Glycation Of Bovine Serum Albumin Research Articles

Alpha amylase, alpha glucosidase and glycation inhibitory activity of Moringa oleifera extracts

Moringa oleifera is a source of food, shelter and traditional medicine for many people in developing countries. It is an exceptional source of vitamins, minerals, amino acids, lipids, carotenoids, flavonoids, sterols and phenolics. Owing to its diverse nutritional and phytochemical composition, it is widely consumed and used in therapeutics. In this study, the aqueous, methanol, hexane and ethyl acetate extracts of M. oleifera seeds, leaves and roots were assessed for in vitro α-amylase, α-glucosidase and glucose-induced bovine serum albumin glycation inhibition. Findings indicate that methanol and hexane leaves extracts demonstrated highest α-amylase inhibitory activity (IC50 = 8.217 and 9.397 mg/ml respectively), though the activities were lower than that of acarbose (IC50 = 0.036 mg/ml). In contrast, hexane root extract exhibited optimal α-glucosidase inhibition and antiglycation effect (IC50 = 0.382 and 0.772 mg/ml, respectively). The extract activity was higher than that of acarbose (IC50 = 0.884 mg/ml), but lesser than rutin (IC50 = 0.199 mg/ml); which were the control for α-glucosidase inhibition and antiglycation studies respectively. In conclusion, suggesting its potentials in regulating postprandial blood glucose, and attenuating the production/accumulation of advanced glycation end product. Thus, M. oleifera extracts exhibited promising antidiabetic activity.

Inhibition of α-amylase, α-glucosidase and pancreatic lipase by phenolic compounds of Rumex maderensis (Madeira sorrel). Influence of simulated gastrointestinal digestion on hyperglycaemia-related damage linked with aldose reductase activity and protein glycation

In this work, we report the in vitro inhibitory potential of Rumex maderensis methanolic extracts (leaves, flowers, and stems) towards key digestive enzymes linked to type-2 diabetes and obesity (α-amylase, α-glucosidase, pancreatic lipase). The inhibitory activity towards aldose reductase and glycation of bovine serum albumin (BSA) is also reported; in these latter assays, the effect of simulated digestion on the bioactivities was evaluated. The inhibitory activities of R. maderensis extracts were statistically compared with the inhibition produced by reference compounds for each assay. The analysed extracts exhibited significant inhibitory activities, which decreased after the gastrointestinal digestion, possibly due to some loss of phenolics that took place during the digestion process. The most important results were observed during the BSA-glycation assay, in which the analysed extracts presented higher potency than a reference compound: aminoguanidine (AMG). This research is the first showing the potential anti-diabetic activity of R. maderensis.

Bis-coumarins; non-cytotoxic selective urease inhibitors and antiglycation agents

The current study is concerned with the identification of lead molecules based on the bis-coumarin scaffold having selective urease inhibitory and antiglycation activities. For that purpose, bis-coumarins (1-44) were synthesized and structurally characterized by different spectroscopic techniques. Eight derivatives 4, 8-10, 14, 17, 34, and 40 demonstrated urease inhibition in the range of IC50 = 4.4 ± 0.21–115.6 ± 2.13 μM, as compared to standard thiourea (IC50 = 21.3 ± 1.3 μM). Especially, compound 17 (IC50 = 4.4 ± 0.21 μM) was found to be five-fold more potent than the standard. Kinetic studies were also performed on compound 17 in order to identify the mechanism of inhibition. Kinetic studies revealed that compound 17 is a competitive inhibitor. Antiglycation activity was evaluated using glycation of bovine serum albumin by methylglyoxal in vitro. Compounds 2, 11-13, 16, 17, 19–22, 35, 37, and 42 showed good to moderate antiglycation activities with IC50 values of 333.63–919.72 μM, as compared to the standard rutin (IC50 = 294.46 ± 1.5 μM). Results of both assays showed that the compounds with urease inhibitory activity did not show any antiglycation potential, and vice versa. Only compound 17 showed dual inhibition potential. All compounds were also evaluated for cytotoxicity. Compounds 17, 19, and 37 showed a weak toxicity towards 3 T3 mouse fibroblast cell line. All other compounds were found to be non-cytotoxic. Urease inhibition is an approach to treat infections caused by ureolytic bacteria whereas inhibition of glycation of proteins is a strategy to avoid late diabetic complications. Therefore, these compounds may serve as leads for further research.

ANTIGLYCATION AND DPP-4 INGIBITION ACTIVITY OF NOVEL AZOLEAZINE-DERIVED COMPOUNDS

As a result of in vitro screening studies to search for the possible antidiabetic activity of a number of azoloazine derivatives, it was found that the compounds are capable of moderate inhibition of dipeptidylpeptidase-4 (DPP-4), inhibiting the enzyme activity by an average of 60 % at a concentration of 100 цМ, which is inferior actions of the reference drug vildagliptin (more than 99 % of the suppression of the activity of DPP-4 at the same concentration). The compounds are also able to significantly slow down glycation of bovine serum albumin (BSA) (the series leader - compound 1c suppresses the glycation reaction of BSA by 74 % at a concentration of 1 mM, compared to 58 % inhibition for the reference compound aminoguanidine). It was not possible to establish the ability of compounds to bind (chelate) Cu2+ in the ascorbic acid autooxidation test, except for compound 1k (it slowed down the reaction by 49 % at a concentration of 40 цМ, which is comparable in activity to the reference drug pioglitazone and is slightly more active than lipoic acid). The restriction for establishing the copper-binding activity of other members of the series is due to the high light absorption at the working wavelength of 265 nm and is not a criterion for excluding chelating properties. The results allow us to conclude that the class of compounds is a promising basis for the further development of tools with anti-glycating activity based on the structures of the representatives of the series.

Polyphenols of Myrica faya inhibit key enzymes linked to type II diabetes and obesity and formation of advanced glycation end-products (in vitro): Potential role in the prevention of diabetic complications

Myrica faya Aiton (fire tree, faya) is an underused species with a diverse flavonoid composition (anthocyanins, flavonols, ellagitannins) which can promote positive effects on human health. M. faya has been reported to possess high antioxidant activities, but its potential in the prevention of type II diabetes has not been evaluated so far. In the present study, eight M. faya samples from different areas of Madeira and Azores archipelagos (Portugal) were collected to determine their phytochemical profile and then tested for their in vitro anti-diabetic and antioxidant activities. The analyzed extracts showed strong inhibitory activities towards α -glucosidase, aldose reductase and glycation of bovine serum albumin (BSA) and moderate effects towards α-amylase and lipase (by comparison with reference compounds). Cyanidin-3-O-glucoside and ellagitannins were the main bioactive agents involved in the anti-diabetic effects of M. faya. Such results may provide important scientific evidence for further utilization of M. faya as dietary or nutraceutical products for the prevention and/or control of hyperglycaemia-associated complications.

Synthesis and Pharmacological Activity of Trifluoromethyl-Containing Imidazo[1,2-A]Benzimidazoles

A series of 2-(4-trifluoromethylphenyl)- and 2-trifluoromethyl-9-dialkylaminoalkylimidazo[1,2-a]benzimidazoles were synthesized for the first time by reacting 2-amino-1-dialkylaminoalkylbenzimidazoles and 2-bromo-1-[(4-trifluoromethyl)phenyl]ethanone or 1-bromo-3,3,3-trifluoroacetone and were tested for analgesic and antiplatelet activity, glycogen phosphorylase and dipeptidyl peptidase-4 inhibitory activity, and in vitro glycation of bovine serum albumin.

Spectroscopic and molecular modelling studies on glycation modified bovine serum albumin with cyanidin-3-O-glucoside

In this study, we report the glycation mediated effect of bovine serum albumin (BSA) on the molecular interaction mechanism of cyanidin-3-O-glucoside (C3G) by molecular modelling, Uv–visible spectroscopy, transmission electron microscopy (TEM), fluorescence spectroscopy, and circular dichroism spectroscopy studies. The structures of advanced glycation end-products (AGEs) modified BSA were modelled, energy minimized and analyzed for binding affinity by molecular docking studies using Autodock Vina. Glycation experiments are carried out using glucose and methylglyoxal to validate the molecular modelling results on the interaction of modified BSA with C3G. The modified structures were characterized by reduction in the binding pocket volume, surface, depth, hydrophobicity, and hydrogen bond donors/acceptors. Arg-194, Arg-196, Arg-198, Arg-217, Arg-409, Lys-114, Lys-116, Lys-204, Lys 221, and Lys-439 were found to be crucial in the context of glycation of BSA. TEM images represented the formation of unique globular aggregates in the event of glycation. Uv–visible spectroscopic studies showed the formation of new chromophores between 300 and 400 nm in the event of glycation. Fluorescence quenching was observed in a differential manner in the presence of C3G on glycation modified BSA. Circular dichroism studies suggested the loss of helical structure and formation of β-sheeted structure upon glycation, but subsequent C3G binding has resulted in the increase towards helical structure. Our findings suggested that drug binding affinity has been certainly impaired due to glycation and subsequent AGE modification. Arg-p modification has more austere impact on the structure and would affect the binding properties. We conclude that C3G had differential modulation of binding properties on glycated BSA which can help to protect the stability and bioavailability that has been impaired due to glycation mediated structural changes.

Characterization of colchicine binding with normal and glycated albumin: In vitro and molecular docking analysis

The transport of more than 90% of the drugs viz. anticoagulants, analgesics, and general anesthetics in the blood takes place by albumin. Hence, albumin is the prime protein needs to be investigated to find out the nature of drug binding. Serum albumin molecules are prone to glycation at elevated blood glucose levels as observed in diabetics. In this piece of work, glycation of bovine serum albumin (BSA) was carried out with glyceraldehyde and characterized by molecular docking and fluorometry techniques. Glycation of BSA showed 25% loss of free amino groups and decreased protein fluorescence (60%) with blue shift of 6 nm. The present study was also designed to evaluate the binding of colchicine (an anti-inflammatory drug) to native and glycated BSA and its ability to displace 8-analino-1-nephthalene sulfonic acid (ANS), from the BSA–ANS complex. Binding of ANS to BSA showed strong binding (Ka = 4.4 μM) with native conformation in comparison to glycated state (Ka = 8.4 μM). On the other hand, colchicine was able to quench the fluorescence of native BSA better than glycated BSA and also showed weaker affinity (Ka = 23 μM) for glycated albumin compared with native state (Ka = 16 μM). Molecular docking study showed that both glyceraldehyde and colchicine bind to common residues located near Sudlow’s site I that explain the lower binding of colchicine in the glycated BSA. Based on our results, we believe that reduced drugs-binding affinity to glycated albumin may lead to drugs accumulation and precipitation in diabetic patients.

Differentiation of glycated residue numbers on heat-induced structural changes of bovine serum albumin.

Glycation is an approach in dealing with heat-induced protein aggregation. The relationship between degree of glycation and heat-induced structural changes is still unclear. The present work investigates the effect of different numbers and sites of glycated residues on heat-induced structural changes of bovine serum albumin (BSA). Glycation of BSA was carried out with xylose (Xyl) and galactose (Gal) by Maillard reaction. Glycated residues in BSA were identified by liquid chromatography-tandem mass spectrometry, and heat-induced protein structural changes were characterized by fluorescence emission and synchronous fluorescence spectra, 8-anilino-1-naphthalenesulfonic acid fluorescence, Fourier transform infrared (FTIR) and circular dichroism (CD) spectra. The numbers of glycated residues were 2 and 13 when BSA was glycated by Gal (BSA - Gal) and Xyl (BSA - Xyl), respectively. There were shifts of maximum wavelengths and decreases in fluorescence intensities for both intrinsic and extrinsic fluorescences; shifts of FTIR amide I, III, and A bands; and decrease or increase of CD band intensities, α-helix and β-sheet percentages when BSA was heated. Glycation with Gal or Xyl restrained in similar degrees those changes, including fluorescence wavelengths, amide I band, CD band intensities, and α-helix and β-sheet percentages. Xyl glycated more residues than Gal, while their effects were similar in restraining heat-induced BSA structural changes. © 2017 Society of Chemical Industry.

Monitoring the protective ability of thymoquinone mixture with p-cymene against bovine serum albumin (BSA) glycation: MCR-ALS analysis based on combined spectroscopic and electrochemical methods

Protein glycation with sugars such as glucose start by the initial reaction between the carbonyl group of sugars and the amino group of proteins such as albumin and hemoglobin. This leads to the generation of Schiff base and following that the amadori and advanced glycation end products (AGEs). AGEs products can store in tissues and blood of diabetic patients. So, they play key roles to generate free radicals, which cause the development of diabetes complications. Inhibition of protein glycation plays an important role in controlling diabetes, so the identification of anti-glycation compounds is now receiving considerable interest. In this study, the protection effects of thymoquinone and its mixture with p-cymene on the glycation of bovine serum albumin (BSA) have been investigated by differential pulse voltammetry (DPV) and UV–vis spectrophotometry (UV–vis) techniques. Also, the multivariate curve resolution–alternating least squares (MCR–ALS) method was used since the results of the experimental measurements have a strongly overlapping signals. Molecular docking was applied to determine the site specific binding of inhibitor with residues of BSA. This study demonstrates that thymoquinone and its mixture with p-cymene have the potent ability to use as a dietary adjuvant against glycation.

The effect of glycation on bovine serum albumin conformation and ligand binding properties with regard to gliclazide

Albumin, the major serum protein, plays a variety of functions, including binding and transporting endogenous and exogenous ligands. Its molecular structure is sensitive to different environmental modifiers, among which glucose is one of the most significant. In vivo albumin glycation occurs under physiological conditions, but it is increased in diabetes. Since bovine serum albumin (BSA) may serve as a model protein in in vitro experiments, we aimed to investigate the impact of glucose-mediated BSA glycation on the binding capacity towards gliclazide, as well as the ability of this drug to prevent glycation of the BSA molecule. To reflect normo- and hyperglycemia, the conditions of the glycation process were established. Structural changes of albumin after interaction with gliclazide (0–14μM) were determined using fluorescence quenching and circular dichroism spectroscopy. Moreover, thermodynamic parameters as well as energy transfer parameters were determined. Calculated Stern-Volmer quenching constants, as well as binding constants for the BSA-gliclazide complex, were lower for the glycated form of albumin than for the unmodified protein. The largest, over 2-fold, decrease in values of binding parameters was observed for the sample with 30mM of glucose, reflecting the poorly controlled diabetic state, which indicates that the degree of glycation had a critical influence on binding with gliclazide. In contrast to significant changes in the tertiary structure of BSA upon binding with gliclazide, only slight changes in the secondary structure were observed, which was reflected by about a 3% decrease of the α-helix content of glycated BSA (regardless of glucose concentration) in comparison to unmodified BSA. The presence of gliclazide during glycation did not affect its progress. The results of this study indicate that glycation significantly changed the binding ability of BSA towards gliclazide and the scale of these changes depended on glucose concentration. It may have a direct impact on the free drug fraction and its pharmacokinetic behavior, including the risk of hypoglycemic episodes or unexpected interactions with other ligands. The use of BSA in examining binding effects upon glycation seems to be good model for preliminary research and may be used to identify a potential drug response in a diabetic state.

Inhibitory effects of curcumin on high glucose-induced damages: Implications for alleviating diabetic complications

Hyperglycemia found in diabetes mellitus causes several physiological abnormalities including the formation of advanced glycation end products (AGEs) and oxidative stress. Accumulation of AGEs and elevation of oxidative stress plays major roles in the development of diabetic complications. Adiponectin secreted from adipocytes is known to improve insulin sensitivity and blood glucose level. Curcumin (CCM), a bioactive component of turmeric, has been reported as a potent antioxidant. Present work aimed to elucidate the roles of CCM in high glucose-induced protein glycation and intracellular events in mature adipocytes. The results demonstrated that CCM inhibited the formation of fluorescent AGEs by approximated 52% at 3 weeks of bovine serum albumin (BSA) glycation with glucose. Correspondingly, CCM decreased the levels of fructosamine and α-dicarbonyl compounds during BSA glycation with glucose. These data suggested that CCM might be a new promising anti-glycation agent. Also, CCM reduced high glucose-induced oxidative stress in a dose dependent manner, whereas CCM treatment time-dependently elevated the expression of adiponectin gene in 3T3-L1 adipocytes. The findings from this study suggested the possibility of therapeutic use of CCM for the prevention of diabetic complications and obesity-related diseases.

Glycolytic enzyme inhibitory and antiglycation potential of rutin

The aim of the present was to determine the mechanism for the antidiabetic potential exerted by rutin by studying its effect on the glycolytic enzyme inhibitory and antiglycation potential. For the determination of glycolytic enzyme inhibitory potential of rutin, porcine pancreatic amylase inhibitory assay and α-glucosidase inhibitory assay were performed. The antiglycation potential was determined by glycation of bovine serum albumin followed by antiglycation estimation of fructosamines adducts, protein carbonyls, protein thiols, congo red absorbance. Rutin showed a significant inhibition of α-amylase (p < 0.001; 53.66%) and α-glucosidase (p < 0.001; 52.56%). To study antiglycation potential, various parameters were determined and fructosamine inhibition was found to be 35.55%, protein carbonyls were inhibited up to 13.49%. Protein thiols were inhibited up to 80.27%. In the present study, it was concluded that rutin showed glycolytic enzyme inhibitory and antiglycation potential.

Pectin lyase-modified red ginseng extract exhibits potent anti-glycation effects in vitro and in vivo.

[Purpose]GS-E3D is a newly developed pectin lyase-modified red ginseng extract. The purpose of this study was to evaluate the inhibitory effects of GS-E3D against advanced glycation end products. [Methods]In this study, we evaluated the inhibitory effects of GS-E3D on the formation of advanced glycation end products (AGEs) and their cross-linking with collagen in vitro and in streptozotocin-induced diabetic rats. [Results]An in vitro assay for the glycation of bovine serum albumin by methylglyoxal showed that GS-E3D inhibited AGE formation at an IC50 value of 19.65 ± 4.35 μg/mL. In addition, GS-E3D showed a potent inhibitory effect (IC50 = 0.42 ± 0.08 mg/mL) on the cross-linking of AGEs with collagen. However, GS-E3D showed no effect on preformed AGEs cross-linked with collagen in the breakdown assay. To determine whether GS-E3D inhibits AGE formation and their cross-linking with proteins in vivo, streptozotocin induced diabetic rats were treated with GS-E3D (25, 50, and 100 mg/kg/day) for 6 weeks. The administration of GS-E3D decreased serum levels of AGEs and their cross linking with proteins in diabetic rats. [Conclusion]The inhibitory effects of this agent on advanced glycation in vitro and in vivo suggested that it may have a potential therapeutic role in controlling diabetes-induced AGE burden in various tissues.

Molecular recognition of glyconanoparticles by RCA and E. coli K88 - designing transports for targeted therapy.

The targeted drug delivery has been studied as one of the main methods in medicine to ensure successful treatments of diseases. Pharmaceutical sciences are using micro or nano carriers to obtain a controlled delivery of drugs, able to selectively interact with pathogens, cells or tissues. In this work, we modified bovine serum albumin (BSA) with lactose, obtaining a neoglycan (BSA-Lac). Subsequently, we synthesized glyconanoparticles (NPBSA-Lac) with the premise that it would be recognized by microbial galactose specific lectins. NPBSA-Lac were tested for bio-recognition with adhesins of E. coli K88 and Ricinus communis agglutinin I (RCA). Glycation of BSA with lactose was analyzed by electrophoresis, infrared spectroscopy and fluorescence. Approximately 41 lactoses per BSA molecule were estimated. Nanoparticles were obtained using water in oil emulsion method and spheroid morphology with a range size of 300-500 nm was observed. Specific recognition of NPBSA-Lac by RCA and E. coli K88 was displayed by aggregation of nanoparticles analyzed by dynamic light scattering and atomic force microscopy. The results indicate that the lactosylated nanovectors could be targeted at the E. coli K88 adhesin and potentially could be used as a transporter for an antibacterial drug.

Jakyakgamcho-tang and Its Major Component, Paeonia Lactiflora, Exhibit Potent Anti-glycation Properties

[Purpose]Advanced glycation end products (AGEs) have been implicated in the pathogenesis of diabetes and other age-related diseases. AGE inhibitors or breakers, such as aminoguanidine and alagebrium, have been proposed as therapeutic agents for AGE-related disorders. Jakyakgamcho-tang (JGT) is a well-known traditional herbal formula, which consists of the radix of Paeonia lactiflora Pallas (PR) and the radix and rhizome of Glycyrrhiza uralensis Fisch (GR). The purpose of this study was to evaluate the inhibitory and breaking activities of JGT, PR, and GR against AGEs.[Methods]JGT, PR, and GR extracts were prepared in hot water. We performed in vitro assays to evaluate their inhibitory activity against glycation of bovine serum albumin (BSA) by high glucose and their ability to break the already formed AGEs.[Results]In the in vitro AGE formation assay, JGT and PR dose-dependently inhibited AGE-BSA formation (half-maximal inhibitory concentration, IC50, = 41.41 ± 0.36 and 6.84 ± 0.09 μg/mL, respectively). In the breakdown assay of the preformed AGE-BSA-collagen complexes, JGT and PR exhibited potent breaking activities (IC50 = 6.72 ± 1.86 and 7.45 ± 0.47 μg/mL, respectively). However, GR showed a weaker inhibitory activity and no breaking activity against AGEs.[Conclusion]This study suggests that JGT and PR could be valuable drug candidates for treatment of AGE-related diseases by reducing AGE burden.

Inhibitory action on the production of advanced glycation end products (AGEs) and suppression of free radicals in vitro by a Sri Lankan polyherbal formulation Nawarathne Kalka

BackgroundAdvanced glycation end products (AGEs) and free radicals are inflammatory mediators and are implicated in many diseases such as diabetes, cancer, rheumatoid arthritis etc. Multi targeted poly herbal drug systems like Nawarathne Kalka (NK) are able to quench the overall effect of these mediators as they contain good combinations of phytochemicals that have least side effects in contrast to modern medicinal drugs. The objectives of this study were to evaluate phytochemical composition, free radical scavenging activity, cytotoxicity and the inhibitory action on the formation of AGEs by aqueous extract of NK.MethodsTotal phenolic content (TPC) and total flavonoid content (TFC) were determined using Folin ciocalteu method and aluminium chloride assay respectively. Free radical scavenging activity was assessed by DPPH radical scavenging assay (DRSA), phosphomolybdenum reduction antioxidant assay (PRAA) and nitric oxide (NO) scavenging assay. Brine Shrimp Lethality (BSL) bioassay was performed as preliminary screening for cytotoxic activity. Inhibitory action on AGE formation was evaluated using fructose mediated glycation of bovine serum albumin using fluorescence spectroscopic method.ResultsThe TPC and TFC were 75.1 ± 3.0 mg/g gallic acid equivalents and 68.7 ± 7.8 mg/g epigallocatechin gallate equivalents. The DRSA yielded EC50 of 19.15 ± 2.24 μg mL−1 for NK. DRSA of NK extract was greater than butylated hydroxy toluene (EC50 = 96.50 ± 4.51 μg mL−1) but lesser than L-ascorbic acid (EC50 = 5.60 ± 0.51 μg mL−1). The total antioxidant capacity of NK as evidenced by PRAA was 106.4 ± 8.2 mg/g L-ascorbic acid equivalents. NK showed EC50 value of 99.3 ± 8.4 μg mL−1 in the NO scavenging assay compared to the standard ascorbic acid (EC50 = 7.3 ± 0.3 μg mL−1). The extract indicated moderate cytotoxic activity in the BSL bioassay. The extract showed effective inhibitory action on the formation of AGEs with EC50 values of 116 ± 19 μg mL−1, 125 ± 35 μg mL−1 and 84 ± 28 μg mL−1 in data obtained over three consecutive weeks respectively. Comparatively the reference standard, aminoguanidine at a concentration of 500 μg mL−1 demonstrated 65 % inhibition on the formation of AGE after one week of sample incubation.ConclusionsThe results proved the potential of NK as a free radical scavenger, moderate cytotoxic agent and an inhibitor on the formation of advanced glycation end-products.

Antiglycation and cell protective actions of metformin and glipizide in erythrocytes and monocytes

Chronic hyperglycaemia causes glycation which subsequently results in the long-term complications of diabetes. Albumin, the major plasma protein is more sensitive to glycation resulting in structural, biological and physiological modifications. The long-term benefits of commonly used anti-diabetic drugs such as metformin and glipizide in diabetic patients are well understood. However, no extensive study has been performed to assess their role in the glycation induced albumin modifications and cellular protection. We carried out the glycation of bovine serum albumin using methylglyoxal as a glycating agent in absence or presence of metformin and glipizide to establish their anti-glycation action. Different glycation markers (fructosamine, carbonyl groups, free thiol groups and β-amyloid aggregation) and protein structural markers (absorption spectroscopy and native-polyacrylamide gel electrophoresis) were examined. Further THP-1 cells (monocytes) and erythrocytes were treated with drugs that were exposed to glycated albumin samples for 24 h, respectively at 37 °C to investigate the cytoprotective actions of drugs against glycation. After the treatment different anti-oxidant indices (catalase, glutathione, superoxide dismutase and nitric oxide), cell viability, lipid peroxidation and erythrocyte hemolysis were determined. Treatment with metformin and glipizide during in vitro albumin glycation significantly reduced the formation of glycation adducts and inhibited structural modifications. They restored the level of antioxidants in THP-1 and erythrocytes cells treated with glycated albumin thus protecting cells. Our results suggested protection mode of albumin glycation through inhibition by metformin and glipizide. Additionally, they exerted inhibitory actions on glycation-induced cellular damage by restoring cellular antioxidant defense.

In vitro investigation on the antiglycative and carbonyl trapping activities of hydroxytyrosol

Advanced glycation end products (AGEs) are involved in the aging and the development of common chronic diseases. Hydroxytyrosol (HT) and its acetate derivative (HTA) exert a significant inhibitory activity on the formation of fluorescent AGEs in bovine serum albumin glycation model systems induced by methylglyoxal (IC50 value of 0.48 and 0.58 µmol/mL, respectively) and glucose (IC50 2.30 and 2.92 µmol/mL, respectively). Furthermore, HT and HTA showed a relevant carbonyl scavenging capacity toward methylglyoxal and glyoxal, which are the most potent promoters of the glycation in vivo, at molar reaction rates from 0.2 to 10 (carbonyl:phenol). However, carbonyl trapping capacity was significantly more effective against methylglyoxal (IC50 0.19 µmol/mL) than glyoxal (IC50 0.26 µmol/mL). At equimolar concentrations, the ester linkage did not significantly affect the antiglycative activity and carbonyl trapping capacity of the orthodiphenolic ring structure. Results were confirmed with the specific inhibition of the formation of the principal AGEs. Formation of carboxymethyl-lysine, argpyrimidine and carboxyethyl-lysine was significantly reduced by 61.9, 71.4 and 20.9 %, respectively. HT and its esters could be considered for upscaling studies as promising natural strategy against adverse consequences of protein glycation.

Inhibition of advanced glycation end product formation by burdock root extract

Purpose: Diabetic complications are a major concern to manage progression of diabetes. Production of advanced glycation end products (AGEs) due to high blood glucose is one of the mechanisms leading to diabetic complications. Multiple pharmacologic AGE inhibitory agents are currently under development, but clinical applications are still limited due to safety issues. Thus, it is necessary to identify a safe anti-glycation agent. It is known that burdock roots have antioxidant, anti-inflammatory, and anti-cancer activities. The objective of the present study was to investigate the inhibitory role of burdock roots on the formation of high glucose-induced glycation of bovine serum albumin (BSA). Methods: In this study, glycation of BSA by glucose, galactose, or fructose at 37℃ for 3 weeks was assessed based on levels of α-dicarbonyl compounds (early-stage glycation products), fructosamine (intermediate products of glycation), and fluorescent AGEs (late-stage glycation products). In order to compare the inhibitory actions of burdock root extract in AGE formation, aminoguanidine (AG), a pharmacological AGE inhibitor, was used as a positive control. Results: BSA glycation by glucose, fructose, and galatose was dose- and time-dependently produced. Burdock root extract at a concentration of 4 mg/mL almost completely inhibited glucose-induced BSA glycation. The results demonstrate that burdock root extract inhibited AGE formation with an IC 50 value of 1.534 mg/mL, and inhibitory activity was found to be more effective than the standard anti-glycation agent aminoguanidine. This study identified a novel function of burdock root as a potential anti-glycation agent. Conclusion: Our findings suggest that burdock root could be beneficial for preventing diabetic complications.