Anti-angiogenic/proliferative behavior of a “4-aryl-4H-chromene” on blood vessel’s endothelial cells: A possible evidence on dual “anti-tumor” activity

Effect of Substituents on the Crystal Structures, Optical Properties, and Catalytic Activity of Homoleptic Zn(II) and Cd(II) β-oxodithioester Complexes

Five novel zinc(II) and cadmium(II) β-oxodithioester complexes, [Zn(L1)₂] (1), [Zn(L2)₂]_n (2), [Zn(L3)₂]_n (3) [Cd(L1)₂]_n (4), [Cd(L2)₂]_n (5), with β-oxodithioester ligands, where L1 = 3-(methylthio)-1-(thiophen-2-yl)-3-thioxoprop-1-en-1-olate, L2 = 3-(methylthio)-1-(pyridin-3-yl)-3-thioxoprop-1-en-1-olate, and L3 = 3-(methylthio)-1-(pyridin-4-yl)-3-thioxoprop-1-en-1-olate, were synthesized and characterized by elemental analysis, IR, UV-vis, and NMR spectroscopy (¹H and ¹³C{¹H}). The solid-state structures of all complexes were ascertained by single-crystal X-ray crystallography. The β-oxodithioester ligands are bonded to Zn(II)/Cd(II) metal ions in an O^∧S and N chelating/chelating-bridging fashion leading to the formation of 1D (in 2-4) and 2D (in 5) coordination polymeric structures, but complex 1 was obtained as a discrete tetrahedral molecule. Complex 4 crystallizes in the C2 chiral space group and has been studied using circular dichroism (CD) spectroscopy. The multidimensional assemblies in these complexes are stabilized by many important noncovalent C-H···π (ZnOSC₃, chelate), π···π, C-H···π, and H···H interactions. The catalytic activities of 1-5 in reactions involving C-C and C-O bond formation have been studied, and the results indicated that complex 3 can be efficiently utilized as a heterogeneous bifunctional catalyst for the Knoevenagel condensation and multicomponent reactions to develop biologically important organic molecules. The luminescent properties of complexes were also studied. Interestingly, zinc complexes 1-3 showed strong lumniscent emission in the solid state, whereas cadmium complexes 4 and 5 exhibited bright luminescent emission in the solution phase. The semiconducting behavior of the complexes was studied by solid-state diffuse reflectance spectra (DRS), which showed optical band gaps in the range of 2.49-2.62 eV.

Novel Biomass Derived from Grape Pomace Waste as an Efficient Nanocatalyst for the Synthesis of Dibenzoxanthene, Tetraketone, bis(indolyl)alkane and Chromene Derivatives and their Antimicrobial Evaluation

BACKGROUND

Sulfonated carbon-based solid acids (CBSAs) have been reported as an efficient solid acid catalyst for many acid-catalyzed reactions. Furthermore, the use of carbon obtained from biomass waste has been explored and these materials showed a higher catalytic performance and higher stability compared to other solid acids.

OBJECTIVE

Novel biomass carbon-based solid acids nanoparticles with high catalytic activity in organic transformation, such as Grape pomace waste-SO3H Nanoparticles (GPW-SO3H NPs), were successfully synthesized.

MATERIALS AND METHODS

Grape pomace waste-SO3H Nanoparticles (GPW-SO3H NPs) were successfully synthesized. The grape pomace waste was dried in an oven at a temperature of 70°C and crushed to powder using an electric spice grinder. A mixture of powdered grape pomace waste (1 g) and concentrated sulfuric acid (>98%, 10 mL) was stirred at room temperature. Then, the resultant mixture was transferred into a 100 mL sealed Teflon-lined autoclave and kept at 180°C for 12 h. After cooling to room temperature, the resulting black solid was dried at 100°C in an oven under vacuum and the sulfonic acid-functionalized magnetic nanoparticles (Fe3O4@C-SO3H) were obtained.

RESULTS AND DISCUSSIONS

The catalytic activity of GPW-SO3H was assessed through an easy and rapid protocol developed for the one-pot synthesis of 14-aryl-14-H-dibenzo [a,j]xanthene, arylmethylene [bis(3- hydroxy-2-cyclohexene-1-one)], bis(indolyl)alkane and 2-amino-4-aryl-7-hydroxy-4H-chromene-3-carbonitrile derivatives in excellent yields. The advantages of this method include use of waste material for catalyst synthesis, high yields, mild reaction conditions, uncomplicated work-up procedures, neutral conditions, and recoverable catalyst.

CONCLUSION

We have shown that biomass-derived solid acids, prepared from grape pomace waste, serve as a non-toxic, inexpensive and a promising eco-friendly and novel carbon-based solid acid nanocatalyst for organic transformations.

Design, Synthesis and Biological Evaluation of Novel 5H-Chromenopyridines as Potential Anti-Cancer Agents

A novel series of 5H-chromenopyridines was identified as anticancer agents in our continuing effort to discover and develop new small molecule anti-proliferative agents. Based on our initial lead SP-6-27 compound, we designed and synthesized novel tricyclic 5H-thiochromenopyridine and 5H-chromenopyridine analogs to evaluate the impact of an additional ring, as well as conformational flexibility on cytotoxic activity against human melanoma and glioma cell lines. All of the 5H-thiochromenopyridines have been achieved in good yields (89%–93%) using a single-step, three-component cyclization without the need for purification. The 5H-chromenopyridine analog of the potent 5H-thiochromenopyride was obtained in a good yield upon purification. All newly-prepared 5H-thiochromenopyridines showed good to moderate cytotoxicity against three melanoma and two glioma cell lines (3–15 μM). However, the 5H-chromenopyridine analogue that we prepared in our laboratory lost cytotoxic activity. The moderate cytotoxic activity of 5H-thiochromenopyridines shows the promise of developing chromenopyridines as potential anticancer agents.

Engineering of a disulfide loop instead of a Zn binding loop restores the anti-proliferative, anti-angiogenic and anti-tumor activities of the N-terminal fragment of endostatin: Mechanistic and therapeutic insights

Although considerable effort has been devoted to understanding the molecular mechanism of endostatin's anti-cancer activity, the role of its Zn bound N-terminal loop has not been completely clarified. To investigate whether Zn binding or the N-terminal loop is involved in the anti-cancer properties of endostatin, we compared the structure and biological activity of a native Zn binding endostatin peptide (ES-Zn) with three variants: a Zn free variant (ES), a variant containing both a Zn binding site and a disulfide bond (ES-SSZn), and a variant including a disulfide loop but incapable of Zn binding (ES-SS). Spectroscopic studies indicated that ES-Zn and ES-SS consist of random coil and β structures, whereas ES-SSZn and ES fold into random coils. Theoretical analysis proposed that ES-Zn and ES-SS have a similar binding site to αVβ3 integrin. The anti-proliferative activity of endostatin was retained by all peptides except ES, and the in vitro anti-angiogenic property was preserved in ES-Zn and ES-SS. Remarkably, breast tumor growth and CD31 activity were inhibited more effectively by ES-SS than by ES-Zn. Therefore, a correlation exists between the N-terminal loop and anti-cancer properties of endostatin fragment and a disulfide loop may be more promising than a Zn binding loop for inhibiting tumor growth.

A conformation-based phage-display panning to screen neutralizing anti-VEGF VHHs with VEGFR2 mimicry behavior

The potency of VEGF-based anti-angiogenic strategies in cancer therapy and the brilliant characteristics of VHHs motivated us to directly block VEGF binding to its receptor with neutralizing single domain antibodies, thereby fading away the VEGF signaling pathway. Considering with high resolution crystal structure of VEGF-RBD/VEGFR2 complex, we could adopt a combinatorial screening strategy: stringent panning and competition ELISA, to direct the panning procedure to dominantly screen the favorable binders that bind and block the key functional regions of VEGF. Based on competition assay, the majority of the screened clones (82%) showed the VEGFR2 mimicry behavior for binding to VEGF molecule. The phage pool gets enriched in favor of sequences that bind the receptor binding sites of VEGF. Different immunoassays and molecular docking simulation verified that all selected VHHs could bind and cover the receptor binding sites of VEGF. Consequently, some modifications in panning procedure with considering the structural features and detailed information of functional regions of a protein antigen, led us to successfully trap the high-affinity specific binders against its hot functional regions. Since the selected VHHs could cover the receptor binding site of VEGF and block VEGF binding to the receptor, they might be promising candidates for anti-angiogenic therapies.

Tris-hydroxymethylaminomethane (THAM): a novel organocatalyst for a environmentally benign synthesis of medicinally important tetrahydrobenzo[b]pyrans and pyran-annulated heterocycles

Tris-hydroxymethylaminomethane (THAM): a novel, low cost, green catalyst for the synthesis of medicinally important pyrans and pyran-annulated heterocycles.

Chromenes: potential new chemotherapeutic agents for cancer

Cancer is a major devastating disease, and is a leading cause of death worldwide. Despite the progress in cancer treatment, cancer mortality rate remains high. Therefore, the discovery and development of improved anticancer drugs to treat cancer are needed. 4H-chromenes have strong cytotoxicity against a panel of human cancer cell lines involving pathways that include microtubule depolarization and tumor vasculature disruption. A chromene analog, Crolibulin™ (EPC2407) is currently in Phase I/II clinical trials for the treatment of advanced solid tumors. This article reviews the general synthesis, biological activities and structure–activity relatinships of different classes of chromenes.

Molecular cloning, expression and purification of recombinant soluble mouse endostatin as an anti-angiogenic protein in Escherichia coli

Inhibition of angiogenesis has become a particular interest for treatment of solid tumors. Endostatin, a C-terminal fragment of collagen XVIII, has been reported to exhibit potent inhibitory effect on endothelial cells proliferation, migration and tube formation. In this research, the cDNA library of endostatin was synthesized from mouse liver and inserted into the SacI and SalI enzyme-cutting sites of pUC18 cloning vector. The recombinant vector was transferred into Escherichia coli DH5a and the recombinant clone was selected on LB agar plate plus ampicillin. PCR analysis and DNA sequencing proved the presence of intact endostatin gene in pUC18. The endostatin gene subcloned into pET32a expression vector and the competent bacterial cells of E. coli BL21 were transformed by the vector harboring endostatin gene. In the optimum conditions, expression plasmid was induced with IPTG and recombinant soluble endostatin as a fusion with thioredoxin was purified with Ni-NTA (Ni(2+)-nitrilotriacetate) resin. The results showed that soluble recombinant endostatin as a fusion protein with thioredoxin is a homogenous polypeptide that inhibits angiogenesis (capillary tube formation) in human umbilical vein endothelial cells by 200 ng/ml.