Anti-glycation and anti-oxidative effects of a phenolic-enriched maple syrup extract and its protective effects on normal human colon cells

Melatonin protects Kir2.1 function in an oxidative stress-related model of aging neuroglia

Melatonin is a pleiotropic biofactor and an effective antioxidant and free radical scavenger and, as such, can be protective in oxidative stress-related brain conditions including epilepsy and aging. To test the potential protective effect of melatonin on brain homeostasis and identify the corresponding molecular targets, we established a new model of oxidative stress-related aging neuroglia represented by U-87 MG cells exposed to D-galactose (D-Gal). This model was characterized by a substantial elevation of markers of oxidative stress, lipid peroxidation, and protein oxidation. The function of the inward rectifying K+ channel Kir2.1, which was identified as the main Kir channel endogenously expressed in these cells, was dramatically impaired. Kir2.1 was unlikely a direct target of oxidative stress, but the loss of function resulted from a reduction of protein abundance, with no alterations in transcript levels and trafficking to the cell surface. Importantly, melatonin reverted these changes. All findings, including the melatonin antioxidant effect, were reproduced in heterologous expression systems. We conclude that the glial Kir2.1 can be a target of oxidative stress and further suggest that inhibition of its function might alter the extracellular K+ buffering in the brain, therefore contributing to neuronal hyperexcitability and epileptogenesis during aging. Melatonin can play a protective role in this context.

Exploring immunoregulatory properties of a phenolic-enriched maple syrup extract through integrated proteomics and in vitro assays

Our laboratory has established a comprehensive program to investigate the phytochemical composition and nutritional/medicinal properties of phenolic-enriched maple syrup extract (MSX). Previous studies support MSX's therapeutic potential in diverse disease models, primarily through its anti-inflammatory effects. We recently demonstrated MSX's ability to regulate inflammatory signaling pathways and modulate inflammatory markers and proteins in a lipopolysaccharide (LPS)-induced peritonitis mouse model. However, MSX's immunoregulatory properties remain unknown. Herein, we investigated MSX's immunoregulatory properties for the first time using an integrated approach, combining data-dependent acquisition (DDA) and data-independent acquisition (DIA) strategies in a proteomic analysis of spleen tissue collected from the aforementioned peritonitis mouse model. Additionally, we conducted immune cell activation assays using macrophages and T lymphocytes. The DIA analysis unveiled a distinctive expression pattern involving three proteins-Krt83, Thoc2, and Vps16-which were present in both the control and MSX-treated groups but absent in the LPS-induced model group. Furthermore, proteins Ppih and Dpp9 exhibited significant reductions in the MSX-treated group. Ingenuity pathway analysis indicated that MSX may modulate several critical signaling pathways, exerting a suppressive effect on immune responses in various cell types involved in both innate and adaptive immunity. Our in vitro cell assays supported findings from the proteomics, revealing that MSX significantly reduced the levels of interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) in LPS-stimulated human macrophage cells, as well as the levels of IL-2 in anti-CD3/anti-CD28-induced Jurkat T cells. Taken together, our investigations provide evidence that MSX exerts immune regulatory effects that impact both innate and adaptive immunity, which adds to the data supporting MSX's development as a functional food.

The Physicochemical Characterization and In Vitro Digestibility of Maple Sugar Sand and Downgraded Maple Syrups

The maple syrup industry generates substandard syrups and sugar sand as by-products, which are underused. In this study, we conducted a comprehensive analysis of the physicochemical composition of these products to assess their potential for valorization. Using HPLC analysis, we measured sugar and organic acid content as well as total polyphenol content using the Folin-Ciocalteu method. Additionally, we evaluated the in vitro digestibility using the TIM-1 model. We showed that the composition of ropy and buddy downgraded syrups is comparable to that of standard maple syrup, whereas sugar sand's composition is highly variable, with carbohydrate content ranging from 5.01 mg/g to 652.89 mg/g and polyphenol content ranging from 11.30 µg/g to 120.95 µg/g. In vitro bioaccessibility reached 70% of total sugars for all by-products. Organic acid bioaccessibility from sugar sand and syrup reached 76% and 109% relative to standard maple syrup, respectively. Polyphenol bioaccessibility exceeded 100% during digestion. This can be attributed to favorable extraction conditions, the breakdown of complex polyphenol forms and the food matrix. In conclusion, our study demonstrates that sugar sand and downgraded maple syrups exhibit digestibility comparable to that of standard maple syrup. Consequently, they hold potential as a source of polyphenols, sugar or organic acids for applications such as industrial fermentation or livestock feeds.

Nutritional, pharmacological, and sensory properties of maple syrup: A comprehensive review

Maple syrup is a naturally sweet product consumed directly or introduced in the preparation of various maple-derived food products. Several studies have described the chemical isolation and identification of maple syrup compounds, with some presenting pharmacological properties. However, a detailed review on maple syrup nutritional properties has not been undertaken. This review presents detailed information about the nutritional, organoleptic, and pharmacological properties of maple syrup. Studies carried out on animal models and a limited number of human models emphasize the potential benefits of maple syrup as a substitute for refined sugars, indicating that it could contribute to improved metabolic health when used in moderation. However, further medical and nutritional health studies based on human health assessments are needed to better understand the mechanisms of action of the various components of maple syrup and its potential therapeutic properties to demonstrate a stronger justification for its consumption relative to refined sugars. In addition, we compare maple syrup and common sweeteners to provide a further critical perspective on the potential nutritional and health benefits of maple syrup.

Uncovering the anti-inflammatory mechanisms of phenolic-enriched maple syrup extract in lipopolysaccharide-induced peritonitis in mice: insights from data-independent acquisition proteomics analysis

Our group has previously reported on the phytochemical composition and biological activities of a phenolic-enriched maple syrup extract (MSX), which showed promising anti-inflammatory effects in several disease models including diabetes and Alzheimer's disease. However, the efficacious doses of MSX and its molecular targets involved in the anti-inflammatory effects are not fully elucidated. Herein, the efficacy of MSX in a peritonitis mouse model was evaluated in a dose-finding study and the underlying mechanisms were explored using data-independent acquisition (DIA) proteomics assay. MSX (at 15, 30 and 60 mg kg-1) alleviated lipopolysaccharide-induced peritonitis by reducing the levels of pro-inflammatory cytokines including interleukin-1 beta (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) in the serum and major organs of the mice. Furthermore, DIA proteomics analyses identified a panel of proteins that were significantly altered (both up- and down-regulated) in the peritonitis group, which were counteracted by the MSX treatments. MSX treatment also modulated several inflammatory upstream regulators including interferon gamma and TNF. Ingenuity pathway analysis suggested that MSX may modulate several signaling pathways in the processes of initiation of cytokine storm, activation of liver regeneration, and suppression of hepatocyte apoptosis. Together, these proteomic and in vivo findings indicate that MSX could regulate inflammation signaling pathways and modulate inflammatory markers and proteins, providing critical insight to its therapeutic potential.

In vivo antidiabetic effects of phenolic compounds of spinach, mustard, and cabbage leaves in mice

Leafy vegetables are considered to have health-promoting potentials, mainly attributed to bioactive phenolic compounds. The antidiabetic effects of spinach, mustard, and cabbage were studied by feeding their phenolic-rich aqueous extracts to alloxan-induced diabetic mice. The antioxidant, biochemical, histopathological, and hematological indices of the control, diabetic, and treated mice were studied. Phenolic compounds present in the extracts were identified and quantified using HPLC-DAD. Results showed ten, nineteen, and eleven phenolic compounds in spinach, mustard, and cabbage leave aqueous extracts, respectively. The body weight, tissue total glutathione (GSH) contents, fasting blood sugar, liver function tests, renal function tests, and lipid profile of the mice were affected by diabetes and were significantly improved by the extract treatments. Likewise, hematological indices and tissues histological studies also showed recovery from diabetic stress in treated mice. The study's findings highlight that the selected leafy vegetables potentially mitigate diabetic complications. Among the studied vegetables, cabbage extract was comparatively more active in ameliorating diabetic stress.

Acertannin Prevented Dextran Sulfate Sodium-induced Colitis by Inhibiting the Colonic Expression of IL-23 and TNF-α in C57BL/6J Mice

The present study investigates the effects of acertannin on colitis induced by dextran sulfate sodium (DSS) and changes in the colonic levels of the cytokines interleukin (IL)-1β, IL-6, IL-10, IL-23, tumor necrosis factor (TNF)-α, the chemokine monocyte chemoattractant protein (MCP)-1, and vascular endothelial growth factor (VEGF).We examine the following: inflammatory colitis was induced in mice by 2% DSS drinking water given ad libitum for 7 days. Red blood cell, platelets, and leukocyte counts and hematocrit (Ht), hemoglobin (Hb), and colonic cytokine and chemokine levels were measured. The disease activity index (DAI) was lower in DSS-treated mice orally administered acertannin (30 and 100 mg/kg) than in DSS-treated mice. Acertannin (100 mg/kg) inhibited reductions in the red blood cell count and Hb and Ht levels in DSS-treated mice. Acertannin prevented DDS-induced mucosal membrane ulceration of the colon and significantly inhibited the increased colonic levels of IL-23 and TNF-α. Our findings suggest that acertannin has potential as a treatment for inflammatory bowel disease (IBD).

Acertannin prevents azoxymethane/dextran sulfate sodium-induced colon cancer growth by inhibiting the colonic expression of interleukin-1β, monocyte chemoattractant protein-1, cyclooxygenase-2, and thymocyte selection-associated high mobility group box proteins (TOX)/TOX2 in C57BL/6J mice

Colon cancer was the second leading cause of cancer-related death in 2019. We herein investigated the effects of acertannin containing Acer species on azoxymethane (AOM)/dextran sulfate sodium (DDS)-induced colon cancer growth and changes in the colonic levels of interleukin (IL)-1β, monocyte chemoattractant protein (MCP)-1, IL-10, and programmed cell death-1 (PD-1). Colorectal carcinogenesis was induced by an intraperitoneal injection of AOM (10 mg/kg) on days 0 and 27. Mice were given 1% (w/v) DSS drinking water ad libitum on days 7-14, 32-33, and 35-38. Acertannin (30 and 100 mg/kg) was orally administered on days 1-16, discontinued for 11 days (days 16-26), and then administered again on days 27-41. The colonic levels of cytokines, a chemokine, and PD-1 were measured using the respective ELISA kits. The number and area of tumors in mice treated with acertannin (100 mg/kg) decreased by 53.9 and 63.1%, respectively. Furthermore, the colonic levels of IL-1β, MCP-1, IL-10, and PD-1 showed reductions of 57.3, 62.9, 62.8, and 100%, respectively, while the numbers of cyclooxygenase-2 (COX-2)-, thymocyte selection-associated high mobility group box proteins (TOX)/TOX2-, PD-1-, and signal transducer and activator of transcription 3 (STAT3) phosphorylation-positive numbers decreased by 79.6, 77.9, 93.8, and 100%, respectively. In conclusion, the inhibitory effects of acertannin on AOM/DSS-induced colon tumor growth appear to be associated with reductions in the colonic levels of IL-1β, MCP-1, IL-10, and PD-1 through the down-regulated expression of COX-2 and TOX/TOX2 in the tumor microenvironment.

Inhibitory effect of Ginkgo biloba seeds peptides on methylglyoxal-induced glycations

The aim of this study was to investigate the antiglycation activity and mechanism of two identified peptides, Valine-Valine-Phenylalanine-Proline-Glycine-Cysteine-Proline-Glutamic acid (VVFPGCPE) and Serine-Valine-Aspartic acid-Aspartic acid-Proline-Arginine-Threonine-Lysine (SVDDPRTL), from Ginkgo biloba seeds protein hydrolysates. Both VVFPGCPE and SVDDPRTL were efficient in bovine serum albumin (BSA)-methylglyoxal (MGO) model to inhibit BSA glycation, while VVFPGCPE showed higher antiglycation activity than SVDDPRTL. In antioxidant assays, VVFPGCPE scavenged more hydroxyl and super anion radicals, and chelated more Fe²⁺. Moreover, VVFPGCPE was more efficient in alleviating glycoxidation since it retained higher content of tryptophan and reduced dityrosine and kynurenine generation. Compared with SVDDPRTL, VVFPGCPE showed better performance in inhibiting protein aggregation and amyloid-like fibrillation formation. Therefore, VVFPGCPE was selected for further mechanism study. The circular dichroism analysis suggested VVFPGCPE could preserve α-helix structure and stabilize protein structure. The MGO trapping assay indicated VVFPGCPE (5 mg/mL) could capture 66.25% MGO within 24 h, and the mass spectrometry revealed VVFPGCPE could trap MGO by forming VVFPGCPE-mono-MGO adducts. Besides, molecular simulations suggested VVFPGCPE could interact with key glycation residues, arginine and lysine residues, of BSA mainly through van der Waals and hydrogen bonds. This study might supply a theoretical basis for the development of VVFPGCPE as an effective antiglycation agent.

What Is Authentic Maple Water? A Twelve-Month Shelf-Life Study of the Chemical Composition of Maple Water and Its Biological Activities

Maple water (maple sap) products are produced from sap tapped directly from maple trees, but there is confusion and lack of industry consensus and consumer knowledge as to what constitutes 'authentic' maple water. With an immense potential for growth in the multi-billion dollar functional beverage market, the market promotion of maple water products hinges on establishing standards of identity (SI), which are currently lacking. Herein, we aim to provide publishable SI and compositional chemistry findings of maple water. The chemical composition (including polyphenols, sugars, amino acids, and organic acids) of a pasteurized maple water was monitored over a 12-month (at 0, 4, 8, and 12 months) shelf-life. Furthermore, LC-MS/MS and molecular networking-based methods were developed to identify the phytochemical profile of a maple water extract (MWX) and to compare it to a previously chemically characterized phenolic-enriched maple syrup extract (MSX). Both MSX and MWX have similar phytochemical profiles and chemical characteristics. In addition, MSX and MWX showed moderate antioxidant capacity (in free radical scavenging and anti-tyrosinase assays) and anti-inflammatory effects (in soluble epoxide hydrolase and cyclooxygenase-2 inhibition assays). Our findings provide critical information on the SI and stability (in chemical composition) of maple water, which will help define, authenticate, and distinguish it from other functional beverages, thereby positioning the maple industry for promotion and growth in this market sector.

Maple Syrup: Chemical Analysis and Nutritional Profile, Health Impacts, Safety and Quality Control, and Food Industry Applications

Maple syrup is a delicacy prepared by boiling the sap taken from numerous Acer species, primarily sugar maple trees. Compared to other natural sweeteners, maple syrup is believed to be preferable to refined sugar for its high concentration of phenolic compounds and mineral content. The presence of organic acids (malic acid), amino acids and relevant amounts of minerals, such as potassium, calcium, zinc and manganese, make maple syrup unique. Given the growing demand for naturally derived sweeteners over the past decade, this review paper deals with and discusses in detail the most important aspects of chemical maple syrup analyses, with a particular emphasis on the advantages and disadvantages of the different analytical approaches. A successful utilization on the application of maple syrup in the food industry, will rely on a better understanding of its safety, quality control, nutritional profile, and health impacts, including its sustainability issues.

Development of Evaluation Methods for Anti-Glycation Activity and Functional Ingredients Contained in Coriander and Fennel Seeds

Spices are known to have various physiological functions. We focused on the anti-glycation effects of spices, researched anti-glycation active ingredients in coriander (Coriandrum sativum L.) and fennel (Foeniculum vulgare) seeds, and conducted experiments using human skin-derived fibroblast TIG-110 cells as a model of glycation. We isolated 11 compounds from two spice seeds and found several substances that showed anti-glycation activity. A new compound (5,5′-diallyl-2,2′-diglucopyranosyl-3,3′-dimethoxy diphenyl ether) was isolated from fennel seeds and showed high anti-glycation activity with an IC50 value of 0.08 mM, thereby indicating a high anti-glycosylation activity. In this study, we established a glyoxal (GO)-induced glycation test method for human skin cells, confirmed the anti-glycation effect of spice seeds using this glycation induction model, and found that the exposure of TIG-110 human skin-derived fibroblast cells to GO reduced cell viability. The most stable conditions for cell viability were found to be a GO concentration of 1.25 mM and a culture time of 48 h. We evaluated extracts and isolates of spice seeds using this model as a model test for glycation induction. We conducted qualitative and quantitative analyses of carboxymethyl lysine (CML), a type of AGE, to determine the relationship between cell viability and AGEs. The relationship between cell viability and the amount of CML was correlated. Establishing a glycation induction model test using skin cells makes it possible to quickly screen extracts of natural ingredients in the future. Moreover, the results of this model showed that extracts of two spice seeds and their isolates have high anti-glycation activity, and they are expected to be used as cosmetics, health foods, and pharmaceutical ingredients.

High Fructose Negatively Impacts Proliferation of NSC-34 Motor Neuron Cell Line

Objectives The main aim of this study is to identify the deleterious effects of indiscriminately consumed high fructose on motor neurons that are critically affected in many neurological conditions causing movement disorders including paralysis.

Materials and Methods Neuroblastoma x mouse spinal cord motor neuron cell line (NSC-34) motor neuron cell lines were treated with high fructose and oxygen supplementation (18.8%) and assayed for cell proliferation/death, reactive oxygen species (ROS) generation, and oxidative stress response induction

Statistical Analysis Mean and standard deviation, significance with and without high fructose (F)-5%, were estimated by t-tests using GraphPad Prism ver. 8.2.1

Results F-5% along with O2 (18.8%) annihilates the cells (∼85%) by day10 and inhibits cell division as observed by the presence of multinucleated cells. Unexpectedly, 1 to 2% of cells that survived, differentiated and displayed progressive neurite extension. Though not healthy, they were viable up to 80 days. F-5% increased ROS levels (∼34%) not accompanied by concomitant enhanced expression of oxidative stress response regulator, the transcription factor, nrf-2, or downstream effector, sod-1.

Conclusion High fructose is extremely harmful to NSC-34 motor neuron cell line.

Chemical composition and mineralogical residence of maple syrup: A comprehensive review

Maple syrup is a sweet-tasting product prepared by boiling and concentrating the sap of sugar maple (Acer saccharum March). Because of its potential health benefits (except for people with diabetes and those with blood sugar problems), desirable flavor, and taste,maple syrup is one of most popular natural products in the world.Maple syrup fundamentally consists of both organic and inorganic components. The composition of maple syrup plays an important role in determining its flavour, smell, color, and distinguishes it from other sugar syrups. Maple syrup constituents have been identified by different analytical techniques typically based onspectroscopy or spectrometry. Herein, we present the first comprehensive review of all available information on the chemical composition and mineralogical residence of maple syrup collected from over 117 years of published literature.

Chemistry, processing, and functionality of maple food products: An updated comprehensive review

Maple sap is a rich nutrient matrix collected from Acer trees to produce several food products (i.e., sap, water, extract, syrup, and sugar), of which syrup is the most famous in the food industry for its distinct taste and flavor. Maple syrup is produced from the sap of several species (Acer saccharum, Acer nigrum, and Acer rubrum) of maple. Maple syrup is chiefly produced through the concentration of sap via thermal evaporation (pan evaporation) or membrane separation. Each processing technique affects the quality and characteristics of processed maple products. The chemistry of maple products is dominated by a myriad of other phytoconstituents other than sugar, that is, phenolics, to mediate for its many health benefits. The health-promoting effects of maple products included antioxidant, antimicrobial, antimutagenic, anti-inflammatory, and antiproliferative activities. This review capitalizes on maple food products focusing on their chemistry, processing, and health benefits compared with other sugar sweeteners. The impact of processing on maple syrup composition and biological effects in relation to original maple sap are further presented. PRACTICAL APPLICATIONS: Maple food products are natural sweeteners of significant importance due to their economic, nutritional, and health benefits. Apart from the predominant ingredient sucrose, the chemical composition of maple products comprises phenolics, pyrazines, vitamins, minerals, organic acids, and phytohormones. These bioactive compounds are of potential value owing to their health-promoting benefits, including antioxidant, antiproliferative, and antimutagenic effects. Quebecol, lariciresinol, and secoisolariciresinol are suggested as distinct markers for maple products and not common in other plant-derived syrups. Several factors, including the processing parameters and the phytochemical profile, affect maple products' flavor and color. In addition, microbial contamination of maple sap can also affect maple product quality. Further research on the effect of processing techniques and environmental conditions on the phytochemicals profile and biological effects of maple food products should now follow. Application of other omics tools, that is, genomics, proteomics, and metabolomics, to understand maple syrup effects on the human body can help reveal its exact action mechanisms or points for any potential health hazards for certain ailments.

Chinese bayberry (Myrica rubra) phenolics mitigated protein glycoxidation and formation of advanced glycation end-products: A mechanistic investigation

Protein glycation and formation of advanced glycation end-products (AGEs) impose threats to the human health. This study firstly investigated the inhibition of Chinese bayberry (Myrica rubra) phenolics on AGEs formation through mechanistic analysis. Four common Chinese bayberry cultivars were selected to prepare phenolic-rich extracts (CBEs) and characterized for phenolic composition, and their anti-AGE properties were evaluated in multiple in vitro systems. Total sixteen phenolics were quantified in CBEs by UPLC-ESI-MS/MS. CBEs reduced total and specific fluorescent AGEs formation in various simulating models, and protected the protein from structural modification, oxidation, and cross-linking. Mechanistic analysis unveiled that scavenging of free radicals, inactivation of transition metals, interaction with protein to form complexes, and trapping of reactive α-dicarbonyls to form adducts underlain the mechanisms of the anti-glycative actions of CBEs. Chinese bayberry fruits, especially the cultivars Biqi and Wuzi, may be a promising dietary strategy to mitigate AGEs load in the human body.

The Taming of Nuclear Factor Erythroid-2-Related Factor-2 (Nrf2) Deglycation by Fructosamine-3-Kinase (FN3K)-Inhibitors-A Novel Strategy to Combat Cancers

Simple Summary

Aim of this review is to provide an overview on (a) Fructosamine-3-Kinase (FN3K) and its role in regulating Nuclear Factor Erythorid-2-Related Factor-2 (Nrf2); (b) the role of glycation and deglycation mechanisms in modulating the functional properties of proteins, in particular, the Nrf2; (c) the dual role of Nrf2 in the prevention and treatment of cancers. Since controlling the glycation of Nrf2 is one of the key mechanisms determining the fate of a cell; whether to get transformed into a cancerous one or to stay as a normal one, it is important to regulate Nrf2 and deglycating FN3K using pharmacological agents. Inhibitors of FN3K are being explored currently to modulate Nrf2 activity thereby control the cancers.

Abstract

Glycated stress is mediated by the advanced glycation end products (AGE) and the binding of AGEs to the receptors for advanced glycation end products (RAGEs) in cancer cells. RAGEs are involved in mediating tumorigenesis of multiple cancers through the modulation of several downstream signaling cascades. Glycated stress modulates various signaling pathways that include p38 mitogen-activated protein kinase (p38 MAPK), nuclear factor kappa–B (NF-κB), tumor necrosis factor (TNF)-α, etc., which further foster the uncontrolled proliferation, growth, metastasis, angiogenesis, drug resistance, and evasion of apoptosis in several cancers. In this review, a balanced overview on the role of glycation and deglycation in modulating several signaling cascades that are involved in the progression of cancers was discussed. Further, we have highlighted the functional role of deglycating enzyme fructosamine-3-kinase (FN3K) on Nrf2-driven cancers. The activity of FN3K is attributed to its ability to deglycate Nrf2, a master regulator of oxidative stress in cells. FN3K is a unique protein that mediates deglycation by phosphorylating basic amino acids lysine and arginine in various proteins such as Nrf2. Deglycated Nrf2 is stable and binds to small musculoaponeurotic fibrosarcoma (sMAF) proteins, thereby activating cellular antioxidant mechanisms to protect cells from oxidative stress. This cellular protection offered by Nrf2 activation, in one way, prevents the transformation of a normal cell into a cancer cell; however, in the other way, it helps a cancer cell not only to survive under hypoxic conditions but also, to stay protected from various chemo- and radio-therapeutic treatments. Therefore, the activation of Nrf2 is similar to a double-edged sword and, if not controlled properly, can lead to the development of many solid tumors. Hence, there is a need to develop novel small molecule modulators/phytochemicals that can regulate FN3K activity, thereby maintaining Nrf2 in a controlled activation state.

Phenolic-enriched maple syrup extract protects human keratinocytes against hydrogen peroxide and methylglyoxal induced cytotoxicity

Reactive carbonyl species including methylglyoxal (MGO) are oxidation metabolites of glucose and precursors of advanced glycation end products (AGEs). They are important mediators of cellular oxidative stress and exacerbate skin complications. Published data supports that certain phenolic compounds can exert cellular protective effects by their antioxidant activity. A phenolic-enriched maple syrup extract (MSX) was previously reported to show protective effects against AGEs- and MGO-induced cytotoxicity in human colon cells but its skin protective effects remain unknown. The protective effects of MSX were evaluated against hydrogen peroxide (H2 O2 )- and MGO-induced cytotoxicity in human keratinocytes (HaCaT cells). Cellular viability and antioxidant activity were evaluated by the luminescent cell viability CellTiter-Glo assay and the reactive oxygen species (ROS) assay, respectively. A single-cell gel electrophoresis (Comet assay) was used to measure the strand breaks in the DNA of HaCaT cells. MSX (at 50 μg/mL) ameliorated H2 O2 - and MGO-induced cytotoxicity by increasing cell viability by 21.5% and 25.9%, respectively. MSX reduced H2 O2 - and MGO-induced ROS production by 69.4% and 56.6%, respectively. MSX also reduced MGO-induced DNA damage by 47.5%. MSX showed protective effects against H2 O2 - and MGO-induced cytotoxicity in HaCaT cells supporting its potential for dermatological and/or cosmeceutical applications.

Non-enzymatic glycation of protein induces cancer cell proliferation and its inhibition by quercetin: Spectroscopic, cytotoxicity and molecular docking studies

Methylglyoxal (MG) is a potent glycating agent which reacts with proteins to form advanced glycation end products (AGEs). These chemically stable AGEs crosslink with proteins and could lead to amyloid formation that has the role in several diseases including Alzheimer's and Parkinson's. In this piece of work, glycation-induced conformational changes in HSA were observed with quenching of tryptophan fluorescence by 73.8% (41 nm red shift) and loss of hydrophobicity of HSA. CD spectroscopy result reaffirmed secondary structure changes in HSA. Moreover, MG-induced changes in HSA, proceeds to amyloid structure as characterized by an increase in thioflavin (ThT) fluorescence and transmission electron microscopy (TEM) images of HSA aggregates. Quercetin was found to inhibit both AGEs production and amyloid formation. Viability of MCF-7 cells was found to be increased with AGEs treatment, illustrating proliferation of cancer cells. Wound healing assay also revealed increased proliferation and migration of cells in the presence of AGEs. Additionally, molecular docking analyses were performed to demonstrate interactions involved in the stabilization of HSA-quercetin complex. The binding affinities of quercetin were found to be (K _d = 10⁵ M ^-1) much higher compared with MG (K _d = 10² M ^-1). From this study, it is quite clear that quercetin reverses the effect of MG by sterically inhibiting the interaction between HSA and MG. Communicated by Ramaswamy H. Sarma.

Glucose-mediated protein glycation: Contribution of methanolic extract of Ceratonia siliqua L. in protection and in vitro potential inhibition of acetylcholinesterase

Chronic hyperglycemia presents the major etiology of diabetes mellitus and related complications mainly Alzheimer's disease, via the protein glycation and toxic products generated. In the current study, we investigated the eventual protective effect of the methanolic extract of Ceratonia siliqua L. (CsME) against glucose-mediated glycation in serum bovine albumin. The multi-stage glycation markers, namely fructosamines and advanced glycation end products (AGEs) levels were monitored along with measurement of thiol groups; moreover, the in vitro acetylcholinesterase (AChE) inhibition potential was carried out. HPLC was also assessed. Rutin was the main phenolic compound found in CsME. CsME showed a good capacity to inhibit AGEs, fructosamines and protected thiol groups against glycation. CsME exhibited a great AChE inhibition activity. In the present study, CsME prevented glucose-induced protein glycation, it also exhibited a good inhibition of AChE, suggesting its DM complications such as memory troubles related to AD. PRACTICAL APPLICATIONS: Neurodegenerative disorders ranging from memory troubles to Alzheimer's disease present the most diabetes mellitus complications and mainly attributed to protein glycation process. Currently, there is a strong trend to search for efficient natural sources of glycation and acetylcholinesterase inhibitors to replace the synthetic ones, whose secondary effects were shown. The present article tries to justify scientifically the wide use of Ceratonia siliqua L. in Moroccan folk medicine, demonstrating that the methanolic extract of leaves from this species presents a promising source of new natural compounds inhibiting acetylcholinesterase and acting in vitro against glycation generated compounds. Furthermore, for the first time, Rutin was the main phenolic compound found in this extract, these encouraging results should be coupled with further studies to integrate it in pharmaceutical formulations. As such, this paper should be of interest to a broad readership, including those interested in Biochemistry, Phytochemistry, pharmacology, and neurosciences.

Insights into the Mechanism of Quercetin against BSA-Fructose Glycation by Spectroscopy and High-Resolution Mass Spectrometry: Effect on Physicochemical Properties

Quercetin has been reported to suppress protein glycation or the formation of advanced glycation end-products (AGEs), but the inhibition mechanism related to protein structure and glycation sites and the influence on physicochemical properties remain unclear. The aim of the current research was to investigate the mechanism of quercetin against glycation with BSA-fructose as model by spectroscopic and spectrometric techniques. Changes in physicochemical properties were evaluated by antioxidant activity and emulsifying properties. The results indicated that quercetin dose-dependently inhibited the glycation of BSA by attenuating the alteration of conformational structure and microenvironment induced by glycation. It could also suppress the cross-linking or aggregation of glycated BSA, which reflected in the decreased molecular weight determined by SDS-PAGE and MALDI-TOF. Nanoliquid chromatography coupled to Q-Exactive tandem mass spectrometry analysis revealed the mapping of 20, 23, 19, and 19 glycation sites in glycated BSA with 0, 0.5, 1.5, and 3.0 mM quercetin, respectively. Quercetin changed the glycation sites of BSA, but it could not reduce the number greatly. In addition, quercetin reduced the antioxidant ability and increased the emulsifying properties of BSA, while negligible efficiency was observed on the antioxidant activity and emulsifying activity index of glycated BSA.

Phenolics from Eugenia jambolana seeds with advanced glycation endproduct formation and alpha-glucosidase inhibitory activities

Published data suggest that dietary-derived phenolics exert beneficial effects against hyperglycemia-mediated diseases, such as diabetes, through inhibiting the formation of advanced glycation endproducts (AGEs) and carbohydrate hydrolyzing enzyme activities. In the course of our investigation on the edible berry, Eugenia jambolana (known as Jamun), 21 phenolics (1-21) were isolated and identified from its seeds. Among these, one compound (1) is new and eleven compounds (3, 6, 9-13, 17, and 19-21) are being reported from E. jambolana for the first time. The anti-AGE activities of thirteen pure isolates (2-7, 9-12, 14, 15, and 20) were either comparable or superior to the synthetic anti-glycation agent, aminoguanidine, at three test concentrations (20, 50, and 100 μM) in the BSA-fructose assay. Most of these phenolics with anti-AGE activity exhibited potent free radical scavenging activity in the DPPH assay, and attenuated intracellular levels of LPS-induced reactive oxygen species in RAW264.7 macrophage. In addition, compounds 2-6, and 14 showed superior α-glucosidase inhibitory activity (IC50 = 5.0-21.2 μM) compared to the clinical α-glucosidase inhibitor, acarbose (IC50 = 289.9 μM). This is the first report of the anti-AGE effects of compounds 2-6 and 9-12, and α-glucosidase inhibitory activities of compounds 3-6, 9, 11 and 14. The current study supports the role of phenolics in the antidiabetic properties attributed to this edible berry, and warrants further animal studies to evaluate their potential as dietary agents for the prevention and/or therapy of hyperglycemia-mediated diseases.

Inhibition of Methylglyoxal-Induced Histone H1 Nε-Carboxymethyllysine Formation by (+)-Catechin

Reactive dicarbonyl species (RCS) such as methylglyoxal (MGO) and glyoxal (GO) are common intermediates in protein damage, leading to the formation of advanced glycation end products (AGEs) through nonenzymatic glycation. (+)-Catechin, a natural plant extract from tea, has been evaluated for its ability in trapping GO and MGO. However, (+)-catechin is also reported to have both antioxidant ability and pro-oxidant properties. Until now, whether (+)-catechin can inhibit the formation of nonenzymatic glycation and the mechanism of the inhibition in nucleoprotein nonenzymatic glycation is still unclear. In the present study, histone H1 and MGO were used to establish an in vitro (100 mM phosphate buffer solution (PBS), pH 7.4, 37 °C) protein glycation model to study the trapping ability of (+)-catechin. Our data show that MGO caused dose-dependent protein damage, and the content of MGO-induced Schiff base formation was inhibited by (+)-catechin when the molecular ratio of catechin:MGO was 1:6. The formation of N^ε-carboxymethyllysine (CML) was reduced significantly when the ratio of (+)-catechin and MGO was 1:1, which was similar to the inhibition effect of aminoguanidine (AG). The formation of CML under in vitro conditions can be inhibited by low concentration (12.5-100 μM) of (+)-catechin but not with high concentration (200-800 μM) of (+)-catechin. The reason is that the high concentration of (+)-catechin did not inhibit CML formations due to H₂O₂ produced by (+)-catechin. In the presence of catalase, catechin can inhibit MGO-induced CML formation. In conclusion, the trapping ability of (+)-catechin may be more effective at the early stage of nonenzymatic glycation. However, a high concentration (200-800 μM) of (+)-catechin may not inhibit the formation of CML because it induced the increase of H₂O₂ formation.

Evaluation of Polyphenol Anthocyanin-Enriched Extracts of Blackberry, Black Raspberry, Blueberry, Cranberry, Red Raspberry, and Strawberry for Free Radical Scavenging, Reactive Carbonyl Species Trapping, Anti-Glycation, Anti-β-Amyloid Aggregation, and Microglial Neuroprotective Effects

Glycation is associated with several neurodegenerative disorders, including Alzheimer’s disease (AD), where it potentiates the aggregation and toxicity of proteins such as β-amyloid (Aβ). Published studies support the anti-glycation and neuroprotective effects of several polyphenol-rich fruits, including berries, which are rich in anthocyanins. Herein, blackberry, black raspberry, blueberry, cranberry, red raspberry, and strawberry extracts were evaluated for: (1) total phenolic and anthocyanins contents, (2) free radical (DPPH) scavenging and reactive carbonyl species (methylglyoxal; MGO) trapping, (3) anti-glycation (using BSA-fructose and BSA-MGO models), (4) anti-Aβ aggregation (using thermal- and MGO-induced fibrillation models), and, (5) murine microglia (BV-2) neuroprotective properties. Berry crude extracts (CE) were fractionated to yield anthocyanins-free (ACF) and anthocyanins-enriched (ACE) extracts. The berry ACEs (at 100 μg/mL) showed superior free radical scavenging, reactive carbonyl species trapping, and anti-glycation effects compared to their respective ACFs. The berry ACEs (at 100 μg/mL) inhibited both thermal- and MGO-induced Aβ fibrillation. In addition, the berry ACEs (at 20 μg/mL) reduced H₂O₂-induced reactive oxygen species production, and lipopolysaccharide-induced nitric oxide species in BV-2 microglia as well as decreased H₂O₂-induced cytotoxicity and caspase-3/7 activity in BV-2 microglia. The free radical scavenging, reactive carbonyl trapping, anti-glycation, anti-Aβ fibrillation, and microglial neuroprotective effects of these berry extracts warrant further in vivo studies to evaluate their potential neuroprotective effects against AD.

Inhibition of advanced glycation endproducts during fish sausage preparation by transglutaminase and chitosan oligosaccharides induced enzymatic glycosylation

A non-antioxidative method in which glycosylation induced by transglutaminase “replaced” glycation to inhibit the formation of AGEs in real foods.

Anti-Diabetic Effects of Phenolic Extract from Rambutan Peels (Nephelium lappaceum) in High-Fat Diet and Streptozotocin-Induced Diabetic Mice

Recent studies have shown that rambutan peel phenolic (RPP) extract demonstrate high antioxidant and antiglycation activities in vitro and in vivo. This study further evaluated the anti-diabetic activity of RPP in a mouse model of Type II diabetes induced by streptozotocin combined with high-fat diet. Results showed that RPP increased the body weight and reduced the fasting blood glucose level of the diabetic mice. RPP significantly reduced the serum levels of total cholesterol, triglyceride, creatinine, and glycated serum protein in diabetic mice in a dose-dependent manner. Glycogen content in mice liver was recovered by RPP, which further increased the activity of superoxide dismutase and glutathione peroxidase and reduced lipid peroxidation in diabetic mice. Histological analysis showed that RPP effectively protected the tissue structure of the liver, kidney, and pancreas. In addition, RPP decreased the mesangial index and inhibited the expression of TGF-β in the kidney of diabetic mice.

Isolation, Identification, and Biological Evaluation of Phenolic Compounds from a Traditional North American Confectionery, Maple Sugar

Maple sap, collected from the sugar maple (Acer saccharum) tree, is boiled to produce the popular plant-derived sweetener, maple syrup, which can then be further evaporated to yield a traditional North American confectionery, maple sugar. Although maple sap and maple syrup have been previously studied, the phytochemical constituents of maple sugar are unknown. Herein, 30 phenolic compounds, 1-30, primarily lignans, were isolated and identified (by HRESIMS and NMR) from maple sugar. The isolates included the phenylpropanoid-based lignan tetramers (erythro,erythro)-4″,4‴-dihydroxy-3,3',3″,3‴,5,5'-hexamethoxy-7,9';7',9-diepoxy-4,8″;4',8‴-bisoxy-8,8'-dineolignan-7″,7‴,9″,9‴-tetraol, 29, and (threo,erythro)-4″,4‴-dihydroxy-3,3',3″,3‴,5,5'-hexamethoxy-7,9';7',9-diepoxy-4,8″;4',8‴-bisoxy-8,8'-dineolignan-7″,7‴,9″,9‴-tetraol, 30, neither of which have been identified from maple sap or maple syrup before. Twenty of the isolates (selected on the basis of sample quantity available) were evaluated for their potential biological effects against lipopolysaccharide-induced inflammation in BV-2 microglia in vitro and juglone-induced oxidative stress in Caenorhabditis elegans in vivo. The current study increases scientific knowledge of possible bioactive compounds present in maple-derived foods including maple sugar.