Water-Soluble Products of Photooxidative Destruction of the Bisretinoid A2E Cause Proteins Modification in the Dark.

Aging of the retina is accompanied by a sharp increase in the content of lipofuscin granules and bisretinoid A2E in the cells of the retinal pigment epithelium (RPE) of the human eye. It is known that A2E can have a toxic effect on RPE cells. However, the specific mechanisms of the toxic effect of A2E are poorly understood. We investigated the effect of the products of photooxidative destruction of A2E on the modification of bovine serum albumin (BSA) and hemoglobin from bovine erythrocytes. A2E was irradiated with a blue light-emitting diode (LED) source (450 nm) or full visible light (400-700 nm) of a halogen lamp, and the resulting water-soluble products of photooxidative destruction were investigated for the content of carbonyl compounds by mass spectrometry and reaction with thiobarbituric acid. It has been shown that water-soluble products formed during A2E photooxidation and containing carbonyl compounds cause modification of serum albumin and hemoglobin, measured by an increase in fluorescence intensity at 440-455 nm. The antiglycation agent aminoguanidine inhibited the process of modification of proteins. It is assumed that water-soluble carbonyl products formed as a result of A2E photodestruction led to the formation of modified proteins, activation of the inflammation process, and, as a consequence, to the progression of various senile eye pathologies.

Plasma membrane rigidity effects of 4-hydroxy-2-nonenal in Leishmania, erythrocyte and macrophage.

4-hydroxy-2-nonenal (HNE) is a reactive aldehyde produced by cells under conditions of oxidative stress, which has been shown to react with proteins and phosphatidylethanolamine in biological membranes. Using electron paramagnetic resonance (EPR) spectroscopy of a spin label it was demonstrated that 2 h of treatment with HNE causes membrane rigidity in promastigotes of Leishmania (L.) amazonensis, J774.A1 macrophages and erythrocytes. Remarkable fluidity-reducing effects on the parasite membrane were observed at HNE concentrations approximately 4-fold lower than in the case of erythrocyte and macrophage membranes. Autofluorescence of the parasites in PBS suspension (1 × 107 cell/mL) with excitation at 354 nm showed a linear increase of intensity in the range of 400 to 600 nm over 3 h after treatment with 30 µM HNE. Parasite ghosts prepared after this period of HNE treatment showed a high degree of membrane rigidity. Bovine serum albumin (BSA) in PBS treated with HNE for 2 h showed an increase in molecular dynamics and suffered a decrease in its ability to bind a lipid probe. In addition, the antiproliferative activity of L. amazonensis promastigotes, macrophage cytotoxicity and hemolytic potential were assessed for HNE. An IC50 of 24 µM was found, which was a concentration > 10 times lower than the cytotoxic and hemolytic concentrations of HNE. These results indicate that the action of HNE has high selectivity indices for the parasite as opposed to the macrophage and erythrocyte.

Effect of Dinitrosyl Iron Complex on Albumin Conformation.

Binding of dinitrosyl iron complex (DNIC) to albumin was studied using time-resolved fluorescence (TRF) and electron spin resonance (ESR) spectroscopy. It was found that the fluorescence lifetime of bovine serum albumin (BSA) and human serum albumin (HSA) decreases with binding and depends on DNIC concentration. The observed biexponential pattern of the BSA tryptophan (Trp) fluorescence decay is explained by the presence of two tryptophan residues in the protein molecule. We believe that DNIC forms stable complexes with the cysteine (Cys34) residue in the domain I of albumin. It was shown that the lifetime of albumin tryptophan fluorescence decreased during co-incubation of BSA with DNICs and glutathione. Effects of DNIC on the binding of specific spin-labeled fatty acids with albumin in human blood plasma were studied in vitro. The presence of DNIC in blood plasma does not change conformation of albumin domains II and III. We suggest that the most possible interaction between DNICs and albumin is the formation of a complex; and nitrosylation of the cysteine residue in the albumin domain I occurs without the changes in albumin conformation.

Superhemophobic and Antivirofouling Coating for Mechanically Durable and Wash-Stable Medical Textiles.

Medical textiles have a need for repellency to body fluids such as blood, urine, or sweat that may contain infectious vectors that contaminate surfaces and spread to other individuals. Similarly, viral repellency has yet to be demonstrated and long-term mechanical durability is a major challenge. In this work, we demonstrate a simple, durable, and scalable coating on nonwoven polypropylene textile that is both superhemophobic and antivirofouling. The treatment consists of polytetrafluoroethylene (PTFE) nanoparticles in a solvent thermally sintered to polypropylene (PP) microfibers, which creates a robust, low-surface-energy, multilayer, and multilength scale rough surface. The treated textiles demonstrate a static contact angle of 158.3 ± 2.6° and hysteresis of 4.7 ± 1.7° for fetal bovine serum and reduce serum protein adhesion by 89.7 ± 7.3% (0.99 log). The coated textiles reduce the attachment of adenovirus type 4 and 7a virions by 99.2 ± 0.2% and 97.6 ± 0.1% (2.10 and 1.62 log), respectively, compared to noncoated controls. The treated textiles provide these repellencies by maintaining a Cassie-Baxter state of wetting where the surface area in contact with liquids is reduced by an estimated 350 times (2.54 log) compared to control textiles. Moreover, the treated textiles exhibit unprecedented mechanical durability, maintaining their liquid, protein, and viral repellency after extensive and harsh abrasion and washing. The multilayer, multilength scale roughness provides for mechanical durability through self-similarity, and the samples have high-pressure stability with a breakthrough pressure of about 255 kPa. These properties highlight the potential of durable, repellent coatings for medical gowning, scrubs, or other hygiene textile applications.

Homo- and heteroleptic trimethoxy terpyridine-Cu(ii) complexes: synthesis, characterization, DNA/BSA binding, DNA cleavage and cytotoxicity studies.

In the current study, four novel mononuclear Cu(ii) complexes with terpyridine (L) and different co-ligands (phen, bipy, and imd) were synthesized and characterized in detail, where L is 4'-(3,4,5-trimethoxyphenyl)-2,2':6',2''-terpyridine. The identity and purity of all complexes were determined by elemental analysis, spectroscopic techniques (UV-vis, FTIR, ESI-MS, and EPR) and CV, including single crystal X-ray determination of three complexes ([Cu(L)(phen)](ClO4)2 (C-I), [Cu(L)2](ClO4)2 (C-II) and [Cu(L)(imd)(ClO4)](ClO4) (C-IV). DNA binding studies were performed using fluorescence assay and the binding constants were calculated using the Stern-Volmer equation and the modified Stern-Volmer equation. The magnitude of Kapp of all complexes was 105 M-1, indicating moderate intercalative binding between CT-DNA and the complexes. Agarose gel electrophoresis clearly reflected their ability to cleave a double stranded pET-28b plasmid in the presence of an external reducing agent (3-mercapto propionic acid). Steady-state fluorescence quenching was performed to understand their interactions with BSA. The studies suggested a mixed quenching mechanism with an initial static process. Furthermore, the antiproliferative activity of the complexes was evaluated against lung cancer A549 cells and primary mice splenocytes. Interestingly, the complexes show 25-200 fold greater toxicity towards the A549 cells than primary splenocytes, indicating their selectivity towards the former. The good binding behavior of all four complexes towards DNA and BSA and their cytotoxicity render these compounds promising potent anticancer drugs.

Comparative refolding of guanidinium hydrochloride denatured bovine serum albumin assisted by cationic and anionic surfactants via artificial chaperone protocol: Biophysical insight.

In the present study, we report the cooperative refolding/renaturation behaviour of guanidinium hydrochloride (GdnHCl) denatured bovine serum albumin (BSA) in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB), anionic surfactant sodium dodecyl sulphate (SDS) and their catanionic mixture in the solution of 60 mM sodium phosphate buffer of physiological pH 7.4, using artificial chaperone-assisted two-step method. Here, we have employed biophysical techniques to characterize the refolding mechanism of denatured BSA after 200 times of dilution in the presence of cationic, anionic surfactants and their catanionic mixture, separately. We have found that minimum refolding of diluted BSA in the presence of 1:1 rational mixture of CTAB and SDS (CTAB/SDS = 50/50), it may be due to the micelles formation which is responsible for the unordered microstructure aggregate formation. Other mixtures (CTAB/SDS = 20/80 and 80/20) slightly played an effective role during refolding process in the presence of methyl-ß-cyclodextrin. On other hand, CTAB and SDS are more effective and reflect a good renaturation tendency of denatured BSA solution separately and in existence of methyl-ß-cyclodextrin as compare to their mixture compositions. But overall, CTAB has the better renaturation tendency as compare to SDS in the existence of methyl-ß-cyclodextrin. These results ascribed the presence of charge head group and length of hydrophobic tail of CTAB surfactant that plays an important task during electrostatic and hydrophobic interactions at pH 7.4 at which BSA carries negative charge on their surface. These biophysical parameters suggest that, CTAB surfactant assisted artificial chaperone protocol may be utilized in the protein renaturation/refolding studies, which may address the associated problems of biotechnological industries for the development of efficient and inexpensive folding aides, which may also be used to produced genetically engineered cells related diseases, resulting from protein misfolding/aggregation.

Characterizing the interactions of the antipsychotic drug trifluoperazine with bovine serum albumin: Probing the drug-protein and drug-drug interactions using multi-spectroscopic approaches.

Trifluoperazine is a potent antipsychotic drug used in the treatment of neurological disorders. The usage of trifluoperazine is often found to be associated with more adverse side effects as compared to other low-potency antipsychotic agents. Plasma proteins play an inevitable role in determining the pharmacokinetic properties of a drug. Hence, this study was conducted with an aim to characterize the interactions of trifluoperazine with bovine serum albumin and determine the influence of other small molecules on its interaction with serum albumin. Trifluoperazine bound to BSA at two independent sites with Kd values of 9.5 and 172.6 µM. Förster resonance energy transfer and computational docking analysis revealed that both the binding sites of trifluoperazine were located closer to TRP 213 in subdomain IIA of BSA. Evaluation of trifluoperazine-BSA interactions at three different temperatures indicated that there was a stable complex formation between the two molecules at the ground state and that the static quenching mechanism was predominant behind these interactions. Binding studies in the presence of pharmaceutically relevant drugs indicated that warfarin, paracetamol, and caffeine negatively influenced the binding of trifluoperazine on BSA. Lastly, Fourier transformed infrared spectroscopy and circular dichroism spectroscopy indicated that the binding of trifluoperazine induced a conformational change by reducing the α-helical content of BSA. The study implicates that the small molecules which prefer binding to the Sudlow site I of BSA might compete with trifluoperazine for its binding site thereby increasing the concentration of free trifluoperazine in the plasma which could lead to adverse side effects in patients.

In vitro and in vivo anti-arthritic evaluation of Polystichum braunii to validate its folkloric claim.

Medicinal plants are playing an imperative role in the therapy for treating various chronic ailments including arthritis. The present study was focused on finding in-vitro and in-vivo anti-arthritic potential of P. braunii roots. In vitro protein denaturation, membrane stabilization and anti-trypsinase assays were carried out to demonstrate anti-arthritic activity of the extracts. Furthermore, the extracts exerting promising in vitro anti-arthritic potential were tested orally at 150, 300 and 600mg/kg/day against formaldehyde induced arthritis in Wistar rats. The methanolic, aqueous and ethyl acetate extracts of the plant revealed noteworthy in vitro anti-arthritic activities while mitigating formaldehyde induced paw edema in dose dependent manner. Methanolic and aqueous extracts showed the highest inhibition (p<0.05) of paw edema, arthritic indices, reduced elevated level of platelets and leukocytes while increasing hemoglobin and body weight of arthritic rats. Anti-arthritic activity of the plant extracts may be due to inhibition of protein denaturation and lysosomal membrane stabilization. The plant exhibited good anti-arthritic potential.

Lysosome-Targeted Chemotherapeutics: Half-Sandwich Ruthenium(II) Complexes That Are Selectively Toxic to Cancer Cells.

Poor selectivity between cancer cells and normal cells is one of the major limitations of cancer chemotherapy. Lysosome-targeted ruthenium-based complexes target tumor cells selectively, only displaying rather weak cytotoxicity or inactivity toward normal cells. Confocal microscopy was employed for the first time to determine the cellular localization of the half-sandwich Ru complex.

New bio-sensitive and biologically active single crystal of pyrimidine scaffold ligand and its gold and platinum complexes: DFT, antimicrobial, antioxidant, DNA interaction, molecular docking with DNA/BSA and anticancer studies.

Novel gold and platinum complexes [AuL2]·Cl, 1 and [PtL2]·2Cl, 2 with ligand, 2-methoxy-6-((2-(4-(trifluoromethyl)pyrimidin-2-yl)hydrazono)methyl)phenol (HL) have been synthesized and screened for their antimicrobial, antioxidant, DNA binding and anticancer (in vitro) activities. The single crystal of ligand HL was obtained by slow evaporation technique. The molecular structure of HL was confirmed from single crystal X-ray technique. Density functional theory calculations have been performed to gain insights into the electronic structure of these metal complexes. Antimicrobial result shows that, HL and complexes (1 and 2) have good antimicrobial agents against E. coli (bacteria) and C. albicans (fungi) than others bacterial and fungal strains. Antioxidant assay results suggest that, HL and complexes (1 and 2) possess good radical scavenging activity against diverse free radicals (DPPH, SOD, NO and H2O2). The intercalative interactions of HL and complexes (1 and 2) with CT-DNA were confirmed from spectroscopic titrations and viscometric measurements. Furthermore, the interactions of prepared compounds with DNA were confirmed by molecular docking analysis. In order to understand the nature of interactions between these metal complexes and BSA protein results clearly shows that complex 1 binds better than that of complex 2. The antitumor activities of prepared products were tested against single normal and different tumor cell lines by MTT assay. These results reveal that prepared complexes (1 and 2) have significant cytotoxic effect against tumor cell lines.

Acetonitrile as solvent for protein interaction analysis.

Dimethyl sulfoxide (DMSO) is routinely used to dissolve hydrophobic and aromatic substances in drug screening. The dissolved substances are then diluted, e.g., 100-fold, into aqueous media containing their target molecules. Such a practice may be suitable for biological evaluation of the drug substances. However, structural evaluation using spectroscopic techniques, in particular far UV measurements, may be hampered by strong absorbance of DMSO. Here, I have tested acetonitrile (ACN) that is almost exclusively used for reverse phase chromatography of proteins and small organic molecules. Using a small aromatic/hydrophobic molecule, dodecyl-gallate, and bovine serum albumin as a model system, a side-by-side comparison was made for DMSO and ACN with regard to dissolution capability and far UV circular dichroism (CD) performance.

Policosanol composition, antioxidant and anti-arthritic activities of milk thistle (Silybium marianum L.) oil at different seed maturity stages.

BACKGROUND: Several anti-arthritic drugs and synthetic antioxidants have wide pharmaceutical uses and are often associated with various side effects on the human health. Dietary seed oils and their minor components like policosanol may offer an effective alternative treatment for arthritic and oxidative-stress related diseases. The biological effects of seed oils were affected by different parameters such as the stage of seed maturity. Hence, this study seeks to determine the policosanol content, antioxidant and anti-arthritic activities of milk thistle (Silybium marianum L.) oil extracted at various stages of seed maturation. METHODS: Milk thistle oil samples were extracted from seeds collected at three maturation stages (immature, intermediate, and mature). The 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethyl-benzthiazoline-6-sulfonic acid) (ABTS) radical scavenging assays were used to determine the antioxidant activity of the extracted oils. The anti-arthritic activity of oil samples was evaluated with bovine serum protein denaturation and egg albumin denaturation methods. Gas chromatography coupled to mass spectrometry (GC-MS) was employed to determine the policosanol profile. RESULTS: Policosanol profile, antioxidant and anti-arthritic activities of milk thistle oil were influenced by the seed maturity stages. The oil extracted from the immature seeds had the highest total policosanol content (987.68 mg/kg of oil) and displayed the maximum antiradical activity (96.42% and 90.35% for DPPH test and ABTS assay, respectively). Nine aliphatic alcohols were identified in the milk thistle oil. The dominant poliosanol in the mature seed oil was octacosanol (75.44%), while triacontanol was the major compound (40.25%) in the immature seed oil. Additionally, the maximum inhibition of bovine serum protein denaturation (92.53%) and egg albumin denaturation (86.36%) were observed in immature seed oil as compared to mature seed oil. A high correlation was found between the total policosanol content, anti-arthritic activity and antioxidant capacity of oil. CONCLUSIONS: The milk thistle oil exhibited a potential anti-arthritic and antioxidant activities and that it might contribute to the protection of humans from a variety of diseases like rheumatoid arthritis. Also, it could serve as natural antioxidant and anti-arthritic agents for application in the food industries and pharmaceutic. Policosanol level in the seed oils might contribute to their anti-arthritic and antioxidant activities.

Intermolecular interaction of fosinopril with bovine serum albumin (BSA): The multi-spectroscopic and computational investigation.

The intermolecular interaction of fosinopril, an angiotensin converting enzyme inhibitor with bovine serum albumin (BSA), has been investigated in physiological buffer (pH 7.4) by multi-spectroscopic methods and molecular docking technique. The results obtained from fluorescence and UV absorption spectroscopy revealed that the fluorescence quenching mechanism of BSA induced by fosinopril was mediated by the combined dynamic and static quenching, and the static quenching was dominant in this system. The binding constant, Kb , value was found to lie between 2.69 × 103 and 9.55 × 103  M-1 at experimental temperatures (293, 298, 303, and 308 K), implying the low or intermediate binding affinity between fosinopril and BSA. Competitive binding experiments with site markers (phenylbutazone and diazepam) suggested that fosinopril preferentially bound to the site I in sub-domain IIA on BSA, as evidenced by molecular docking analysis. The negative sign for enthalpy change (ΔH0 ) and entropy change (ΔS0 ) indicated that van der Waals force and hydrogen bonds played important roles in the fosinopril-BSA interaction, and 8-anilino-1-naphthalenesulfonate binding assay experiments offered evidence of the involvements of hydrophobic interactions. Moreover, spectroscopic results (synchronous fluorescence, 3-dimensional fluorescence, and Fourier transform infrared spectroscopy) indicated a slight conformational change in BSA upon fosinopril interaction.

Synthesis and structure elucidation of novel salophen-based dioxo-uranium(VI) complexes: In-vitro and in-silico studies of their DNA/BSA-binding properties and anticancer activity.

The synthesis and characterization of three dioxo U(VI) complexes, [UO2(L1)(OH2)], [UO2(L2)DMF], and [UO2(L2)DMSO], [L1]2- = 1,1'-(4-methyl-1,2-phenylenebis (nitrilomethylidyne))di-2-naphtholate: [L2]2- = 1,1'-(o-phenylenebis (nitrilomethylidyne)) di-2-naphtholate, are reported. Elemental analysis, FT-IR, 1HNMR, UV-Vis spectroscopy, molar conductivity and single crystal X-ray diffraction were used to characterize the complexes. It was found that the complexes adopt a distorted pentagonal bipyramidal coordination geometry. The interaction of the synthesized complexes with DNA and bovine serum albumin was thoroughly investigated using both experimental and theoretical studies. UV-Vis absorption and fluorescence quenching techniques were applied to determine the binding parameters as well as the mechanism of the interaction of each complex with DNA and the protein. The results obtained suggested that interaction of the complexes with DNA occurred through partial intercalation into the minor grooves of DNA with binding constants in the range of 0.661 × 105-1.56 × 105 M-1. In addition, interaction of the complexes with bovine serum albumin quenched the fluorescence emission of the tryptophan residues of the protein binding constants and thermodynamic parameters were obtained from the fluorescence quenching experiments at different temperatures. The values of binding constants revealed moderate interactions between the synthesized complexes and the protein suggesting that this protein could act as a suitable vehicle for transportation of the compounds. The results of molecular docking confirmed those of the experimental studies. The anticancer properties of the title complexes were also evaluated through a study of the in vitro cytotoxicity of the compounds against the HT-29 and MCF-7 cancer cell lines and the DPSC normal cell line using an MTT assay.

Study of conformational changes and protein aggregation of bovine serum albumin in presence of Sb(III) and Sb(V).

Antimony is a metalloid that affects biological functions in humans due to a mechanism still not understood. There is no doubt that the toxicity and physicochemical properties of Sb are strongly related with its chemical state. In this paper, the interaction between Sb(III) and Sb(V) with bovine serum albumin (BSA) was investigated in vitro by fluorescence spectroscopy, and circular dichroism (CD) under simulated physiological conditions. Moreover, the coupling of the separation technique, asymmetric flow field-flow fractionation, with elemental mass spectrometry to understand the interaction of Sb(V) and Sb(III) with the BSA was also used. Our results showed a different behaviour of Sb(III) vs. Sb(V) regarding their effects on the interaction with the BSA. The effects in terms of protein aggregates and conformational changes were higher in the presence of Sb(III) compared to Sb(V) which may explain the differences in toxicity between both Sb species in vivo. Obtained results demonstrated the protective effect of GSH that modifies the degree of interaction between the Sb species with BSA. Interestingly, in our experiments it was possible to detect an interaction between BSA and Sb species, which may be related with the presence of labile complex between the Sb and a protein for the first time.

Capsaicin-Coated Silver Nanoparticles Inhibit Amyloid Fibril Formation of Serum Albumin.

We have synthesized capsaicin-coated silver nanoparticles (AgNPs(Cap)) and have tested their anti-amyloid activity, considering serum albumin (BSA) as a model protein. We found that amyloid formation of BSA was strongly suppressed in the presence of AgNPs(Cap). However, isolated capsaicin and uncapped control nanoparticles did not show such an inhibition effect. Bioinformatics analysis reveals CH-π and H-bonding interactions between capsaicin and BSA in the formation of the protein-ligand complex. These results suggest the significance of surface functionalization of nanoparticles with capsaicin, which probably allows capsaicin to effectively interact with the key residues of the amyloidogenic core of BSA.

Effects of perfluorooctane sulfonate on the conformation and activity of bovine serum albumin.

Perfluorooctane sulfonate (PFOS) is among the most prominent contaminates in human serum and has been reported to possess potential toxicity to the human body. In this study, the effects of PFOS on the conformation and activity of bovine serum albumin (BSA) were investigated in vitro. The results indicated that the binding interaction of PFOS with BSA destroyed the tertiary and secondary structures of protein with the loss of α-helix structure and the increasing of hydrophobic microenvironment of the Trp or Tyr residues. During the thermal denaturation protein, PFOS increases the protein stability of BSA. The proportion of α-helix decreased on increasing the PFOS concentration and the microenvironment of the Trp or Tyr residues becomes more hydrophobic. The results from molecular modeling indicated that BSA had not only one possible binding site to bind with PFOS by the polar interaction, hydrogen bonds and hydrophobic forces. In addition, the BSA relative activities were decreased with the increase of PFOS concentration. Such loss of BSA activity in the presence of PFOS indicated that one of the binding sites in BSA is located in subdomain IIIA, which is in good agreement with the fluorescence spectroscopic experiments and molecular modeling results. This study offers a comprehensive picture of the interactions of PFOS with serum albumin and provides insights into the toxicological effect of perfluoroalkylated substances.

Glucitol-core containing gallotannins inhibit the formation of advanced glycation end-products mediated by their antioxidant potential.

Glucitol-core containing gallotannins (GCGs) are polyphenols containing galloyl groups attached to a 1,5-anhydro-d-glucitol core, which is uncommon among naturally occurring plant gallotannins. GCGs have only been isolated from maple (Acer) species, including the red maple (Acer rubrum), a medicinal plant which along with the sugar maple (Acer saccharum), are the major sources of the natural sweetener, maple syrup. GCGs are reported to show antioxidant, α-glucosidase inhibitory, and antidiabetic effects, but their antiglycating potential is unknown. Herein, the inhibitory effects of five GCGs (containing 1-4 galloyls) on the formation of advanced glycation end-products (AGEs) were evaluated by MALDI-TOF mass spectroscopy, and BSA-fructose, and G.K. peptide-ribose assays. The GCGs showed superior activities compared to the synthetic antiglycating agent, aminoguanidine (IC50 15.8-151.3 vs. >300 µM) at the early, middle, and late stages of glycation. Circular dichroism data revealed that the GCGs were able to protect the secondary structure of BSA protein from glycation. The GCGs did not inhibit AGE formation by the trapping of reactive carbonyl species, namely, methylglyoxal, but showed free radical scavenging activities in the DPPH assay. The free radical quenching properties of the GCGs were further confirmed by electron paramagnetic resonance spectroscopy using ginnalin A (contains 2 galloyls) as a representative GCG. In addition, this GCG chelated ferrous iron, an oxidative catalyst of AGE formation, supported a potential antioxidant mechanism of antiglycating activity for these polyphenols. Therefore, GCGs should be further investigated for their antidiabetic potential given their antioxidant, α-glucosidase inhibitory, and antiglycating properties.

Advanced glycation end products induce differential structural modifications and fibrillation of albumin.

Glycation induced amyloid fibrillation is fundamental to the development of many neurodegenerative and cardiovascular complications. Excessive non-enzymatic glycation in conditions such as hyperglycaemia results in the increased accumulation of advanced glycation end products (AGEs). AGEs are highly reactive pro-oxidants, which can lead to the activation of inflammatory pathways and development of oxidative stress. Recently, the effect of non-enzymatic glycation on protein structure has been the major research area, but the role of specific AGEs in such structural alteration and induction of fibrillation remains undefined. In this study, we determined the specific AGEs mediated structural modifications in albumin mainly considering carboxymethyllysine (CML), carboxyethyllysine (CEL), and argpyrimidine (Arg-P) which are the major AGEs formed in the body. We studied the secondary structural changes based on circular dichroism (CD) and spectroscopic analysis. The AGEs induced fibrillation was determined by Congo red binding and examination of scanning and transmission electron micrographs. The amyloidogenic regions in the sequence of BSA were determined using FoldAmyloid. It was observed that CEL modification of BSA leads to the development of fibrillar structures, which was evident from both secondary structure changes and TEM analysis.

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 ß-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.