Inhibitory effect of gallic acid on advanced glycation end products induced up-regulation of inflammatory cytokines and matrix proteins in H9C2 (2-1) cells

Chitosan-gallic acid conjugate with enhanced functional properties and synergistic wound healing effect

Chitosan-gallic acid conjugates were synthesized by carbodiimide method and characterized by physicochemical methods (UV-vis, FTIR, 1H NMR, TGA). The FTIR and NMR assays confirmed that the chemical interaction occurred solely due to the formation of an amide bond. It was established that by varying the ratio of the components during synthesis it is possible to obtain conjugates with desired conjugation ratio, grafting efficiency and gallic acid content up to 8.09 ± 1.72 %, 70.51 ± 9.45 % and 79.9 ± 2.4 μg gallic acid/mg chitosan, respectively. Chitosan-gallic acid conjugate with a 5 % conjugation ratio demonstrated excellent antioxidant properties: the IC50 value for ABTS radical scavenging activity was 0.0073 ± 0.0001 mg/mL. In vitro tests showed that conjugation of chitosan with gallic acid provided the antiglycemic activity of the material and its good biocompatibility. A low level of cytotoxicity was recorded in the HaCaT cell line model (IC50 was 1030.4 μg/mL). The received eco-friendly chitosan-gallic acid conjugate effectively inhibited the growth of thermophilic spore-forming bacteria G. thermodenitrificans and the resistant to classical antibiotics strain A. palidus. The results of an in vivo comparative analysis showed that chitosan-gallic acid conjugate had excellent wound healing properties due to the synergism of the polysaccharide and the natural antioxidant.

Gallic acid: a dietary metabolite's therapeutic potential in the management of atherosclerotic cardiovascular disease

Atherosclerotic cardiovascular disease (ASCVD) causes significant morbidity and mortality globally. Most of the chemicals specifically target certain pathways and minimally impact other diseases associated with ASCVD. Moreover, interactions of these drugs can cause toxic reactions. Consequently, the exploration of multi-targeted and safe medications for treating and preventing ASCVD has become an increasingly popular trend. Gallic acid (GA), a natural secondary metabolite found in various fruits, plants, and nuts, has demonstrated potentials in preventing and treating ASCVD, in addition to its known antioxidant and anti-inflammatory effects. It alleviates the entire process of atherosclerosis (AS) by reducing oxidative stress, improving endothelial dysfunction, and inhibiting platelet activation and aggregation. Additionally, GA can treat ASCVD-related diseases, such as coronary heart disease (CHD) and cerebral ischemia. However, the pharmacological actions of GA in the prevention and treatment of ASCVD have not been comprehensively reviewed, which limits its clinical development. This review primarily summarizes the in vitro and in vivo pharmacological actions of GA on the related risk factors of ASCVD, AS, and ASCVD. Additionally, it provides a comprehensive overview of the toxicity, extraction, synthesis, pharmacokinetics, and pharmaceutics of GA,aimed to enhance understanding of its clinical applications and further research and development.

In Vitro and Molecular Docking Studies of Antiglycation Potential of Phenolic Compounds in Date Palm (Phoenix dactylifera L.) Fruit: Exploring Local Varieties in the Food Industry

The Moroccan date-growing sector is rich in a wide diversity of varieties but faces major challenges, notably the undervaluation of certain varieties intended mainly for animal feed. In this study, our objective was to evaluate the antiglycation activity of four date varieties, including three low-market-value varieties and one high-market-value variety, harvested during two seasons (2021 and 2022). In addition, to improve our knowledge of the antiglycation potential, molecular docking analyses were carried out. The results of the antiglycation activity of the date extracts showed strong activity, particularly for the ‘Khalt Khal’ variety, which showed a 50% inhibition concentration (IC50) of 1.83 mg/mL and 2 mg/mL in 2021 and 2022, respectively. In addition, the molecular docking analysis also showed the possible link between the bioactive compounds identified and their mechanisms of action. Our findings suggest new evidence for the antiglycation properties of the bioactive compounds present in dates. These results suggest the use of these varieties as a source of bioactive molecules or as a food additive. This could make it possible to create medicines or food products with a high commercial value using dates, which could help to treat the complications associated with glycation.

Ethnobotanical Uses and Pharmacological Activities of Moroccan Ephedra Species

Ephedra species are among the most popular herbs used in traditional medicine for a long time. The ancient Chinese medical book "Treatise on Febrile Diseases" refers to the classic traditional Chinese medicine prescription Ge Gen decoction, which consists of seven herbs, including an Ephedra species. Ephedra species are utilized all over the world to treat symptoms of the common cold and coughs, and to combat major human diseases, such as asthma, cancers, diabetes, cardiovascular and digestive disorders, and microbial infections. This study aimed at identifying specific Ephedra species used traditionally in Morocco for therapeutic purposes. The plant parts, their preparation process, and the treated pathologies were identified and analyzed. The results revealed five ethnobotanically important species of Ephedra: Ephedra alata Decne, Ephedra altissima Desf., Ephedra distachya L., Ephedra fragilis Desf., and Ephedra nebrodensis Tineo. These species are used traditionally in Morocco for treating people with diabetes, cancer, rheumatism, cold and asthma, hypertension, influenza virus infection, and respiratory ailments. In addition, they are occasionally used as calefacient agents, to regulate weight, or for capillary care. Few studies have underlined the antibacterial and antioxidant activities of some of these Moroccan Ephedra species, but little information is available regarding the natural products at the origin of the bioactivities. Further phytochemical investigations and clinical data are encouraged to better support the use of these plants.

Anti-Glucotoxicity Effect of Phytoconstituents via Inhibiting MGO-AGEs Formation and Breaking MGO-AGEs

The therapeutic benefits of phytochemicals in the treatment of various illnesses and disorders are well documented. They show significant promise for the discovery and creation of novel medications for treating a variety of human diseases. Numerous phytoconstituents have shown antibiotic, antioxidant, and wound-healing effects in the conventional system. Traditional medicines based on alkaloids, phenolics, tannins, saponins, terpenes, steroids, flavonoids, glycosides, and phytosterols have been in use for a long time and are crucial as alternative treatments. These phytochemical elements are crucial for scavenging free radicals, capturing reactive carbonyl species, changing protein glycation sites, inactivating carbohydrate hydrolases, fighting pathological conditions, and accelerating the healing of wounds. In this review, 221 research papers have been reviewed. This research sought to provide an update on the types and methods of formation of methylglyoxal-advanced glycation end products (MGO-AGEs) and molecular pathways induced by AGEs during the progression of the chronic complications of diabetes and associated diseases as well as to discuss the role of phytoconstituents in MGO scavenging and AGEs breaking. The development and commercialization of functional foods using these natural compounds can provide potential health benefits.

Receptor for Advanced Glycation End Product, Organ Crosstalk, and Pathomechanism Targets for Comprehensive Molecular Therapeutics in Diabetic Ischemic Stroke

Diabetes mellitus, a well-established risk factor for stroke, is related to higher mortality and poorer outcomes following the stroke event. Advanced glycation end products(AGEs), their receptors RAGEs, other ligands, and several other processes contribute to the cerebrovascular pathomechanism interaction in the diabetes-ischemic stroke combination. Critical reappraisal of molecular targets and therapeutic agents to mitigate them is required to identify key elements for therapeutic interventions that may improve patient outcomes. This scoping review maps evidence on the key roles of AGEs, RAGEs, other ligands such as Leukotriene B4 (LTB4), High-mobility group box 1 (HMGB1) nuclear protein, brain-kidney-muscle crosstalk, alternate pathomechanisms in neurodegeneration, and cognitive decline related to diabetic ischemic stroke. RAGE, HMGB1, nitric oxide, and polyamine mechanisms are important therapeutic targets, inflicting common consequences of neuroinflammation and oxidative stress. Experimental findings on a number of existing-emerging therapeutic agents and natural compounds against key targets are promising. The lack of large clinical trials with adequate follow-up periods is a gap that requires addressing to validate the emerging therapeutic agents. Five therapeutic components, which include agents to mitigate the AGE-RAGE axis, improved biomarkers for risk stratification, better renal dysfunction management, adjunctive anti-inflammatory-antioxidant therapies, and innovative neuromuscular stimulation for rehabilitation, are identified. A comprehensive therapeutic strategy that features all the identified components is needed for outcome improvement in diabetic stroke patients.

Impact of Drying Processes on Phenolics and In Vitro Health-Related Activities of Indigenous Plants in Thailand

Thailand has vast areas of tropical forests with many indigenous plants, but limited information is available on their phytochemical profile and in vitro inhibitions of enzymatic and nonenzymatic reactions. This study investigated phenolic profiles using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS), antioxidant activities, and in vitro inhibitory activities of 10 indigenous plants on key enzymes related to obesity (lipase), diabetes (α-amylase and α-glucosidase), and Alzheimer's disease (cholinesterases and β-secretase). The nonenzymatic anti-glycation reaction was also investigated. The 10 indigenous plants were Albizia lebbeck (L.) Benth, Alpinia malaccensis (Burm.) Roscoe, Careya arborea Roxb., Diplazium esculentum (Retz.) Swartz, Kaempferia roscoeana Wall., Millettia brandisiana Kurz., Momordica charantia, Phyllanthusemblica L., Zingiber cassumunar Roxb, and Zingiber citriodorum J. Mood & T. Theleide. Preparations were made by either freeze-drying or oven-drying processes. Results suggested that the drying processes had a minor impact on in vitro inhibitions of enzymatic and nonenzymatic reactions (<4-fold difference). P. emblica was the most potent antioxidant provider with high anti-glycation activity (>80% inhibition using the extract concentration of ≤6 mg/mL), while D. esculentum effectively inhibited β-secretase activity (>80% inhibition using the extract concentration of 10 mg/mL). C. arborea exhibited the highest inhibitory activities against lipase (47-51% inhibition using the extract concentration of 1 mg/mL) and cholinesterases (>60% inhibition using the extract concentration of 2 mg/mL), while Mi. brandisiana dominantly provided α-amylase and α-glucosidase inhibitors (>80% inhibition using the extract concentration of ≤2 mg/mL). Information obtained from this research may support usage of the oven-drying method due to its lower cost and easier preparation step for these studied plant species and plant parts. Furthermore, the information on in vitro inhibitions of enzymatic and nonenzymatic reactions could be used as fundamental knowledge for further investigations into other biological activities such as cell culture or in vivo experiments of these health-beneficial plants.

Inhibition of Advanced Glycation End Product Formation in Rat Tail Tendons by Polydatin and p-Coumaric acid: an In Vitro Study

Advanced glycation end products (AGEs) formed through non-enzymatic glycosylation between a protein and sugar molecule are highly harmful to the human body. In hyperglycemic patients, AGE formation is more due to high glucose circulating in the blood, causing inter and intra molecular cross-linking of collagen leading to reduction of collagen elasticity. This cross-linked collagen develops resistance to matrix metalloproteinases leading to impaired collagen turnover. The aim of this work is to determine the anti-glycation effects of polydatin and p-coumaric acid in preventing collagen cross-linking by incubating rat tail tendons (RTTs) as collagen source in high glucose concentration (50 mM) for a week. The RTTs were then characterized for tensile strength, cross-linking efficiency, circular dichroism spectrometry, collagen, glucose, and aldehyde contents. Electrophoresis was carried out to evaluate the level of cross-linking in collagen and the results confirmed the ability of the drugs in preventing complex intermolecular cross-link formation induced by non-enzymatic glycosylation. CD data showed alteration in the secondary structure of collagen where AGE formation had occurred. More collagen was extracted by pepsin from RTTs treated with glucose alone (6.88 mg/10 mg tendon) when compared with drug-treated groups (4.25, 2.56 mg/10 mg tendon for polydatin and p-coumaric acid, respectively). Tensile strength (20.66% and 18.95%), cross-linking percentage (32.5% and 29.84%), and glucose content (2.3 and 1.8 mg/100 mg) of drug-treated groups were similar to the positive control (19.07%, 30.13%, and 2.61 mg/100 mg) thus proving the anti-glycation potential of the drugs. Hence, both polydatin and p-coumaric acid could play a pivotal role in preventing AGE formation.

Novel advances in inhibiting advanced glycation end product formation using natural compounds

Advanced glycation end products (AGEs) are a group of complex compounds generated by nonenzymatic interactions between proteins and reducing sugars or lipids. AGEs accumulate in vivo and activate various signaling pathways closely related to the occurrence of various chronic metabolic diseases. In this paper, we describe the process through which AGEs are formed, the classification of AGEs, and biological effects of AGEs on human health. Most importantly, we review recent progress in natural compound-based AGE formation inhibitors. Major classes of natural inhibitors, including polyphenols, polysaccharides, terpenoids, vitamins and alkaloids, have been described. Their mechanisms of action have been summarized as scavenging free radicals, chelating metal ions, capturing active carbonyl compounds, protecting protein glycation sites, and lowering blood glucose levels. Although these natural compounds have good antiglycation activity, to date, they are not widely used in the clinic, likely because of their low content levels. However, these natural compounds and their molecular frameworks will play a valuable role in inspiring drug discovery.

Antioxidant and Antiglycation Effects of Polyphenol Compounds Extracted from Hazelnut Skin on Advanced Glycation End-Products (AGEs) Formation

The advanced glycation end-products (AGEs) arise from non-enzymatic reactions of sugar with protein side chains, some of which are oxido-reductive in nature. Enhanced production of AGEs plays an important role in the pathogenesis of diabetic complications as well as in natural aging, renal failure, oxidative stress, and chronic inflammation. The aim of this work is to study antiglycation effects of polyphenol compounds extracted by hazelnut skin that represents an example of polyphenols-rich food industry by-product, on AGEs formation. AGEs derived from incubation of bovine serum albumin (BSA) and methylglyoxal (MGO) were characterized by fluorescence. The phenolics identification and total polyphenol content in hazelnut skin extracts were analyzed by HPLC-MS and the Folin–Ciocalteu method, respectively. Antioxidant efficacy was evaluated by monitoring total antioxidant activity to assess the ABTS radical scavenging activity of samples by TEAC assay and oxygen radical absorbance capacity (ORAC) assay, expressed as millimoles of Trolox equivalents per gram of sample. Data here presented suggest that phenolic compounds in hazelnut skin have an inhibitory effect on the BSA-AGEs model in vitro, and this effect is concentration-dependent. The putative role of the hazelnut skin antioxidative properties for hindering AGEs formation is also discussed. Because of AGEs contribution to the pathogenesis of several chronic diseases, foods enriched, or supplements containing natural bioactive molecules able to inhibit their production could be an interesting new strategy for supporting therapeutic approaches with a positive effect on human health.

Chemical, biological and molecular modelling analyses to probe into the pharmacological potential of Antidesma madagascariense Lam.: A multifunctional agent for developing novel therapeutic formulations

Antidesma madagascariense Lam. (AM), an indigenous medicinal plant to the Mascarene Islands, is used for the treatment of several diseases. We endeavoured to validate its use via evaluating the kinetics of inhibition of crude aqueous extract (CAE) and crude methanol extract (CME) of AM against key metabolic enzymes (pancreatic lipase, cholesterol esterase [CEase], acetylcholinesterase [AChE], and urease). In vitro antiglycation, antioxidant, cytotoxicity using iCELLigence real time cell analysis system and WST-1 methods, were used. LC-ESI-MS/MS was employed to determine the phenolic composition of the extracts and interaction of selected compounds to the studied enzymes was determined using in silico docking. AChE was inhibited by the CME of AM and CEase by the CAE. Both extracts were active inhibitors of urease and pancreatic lipase. Hyperoside (271.97 μg/g extract), present in large amount in the CME, docked to the enzymatic pocket of urease and CEase. The extracts showed competitive and mixed inhibition of urease and pancreatic lipase, respectively. The antioxidant capacity of the CME (6.61 μg GAE/mg crude extract) was higher compared to CAE (2.20 μg GAE/mg crude extract). AM extracts were significantly (p <  0.05) less potent than aminoguanidine in preventing advanced glycation end products formation. Toxicological screening revealed that both extracts were non-toxic on HEK-293 cells. AM crude extracts at concentrations ranging from 78 to 312 μg/ml did not cause a visible change in cell morphology compared to control. This study supports the safe use of AM as a biomedicine for the management and/or treatment of common non-communicable diseases.

Diet with high content of advanced glycation end products induces systemic inflammation and weight gain in experimental mice: Protective role of curcumin and gallic acid

The present study was aimed to investigate the effect of diet derived AGEs (dAGEs) on the circulatory levels of pro-inflammatory cytokines, chemokines and to evaluate the protective efficacy of natural anti-oxidants curcumin (CU) and gallic acid (GA) respectively against the dAGEs-induced systemic inflammation in experimental Swiss albino mice. The experimental mice were fed with dAGEs in the presence and absence of CU and GA for 6 months. The levels of 40 circulatory pro-inflammatory cytokines and chemokines were evaluated using Proteome-Cytokine Array kit. In addition, serum levels of N-ɛCML, CRP and HbA1c were estimated by ELISA method. Among the sixteen pro- and anti-inflammatory cytokines analysed, five (IL-16, IL-1α, ICAM, TIMP-1 and C5a) were found to be highly expressed (3.5-fold) and eleven cytokines were moderately expressed (2-fold) in dAGEs fed mice. In case of chemokines, three (BLC, SDF-1 and MCP-1) were found to be highly expressed (4-fold) and ten showed moderate expression (2-fold) as compared with basal diet fed mice. Interestingly, CU or GA co-treatment normalized the levels of circulatory pro- and anti-inflammatory cytokines, chemokines, N-ɛCML, CRP and HbA1c levels. Together, the present study suggests that dAGEs are positively associated with the development of systemic inflammation in experimental mice.

Phenolic compounds isolated from fermented blueberry juice decrease hepatocellular glucose output and enhance muscle glucose uptake in cultured murine and human cells

Background

We recently reported that blueberry juice fermented (FJ) with Serratia vaccinii bacterium has antidiabetic activities both in vivo and in vitro. The purpose of this project was to elucidate the effect of FJ on glucose homeostasis in liver and skeletal muscle cells and to identify active fractions/compounds responsible for this effect.

Methods

FJ was fractionated using standard chromatography procedures. Hepatic (H4IIE, HepG2) and skeletal muscle cells (C2C12) were treated with maximum non-toxic concentrations of FJ, fractions and isolated compounds thereof. Glucose-6-phosphatase (G6Pase) activity was measured using glucose oxidase method. To measure glucose uptake and glycogen synthase (GS) activity, radioactive assays were used.

Results

Fractionation of FJ yielded seven fractions. FJ and its phenolic fractions F2, F3-1 and F3-2 respectively inhibited G-6Pase by 31, 45, 51 and 26%; activated GS by 2.3-, 2.3-, 2.2- and 2-fold; and stimulated glucose uptake by 19, 25, 18 and 15%, as compared to DMSO vehicle control. Subfractionation of the active fractions yielded 4 compounds (catechol, chlorogenic, gallic and protocatechuic acid). Catechol, yielding the greatest bioactivity in G6Pase and glucose uptake assays, decreased G6Pase activity by 54%, increased GS by 2-fold and stimulated glucose uptake by 44% at 45.5 μM.

Conclusions

This study identifies novel potential antidiabetic compounds that can help standardize FJ.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-017-1650-2) contains supplementary material, which is available to authorized users.

Alpha-mangostin attenuation of hyperglycemia-induced ocular hypoperfusion and blood retinal barrier leakage in the early stage of type 2 diabetes rats

The present study examined effects of alpha-mangostin (α-MG) supplementation on the retinal microvasculature, including ocular blood flow (OBF) and blood-retinal barrier (BRB) permeability in a type 2 diabetic animal model. Male Sprague-Dawley rats were divided into four groups: normal control and diabetes with or without α-MG supplementation. Alpha-mangostin (200 mg/Kg/day) was administered by gavage feeding for 8 weeks. The effects of α-MG on biochemical and physiological parameters including mean arterial pressure (MAP), OBF, and BRB leakage were investigated. Additionally, levels of retinal malondialdehyde (MDA), advance glycation end products (AGEs), receptor of advance glycation end products (RAGE), tumour necrosis factor alpha (TNF-α), and vascular endothelial growth factor (VEGF) were evaluated. The elevated blood glucose, HbA1c, cholesterol, triglyceride, serum insulin, and HOMA-IR were observed in DM2 rats. Moreover, DM2 rats had significantly decreased OBF but statistically increased MAP and leakage of the BRB. The α-MG-treated DM2 rats showed significantly lower levels of retinal MDA, AGEs, RAGE, TNF-α, and VEGF than the untreated group. Interestingly, α-MG supplementation significantly increased OBF while it decreased MAP and leakage of BRB. In conclusion, α-MG supplementation could restore OBF and improve the BRB integrity, indicating its properties closely associated with antihyperglycemic, antioxidant, anti-inflammatory, and antiglycation activities.

Gallic Acid Decreases Inflammatory Cytokine Secretion Through Histone Acetyltransferase/Histone Deacetylase Regulation in High Glucose-Induced Human Monocytes

Hyperglycemia contributes to diabetes and several diabetes-related complications. Gallic acid is a polyhydroxy phenolic compound found in various natural products. In this study, we investigated the effects and mechanism of gallic acid on proinflammatory cytokine secretion in high glucose-induced human monocytes (THP-1 cells). THP-1 cells were cultured under normoglycemic or hyperglycemic conditions, in the absence or presence of gallic acid. Hyperglycemic conditions significantly induced histone acetylation, nuclear factor-κB (NF-κB) activation, and proinflammatory cytokine release from THP-1 cells, whereas gallic acid suppressed NF-κB activity and cytokine release. It also significantly reduced CREB-binding protein/p300 (CBP/p300, a NF-κB coactivator) gene expression, acetylation levels, and CBP/p300 histone acetyltransferase (HAT) activity. In addition, histone deacetylase 2 (HDAC2) expression was significantly induced. These results suggest that gallic acid inhibits hyperglycemic-induced cytokine production in monocytes through epigenetic changes involving NF-κB. Therefore, gallic acid may have potential for the treatment and prevention of diabetes and its complications.

Protective activity of gallic acid against glyoxal -induced renal fibrosis in experimental rats

This study was designed to evaluate the protective activity of gallic acid (GA) against glyoxal (GO) an advanced glycation intermediate-induced renal fibrosis in experimental rats. Glyoxal (i.p) at a dose of 15 mg/Kg body weight/day for 4 weeks induces renal fibrosis. GA was administered orally (100 mg/Kg body weight/day) along with GO for 4 weeks. The anti-fibrotic activity of GA was analyzed by measuring the collagen synthesis and deposition in renal tissues using mRNA expression analysis and Masson trichrome staining (MTS), respectively. The nephroprotective potential of GA was assessed by quantifying the markers of kidney damage such as serum blood-urea-nitrogen (BUN), creatinine (CR) and alkaline phosphatase (AP). Moreover, basement membrane damage in renal tissues was analysed by periodic acid Schiff’s (PAS) staining. GA co-treatment markedly suppressed the GO-induced elevation in mRNA expression of collagenIand III, MMP-2, MMP-9 and NOX (p < 0.05, respectively) genes as compared with GO alone infused rats. In addition, GA co-treatment significantly attenuated the GO -induced elevation in serum markers such as BUN, CR and AP levels (p < 0.05, respectively). Furthermore, GA co-treatment restored back the decreased renal super oxide dismutase (SOD) activity (p < 0.05) thereby assuage the reactive oxygen species (ROS) generation, and maintained the normal architecture of glomerulus. The present study clearly indicates that GO -induces renal fibrosis by enhancing GO/receptor of advanced glycation end product (RAGE) induced ROS generation and GA effectively counteracted GO-induced renal fibrosis by its ROS quenching and anti-glycation activity.

Role of advanced glycation end products in cellular signaling

Improvements in health care and lifestyle have led to an elevated lifespan and increased focus on age-associated diseases, such as neurodegeneration, cardiovascular disease, frailty and arteriosclerosis. In all these chronic diseases protein, lipid or nucleic acid modifications are involved, including cross-linked and non-degradable aggregates, such as advanced glycation end products (AGEs). Formation of endogenous or uptake of dietary AGEs can lead to further protein modifications and activation of several inflammatory signaling pathways. This review will give an overview of the most prominent AGE-mediated signaling cascades, AGE receptor interactions, prevention of AGE formation and the impact of AGEs during pathophysiological processes.