Eugenol prevents amyloid formation of proteins and inhibits amyloid-induced hemolysis

Cu(II) Specifically Disassembles Insulin Amyloid Nanostructures via Direct Interaction with Cross-β Fibrils

In this work, we demonstrate direct evidence of the antiamyloid potential of Cu(II) ions against amyloid formation of insulin. The Cu(II) ions were found to efficiently disassemble the preformed amyloid nanostructures into soluble species and suppress monomer fibrillation under aggregation-prone conditions. The direct interaction of Cu(II) ions with the cross-β structure of amyloid fibrils causes substantial disruption of both the interchain and intrachain interactions, predominantly the H-bonds and hydrophobic contacts. Further, the Cu(II) ions show a strong affinity for the aggregation-prone conformers of the protein and inhibit their spontaneous self-assembly. These results reveal the possible molecular mechanism for the antiamyloidogenic potential of Cu(II) which could be important for the development of metal-ion specific therapeutic strategies against amyloid linked complications.

Biomimetic green synthesis of ZnO nanoflowers using α-amylase: from antimicrobial to toxicological evaluation

Biologically mediated synthesis of nanomaterials has emerged as an ecologically benign and biocompatible approach. Our study explores enzymatic synthesis, utilizing α-amylase to synthesize ZnO nanoflowers (ZnO-NFs). X-ray diffraction and energy-dispersive X-ray spectroscopy revealed crystal structure and elemental composition. Dynamic light scattering analysis indicates that ZnO-NFs possess a size of 101 nm. Transmission electron microscopy showed a star-shaped morphology of ZnO-NFs with petal-like structures. ZnO-NFs exhibit potent photocatalytic properties, degrading 90% eosin, 87% methylene blue, and 81% reactive red dyes under UV light, with kinetics fitting the Langmuir-Hinshelwood pseudo-first-order rate law. The impact of pH and interfering substances on dye degradation was explored. ZnO-NFs display efficient bacteriocidal activity against different Gram-positive and negative strains, antibiofilm potential (especially with P. aeruginosa), and hemocompatibility up to 600 ppm, suggesting versatile potential in healthcare and environmental remediation applications.

Chemical fingerprinting, antimicrobial, antioxidant, anti-inflammatory, and anticancer potential of greenly synthesized silver nanoparticles from pistachio (Pistacia vera) nuts and senna (Cassia angustifolia Vahl.) leaves

There is a growing interest in standardizing the biocompatible, cost-effective, and eco-friendly manufacturing techniques for metallic nanostructures due to their widespread applications in the industrial and medical sectors. In recent decades, green synthesis has been proven as the most suitable technique for synthesizing metal nanoparticles. The present research study investigates the use of Cassia angustifolia (senna) leaves and Pistacia vera (Pistachio) nuts to prepare crude aqueous extracts, ethanolic extracts, and biogenic silver nanoparticles (AgNPs). The prepared aqueous extracts were used as reducing, stabilizing, and capping agents for the production of silver nanoparticles. These AgNPs were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and ultraviolet-visible (UV-Vis) spectroscopy. The outcomes validated the formation of stable AgNPs with bioactive functional components. In vitro antibacterial, anticancer, anti-inflammatory, and antioxidant potentials were assessed by Kirby-Bauer disk diffusion test, MIC test, MBC test, MTT assay, BSA denaturation inhibition assay, and DPPH antioxidant assay, respectively. Results confirmed that the tested plant extract possesses a variety of bioactive compounds with various biological activities and is therapeutically effective. These findings verified that C. angustifolia and P. vera are promising bioresources for the synthesis of therapeutic extracts and nanostructures with commendable therapeutic potency.

Furosemide Derails Human Lysozyme Fibrillation by Interacting with Aggregation Hot Spots: A Biophysical Comprehension

Kidney-associated human lysozyme amyloidosis leads to renal impairments;thus, patients are often prescribed furosemide. Based on this fact, the effect of furosemide on induced human lysozyme fibrillation, in vitro, is evaluated by spectroscopic, calorimetric, computational, and cellular-based assays/methods. Results show that furosemide increases the lag phase and decreases the apparent rate of aggregation of human lysozyme, thereby decelerating the nucleation phase and amyloid fibril formation, as confirmed by the decrease in the level of Thioflavin-T fluorescence. Fewer entities of hydrodynamic radii of ∼171 nm instead of amyloid fibrils (∼412 nm) are detected in human lysozyme in the presence of furosemide by dynamic light scattering. Moreover, furosemide decreases the extent of conversion of the α/β structure of human lysozyme into a predominant β-sheet. The isothermal titration calorimetry established that furosemide forms a complex with human lysozyme, which was also confirmed through fluorescence quenching and computational studies. Also, human lysozyme lytic activity is inhibited competitively by furosemide due to the involvement of amino acid residues of the active site in catalysis, as well as complex formation. Conclusively, furosemide interacts with Gln58, Ile59, Asn60, Ala108, and Trp109 of aggregation-prone regions 2 and 4 of human lysozyme, thereby masking its sites of aggregation and generating only lower-order entities that are less toxic to red blood cells than the fibrils. Thus, furosemide slows the progression of amyloid fibrillation in human lysozyme.

Pharmacodynamic, pharmacokinetic, toxicity, and recent advances in Eugenol's potential benefits against natural and chemical noxious agents: A mechanistic review

The active biological phytochemicals, crucial compounds employed in creating hundreds of medications, are derived from valuable and medicinally significant plants. These phytochemicals offer excellent protection from various illnesses, including inflammatory disorders and chronic conditions caused by oxidative stress. A phenolic monoterpenoid known as eugenol (EUG), it is typically found in the essential oils of many plant species from the Myristicaceae, Myrtaceae, Lamiaceae, and Lauraceae families. One of the main ingredients of clove oil (Syzygium aromaticum (L.), Myrtaceae), it has several applications in industry, including flavoring food, pharmaceutics, dentistry, agriculture, and cosmeceuticals. Due to its excellent potential for avoiding many chronic illnesses, it has lately attracted attention. EUG has been classified as a nonmutant, generally acknowledged as a safe (GRAS) chemical by the World Health Organization (WHO). According to the existing research, EUG possesses notable anti-inflammatory, antioxidant, analgesic, antibacterial, antispasmodic, and apoptosis-promoting properties, which have lately gained attention for its ability to control chronic inflammation, oxidative stress, and mitochondrial malfunction and dramatically impact human wellness. The purpose of this review is to evaluate the scientific evidence from the most significant research studies that have been published regarding the protective role and detoxifying effects of EUG against a wide range of toxins, including biological and chemical toxins, as well as different drugs and pesticides that produce a variety of toxicities, throughout view of the possible advantages of EUG.

Revisiting the Multifaceted Therapeutic Potential of Withaferin A (WA), a Novel Steroidal Lactone, W-ferinAmax Ashwagandha, from Withania Somnifera (L) Dunal

Withania somnifera (L.) Dunal, abundant in the Indian subcontinent as Ashwagandha or winter cherry, is a herb of unprecedented therapeutic value. The number of ailments for which crude Ashwagandha extract can be used as a preventive or curative is practically limitless; and this explains why its use has been in vogue in ancient Ayurveda since at-least about four thousand years. The therapeutic potential of Ashwagandha mainly owes from its reservoir of alkaloids (isopelletierine, anaferine), steroidal lactones (withanolides) and saponins with an extra acyl group (sitoindoside VII and VIII). Withaferin A is an exceptionally potent withanolide which is found in high concentrations in W. somnifera plant extracts. The high reactivity of Withaferin A owes to the presence of a C-28 ergostane network with multiple sites of unsaturation and differential oxygenation. It interacts with the effectors of multiple signaling pathways involved in inflammatory response, oxidative stress response, cell cycle regulation and synaptic transmission and has been found to be significantly effective in inducing programmed cell death in cancer cells, restoring cognitive health, managing diabetes, alleviating metabolic disorders, and rejuvenating the overall body homeostasis. Additionally, recent studies suggest that Withaferin A (WA) has the potential to prevent viral endocytosis by sequestering TMPRSS2, the host transmembrane protease, without altering ACE-2 expression. The scope of performing subtle structural modifications in this multi-ring compound is believed to further expand its pharmacotherapeutic horizon. Very recently, a novel, heavy metal and pesticide free formulation of Ashwagandha whole herb extract, with a significant amount of WA, termed W-ferinAmax Ashwagandha, has been developed. The present review attempts to fathom the present and future of this wonder molecule with comprehensive discussion on its therapeutic potential, safety and toxicity.Key teaching pointsWithania somnifera (L.) Dunal is a medicinal plant with versatile therapeutic values.The therapeutic potential of the plant owes to the presence of withanolides such as Withaferin A.Withaferin A is a C-28 ergostane based triterpenoid with multiple reactive sites of therapeutic potential.It is effective against a broad spectrum of ailments including neurodegenerative disorders, cancer, inflammatory and oxidative stress disorders and it also promotes cardiovascular and sexual health.W-ferinAmax Ashwagandha, is a heavy metal and pesticide free Ashwagandha whole herb extract based formulation with significant amount of Withaferin A.

Initiation of Brain Extract Fibrillation and Effective Cellular Internalization of Tryptophan Fibrils Unveils Its Neurotoxicity Risk

Recent discoveries on the self-assembly of aromatic amino acids into amyloid-like neurotoxic nanostructures have initiated a quest to decode the molecular mechanisms for the initiation of neurodegeneration. Moreover, the multicomponent nature of the amyloid deposits still questions the existing and well-defined amyloid cascade hypothesis. Hence, deciphering the neurotoxicity of amyloid-like nanostructures of aromatic amino acids becomes crucial for understanding the etiology of amyloidogenesis. Here, we demonstrate the cellular internalization and consequential damaging effects of self-assembled amyloid-like tryptophan nanostructures on human neuroblastoma cells. The cell-damaging potential of tryptophan nanostructure seems to be facilitated via ROS generation, necrosis and apoptosis mediated cell death. Further, tryptophan nanostructures were found to be seeding competent conformers, which triggered aggressive aggregation of brain extract components. The early stage intermediate nanostructures possess a higher cross-seeding efficacy than the seeding potential of the matured tryptophan fibrils. In addition to the cell-damaging and cross-seeding effects, tryptophan fibrils were found to catalyze oxidation of neuromodulator dopamine. These findings add more insights into the specific role of tryptophan self-assembly during the pathogenesis of hypertryptophanemia and other amyloid-associated neurodegenerative complications.

Anti-amyloid potential of some phytochemicals against Aβ-peptide and α-synuclein, tau, prion, and Huntingtin protein

Some molecules self-assemble to create complex structures through molecular self-assembly. Hydrogel preparation, tissue repair, and therapeutic drug delivery are a few applications of molecular self-assembly. However, the self-assembly of amino acids, peptides, and proteins forms amyloid fibrils, resulting in various disorders, most notably neurodegenerative ailments. Examples include the self-assembly of phenylalanine, which causes phenylketonuria; Aβ, which causes Alzheimer's disease; the tau protein, which causes both Alzheimer's and Parkinson's diseases; and α-synuclein, which causes Parkinson's illness. This review provides information related to phytochemicals of great significance that can prevent the formation of, or destabilize, amino acid, peptide, and protein self-assemblies.

Biophysical insight into the anti-fibrillation potential of Glyburide for its possible implication in therapeutic intervention of amyloid associated diseases

Protein aggregation is an underlying cause of many neurodegenerative diseases. Also, the overlapping pathological disturbances between neurodegenerative diseases and type-2 diabetes mellitus have urged the scientific community to explore potential of already available anti-diabetic medications in impeding amyloid formation too. Recent study brief out promising potential of an anti-diabetic drug Glyburide(GLY) as an inhibitor of amyloid fibrillation utilizing several biophysical techniques, computational methods and imaging tools. The mechanism of interaction was elucidated and the structural alterations in human serum albumin(HSA) as well as the microenvironment changes of its fluorophores(tryptophan, tyrosine) upon interacting with GLY were studied by spectroscopic techniques like Circular dichroism and synchronous fluorescence. Binding studies detailing about the GLY-HSA complex distance and the energy transfer efficiency was obtained by Fluorescence resonance energy transfer. For aggregation inhibition studies, the existence and size of aggregates formed in HSA and their inhibition by GLY was determined by Turbidity assay, Dynamic light scattering and Rayleigh light scattering along with dye binding assays. The ThT kinetics measurements analysis suggested that GLY deaccelerates fibrillation by decrement of apparent rate(K_app) constant. The inhibitory effect of GLY might be attributed to native structure stabilization of HSA by obstruction into β-sheet conversion as confirmed by CD spectroscopy results. Amyloid inhibition and suppression of amyloid-induced hemolysis by GLY was further delineated by TEM and SEM analysis respectively. All these findings for the first time report the new facet of the anti-amyloidogenic potential of GLY, making it a promising candidate to treat neurodegenerative diseases too in the near future.

Development of a novel fluorescence assay for studying lipid bilayer perturbation induced by amyloidogenic peptides using cell plasma membrane vesicles

Numerous pathophysiological conditions are associated with the misfolding and aggregation of proteins into insoluble amyloid fibrils. The mechanisms by which this process leads to cellular dysfunction remain elusive, though several hypotheses point toward the perturbation of the cell plasma membrane by pre-fibrillar intermediates and/or amyloid growth. However, current models to study membrane perturbations are largely limited to synthetic lipid vesicles and most of experimental approaches cannot be transposed to complex cell-derived plasma membrane systems. Herein, vesicles originating from the plasma membrane of erythrocytes and β-pancreatic cells were used to study the perturbations induced by an amyloidogenic peptide, the islet amyloid polypeptide (IAPP). These biologically relevant lipid vesicles displayed a characteristic clustering in the presence of the amyloidogenic peptide, which was able to rupture membranes. By exploiting Förster resonance energy transfer (FRET), a rapid, simple, and potentially high-throughput assay to detect membrane perturbations of intact mammalian cell plasma membrane vesicles was implemented. The FRET kinetics of membrane perturbations closely correlated with the kinetics of thioflavin-T fluorescence associated with amyloid formation. This novel kinetics assay expands the toolbox available to study amyloid-associated membrane damage, bridging the gap between synthetic lipid vesicles and living cells.

Autooxidation of curcumin in physiological buffer causes an enhanced synergistic anti-amyloid effect

Curcumin is an important food additive that shows multiple medical-benefits including anticarcinogenic, anti-inflammatory, antibiotic and antiamyloid properties. However, understanding the mechanism of curcumin-mediated effects becomes rather complicated since it has low bio-viability and it undergoes autooxidation, influenced by temperature, pH and buffer. We find that curcumin's antiamyloid-potential is not primarily due to curcumin alone, rather due to a synergistic action of curcumin and its autooxidized-products generated during inhibition reactions. In physiological buffer curcumin undergoes thermally induced autooxidation and yields stable compounds which can synergistically work for both inhibition of amyloid aggregation and promotion of amyloid-disaggregation into soluble protein species. Curcumin also showed substantial inhibition effect against coaggregation of different food proteins. Curcumin's strong affinity for the hydrophobic moieties of the aggregation-prone partially-folded insulin structures seems crucial for the inhibition mechanism. Further, autooxidized curcumin products were found to protect UV-induced protein damage. The results provide conceptual foundations highlighting the link between chemistry and antiamyloid-activity of curcumin and may inspire curcumin-based therapeutics against amyloidogenesis.

Mechanistic Insights into the Neuroprotective Potential of Sacred Ficus Trees

Ficus religiosa (Bo tree or sacred fig) and Ficus benghalensis (Indian banyan) are of immense spiritual and therapeutic importance. Various parts of these trees have been investigated for their antioxidant, antimicrobial, anticonvulsant, antidiabetic, anti-inflammatory, analgesic, hepatoprotective, dermoprotective, and nephroprotective properties. Previous reviews of Ficus mostly discussed traditional usages, photochemistry, and pharmacological activities, though comprehensive reviews of the neuroprotective potential of these Ficus species extracts and/or their important phytocompounds are lacking. The interesting phytocompounds from these trees include many bengalenosides, carotenoids, flavonoids (leucopelargonidin-3-O-β-d-glucopyranoside, leucopelargonidin-3-O-α-l-rhamnopyranoside, lupeol, cetyl behenate, and α-amyrin acetate), flavonols (kaempferol, quercetin, myricetin), leucocyanidin, phytosterols (bergapten, bergaptol, lanosterol, β-sitosterol, stigmasterol), terpenes (α-thujene, α-pinene, β-pinene, α-terpinene, limonene, β-ocimene, β-bourbonene, β-caryophyllene, α-trans-bergamotene, α-copaene, aromadendrene, α-humulene, alloaromadendrene, germacrene, γ-cadinene, and δ-cadinene), and diverse polyphenols (tannin, wax, saponin, leucoanthocyanin), contributing significantly to their pharmacological effects, ranging from antimicrobial action to neuroprotection. This review presents extensive mechanistic insights into the neuroprotective potential, especially important phytochemicals from F. religiosa and F. benghalensis. Owing to the complex pathophysiology of neurodegenerative disorders (NDDs), the currently existing drugs merely alleviate the symptoms. Hence, bioactive compounds with potent neuroprotective effects through a multitarget approach would be of great interest in developing pharmacophores for the treatment of NDDs.

A Non-aqueous Capillary Electrophoresis for Determination of Eugenol in Cloves and Dental Preparations

A total non-aqueous capillary electrophoresis method was developed and applied for the first time for the quantification of eugenol in cloves and dental preparations. The optimized conditions included a buffer consisting of 150 mM sodium acetate and 300 μL 1 M acetic acid methanol solution (30 mM), an applied voltage of 25 kV, and a temperature of 25 °C and an applied wavelength of 214 nm. The developed method of determining the eugenol was characterized by the following parameters: a detection time within 1.97 min, good linearity (R2 = 0.9989–0.9999), detection limit at the level from 0.19 to 0.35 µg mL−1, very good extraction yield of 99.6–100.6% from both methanol standard solutions, clove buds’ matrix, and dental preparations. Limit of quantitation at the level from 0.81 to 0.98 µg mL−1. The method is based on the developed one-step extraction procedure. Moreover, the developed method does not require the use of any eugenol solubility enhancers such as SDS.

Effects of eugenol on the behavioral and pathological progression in the MPTP-induced Parkinson's disease mouse model

Parkinson's disease (PD) is the world's second most common neurological disorder. Oxidative stress and neuroinflammation play a crucial role in the pathogenesis of PD. Eugenol is a phytochemical with potent antioxidant and anti-inflammatory activity. The present investigation is aimed to study the effect of eugenol in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced mouse model of PD and its relationship to antioxidant effect. The effects of seven days of oral pre-treatment and post-treatment with three doses of eugenol (25, 50 and 100 mg/kg/day) were investigated against the MPTP-induced PD mouse model. In addition to the assessment of behavioural parameters using various tests (actophotometer, beam walking test, catalepsy, rearing, rotarod), biochemical parameters including lipid peroxidation and reduced glutathione levels in brain tissues, were also estimated in this study. The binding mode of eugenol in the human myeloid differentiation factor-2 (hMD-2) was also studied. Results showed that MPTP administration in mice resulted in the development of motor dysfunction (impaired motor coordination and hypo locomotion) similar to that of PD in different behavioural studies. Pre-treatment with eugenol reversed motor dysfunction caused by MPTP administration while post-treatment with eugenol at a high dose aggravated the symptoms of akinesia associated with MPTP administration. MPTP resulted in increased lipid peroxidation while decreased reduced glutathione levels in the brains of mice. MPTP-induced increased lipid peroxidation and attenuated levels of reduced glutathione were found to be alleviated with eugenol pre-treatment while augmented with eugenol post-treatment. Eugenol showed a binding affinity of -6.897 kcal/mol against the MD2 coreceptor of toll-like receptor-4 (TLR4). Biochemical, as well as neurobehavioral studies, showed that eugenol is having a protective effect, but does not have a curative effect on PD.

The anti-campylobacter activity of eugenol and its potential for poultry meat safety: A review

Poultry is one of the fastest growing industries due to advantages in land use, rapid production and advances in feed technology. The rising trend in the consumption of poultry meat over the last 50 years has also increased concerns about food safety. Campylobacter jejuniis the leading bacterial cause of gastroenteritis, the foremost cause of foodborne deaths. Despite significant progress in food safety methology, the genusCampylobacter remains a common foodborne pathogen in poultry. Increasing consumer demands for natural products require the discovery of new antimicrobials to ensure the safety of poultry meat. Recent studies have revealed that eugenol acts with antimicrobial activity on a wide variety of foodborne microorganisms. Eugenol is generally recognized as safe and is a promising preservative for the food industry. However, specific applications of eugenol need to be identified and validated to clarify the role of the food preservative in poultry meat safety.

Sulfated polysaccharide ascophyllan prevents amyloid fibril formation of human insulin and inhibits amyloid-induced hemolysis and cytotoxicity in PC12 cells

We found that ascophyllan significantly inhibited the fibrillation of human insulin and was the most effective among the sulfated polysaccharides tested. Gel-filtration analysis suggested that ascophyllan was capable of forming a complex with insulin through a weak interaction. Secondary structure transition from native α-helix to β-sheet predominant structure of insulin under the fibrillation conditions was suppressed in the presence of ascophyllan. Interestingly, ascophyllan attenuated insulin fibril-induced hemolysis of human erythrocytes. Moreover, ascophyllan attenuated insulin amyloid-induced cytotoxicity on rat pheochromocytoma PC12 cells and reduced the level of intracellular reactive oxygen species. This is the first report indicating that a sulfated polysaccharide, ascophyllan, can suppress the insulin amyloid fibril formation and inhibit the fibril-induced detrimental bioactivities.

Enhanced Bioavailability of Dihydrotanshinone I-Bovine Serum Albumin Nanoparticles for Stroke Therapy

Dihydrotanshinone I (DHT) is a natural component in Salvia miltiorrhiza and has been widely researched for its multiple bioactivities. However, poor solubility and biocompatibility of DHT limit its desirable application for clinical purposes. Herein, DHT was encapsulated with bovine serum albumin (BSA) to enhance bioavailability. Compared to free DHT, DHT-BSA NPs (nanoparticles) showed an improved solubility in normal saline and increased protection against hydrogen peroxide-induced oxidative damage in PC12 cells. In addition, DHT-BSA NPs administered by intravenous injection displayed a significant efficacy in the middle cerebral artery occlusion/reperfusion models, without any impact on the cerebral blood flow. In summary, DHT-BSA NPs show an enhanced bioavailability compared with free DHT and a successful penetration into the central nervous system for stroke therapy, demonstrating their application potential in cardio-cerebrovascular diseases.

Evidence of Anti-amyloid Characteristics of Plumbagin via Inhibition of Protein Aggregation and Disassembly of Protein Fibrils

The biological consequences associated with the conversion of soluble proteins into insoluble toxic amyloids are not only limited to the onset of neurodegenerative diseases but also to the potential health risks associated with supplements of protein therapeutic agents as well. Hence, finding inhibitors against amyloid formation is important, and natural product-based anti-amyloid compounds have gained much interest because of their higher efficacy and biocompatibility. Plumbagin has been identified as a potential natural product with multiple medical benefits; however, it remains largely unclear whether plumbagin can act against amyloid formation of proteins. Here, we show that plumbagin can effectively inhibit the temperature-induced amyloid aggregation of important proteins (insulin and serum albumin). Both experimental and computational data revealed that the presence of plumbagin in protein solutions, under aggregating conditions, promotes a direct protein-plumbagin interaction, which is predominantly stabilized by stronger H-bonds and hydrophobic interactions. Plumbagin-mediated retention of the native structures of proteins appears to play a crucial role in preventing their conversion into insoluble β-sheet-rich amyloid aggregates. More importantly, the addition of plumbagin into a suspension of protein fibrils triggered their spontaneous disassembly, promoting the release of soluble proteins. The results highlight that a possible synergistic effect via both the stabilization of protein structures and the restriction of the monomer recruitment at the fibril growth sites could be important for the mechanism of plumbagin's anti-aggregation effect. These findings may inspire the development of plumbagin-based formulations to benefit both the prevention and treatment of amyloid-related health complications.

Antioxidant thymoquinone and eugenol alleviate TiO2 nanoparticle-induced toxicity in human blood cells in vitro

Titanium dioxide (TiO₂) nanoparticles (NPs) are used extensively in a variety of commercial, industrial, and medical products, due to which human exposure is inevitable. This study aimed to explore the potential of eugenol and thymoquinone (TQ), two well-known antioxidants, in counteracting the NP-induced toxicity in human blood cells in vitro. Fresh lymphocytes and erythrocytes were isolated from volunteer human blood donors and incubated with 50 μg/mL of TiO₂ NPs in the presence and absence of 50 μM of TQ and 20 μg/mL of eugenol for 3 h. Results showed that NP-treatment-induced hemolysis, oxidative stress, lactate dehydrogenase (LDH) leakage, and reduced ATPase activity in the erythrocytes. In the lymphocytes treated with NPs alone (50 μg/mL), cytotoxicity in MTT assay and DNA damage in comet assay were observed; in addition, mitochondrial membrane potential collapsed and ADP/ATP ratio increased indicating mitochondrial function impairment. However, in the presence of antioxidants, all these NP-induced changes were mitigated significantly. The results were more significant when both antioxidants eugenol and TQ were given together. Thus, it seems that antioxidants eugenol and TQ can be used as a protective agent against TiO₂ NP-induced toxicity.

Blended polar/nonpolar peptide conjugate interferes with human insulin amyloid-mediated cytotoxicity

Insulin, a peptide hormone and a key regulator of blood glucose level, is routinely administered to type-I diabetic patients to achieve the required glycemic control. Insulin aggregation and ensuing amyloidosis has been observed at repeated insulin injection sites and in injectable formulations. The latter occurs due to insulin agglomeration during shipping and storage. Such insulin amyloid leads to enhanced immunogenicity and allow potential attachment to cell membranes leading to cell permeability and apoptosis. Small molecule inhibitors provide useful interruption of this process and inhibit protein misfolding as well as amyloid formation. In this context, we report the propensity of a palmitoylated peptide conjugate to inhibit insulin aggregation and amyloid-mediated cytotoxicity, via designed interference with polypeptide interfacial interactions.

Effects of Eugenol on Memory Performance, Neurogenesis, and Dendritic Complexity of Neurons in Mice Analyzed by Behavioral Tests and Golgi Staining of Brain Tissue

Eugenol, as the main component in clove, has neuroprotective abilities, including its effect to learning memory of mice. However, there is no evidence showing whether eugenol can expand the growth of dendrites in the brain. The objective of this research was to examine the effects of eugenol towards dendritic complexity of neurons, neurogenesis, and memory performance in hippocampus. A total of 21 mice were divided into three groups; (i) mice were administered 30 mg/kg bw eugenol orally, (ii) mice were administered 100 mg/kg bw eugenol orally, and (iii) mice were administered distilled water as control. Mice were kept for 30 consecutive days following the standard animal housing. The memory performance was observed through the Y-arm maze alternation, Novel Object Recognition (NOR), and Morris Water Maze (MWM) test. The brain was dissected and stained with FD Rapid Golgi StainingTM kit to observe dendrites in the dentate gyrus (DG) and cornu ammonis 1 (CA1) region; and Haematoxylin-Eosin (HE) staining to assess neurogenesis in the DG. Our results showed that eugenol enhanced putative neural stem cells (NPCs) and granular cells (GC) number, and also decrease neuronal cell death in DG (p<0.0001). Eugenol also increased dendritic complexity of neurons in DG region; while in CA1, eugenol has given a positive effect only on the basal area. Eugenol increased spatial and recognition memory in mice, indicated by a higher number of correct alternations and discrimination ratio compared to the control group (p<0.05), although escape latency in MWM did not show significant effect (p>0.05). As analyzed by behavioral tests and Golgi staining of brain tissue, eugenol can increase memory performance, neurogenesis, and dendritic complexity of neurons in the DG and CA1 basal region of brain in mice.

Osmoprotectant Coated Thermostable Gold Nanoparticles Efficiently Restrict Temperature-Induced Amyloid Aggregation of Insulin

Naturally occurring osmoprotectants are known to prevent aggregation of proteins under various stress factors including extreme pH and elevated temperature conditions. Here, we synthesized gold nanoparticles coated with selected osmolytes (proline, hydroxyproline, and glycine) and examined their effect on temperature-induced amyloid-formation of insulin hormone. These uniform, thermostable, and hemocompatible gold nanoparticles were capable of inhibiting both spontaneous and seed-induced amyloid aggregation of insulin. Both quenching and docking experiments suggest a direct interaction between the osmoprotectant-coated nanoparticles and aggregation-prone hydrophobic stretches of insulin. Circular-dichroism results confirmed the retention of insulin's native structure in the presence of these nanoparticles. Unlike the indirect solvent-mediated effect of free osmolytes, the inhibition effect of osmolyte-coated gold nanoparticles was observed to be mediated through their direct interaction with insulin. The results signify the protection of the exposed aggregation-prone domains of insulin from temperature-induced self-assembly through osmoprotectant-coated nanoparticles, and such effect may inspire the development of osmolyte-based antiamyloid nanoformulations.

Polyphenol binding disassembles glycation-modified bovine serum albumin amyloid fibrils

Glycation of protein results in the formation of advanced glycation end-products (AGEs) and leads to deposition as amyloid fibrils. Adhesive structural properties of polyphenols to aromatic amino acids draw significance in promoting, accelerating and/or stabilizing on-pathway and off-pathway folding intermediates, although the mechanistic action remains unclear. In this study, polyphenols remodeling mature AGEs modified amyloid fibrils were investigated through UV-visible spectroscopy, fluorescence spectroscopy, transmission electron microscopy, atomic force microscopy, circular dichroism spectroscopy, MALDI-MS/MS analysis and molecular docking studies. Our findings confirmed the glycation-mediated transformation of native protein into β-sheet rich amyloid fibrils. SDS-PAGE results suggested the presence of shorter peptide fragments ranging from ~10 kDa to ~40 kDa. MALDI-MS/MS results identified the plausible sequences to be His105-His181, Arg193-Lys242, Leu325-Tyr410, and Ala451-Tyr529. TEM and AFM results suggested that polyphenols binding mature amyloid fibrils remodel/disassemble them into distinct aggregate structures or non-amyloid fibrils. Circular dichroism studies suggested that polyphenols upon binding amyloid fibrils stabilizes and transforms the secondary structure towards helical or random coil-like conformation. Molecular modeling studies suggested high binding affinity and hydrophobic interaction to be the main driving force in remodeling perspective. Together, our findings suggest that polyphenols could differentially remodel mature AGEs-modified amyloid fibrils into distinct aggregate structures through non-covalent interactions and can alleviate AGEs-mediated amyloidosis.

Polyphenols redirects the self-assembly of serum albumin into hybrid nanostructures

Chronic hyperglycemia results in the formation of advanced glycation end-products (AGEs) and triggers amyloid fibril formation. Molecules designed to inhibit amyloid fibrils function by eliminating toxic oligomers or reducing fibril formation. Here, the bioactivity of polyphenols in redirecting the self-assembly of amyloid fibrils was reported through microscopic, spectroscopic and molecular docking studies. Our findings illustrate that glycation causes BSA to self-assemble into amyloid fibrils. 17 Lys residues had modified to carboxy methyl lysine (CML) but only Lys523 was probable of modifying into carboxy ethyl lysine (CEL). In contrast, only 6 Arg residues are identified to be modified to Argpyrimidine (Arg-p). A simple polyphenol baicalein (BLN) redirect the self-assembly of amyloid fibrils into off-pathway hybrid nanostructures. Circular dichroism spectroscopic studies suggested that in the presence of BLN helical conformation was favored. Molecular modeling studies suggested that hydrogen bonding and hydrophobic interaction of polyphenols preferentially at crucial amyloidogenic regions can hinder amyloid fibrillation (Phe133, Lys136, Tyr137, Ile141, Tyr160 and Arg185). Mass spectrometric results illustrated that the presence of a simple polyphenol BLN several residues are unmodified to CML, CEL or Arg-p. Together, our findings suggest that polyphenols could have a protective effect and the redirection can help alleviate the amyloid fibril formation.

Inhibition of BACE1, MAO-B, cholinesterase enzymes, and anti-amyloidogenic potential of selected natural phytoconstituents: Multi-target-directed ligand approach

Alzheimer's disease (AD) is a neurodegenerative disorder, and multiple factors are involved in disease progression. This is why there is an urgent need to develop novel molecules with multi-target-directed ligands (MTDLs) potential. The current study explores the active phytoconstituents from traditionally used medicinal spices, namely piperine, cinnamaldehyde, eugenol, cuminaldehyde, and alpha-terpinyl acetate for the inhibition of β-secretase, monoamine oxidase, cholinesterase enzymes, anti-aggregation of amyloid β (Aβ) fibrils, and their protective effect against hydrogen peroxide (H₂ O₂ ) and Aβ-induced toxicity. Eugenol showed inhibitory activity against MAO-B enzyme, free radical scavenging activity, and anti-aggregation activity against Aβ peptides than other phytoconstituents. It also demonstrated a significant cytoprotective effect against H₂ O₂ -induced oxidative stress and Aβ-induced cytotoxicity in pheochromocytoma (PC) 12 cells. A molecular docking study of eugenol showed interactions with active site residue of the target enzymes. The study successfully demonstrated that eugenol could have an MTDLs potential better than synthesized drugs used in the treatment of AD. PRACTICAL APPLICATIONS: The present study demonstrated multi-target-directed ligand potential of eugenol and can be developed to treat complex diseases like Alzheimer's. Eugenol can bind to different Alzheimer's targets such as β-secretase (BACE1), Monoamine oxidase B (MAO-B), Cholinesterase's, and amyloid β_1-42 fibrils and might have a disease-modifying potential. The other natural phytoconstituents such as piperine, cinnamaldehyde, cuminaldehyde, and alpha-terpinyl acetate also demonstrated MTDL potential could also be used for developing novel molecules for disease-modifying effect. It also protects against oxidative stress.

Molecular Interaction of Protein-Pigment C-Phycocyanin with Bovine Serum Albumin in a Gomphosis Structure Inhibiting Amyloid Formation

Accumulation of amyloid fibrils in organisms accompanies many diseases. Natural extracts offer an alternative strategy to control the process with potentially fewer side effects. In this study, the inhibition of C-phycocyanin from Spirulina sp. on amyloid formation of bovine serum albumin (BSA) during a 21-day incubation was investigated using fluorescence and circular dichroism (CD), and mechanisms were explored via kinetic fitting and molecular docking. C-phycocyanin (0-50 µg/mL) hindered the amyloid formation process of BSA with increased half-lives (12.43-17.73 days) based on fluorescence intensity. A kinetic model was built and showed that the k₁ decreased from 1.820 × 10^-2 d^-1 to 2.62 × 10^-3 d^-1 with the increase of C-phycocyanin, while k₂ showed no changes, indicating that the inhibition of BSA fibrillation by C-phycocyanin occurred in a spontaneous process instead of self-catalyzed one. CD results show that C-phycocyanin inhibited conformational conversion (α-helices and β-sheets) of BSA from day 6 to day 18. Molecular docking suggested that C-phycocyanin may hinder BSA fibrillation by hydrogen-bonding > 6 of 27 α-helices of BSA in a gomphosis-like structure, but the unblocked BSA α-helices might follow the self-catalytic process subsequently.

Ribosylation induced structural changes in Bovine Serum Albumin: understanding high dietary sugar induced protein aggregation and amyloid formation

Non-enzymatic glycation of proteins is believed to be the root cause of high dietary sugar associated pathophysiological maladies. We investigated the structural changes in protein during progression of glycation using ribosylated Bovine Serum Albumin (BSA). Non enzymatic attachment of about 45 ribose molecules to BSA resulted in gradual reduction of hydrophobicity and aggregation as indicated by red-shifted tryptophan fluorescence, reduced ANS binding and lower anisotropy of FITC-conjugated protein. Parallely, there was a significant decrease of alpha helicity as revealed by Circular Dichroism (CD) and Fourier transformed-Infra Red (FT-IR) spectra. The glycated proteins assumed compact globular structures with enhanced Thioflavin-T binding resembling amyloids. The gross structural transition affected by ribosylation led to enhanced thermostability as indicated by melting temperature and Transmission Electron Microscopy. At a later stage of glycation, the glycated proteins developed non-specific aggregates with increase in size and loss of amyloidogenic behaviour. A parallel non-glycated control incubated under similar conditions indicated that amyloid formation and associated changes were specific for ribosylation and not driven by thermal denaturation due to incubation at 37 °C. Functionality of the glycated protein was significantly altered as probed by Isothermal Titration Calorimetry using polyphenols as substrates. The studies demonstrated that glycation driven globular amyloids form and persist as transient intermediates during formation of misfolded glycated adducts. To the best of our knowledge, the present study is the first systematic attempt to understand glycation associated changes in a protein and provides important insights towards designing therapeutics for arresting dietary sugar induced amyloid formation.

Transbuccal delivery of benznidazole associated with monoterpenes: permeation studies and mechanistic insights

Benznidazole (BZN) represents the only drug currently available for the treatment of Chagas disease in most endemic countries. When administered orally, high doses are required due to its extensive hepatic metabolism and its toxicity represents the main reason for treatment withdrawals. Because of these complications, transbuccal administration of BZN was investigated. This route avoids the first-pass hepatic metabolism and presents high permeability, with direct access to the systemic circulation. BZN was applied on porcine buccal mucosa after pretreatment with pure eugenol, carvacrol or limonene. Thermal (DSC) and spectroscopic (FT-IR) analyzes were performed to investigate the mechanisms of drug absorption enhancement. The permeability coefficient values of BZN increased 2.6, 2.9 and 4.9-fold after pretreatment with eugenol, carvacrol and limonene, respectively. The lag time, in turn, was shortened in the pretreated samples. The DSC and FT-IR analyzes suggested that transport of BZN through the buccal mucosa is associated with log P and size of monoterpenes. Limonene, the most effective absorption enhancer, contributed to greater interaction with non-polar domains of the buccal epithelium. Overall, BZN showed to be efficiently transported through the buccal route, but in vivo pharmacokinetic studies should be performed to confirm these findings.

Amyloid cross-seeding raises new dimensions to understanding of amyloidogenesis mechanism

Hallmarks of most of the amyloid pathologies are surprisingly found to be heterocomponent entities such as inclusions and plaques which contain diverse essential proteins and metabolites. Experimental studies have already revealed the occurrence of coaggregation and cross-seeding during amyloid formation of several proteins and peptides, yielding multicomponent assemblies of amyloid nature. Further, research reports on the co-occurrence of more than one type of amyloid-linked pathologies in the same individual suggest the possible cross-talk among the disease related amyloidogenic protein species during their amyloid growth. In this review paper, we have tried to gain more insight into the process of coaggregation and cross-seeding during amyloid aggregation of proteins, particularly focusing on their relevance to the pathogenesis of the protein misfolding diseases. Revelation of amyloid cross-seeding and coaggregation seems to open new dimensions in our mechanistic understanding of amyloidogenesis and such knowledge may possibly inspire better designing of anti-amyloid therapeutics.

Quantum Dots as Promising Theranostic Tools Against Amyloidosis: A Review

Amyloids are highly ordered beta sheet rich stable protein aggregates, which have been found to play a significant role in the onset of several degenerative diseases such as Alzheimer's disease, Huntington's disease, Parkinson's disease, Type II diabetes mellitus and so on. Aggregation of proteins leading to amyloid fibril formation via intermediate(s), is thought to be a nucleated condensation polymerization process associated with many pathological conditions. There has been extensive research to identify inhibitors of these disease oriented aggregation processes. In recent times, quantum dots, with their unique physico-chemical properties have grabbed the attention of scientific community due to its applications in medical sciences. Quantum dots are nano-particles usually made of semiconductor materials which emit fluorescence upon radiation. The wavelength of fluorescence emission varies with changes in size of quantum dots. Several studies have reported significant inhibitory effects of these quantum dots towards amyloidogenesis, thereby presenting themselves as promising candidates against amyloidosis. Further, studies have also revealed amyloid detection capacity of quantum dots with sensitivity and specificity better than conventional probes. In the current review, we will discuss the various effects of quantum dots on protein aggregation pathways, their mechanism of actions and their potentials as effective therapeutics against amyloidosis.

Monocyclic phenolic compounds stabilize human insulin and suppress its amorphous aggregation: In vitro and in vivo study

Insulin is a small protein with 51 residues that mediates glucose uptake, and an interesting model for studying protein misfolding and aggregation. The aggregated forms of insulin undergo loss of activity and can provoke unwanted immune responses. Use of small molecules is considered to be an affordable method to counteract this aggregation process and stabilize insulin. In this study, aggregated forms of human recombinant insulin have been produced following exposure to high temperature. Aggregation process was followed over time by checking absorbance with spectrophotometry in presence and absence of various concentrations of small phenolic compounds including eugenol and epinephrine. Effects of these compounds on the structure and function of incubated insulin were evaluated by spectrofluorimetry, melting temperature (Tm) measurement and insulin tolerance test on Wistar rats. Formation of heat-induced insulin aggregation can be effectively inhibited by 1 mM eugenol and epinephrine and both compounds were found to preserve insulin activity to a considerable extent. In conclusion, simple aromatic compounds could be tailored to act as potent anti-aggregation compounds for insulin.

Modulating amyloid fibrillation in a minimalist model peptide by intermolecular disulfide chemical reduction

Peptide structural transformation and aggregation is associated with a large number of outsider aetiology diseases, and it is intrinsically linked to amyloid peptide aggregation. Diphenylalanine self-assembled structures are used as robust minimalist beta amyloids not only to elucidate protein aggregation but also to generate hydrogels. Herein, we employed a neutral model peptide Ac-Phe-Phe-Cys-NH2 (Ac-FFC-NH2) to elucidate the role of intermolecular disulfide bonds in protein fibrillation. The Ac-FFC-NH2 peptide initially self-assembles into nanospheres that evolve to amyloid type fibrils under mild oxidative conditions. Incubation of the peptide in the presence of the chemical reduction agent TCEP inhibits the formation of the fibrils, detecting only spherical nanostructures with no secondary structure. Importantly, we triggered the transformation of the preformed linear straight amyloid fibrils to non-fibrillar structures by TCEP treatment. Under this condition, the amyloid bundles are transformed into rings, which evolve to a new spherical microstructure. We showed that the chemical reduction of intermolecular S-S in internal amyloid sequences might favour the off-path intermediates of amyloid fibril growth, even when the fibrils are formed. Our findings demonstrated that in internal amyloid sequences, the formation of intermolecular S-S promotes the formation of amyloid type fibrils; meanwhile, its reduction stabilises non-fibrillar structures. Altogether, this work provides fundamental understanding at the molecular and supramolecular level, thus facilitating the rational design of therapeutic tools for protein aggregation diseases.

Exploration of Fungal Lipase as Direct Target of Eugenol through Spectroscopic Techniques

BACKGROUND

Fungal lipase dependent processes are important for their pathogenicity. Lipases can therefore be explored as direct target of promising herbal antifungals.

OBJECTIVE

We explored Aspergillus niger lipase as a direct target of eugenol through spectroscopic techniques and compare results with Bovine Serum Albumin and lysozyme to comment on selectivity of eugenol towards lipase.

METHODS

In vitro activity assays of lipase are used to determine concentration ranges. UV-Visible, Fluorescence and Circular dichroism spectroscopy were employed to determine binding constant, stoichiometric binding sites and structural changes in Lipase, BSA and lysozyme following incubation with varying concentrations of eugenol.

RESULTS

In activity assays 50% inhibition of lipase was obtained at 0.913 mmoles/litre eugenol. UV-vis spectroscopy shows formation of lipase-eugenol, Bovine Serum Albumin-eugenol and lysozyme-eugenol complex well below this concentration of eugenol. Eugenol binding caused blue shift with Bovine Serum Albumin and lysozyme suggestive of compaction, and red shift with lipase. Negative ellipticity decreased with lipase but increased with Bovine Serum Albumineugenol and lysozyme-eugenol complexes suggesting loss of helical structure for lipase and compaction for Bovine Serum Albumin and lysozyme. Binding of eugenol to lipase was strong (Ka= 4.7 x 106 M-1) as compared to Bovine Serum Albumin and lysozyme. The number of stoichiometric eugenol binding sites on lipase was found to be 2 as compared to 1.37 (Bovine Serum Albumin) and 0.32 (lysozyme). Docking results also suggest strong binding of eugenol with lipase followed by Bovine Serum Albumin and lysozyme.

CONCLUSION

Eugenol is found to be effective inhibitor and disruptor of secondary and tertiary structure of lipase, whereas its binding to Bovine Serum Albumin and lysozyme is found to be weak and less disruptive of structures suggesting selectivity of eugenol towards lipase.

Lead optimization for promising monoamine oxidase inhibitor from eugenol for the treatment of neurological disorder: synthesis and in silico based study

Natural based inhibitors of monoamine oxidase are promising drug candidates for the treatment of several neurodegenerative and neuropsychological disorders including depression, anxiety, Parkinson’s disease and Alzheimer’s disease. In the present study we designed and synthesized the eugenol based derivatives and investigated them for human MAO inhibitory potential as promising candidates for therapeutics of neurological disorders. Moreover, radical scavenging activity of designed derivatives was tested by and H₂O₂ and DPPH scavenging methods. Eugenol based derivatives were designed and synthesized for human MAO inhibitory action. The in silico and in vitro models were utilized for the evaluation of hMAO inhibition. The insight into molecular interactions among the compounds and both hMAO-A and hMAO-B active site was achieved by molecular docking studies. The two spectrophotometric titrations techniques were used to evaluate antioxidant potential. Compounds 5b and 16 were found as most active hMAO-A inhibitors with IC₅₀ values of 5.989 ± 0.007 µM and 7.348 ± 0.027 µM respectively, through an appreciable selectivity index value of 0.19 and 0.14 respectively. In case of hMAO-B inhibition compounds 13a and 13b were found as most active hMAO-B inhibitors with IC₅₀ values of 7.494 ± 0.014 µM and 9.183 ± 0.034 µM receptively and outstanding value of selectivity index of 5.14 and 5.72 respectively. Radical scavenging assay showed that compounds 5b, 5a, 9b, 9a were active antioxidants. The findings of present study indicated excellent correlation among dry lab and wet lab hMAO inhibitory experiments. Interestingly, the compounds exhibiting better MAO inhibition activity was also appeared as good antioxidant agents.

Inhibition of the formation of amyloid-like fibrils with spices, especially cloves

During the study of inhibition of amyloid fibril formation, α-chymotrypsin protein was developed in 55% ethanol at pH 7.0. We investigated the inhibitory effect of different spices on amyloid fibril formation using turbidity measurements and Congo red binding assays. We found that all spices except the black pepper and caraway seed prevented fibril formation. The highest inhibition was measured with the clove, which reduced the amount of aggregates by 90%. We studied the inhibitory effect of the cloves at different concentrations on aggregation, it was found that the inhibitory activity of clove is dependent on concentration. We have measured the total phenolic content of the spice extracts too. Based on all these findings we have come to the following conclusion: Our results indicate that spices can contain other compounds too - not only phenolic compounds - which influence the formation of amyloid fibrils, and the effectiveness of various phenolic compounds are different.

Influence of eugenol on oxidative stress biomarkers in the liver of carrageenan-induced arthritis rats

Background Eugenol is the foremost constituent of clove oil and widely distributed in many plants. It possesses many pharmaceutical applications, including antioxidant, anti-inflammatory, and anti-tumorigenic properties, among others. This study evaluates the influence of eugenol on oxidative stress biomarkers in the liver of carrageenan-induced arthritis (CIA) rats. Methods Sixty albino rats were randomly divided into 10 (n=6) groups. Group I is the control group that received saline solution orally. Groups II and VII rats received 2.5 mg/kg of eugenol orally (EUG-2.5). Rats in groups III/VIII and IV/IX received 5 and 10 mg/kg of eugenol orally (EUG-5 and EUG-10), respectively. Groups V and X received 0.2 mg/kg of dexamethasone (DEX-0.2) orally. Groups VI to X were injected with 1% carrageenan intra-articularly. Behavioral studies were conducted after 21 days of treatment. Thereafter, the animals were sacrificed, and the livers were isolated and used for biochemical analysis. Results Reduced body weight in arthritic rats was recorded compared to normal controls. Reduced tibiofemoral joint edema and increased spontaneous movement were observed in CIA rats with decreased superoxide dismutase, catalase, reduced glutathione (GSH), glutathione peroxidase, and GSH S-transferase activities compared with the normal control group. Increased endogenous enzyme activities and decreased elevated lipid peroxidation were also observed after eugenol treatment. Conclusion Eugenol ameliorates carrageenan-induced oxidative stress in the liver of arthritic rats.

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.

Interactions of natural organic matter on the surface of PVP-capped silver nanoparticle under different aqueous environment

It is now widely accepted that coating on the nano-surface would critically dictate the uptake and cytotoxicity of engineering nanomaterials. However, the influence of natural organic matter (NOM) on the surface is quite limited to humic substances, while the diversity of NOM is neglected. In the present study, we tried to investigate the change of surface in the coexistence of bovine serum albumin (BSA) and humic acid (HA). The isothermal titration calorimetric measurements show that HA can combine with BSA in both freshwater or seawater, however, the patterns are different. In freshwater, HA lowered the adsorption of BSA on PVP-capped AgNPs through complexation with BSA, which prevented the contact of sulfur in BSA with PVP-AgNPs. Then in seawater, BSA retained its sulfur availability to bind with PVP-AgNPs. Furthermore, the toxicity of PVP-AgNPs incubated in the BSA/HA solution was evaluated by measuring the level of reactive oxygen species generated by Escherichia coli. The results indicated that, in seawater, the adsorbed BSA promoted the toxicity of PVP-AgNPs in the presence of Ca²⁺ and Mg²⁺, but the presence of HA limited this effect.

Cyanidin-3-O-glucoside functions like chemical chaperone and attenuates the glycation mediated amyloid formation in albumin

In this study, chemical chaperone like function of cyanidin-3-O-glucoside (C3G) was investigated through fluorescence spectroscopy, UV-visible spectroscopy, circular dichroism spectroscopy, confocal microscopy, scanning electron microscopy and molecular docking studies. Early and advanced glycation inhibitory effect was evaluated by fluorescence spectroscopy and agarose gel electrophoresis. Amyloids were investigated based on their propensity to bind Congo Red (CR) and Thioflavin T (ThT) by multiple microscopic approaches. Circular dichroism studies were used to analyze the changes in the secondary structure due to glycation. C3G effectively inhibited early and advanced glycation by masking like function, carbonyl scavenging and chemical chaperone activity. C3G had molecular interaction with Glu186, Arg427, Ser428, Lys431, Arg435, and Arg458 of BSA. Based on the microscopic analysis, it is evident that C3G can inhibit protein aggregation and amyloid formation. Circular dichroism studies suggested that glycation had resulted in augmented β-sheet propensity, whereas C3G had a protective effect on the helical conformation of BSA. We conclude that C3G has a chemical chaperone like function on the event of glycation mediated amyloid formation in BSA.

Strategically Designed Antifibrotic Gold Nanoparticles to Prevent Collagen Fibril Formation

Because uncontrolled accumulation of collagen fibrils has been implicated in a series of pathologies, inhibition of collagen fibril formation has become one of the necessary strategies to target such collagen-linked complications. The presence of hydroxyproline (Hyp) at the Y position in (Gly-X-Y)_n sequence pattern of collagen is known to facilitate crucial hydrophobic and hydration-linked interactions that promote collagen fibril formation. Here, to target such Hyp-mediated interactions, we have synthesized uniform, thermostable, and hemocompatible Hyp coated gold nanoparticles (AuNPs^HYP) and have examined their inhibition effect on the fibril formation of type I collagen. We found that collagen fibril formation is strongly suppressed in the presence of AuNPs^HYP and no such suppression effect was observed in the presence of free Hyp and control Gly-coated nanoparticles at similar concentrations. Both isothermal titration calorimetric studies and bioinformatics analysis reveal possible interaction between Hyp and (Gly-Pro-Hyp) stretches of collagen triple-helical model peptides. Further, gold nanoparticles coated with proline (AuNPs^PRO) and tryptophan (AuNPs^TRP) also suppressed collagen fibril formation, suggesting their ability to interfere with aromatic-proline as well as hydrophobic interactions between collagen molecules. The Hyp molecules, when surface functionalized, are predicted to interfere with the Hyp-mediated forces that drive collagen self-assembly, and such inhibition effect may help in targeting collagen linked pathologies.