Protective effect of cyanidin against glucose- and methylglyoxal-induced protein glycation and oxidative DNA damage

Berry anthocyanins prevent α-dicarbonyls and advanced glycation end product formation in phosphate-buffered saline-based model systems, cookie and ground pork

α-Dicarbonyls and advanced glycation end products (AGEs) are the heat-induced potential toxicants commonly found in thermally processed foods due to the Maillard reaction. Research has shown that both α-dicarbonyls and AGEs can cause oxidative stress and inflammation and have a positive link with several chronic diseases, such as diabetes. This study found that commonly consumed berry fruits exhibited excellent methylglyoxal (MGO)-trapping and antiglycative activities, positively associated with their total phenolic and flavonoid contents. Blackcurrant exhibited the strongest MGO-trapping and antiglycative activities among the tested berry fruits. In addition, we demonstrated that fortification with blackcurrant significantly reduced α-dicarbonyls and AGEs formation in the chocolate cookies and marinated ground pork. Delphinidin and cyanidin glycosides were identified as the primary bioactive compounds of blackcurrant that trapped MGO to form the corresponding mono- and di-MGO adducts. This study suggested that blackcurrant anthocyanins might serve as a novel additive to reduce the consumption of dietary reactive carbonyl species and AGEs from both animal- and plant-derived processed foods. PRACTICAL APPLICATION: The levels of α-dicarbonyls and advanced glycation end products in ground pork and cookies were significantly reduced when fortified with blackcurrant. The blackcurrant anthocyanins might be a novel agent inhibiting α-dicarbonyls and dietary advanced glycation end products formation in thermally processed foods.

Inhibition and Mechanism of Protein Nonenzymatic Glycation by Lactobacillus fermentum

Lactobacillus fermentum (L. fermentum) was first evaluated as a potential advanced glycation end-product (AGE) formation inhibitor by establishing a bovine serum albumin (BSA) + glucose (glu) glycation model in the present study. The results showed that the highest inhibition rates of pentosidine and total fluorescent AGEs by L. fermentum were approximately 51.67% and 77.22%, respectively, which were higher than that of aminoguanidine (AG). Mechanistic analysis showed that L. fermentum could capture methylglyoxal and glyoxal, inhibit carbonyl and sulfhydryl oxidation, reduce the binding of glucose and amino groups, increase total phenolic content and antioxidant activity, and release intracellular substances to scavenge free radicals; these abilities were the basis of the antiglycation mechanism of L. fermentum. In addition, L. fermentum significantly prevented conformational changes in proteins during glycation, reduced protein cross-linking by 35.67%, and protected the intrinsic fluorophore. Therefore, the inhibition of L. fermentum on glycation mainly occurs through antioxidation, the capture of dicarbonyl compounds, and the protection of the BSA structure. These findings collectively suggest that Lactobacillus is an inhibitor of protein glycation and AGE formation and has the potential for nutraceutical applications.

Hypoglycemic effect of Lactobacillus plantarum-fermented mulberry pomace extract in vitro and in Caenorhabditis elegans

Mulberry pomace is rich in phytochemicals, but there are few studies on its utilization as a by-product. Natural foods containing phytochemicals can alleviate the toxic effects of excessive glucose intake. In this study, we investigated the protective effect of Lactobacillus plantarum-fermented mulberry pomace extract (FMPE) under hyperglycemic conditions. The phenolic compounds and α-glucosidase inhibition of FMPE were determined using UPLC-MS and chemical models. Furthermore, Caenorhabditis elegans was a model system to study the hypoglycemic effects. The results showed that the polyphenolics and α-glucosidase inhibition were improved during fermentation. Three phenolic components (cyanidin, 2,4,6-trihydroxybenzaldehyde, and taxifolin) were important variables for α-glucosidase inhibition. FMPE and the three key compound treatments reduced the glucose content and reactive oxygen species (ROS) level in Caenorhabditis elegans. The protective mechanism occurred by activating DAF-16/FOXO and SKN-1/Nrf2. This study suggests that Lactobacillus plantarum-fermentation was a potential way to utilize mulberry pomace polyphenols as hypoglycemic food ingredients.

Exploring inhibitory effect and mechanism of hesperetin-Cu (II) complex against protein glycation

Inhibition of advanced glycation end products (AGEs) formed in protein glycosylation is crucial for minimizing diabetic complications. Herein, the anti-glycation potential of hesperetin-Cu (II) complex was investigated. Hesperetin-Cu (II) complex strongly inhibited three stages glycosylation products in bovine serum albumin (BSA)-fructose model, especially for the inhibition of AGEs (88.45%), which was stronger than hesperetin (51.76%) and aminoguanidine (22.89%). Meanwhile, hesperetin-Cu (II) complex decreased the levels of BSA carbonylation and oxidation products. 182.50 µg/mL of hesperetin-Cu (II) complex inhibited 66.71% β-crosslinking structures of BSA, and scavenged 59.80% superoxide anions and 79.76% hydroxyl radicals. Moreover, after incubating with methylglyoxal for 24 h, hesperetin-Cu (II) complex removed 85.70% methylglyoxal. The mechanisms of protein antiglycation by hesperetin-Cu (II) complex may be through protecting structure, trapping methylglyoxal, scavenging free radicals and interacting with BSA. This study may contribute to the development of hesperetin-Cu (II) complex as a functional food additive against protein glycation.

The mechanism of in vitro non-enzymatic glycosylation inhibition by Tartary buckwheat's rutin and quercetin

Tartary buckwheat is rich in rutin, quercetin, and other flavonoids, which exert prominent effects by inhibiting non-enzymatic glycosylation. In this study, an in vitro non-enzymatic glycosylation model was established, and the inhibitory effects of rutin and quercetin on the early, middle, and late products of non-enzymatic glycosylation were determined. Furthermore, their effects on the formation of advanced glycation end products (AGEs) and on protein functional groups and secondary structure were analyzed. These findings provided a theoretical basis for further investigation of the mechanism via which Tartary buckwheat's rutin and quercetin inhibited non-enzymatic glycosylation. The results showed that rutin and quercetin inhibited the formation of fructosamine, dicarbonyl compounds, and fluorescent AGE in a concentration-dependent manner. Rutin and quercetin exhibited antioxidant activity and could reduce the formation of protein oxidation products. The highest clearance rates for DPPH and ABTS⁺ were 62.74 % and 71.14 %, respectively.

Food polyphenols and Maillard reaction: regulation effect and chemical mechanism

Maillard reaction is a non-enzymatic thermal reaction during food processing and storage. It massively contributes to the flavor, color, health benefits and safety of foods and could be briefly segmented into initial, intermediate and final stages with the development of a cascade of chemical reactions. During thermal reaction of food ingredients, sugar, protein and amino acids are usually the main substrates, and polyphenols co-existed in food could also participate in the Maillard reaction as a modulator. Polyphenols including flavan-3-ols, hydroxycinnamic acids, flavonoids, and tannins have shown various effects throughout the process of Maillard reaction, including conjugating amino acids/sugars, trapping α-dicarbonyls, capturing Amadori rearrangement products (ARPs), as well as decreasing acrylamide and 5-hydroxymethylfurfural (5-HMF) levels. These effects significantly influenced the flavor, taste and color of processed foods, and also decreased the hazard products' level. The chemical mechanism of polyphenols-Maillard products involved the scavenging of radicals, as well as nucleophilic addition and substitution reactions. In the present review, we concluded and discussed the interaction of polyphenols and Maillard reaction, and proposed some perspectives for future studies.

Major anthocyanins in elderberry effectively trap methylglyoxal and reduce cytotoxicity of methylglyoxal in HepG2 cell line

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The antiglycation effect of elderberries by methylglyoxal (MGO) trapping was studied.

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Cyanidin-3-glucoside and cyanidin-3-sambubioside were almost totally reacted with MGO.

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Quercetin-3-glucoside and quercetin-3-rutinoside trap MGO in less extent.

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Cyanidin-3,5-diglucoside and cyanidin-5-glucoside-3-sambubioside did not react.

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Elderberries phenols trap MGO decreasing the induced MGO cytotoxicity in HepG2 cells.

The accumulation of advanced glycation end-products (AGEs) in the body is implicated in numerous diseases, being methylglyoxal (MGO) one of the main precursors. One of the strategies to reduce AGEs accumulation might be acting in an early stage of glycation by trapping MGO. Thus, this work aimed to evaluate, for the first time, the potential of elderberries polyphenols to trap MGO, access the formation of MGO adducts, and evaluate the cytoprotection effect in HepG2 and Caco-2 cells. The results demonstrated that monoglycosylated anthocyanins (cyanidin-3-glucoside and cyanidin-3-sambubioside) are very efficient in trapping MGO, forming mono- and di-adducts. Quercetin-3-glucoside and quercetin-3-rutinoside reacted slowly, while diglycosylated anthocyanins did not react. The trapping of MGO by elderberry monoglycosylated anthocyanins significantly decreased the MGO cytotoxicity in HepG2 cells (∼70 % of cell viability), while the effect in Caco-2 cells was lower (∼50 %). Thus, elderberry phenolics present antiglycation potential by trapping MGO.

Recent trends in extraction of plant bioactives using green technologies: A review

Phenolic compounds from plant sources have significant health-promoting properties and are known to be an integral part of folk and herbal medicines. Consumption of phenolics is known to alleviate the risk of various lifestyle diseases including cancer, cardiovascular, diabetes, and Alzheimer's. In this context, numerous plant crops have been explored and characterized based on phenolic compounds for their use as supplements, nutraceutical, and pharmaceuticals. The present review highlights some important source of bioactive phenolic compounds and novel technologies for their efficient extraction. These techniques include the use of microwave, ultrasound, and supercritical methods. Besides, the review will also highlight the use of response surface methodology (RSM) as a statistical tool for optimizing the recoveries of the phenolic bioactives from plant-based matrices.

Genome-Protecting Compounds as Potential Geroprotectors

Throughout life, organisms are exposed to various exogenous and endogenous factors that cause DNA damages and somatic mutations provoking genomic instability. At a young age, compensatory mechanisms of genome protection are activated to prevent phenotypic and functional changes. However, the increasing stress and age-related deterioration in the functioning of these mechanisms result in damage accumulation, overcoming the functional threshold. This leads to aging and the development of age-related diseases. There are several ways to counteract these changes: 1) prevention of DNA damage through stimulation of antioxidant and detoxification systems, as well as transition metal chelation; 2) regulation of DNA methylation, chromatin structure, non-coding RNA activity and prevention of nuclear architecture alterations; 3) improving DNA damage response and repair; 4) selective removal of damaged non-functional and senescent cells. In the article, we have reviewed data about the effects of various trace elements, vitamins, polyphenols, terpenes, and other phytochemicals, as well as a number of synthetic pharmacological substances in these ways. Most of the compounds demonstrate the geroprotective potential and increase the lifespan in model organisms. However, their genome-protecting effects are non-selective and often are conditioned by hormesis. Consequently, the development of selective drugs targeting genome protection is an advanced direction.

Cyanidin-related antidepressant-like efficacy requires PI3K/AKT/FoxG1/FGF-2 pathway modulated enhancement of neuronal differentiation and dendritic maturation

BACKGROUND

Cyanidin (CY) is one of the most abundant anthocyanidins found in red-purple diet sources such as grapes, blueberries and purple corns. CY has been proven to exhibit a wide range of biological functions including antioxidant, antiviral, anticarcinogenic and anti-inflammatory properties.

PURPOSE

This study investigated the anti-depressive activity of CY and its related mechanism.

METHODS

In the behavioral tests, CY-related effects on depressive symptoms were evaluated. Then the changes in PI3K/AKT/FOXG1/FGF-2 signaling and adult neurogenesis including doublecortin (DCX+) cell number, dendritic length, secondary and third dendrites number in the hippocampus were investigated by Immunofluorescence and Western blot analyses. PI3K antagonist LY 294,002 was used to verify the unique impact of PI3K/AKT/FoxG1/FGF-2 signaling on CY-related antidepressant efficacy.

RESULTS

CY grossly reversed CUMS-induced behavioral defects, The DCX+ cell number and protein levels increased in CUMS mice receiving CY administration. LY 294,002 successfully blocked CY-induced improvements in depressive behaviors, neurogenesis, and protein levels in CUMS mice.

CONCLUSION

The findings demonstrated that CY was efficacious in alleviating depression-like symptoms, which was dependent on PI3K/AKT/FoxG1/FGF-2 signaling-modulated neurogenesis enhancement.

Cyanidin Attenuates Methylglyoxal-Induced Oxidative Stress and Apoptosis in INS-1 Pancreatic β-Cells by Increasing Glyoxalase-1 Activity

Recently, the mechanisms responsible for anti-glycation activity of cyanidin and its derivatives on the inhibition of methylglyoxal (MG)-induced protein glycation and advanced glycation-end products (AGEs) as well as oxidative DNA damage were reported. In this study, we investigated the protective effect of cyanidin against MG-induced oxidative stress and apoptosis in rat INS-1 pancreatic β-cells. Exposure of cells to cytotoxic levels of MG (500 µM) for 12 h caused a significant reduction in cell viability. However, the pretreatment of cells with cyanidin alone (6.25–100 μM) for 12 h, or cotreatment of cells with cyanidin (3.13–100 μM) and MG, protected against cell cytotoxicity. In the cotreatment condition, cyanidin (33.3 and 100 μM) also decreased MG-induced apoptosis as determined by caspase-3 activity. Furthermore, INS-1 cells treated with MG increased the generation of reactive oxygen species (ROS) during a 6 h exposure. The MG-induced increase in ROS production was inhibited by cyanidin (33.3 and 100 μM) after 3 h stimulation. Furthermore, MG diminished the activity of glyoxalase 1 (Glo-1) and its gene expression as well as the level of total glutathione. In contrast, cyanidin reversed the inhibitory effect of MG on Glo-1 activity and glutathione levels. Interestingly, cyanidin alone was capable of increasing Glo-1 activity and glutathione levels without affecting Glo-1 mRNA expression. These findings suggest that cyanidin exerts a protective effect against MG-induced oxidative stress and apoptosis in pancreatic β-cells by increasing the activity of Glo-1.

A New Italian Purple Corn Variety (Moradyn) Byproduct Extract: Antiglycative and Hypoglycemic In Vitro Activities and Preliminary Bioaccessibility Studies

The reuse of byproducts from agricultural and food industries represents the key factor in a circular economy, whose interest has grown in the last two decades. Thus, the extraction of bioactives from agro-industrial byproducts is a potential source of valuable molecules. The aim of this work was to investigate the in vitro capacity of byproducts from a new Italian corn variety, named Moradyn, to inhibit the accumulation of advanced glycation end products (AGEs) involved in several chronic age-related disorders. In addition, the hypoglycemic effect of Moradyn was tested by in vitro enzymatic systems. A Moradyn phytocomplex and its purified anthocyanin fraction were able to inhibit fructosamine formation and exhibited antiglycative properties when tested using BSA-sugars and BSA-methylglyoxal assays. These properties could be attributed to the polyphenols, mainly anthocyanins and flavonols, detected by RP-HPLC-DAD-ESI-MSⁿ. Finally, a Moradyn phytocomplex was submitted to a simulated in vitro digestion process to study its bioaccessibility. Moradyn could be considered as a promising food ingredient in the context of typical type 2 diabetes risk factors and the study will continue in the optimization of the ideal formulation to preserve its bioactivities from digestion.

Dietary antioxidants remodel DNA methylation patterns in chronic disease

Chronic diseases account for over 60% of all deaths worldwide according to the World Health Organization reports. Majority of cases are triggered by environmental exposures that lead to aberrant changes in the epigenome, specifically, the DNA methylation patterns. These changes result in altered expression of gene networks and activity of signalling pathways. Dietary antioxidants, including catechins, flavonoids, anthocyanins, stilbenes and carotenoids, demonstrate benefits in the prevention and/or support of therapy in chronic diseases. This review provides a comprehensive discussion of potential epigenetic mechanisms of antioxidant compounds in reversing altered patterns of DNA methylation in chronic disease. Antioxidants remodel the DNA methylation patterns through multiple mechanisms, including regulation of epigenetic enzymes and chromatin remodelling complexes. These effects can further contribute to antioxidant properties of the compounds. On the other hand, decrease in oxidative stress itself can impact DNA methylation delivering additional link between antioxidant mechanisms and epigenetic effects of the compounds. LINKED ARTICLES: This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc.

Dicarbonyl Stress at the Crossroads of Healthy and Unhealthy Aging

Dicarbonyl stress occurs when dicarbonyl metabolites (i.e., methylglyoxal, glyoxal and 3-deoxyglucosone) accumulate as a consequence of their increased production and/or decreased detoxification. This toxic condition has been associated with metabolic and age-related diseases, both of which are characterized by a pro-inflammatory and pro-oxidant state. Methylglyoxal (MGO) is the most reactive dicarbonyl and the one with the highest endogenous flux. It is the precursor of the major quantitative advanced glycated products (AGEs) in physiological systems, arginine-derived hydroimidazolones, which accumulate in aging and dysfunctional tissues. The aging process is characterized by a decline in the functional properties of cells, tissues and whole organs, starting from the perturbation of crucial cellular processes, including mitochondrial function, proteostasis and stress-scavenging systems. Increasing studies are corroborating the causal relationship between MGO-derived AGEs and age-related tissue dysfunction, unveiling a previously underestimated role of dicarbonyl stress in determining healthy or unhealthy aging. This review summarizes the latest evidence supporting a causal role of dicarbonyl stress in age-related diseases, including diabetes mellitus, cardiovascular disease and neurodegeneration.

Superoxide Scavenging and Antiglycation Activity of Rhinacanthins-rich Extract Obtained from the Leaves of Rhinacanthus nasutus

Background:

Oxidative stress and nonenzymatic protein glycation lead to serious diabetic complications that increase the risk of mortality. Rhinacanthus nasutus leaf crude extracts are previously reported for their antidiabetic, antiglycation, and antioxidant potential.

Objective:

The present study was performed to prepare a standardized rhinacanthins-rich extract (RRE) and evaluate its superoxide scavenging and antiglycation effects as compared to its marker compounds, namely, rhinacanthin-C (RC), rhinacanthin-D (RD), and rhinacanthin-N (RN).

Materials and Methods:

RRE was obtained by microwave-assisted green extraction along with a simple step of fractionation using Amberlite^® column. RC, RD, and RN were isolated from the RRE using silica gel column chromatography. Superoxide scavenging activity was performed by cyclic voltammetry, and fructose-mediated human serum albumin glycation model was used for antiglycation activity. In silico studies were conducted to identify the structure-activity relationships of rhinacanthins.

Results:

On the basis of kinetic measurements, RRE exhibited the most potent antioxidant activity via E_rC_i mechanism, with a 50% inhibitory concentration (IC₅₀) value of 8.0 μg/mL, antioxidant capacity of 39439 M⁻¹, and binding constant of 45709 M⁻¹. Antiglycation assay showed that RRE exhibited almost equivalent glycation inhibitory effect to that of RC, with IC₅₀ values of 39.7 and 37.3 μg/mL, respectively, but higher than that of RD (IC₅₀ of 50.4 μg/mL), RN (IC₅₀ of 89.5 μg/mL), as well as the positive control, rutin (IC₅₀ of 41.5 μg/mL).

Conclusions:

The potent superoxide scavenging and albumin glycation inhibitory effect of RRE rationalized its therapeutic application in various chronic diseases, especially in the complications of diabetes.

SUMMARY

Rhinacanthins-rich extract (RRE) exhibited potent superoxide scavenging activity

RRE and rhinacanthin-C showed remarkable and comparable antiglycation effect

Rhinacanthins exhibited antiglycation activity by masking specific residues of albumin.

Abbreviations used: RRE: Rhinacanthins-rich extract; RC: Rhinacanthin-C; RD: Rhinacanthin-D; RN: Rhinacanthin-N; IC₅₀: 50% inhibitory concentration; Kao: Antioxidant activity coefficient; Kb: Binding constant; E_rC_i: Reversible electron transfer followed by an irreversible chemical reaction; DM: Diabetes mellitus; AGEPs: Advanced glycation end products; NMR: Nuclear magnetic resonance; HPLC: High-performance liquid chromatography; CV: Cyclic voltammetry; DMSO: Dimethyl sulfoxide; Ipa: Anodic peak current; Ipc: Cathodic peak current; HSA: Human serum albumin; MOE: Molecular operating environment; PASSonline: Online prediction of activity spectra for substances.

Effects of nutrient and bioactive food components on Alzheimer's disease and epigenetic

Alzheimer's disease (AD) is the most common form of dementia in the elderly and is a chronic neurodegenerative disease that is becoming widespread. For this reason, in recent years factors affecting the development, progression and cognitive function of the AD have been emphasized. Nutrients and other bioactive nutrients are among the factors that are effective in AD. In particular, vitamins A, C and E, vitamins B₁, B₆ and B₁₂, folate, magnesium, choline, inositol, anthocyanins, isoflavones etc. nutrients and bioactive nutrients are known to be effective in the development of AD. Nutrients and nutrient components may also have an epigenetic effect on AD. At the same time, nutrients and bioactive food components slow down the progression of the disease. For this reason, the effect of nutrients and food components on AD was examined in this review.

Cyanidin Stimulates Insulin Secretion and Pancreatic β-Cell Gene Expression through Activation of l-type Voltage-Dependent Ca2+ Channels

Cyanidin is a natural anthocyanidin present in fruits and vegetables with anti-diabetic properties including stimulation of insulin secretion. However, its mechanism of action remains unknown. In this study, we elucidated the mechanisms of cyanidin for stimulatory insulin secretion from pancreatic β-cells. Rat pancreatic β-cells INS-1 were used to investigate the effects of cyanidin on insulin secretion, intracellular Ca²⁺ signaling, and gene expression. We detected the presence of cyanidin in the intracellular space of β-cells. Cyanidin stimulated insulin secretion and increased intracellular Ca²⁺ signals in a concentration-dependent manner. The Ca²⁺ signals were abolished by nimodipine, an l-type voltage-dependent Ca²⁺ channel (VDCC) blocker or under extracellular Ca²⁺ free conditions. Stimulation of cells with cyanidin activated currents typical for VDCCs and up-regulated the expression of glucose transporter 2 (GLUT2), Kir_6.2, and Cav_1.2 genes. Our findings indicate that cyanidin diffuses across the plasma membrane, leading to activation of l-type VDCCs. The increase in intracellular Ca²⁺ stimulated insulin secretion and the expression of genes involved in this process. These findings suggest that cyanidin could be used as a promising agent to stimulate insulin secretion.