Synthesis, in silico, in vitro and in vivo studies of novel natural-based arylidenes curcumin as potential glycohydrolase digestive enzymes inhibitors.

Diabetes is one of the most common metabolic diseases in humans and the use of herbal medicines is of great clinical importance to inhibit carbohydrate-hydrolyzing enzymes and reduce blood glucose levels in diabetic patients. Inhibition of glycosidase activity is an effective way to treat and prevent diabetes. Therefore, in this study, curcumin-based benzaldehyde derivatives were synthesized and used as influential agents in the treatment of diabetes with inhibitory properties against two carbohydrate-hydrolyzing enzymes α-glucosidase (α-Glu) and α-amylase (α-Amy) as significant therapeutic targets for reducing postprandial hyperglycemia. Overall, the findings showed that due to the specific inhibitory activity against α-Glu in comparison with α-Amy, as well as more stability and antioxidant activity than curcumin, C5 and C8 derivatives are potentially important anti-diabetic drugs, not only to decrease glycemic index but also to limit the activity of the main production pathways of reactive oxygen species (ROS) in diabetic patients.Communicated by Ramaswamy H. Sarma.

Design, synthesis, spectroscopic characterizations, antidiabetic, in silico and kinetic evaluation of novel curcumin-fused aldohexoses.

Curcumin (bis-α,ß-unsaturated ß-diketone) plays an important role in the prevention of numerous diseases, including diabetes. Curcumin, as an enzyme inhibitor, has ideal structural properties including hydrophobic nature, flexible backbone, and several available hydrogen bond (H-bond) donors and acceptors. In this study, curcumin-fused aldohexose derivatives 3(a-c) were synthesized and used as influential agents in the treatment of diabetes with inhibitory properties against two carbohydrate-hydrolyzing enzymes α-glucosidase (α-Gls) and α-amylase (α-Amy) which are known to be significant therapeutic targets for the reduction of postprandial hyperglycemia. These compounds were isolated, purified, and then spectrally characterized via FT-IR, Mass, 1H, and 13C NMR, which strongly confirmed the targeted product's formation. Also, their inhibitory properties against α-Gls and α-Amy were evaluated spectroscopically. The Results indicated that all compounds strongly inhibited α-Amy and α-Gls by mixed and competitive mechanisms, respectively. The intrinsic fluorescence of α-Amy was quenched by the interaction with compounds 1 and 3b through a dynamic quenching mechanism, and the 1 and 3b/α-Amy complexes were spontaneously formed, mainly driven by the hydrophobic interaction and hydrogen bonding. Fourier transform infrared spectra (FT-IR) comprehensively verified that the binding of compounds 1 and 3b to α-Amy would change the conformation and microenvironment of α-Amy, thereby inhibiting the enzyme activity. Docking and molecular dynamics (MD) simulations showed that all compounds interacted with amino acid residues located in the active pocket site of the proteins. In vivo studies confirmed the plasma glucose diminution after the administration of compound 3b to Wistar rats. Accordingly, the results of the current work may prompt the scientific communities to investigate the possibility of compound 3b application in the clinic.

Synthesis and Potential Antidiabetic Properties of Curcumin-Based Derivatives: An In Vitro and In Silico Study of α-Glucosidase and α-Amylase Inhibition.

BACKGROUND: Over the past twenty years, the prevalence of diabetes as one of the most common metabolic diseases has become a public health problem worldwide. Blood glucose control is important in delaying the onset and progression of diabetes-related complications. α-Glycosidase (α- Glu) and α-amylase (α-Amy) are important enzymes in glucose metabolism. Diabetic control through the inhibition of carbohydrate hydrolyzing enzymes is established as an effective strategy. METHODS: In this study, curcumin-based benzaldehyde derivatives with high stability, bioavailability, and favorable efficiency were synthesized. RESULTS: The results showed that L13, L8, and L11 derivatives have the highest inhibitory effect on α-Glu with IC50 values of 18.65, 20.6, and 31.7 µM and, also L11, L13, and L8 derivatives have the highest inhibitory effect on α-Amy with IC50 value of 14.8, 21.8, and 44.9 µM respectively. Furthermore, enzyme inhibitory kinetic characterization was also performed to understand the mechanism of enzyme inhibition. CONCLUSION: L13, compared to the other compounds, exhibited acceptable inhibitory activity against both enzymes. The L13 derivative could be an appropriate candidate for further study through the rational drug design to the exploration of a new class of powerful anti-diabetic drugs considering the antioxidant properties of the synthesized compounds. The derivative helps reduce the glycemic index and limits the activity of the major reactive oxygen species (ROS) producing pathways.

The application of the QDs/H2O2 chemiluminescence system in HRP assay and HRP-based immunoassay.

Horseradish peroxidase (HRP) is usually used as a label enzyme in immunoassay so the method used for HRP detection in enzyme immunoassay (EIA) plays a key role in sensitivity and precision. The catalytic activity of HRP does not strictly follow classic Michaelis-Menten kinetics, probably due to the inactivation of the enzyme at high concentrations of H2O2. In this paper, a highly sensitive alternative procedure for the HRP assay using H2O2-sensitive CdTe quantum dots as a chemiluminescence (CL) system is reported. This method can measure a much more accurate and reliable value of Km (187 mM H2O2) in comparison with the standard detection method. This system also was applied to thyroid hormone (T4) detection using HRP-based immunoassay. The QD/H2O2 system exhibits a higher linear range of 0.2-16 µg/dL with the improved LOD value of 0.06 µg/dL and selective response to T4, which was better than the commercial colorimetric immunoassay. Meanwhile, the proposed method has been successfully applied to the clinical determination of T4 in the serum samples, and the results confirmed an excellent correlation with the conventional ELISA method (R2 = 0.9832), indicating the potential applications of the method for clinical diagnosis as well.

Mutual effects of protein corona formation on CdTe quantum dots.

Future biomedical applications of nanoparticles will encounter these particles with patients' serum which might affect the properties and stability of quantum dots and serum proteins at the desired site of action. Therefore, it is essential to clarify the patient-specific serum components, serve as major interaction partners, the spatial distribution of these, and consequently the time-dependent effects of nanoparticle-protein interaction. Here, a biochemical and structural study was performed on the protein corona formation and the corresponding interaction of different sizes of CdTe QDs with human serum proteins to determine if the mutual effects on optical properties by using electrophoresis, chemiluminescence, and fluorescence spectroscopy. The results revealed that interaction with human serum significantly enhanced the stability and photoluminescence of quantum dots. Structural studies of HSA-coated CdTe QDs also showed that corona formation has no adverse effects on protein structure, and the reduction in fluorescence emissions of HSA is due to the direct quenching of aromatics residues by the quantum dot. Improving nanoparticle properties, as well as the lack of structural changes in HSA, can be very useful in biomedical applications and in vivo studies where stability is important.

Enhanced sensitivity of VEGF detection using catalase-mediated chemiluminescence immunoassay based on CdTe QD/H2O2 system.

BACKGROUND: Since vascular endothelial growth factor (VEGF) is a significant regulator of cancer angiogenesis, it is essential to develop a technology for its sensitive detection. Herein, we sensitized a chemiluminescence (CL) immunoassay through the combination of H2O2-sensitive TGA-CdTe quantum dot (QD) as signal transduction, dextran as a cross-linker to prepare enzyme-labeled antigen and the ultrahigh bioactivity of catalase (CAT) as reporter enzyme. RESULTS: Under the optimized experimental conditions, the chemiluminescence enzyme-linked immunosorbent assay (CL-ELISA) method can detect VEGF in the excellent linear range of 2-35,000 pg mL-1, with a detection limit (S/N = 3) of 0.5 pg mL-1 which was approximately ten times lower than the commercial colorimetric immunoassay. This proposed method has been successfully applied to the clinical determination of VEGF in the human serum samples, and the results illustrated an excellent correlation with the conventional ELISA method (R2 = 0.997). The suitable recovery rate of the method in the serum ranged from 97 to 107%, with a relative standard deviation of 1.2% to 13.4%. CONCLUSIONS: The novel immunoassay proposes a highly sensitive, specific, and stable method for very low levels detection of VEGF that can be used in the primary diagnosis of tumors. With the well-designed sensing platform, this approach has a broad potential to be applied for quantitative analysis of numerous disease-related protein biomarkers for which antibodies are available.

Bioluminescence Detection of Superoxide Anion Using Aequorin.

Although the superoxide anion (O2-·) is generated during normal cellular respiration and has fundamental roles in a wide range of cellular processes, such as cell proliferation, migration, apoptosis, and homeostasis, its dysregulation is associated with a variety of diseases. Regarding these prominent roles in biological systems, the development of accurate methods for quantification of superoxide anion has attracted tremendous research attention. Here, we evaluated aequorin, a calcium-dependent photoprotein, as a potential bioluminescent reporter protein of superoxide anion. The mechanism is based on the measurement of aequorin bioluminescence, where the lower the concentration of coelenterazine under the oxidation of superoxide anion, the lower the amount aequorin regeneration, leading to a decrease in bioluminescence. The bioluminescence intensity of aequorin was proportional to the concentration of superoxide anion in the range from 4 to 40 000 pM with a detection limit (S/N = 3) of 1.2 pM, which was 5000-fold lower than those of the chemiluminescence methods. The proposed method exhibited high sensitivity and has been successfully applied to the determination of superoxide anion in the plant cell samples. The results could suggest a photoprotein-based bioluminescence system as a highly sensitive, specific, and simple bioluminescent probe for in vitro detection of superoxide anion.

A chemiluminescence-based catalase assay using H2O2-sensitive CdTe quantum dots.

A method is described for the chemiluminescence based determination of the activity of catalase (CAT) using H2O2-sensitive CdTe quantum dots (QDs). It is based on the finding that the chemiluminescence (CL) of the CdTe/H2O2 system is reduced due to the consumption of H2O2 by the catalytic action of CAT. The Michaelis constant is calculated to be 519 ± 27 mM, showing the potential of the method to accurately measure the Km compared to the standard method. The method does not require QDs to be conjugated to biological/organic molecules and therefore is considered to be a rapid and convenient method for determination of CAT in real samples. At an incubation time of 2 s, the LOD was calculated to be 4.5 unit/mL, with a linear range from 6 to 400 unit/mL. The assay is sensitive, simple, and suitable for practical applications. Graphical abstract Schematic representation of chemiluminescence-based catalase U(CAT) assay using the CdSe QD/H2O2 system. The reduction of H2O2 is reflected by the chemiluminescence of the QDs. A mechanism is put forward based on the changes in chemiluminescence intensity of the QDs by the consumption of H2O2 due to the catalytic action of CAT.

Development of a highly-potent anti-angiogenic VEGF8-109 heterodimer by directed blocking of its VEGFR-2 binding site.

Angiogenesis is a hallmark of various pathological conditions and is controlled by a variety of angiogenic factors. Blockade of vascular endothelial growth factor (VEGF) as the most pivotal stimulator of angiogenesis offers a promising therapeutic approach for some diseases, typically cancer. In the present study, a heterodimeric antagonistic VEGF was precisely designed based on structural information of recently-crystallized VEGF/VEGF receptor-2 (VEGFR-2/fetal liver kinase 1/kinase domain region) complex. Directed blocking of kinase domain region occurs via substitution of a VEGF receptor binding site by two peptide segments in one pole, whereas the binding domain of the other pole of VEGF was intact. Candidate peptides for substitution were selected considering to some sequence and structural criteria. A reliable model of modified VEGF was built, refined using molecular dynamics simulation and docked with VEGFR-2. Docking analysis revealed that binding affinity of mutant VEGF was notably diminished, corroborating our design. Heterodimeric VEGF was expressed, refolded and highly purified by two-step affinity chromatography. Dimerization of this antagonist was confirmed using some analytical techniques. Spectroscopic studies assured us to obtain the heterodimeric form of VEGF. Some angiogenic in vitro assays such endothelial cell proliferation and tube formation indicated that this antagonist is not only strongly capable of inhibiting angiogenesis (half maximal inhibitory concentration of 33 and 24 ng · mL(-1) , respectively), but also showed the highest inhibitory effect compared to all other heterodimeric VEGF variants. The high anti-angiogenic potency of this VEGF antagonist may allow its future use as an anti-tumor agent.