displayed by this review indicate that anthocyanins are a useful tool for developing prebiotic products. The better activities of the new anthocyanins formed by embedding and modification may make them become more effective raw materials. Our review provides a scientific basis for the future research and application of anthocyanins.

In vitro digestibility and fermentability profiles of wheat starch modified by chlorogenic acid

This study was designed to investigate the effect of chlorogenic acid (CA) on starch digestibility and fermentability in vitro. Compared with wheat starch (WS), WS-CA complexes exhibited a looser porous gel matrix, and higher solubility and swelling power with the addition of different proportion of CA. The WS-CA complexes significantly reduced the digestive rate of the gelatinized WS, and increased the proportion of resistant starch (RS) ranging from 31.70 % to 69.63 % much higher than that in the gelatinized WS (26.34 %). The residual WS-CA complexes after 24 h of fermentation with human feces induced the production of short-chain fatty acid, as well as the proliferation of gut microbiota such as genera Megamonas and Parabacteroides positively associated with the improvement of human health. The results suggest that complex of starch and CA could be a promising method for developing starchy foods with lower starch hydrolysis and promoting the growth of probiotics.

Inhibitory Effects against Alpha-Amylase of an Enriched Polyphenol Extract from Pericarp of Mangosteen (Garcinia mangostana)

The pericarp of mangosteen, a by-product of the mangosteen, is rich in polyphenols. In this study, an efficient and environmentally friendly method for preparative enrichment of polyphenols from mangosteen pericarp (MPPs) was developed, and the inhibitory effects on starch digestion were also evaluated. It was found that the optimal extract method of MPPs was at a solid to solvent ratio of 1:50 g/mL, pH of 2, and at 80 °C for 2 h. The IC₅₀ of MPPs for α-amylase was 0.28 mg/mL. Based on the fluorescence quenching results, we presumed that MPPs could alter the natural structure of α-amylase, resulting in inhibitory activity on α-amylase. In addition, MPPs significantly reduced the blood glucose peak and AUC of glucose responses in rats after ingestion of the starch solution. Taken together, MPPs may have the potential as a functional supplement for blood glucose control and diabetes prevention.

Enhanced bioavailability and anti-hyperglycemic activity of young apple polyphenols by complexation with whey protein isolates

This study aims to evaluate the effects of complexation of whey protein isolate (WPI) and young apple polyphenols (YAP) on the bioavailability and anti-hyperglycemic activity of YAP. Two types of WPI-YAP complexes were fabricated by mixing WPI with YAP at 25℃ (WPI-YAP) and 90℃ (WPI-YAP-H), respectively. The intermolecular interactions between WPI and YAP were investigated by fluorescence spectroscopy and circular dichroism analyses. The in vitro bioaccessibility and bioavailability of YAP were determined using a simulated gastrointestinal digestion and human Caco-2 cells model. It was found that the total polyphenols transport efficiency was improved from 39.8% (YAP) to 48.2% (WPI-YAP) and 56.1% (WPI-YAP-H), indicating that the bioavailability of YAP was improved by complexation with WPI. Besides, after complexation with WPI, YAP displayed an improved in vivo effect on alleviating the increase in postprandial blood glucose level than the pure YAP, with WPI-YAP-H showing a better effect. This finding indicates that co-complexation of YAP with WPI is an effective way to improve the functionality of YAP, and the WPI-YAP complexes are also expected to have potential application in designing YAP-containing functional foods. PRACTICAL APPLICATION: The research provided a method to improve the bioavavibility of polyphenols, and the WPI-YAP complex can be developed in designing polyphenols related functional foods.

Omnifarious fruit polyphenols: an omnipotent strategy to prevent and intervene diabetes and related complication?

Diabetes mellitus is a metabolic syndrome which cannot be cured. Recently, considerable interest has been focused on food ingredients to prevent and intervene in complications of diabetes. Polyphenolic compounds are one of the bioactive phytochemical constituents with various biological activities, which have drawn increasing interest in human health. Fruits are part of the polyphenol sources in daily food consumption. Fruit-derived polyphenols possess the anti-diabetic activity that has already been proved either from in vitro studies or in vivo studies. The mechanisms of fruit polyphenols in treating diabetes and related complications are under discussion. This is a comprehensive review on polyphenols from the edible parts of fruits, including those from citrus, berries, apples, cherries, mangoes, mangosteens, pomegranates, and other fruits regarding their potential benefits in preventing and treating diabetes mellitus. The signal pathways of characteristic polyphenols derived from fruits in reducing high blood glucose and intervening hyperglycemia-induced diabetic complications were summarized.

Using Biological Elicitation to Improve Type 2 Diabetes Targeted Food Quality of Stored Apple

Food quality improvements of fresh fruits targeting both food preservation and human health is essential to advance healthy dietary options and to mitigate imbalanced nutrition-linked non-communicable chronic disease (NCDs) challenges globally. Specifically, protective phenolic bioactives of fruits with dual functional benefits can be harnessed to advance innovations for improving nutritional quality and post-harvest shelf-life of perishable fruits. Based on this rationale the dual functional benefits of plant phenolics were harnessed using novel biological elicitation strategies to modulate phenolic bioactive-linked protective responses in apple during storage in two interrelated studies. Bioprocessed food-grade elicitors [water soluble chitosan oligosaccharide -(COS) and phenolic enriched oregano extracts-(OX)] were targeted as post-harvest dipping treatments (2 & 4 g/ L) and compared with diphenylamine (DPA) (1 & 2 g/L) to enhance phenolic-linked antioxidant and anti-diabetic (type 2 diabetes) relevant properties of Cortland apple during 3 months of storage (4°C). The selection of bio-elicitors and respective doses were based on the foundations of the previous related study, which resulted in reduction of superficial scald of Cortland apple during storage. Apples sampled over 3 months as aqueous and ethanol (12%) extracts of peel and pulp were analyzed separately for total soluble phenolic content, phenolic profile, antioxidant activity, and glucose metabolism relevant α-amylase and α-glucosidase enzyme inhibitory activities using in vitro assay models. Enhanced soluble phenolic content and associated antioxidant activity were observed in ethanol (12%) extracts of apple peel with 4 g/L COS elicitor treatments after 2 and 3 months of storage. High chlorogenic acid and quercetin derivatives were found in peel extracts of Cortland apple, while pulp extracts had high chlorogenic and gallic acids. Additionally, high α-glucosidase enzyme inhibitory activity, which is relevant for managing post-prandial hyperglycemia of type 2 diabetes was also observed in bio-elicited apple peel and pulp extracts. Therefore, results of these two interrelated studies indicate that bioprocessed food grade elicitor such as OX and COS can be recruited as a novel tool to enhance protective phenolic responses for improving type 2 diabetes targeted food quality and post-harvest storage quality of apple.

Effects of two contrasting dietary polysaccharides and tannic acid on the digestive and physicochemical properties of wheat starch

In this study, konjac glucomannan, κ-carrageenan, and tannic acid were selected to study the effects of different combinations on the in vitro digestibility and physicochemical properties of wheat starch. Results showed that the addition of konjac glucomannan, κ-carrageenan, and tannic acid could decrease the digestion of starch and increase the content of resistant starch. Besides, the two polysaccharides weakened the extent of tannic acid on starch digestion. Moreover, although the two polysaccharides had different effects on the in vitro digestion of starch, they had no significant increase in the content of resistant starch. DSC and XRD results demonstrated that the polysaccharides and tannic acid showed synergistic effects on the rebuilding of starch microstructure. FTIR results further manifested that κ-carrageenan and konjac glucomannan could significantly increase the strength of hydrogen bonds in starch. At the same time, the addition of tannic acid would weaken the molecular interaction between polysaccharides and starch. SEM and CLSM results showed that tannic acid added to the polysaccharide-starch mixture not only interacted with starch but also influenced the structure of polysaccharide gel.

Extraction of Phenolic Compounds from Fresh Apple Pomace by Different Non-Conventional Techniques

Red Delicious apple pomace was produced at laboratory scale with a domestic blender and different non-conventional extraction techniques were performed to isolate phenolic compounds, such as ultrasound-assisted extraction (UAE), ultraturrax extraction (UTE), accelerated solvent extraction (ASE) and pulsed electric field (PEF) extraction pre-treatment. Total phenolic content (TPC) was determined by Folin-Ciocalteu assay. Phloridzin, the main phenolic compound in apples, was determined by chromatographic analysis Q-TOF-LC/MS. The results obtained with these techniques were compared in order to identify the most efficient method to recover polyphenols. The highest value of TPC (1062.92 ± 59.80 µg GAE/g fresh apple pomace) was obtained when UAE was performed with EtOH:H₂O (50:50, v/v), while ASE with EtOH:H₂O (30:70, v/v) at 40 °C and 50% of flush was the most efficient technique in the recovery of phloridzin. The concentration of the main phenolic compounds ranged from 385.84 to 650.56 µg/g fresh apple pomace. The obtained results confirm that apple pomace represents an interesti-ng by-product, due to the presence of phenolic compounds. In particular, phloridzin could be considered a biomarker to determine the quality of numerous apple products. Therefore, this research could be a good starting point to develop a value-added product such as a functional food or nutraceutical.

Number of galloyl moiety and intramolecular bonds in galloyl-based polyphenols affect their interaction with alpha-glucosidase

The inhibition of α-glucosidase by nine galloyl-based polyphenols with free and unfree galloyl moieties (GMs) was studied. The results show that the inhibitory activity increased with the free GM number increasing. For the compounds with unfree GMs, ellagic acid and hexahydroxydiphenoyl group contributed to the enzyme inhibition. Free GMs could bind not only with the active site of α-glucosidase (competitive inhibition character), but also with the non-active sites (uncompetitive one); however, the former binding interaction was stronger than the latter one. All polyphenols that had inhibitory effects quenched α-glucosidase fluorescence in a static mode through forming a polyphenol-enzyme complex. The number of amino acid residues involved in polyphenol-enzyme binding interactions (hydrogen bonding and π-conjugations) increased with the inhibitory activity increasing. Additionally, two polyphenols with 5 free GMs showing certain hypoglycemic effects in maltose-loading test suggests that GM may be an advisable functional factor for alleviation of type II diabetes symptoms.

The Perspective of Croatian Old Apple Cultivars in Extensive Farming for the Production of Functional Foods

The Republic of Croatia has a long tradition of fruit growing due to its geographical location, climatic conditions, and high quality of fruit crops, especially apple fruits. Apples can be used for the formulation of functional foods either in processed form (e.g., juice), or as a by-product (e.g., apple pomace). However, there is a growing demand for functional foods derived from ancient and traditional plant sources as they are recognized as a very valuable source of health-promoting bioactive ingredients. Similarly, old apple cultivars (Malus domestica Borkh.) are characterized by good morphological and pomological properties, less need for chemicals during cultivation and the higher share of biologically active compounds (BACs) with better sensory acceptability compared to commercial cultivars. However, their nutritional and biological potential is underestimated, as is their ability to be processed into functional food. The importance in preserving old apple cultivars can also be seen in their significance for improving the nutritional composition of other apple cultivars through innovative cultivation strategies, and therefore old local apple cultivars could be of great importance in future breeding programs.

Thermally processed lignin reduces the apparent hydrolysis rate of pancreatic α-amylase in starchy foods

Lignin, despite being the second most abundant constituent of plant cell walls, is thought to be chemically inert during gastrointestinal digestion and therefore attracts little attention for its role in the human diet. This study explores the heat modifications of lignin to derive species capable of slowing starch digestion in vitro. We applied various advanced biochemical (e.g. enzymic digestion, solubility) and physio-chemical (e.g. scanning electron microscopy, Fourier-Transform-Infrared Spectroscopy, ¹³C-NMR) analyses to characterize the structure-function of lignin induced by heat treatment. It was found that lignin thermally processed above 300 °C reduced the apparent hydrolysis rate of pancreatic α-amylase, which is ascribed mainly to the insoluble lignin with a modified particle surface morphology. Further kinetic experiments showed that lignin species derived by thermal processing slowed in vitro digestion rates of potato starch and pasta. These findings highlight the potential for utilizing thermally processed lignin in slowing digestion of starchy foods.

Structural changes of rice starch and activity inhibition of starch digestive enzymes by anthocyanins retarded starch digestibility

The effects of anthocyanins on in vitro and in vivo digestibility of rice starch were evaluated in this study. Then, the effects of anthocyanins on physicochemical properties of rice starch and on starch digestive enzymes (α-amylase and α-glucosidase) were investigated to understand the mechanism of the effects of anthocyanins on starch digestibility. Characterization of physicochemical properties of rice starch indicates a structural change due to the presence of anthocyanins, hindering its access to starch digestive enzymes. Besides, anthocyanins inhibited the activities of starch digestive enzymes by binding to their active sites, competing with the substrates and changing the secondary structure of the enzymes. The above stated changes of rice starch and starch digestive enzymes due to the presence of anthocyanins both contributed to retarding the digestibility of rice starch. This study could offer some theoretical guidance to the development of new type rice-based food with low glycemic index.

Modulation of gelatinized wheat starch digestion and fermentation profiles by young apple polyphenols in vitro

To evaluate the effect of young apple polyphenols (YAP) on starch digestion and gut microbiota, complexes of native wheat starch (NWS) with YAP, and their main components chlorogenic acid (CA) and phlorizin (P) were fabricated and gelatinized. Through XRD and FTIR analysis, it was found that the partial crystalline structure of NWS was destroyed during gelatinization, and the addition of P decreased the extent of destruction. Then, the gelatinized starchy samples were subjected to in vitro digestion. The wheat starch (WS)-phenolic compound complexes significantly suppressed the digestion rate and increased the proportion of resistant starch (RS) in WS. Furthermore, the residual starchy components after digestion were fermented by human fecal samples for 24 h. The WS-YAP complex greatly increased the concentration of short-chain fatty acids (SCFAs), especially acetic and propionic acids, and enhanced the growth of health-promoting gut microbiota such as Prevotella. Conclusively, YAP was shown to play a positive role in maintaining blood glucose balance and intestinal health.

Polyphenolic inhibition of enterocytic starch digestion enzymes and glucose transporters for managing type 2 diabetes may be reduced in food systems

With the current global surge in diabetes cases, there is a growing interest in slowing and managing diabetes and its effects. While there are medications that can be used, they have adverse side effects such as hypoglycemia and weight gain. To overcome these problems, bioactive compounds commonly found in fruits, vegetables and cereal grains are used to slow starch digestion and transport of simple sugars across the intestinal epithelia thereby reducing plasma blood glucose spike. These effects are achieved through inhibition of amylases, glucosidases and glucose transporters present in the gastrointestinal tract and brush boarder membrane. The extent of inhibition by polyphenols is dependent on molecular structure, doses and food matrix. Glycemic lowering effect of polyphenols have been demonstrated both in in vivo and in vitro studies. However, when these compounds are incorporated in food systems, they can interact with other polymers in the food matrix leading to lesser inhibition of digestion and/or glucose transporters compared to isolated or pure compounds as often witnessed in most in vitro studies.

A systematic review of in vitro studies evaluating the inhibitory effects of polyphenol-rich fruit extracts on carbohydrate digestive enzymes activity: a focus on culinary fruits consumed in Europe

Evidence shows that polyphenols can attenuate postprandial blood glucose responses to meals containing digestible carbohydrate. Polyphenol-rich plant extracts are emerging as potential ingredients in functional foods and/or beverages despite limited understanding of their physiological effects. Many studies have investigated the mechanisms of polyphenol-rich fruit extracts on inhibition of digestive enzymes. However, the evidence available has yet to be critically evaluated systematically. This report reviews the in vitro literature to quantify the effect of fruit polyphenol extracts on the activities of digestive carbohydrases. A systematic literature search was conducted using six science databases. Included studies, totaling 34 in number, were in vitro digestion models which quantified gut digestive enzyme(s) activity on starch digestion in the presence of fruit polyphenol extracts. Most studies assessed the effects of fruit extracts on either α-amylase (n = 30) or α-glucosidase (n = 30) activity. Studies were consistent overall in showing stronger inhibition of α-amylase compared to α-glucosidase by proanthocyanidin- and/or ellagitannin-rich fruit extracts. Recommendations are proposed for future reporting of this type of research to enable meaningful synthesis of the literature as a whole. Such knowledge could allow effective choices to be made for development of novel functional foods and beverages.

Pleiotropic effects of polyphenols on glucose and lipid metabolism: Focus on clinical trials

Epidemiological evidence from observational studies suggests that dietary polyphenols (PPs) - phytochemicals found in a variety of plant-based foods - can reduce the risk of developing type 2 diabetes mellitus (T2DM). Clinical trials have also indicated that PPs may help manage the two key features of T2DM, hyperglycemia and dyslipidemia. Since the incidence of T2DM is dramatically increasing worldwide, identifying food-based approaches that can reduce the risk of developing it and help manage its main risk factors in early-stage disease has clinical and socioeconomic relevance. After a brief overview of current epidemiological data on the incidence of T2DM in individuals consuming PP-rich diets, we review the evidence from clinical trials investigating PP-enriched foods and/or PP-based nutraceutical compounds, report their main results, and highlight the knowledge gaps that should be bridged to enhance our understanding of the role of PPs in T2DM development and management.

Potential anti-diabetic properties of Merlot grape pomace extract: An in vitro, in silico and in vivo study of α-amylase and α-glucosidase inhibition

A practical approach to control glycemia in diabetes is to use plant natural products that delay hydrolysis of complex sugars and promote the diminution of the release of glucosyl units into the blood plasma. Polyphenolics have been described as being effective in inhibiting amylases and α-glucosidases. Grape pomace is an important sub product of the wine industry, still rich in many compounds such as polyphenolics. In this context, the purpose of this study was to search for possible effects of a grape pomace extract on salivary and pancreatic α-amylases and α-glucosidase, as well as on intestinal glucose absorption. The Merlot grape pomace extract (MGPE) was prepared using a hydroalcoholic mixture (40% ethanol + 60% water). In vitro inhibition was quantified using potato starch (for amylases) and maltose (for α-glucosidase) as substrates. In vivo inhibition was evaluated by running starch and maltose tolerance tests in rats with or without administration of MGPE. Ranking of the extract compounds for its affinity to the α-amylases was accomplished by computer simulations using three different programs. Both α-amylases, pancreatic and salivary, were inhibited by the MGPE. No inhibition on α-glucosidase, however, was detected. The IC₅₀ values were 90 ± 10 μg/mL and 143 ± 15 μg/mL for salivary and pancreatic amylases, respectively. Kinetically this inhibition showed a complex pattern, with multiple binding of the extract constituents to the enzymes. Furthermore, the in silico docking simulations indicated that several phenolic substances, e.g., peonidin-3-O-acetylglucoside, quercetin-3-O-glucuronide and isorhamnetin-3-O-glucoside, besides catechin, were the most likely polyphenols responsible for the α-amylase inhibition caused by MGPE. The hyperglycemic burst, an usual phenomenon that follows starch administration, was substantially inhibited by the MGPE. Our results suggest that the MGPE can be adequate for maintaining normal blood levels after food ingestion.

Analysis of inhibitory interaction between epigallocatechin gallate and alpha-glucosidase: A spectroscopy and molecular simulation study

Alpha-glucosidase is one of the main enzymes responsible for digesting starch. Inhibiting its activity is therefore being targeted as a strategy for tackling diabetes. Certain food components have the potential to act as natural α-glucosidase (SCG) inhibitors, such as the polyphenols found in tea. In this study, epigallocatechin gallate (EGCG) was shown to strongly inhibit SCG activity (IC₅₀ value = 3.7 × 10^-5 M). Multi-spectroscopic binding molecular simulations indicated that EGCG spontaneously bound to SCG through a combination of hydrogen bonding and hydrophobic interactions. The hypothesis was supported by the results from intrinsic fluorescence quenching, conformational change, surface hydrophobicity decrease, and molecular docking analysis of the SCG after binding. Molecular docking provided powerful visual insights into the nature of the molecular interactions involved. This research provides important new information about the interaction mechanism of EGCG and SCG, which may be beneficial to the development of functional foods to prevent diabetes.

Traditional, Indigenous Apple Varieties, a Fruit with Potential for Beneficial Effects: Their Quality Traits and Bioactive Polyphenol Contents

Earlier studies suggested that traditional apple varieties have quality traits well accepted by consumers and beneficial effects on human health. The aim was to collect 25 traditional apple varieties grown in Croatia and to determine, for the first time in so many details, their external (weight, height, width, shape, color), internal quality traits (firmness, starch decomposition index, maturity index, soluble solid concentration, total acids, soluble solid/total acids ratio, pH), and seed characteristics. In addition, individual polyphenols were determined in the flesh and peel, by using RP-HPLC. All was compared to the commercial variety ‘Idared’. Quality parameters of these varieties were similar to those of the commercial variety. The flesh and peel contained flavan-3-ols, dihydrochalcones, phenolic acids, and flavonols, while anthocyanins were additionally found in the peel. Total polyphenols in the peel (536–3801 mg kg⁻¹ fresh weight (FW)) and in the flesh (79–1294 mg kg⁻¹ FW) of the majority of varieties were higher than in the commercial variety. Principal component analysis showed possible clustering according to polyphenol amounts. According to the observed diversity of quality traits and bioactive polyphenol contents, the traditional varieties have potential for consumer acceptance and increased cultivation.

Number of galloyl moieties and molecular flexibility are both important in alpha-amylase inhibition by galloyl-based polyphenols

The inhibition of porcine pancreatic α-amylase (PPA) by 9 galloyl-based polyphenols was evaluatedviainitial digestion velocity, IC₅₀, inhibition kinetics, fluorescence quenching and molecular docking studies.

Comparison of Phytochemical Differences of the Pulp of Different Peach [Prunus persica (L.) Batsch] Cultivars with Alpha-Glucosidase Inhibitory Activity Variations in China Using UPLC-Q-TOF/MS

In order to fully understand the variation of the fruit alpha-glucosidase inhibitory activity-related phytochemical basis in the Chinese peach [Prunus persica (L.) Batsch], mature fruit from 33 cultivars was used for the investigation of fruit phenolic phytochemical attributes, including total phenolics, flavonoids, anthocyanins, and procyanidins, as well as the alpha-glucosidase inhibitory activity in vitro. Alpha-glucosidase inhibitory activity varied significantly among tested peach cultivars and was strongly correlated with total phenolics, total procyanidins, and total flavonoids. Untargeted UPLC-Q-TOF/MS-based metabolomics were used to comprehensively discriminate between peaches with different inhibitory activity on alpha-glucosidase. Principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA) were used for this process. Twenty-three differential compounds were identified between peach cultivars with high and low alpha-glucosidase inhibitory activity, and nine, including procyanidin C1, procyanidin trimer isomer 1, procyanidin trimer isomer 2, procyanidin B1, procyanidin dimer, epicatechin-epicatechin-epicatechin, phloridzin, kaempferol 3-(2'',6''-di-(E)-p-coumarylglucoside), and luteolin 3'-methyl ether 7-malonylglucoside, were identified as marker compounds responsible for the discrimination. Overall, variations in metabolites in peach pulp reflect the diversity in peach germplasm, and these nine compounds are good candidate markers for future genetic breeding of peach fruit with high alpha-glucosidase inhibitory activity.