A new chitosan-thymine conjugate: synthesis, characterization and biological activity

Conjugation of chitosan with nucleobases is expected to expand its not only antimicrobial activity but also anti-cancer activity. Here, we report the synthesis of a novel chitosan-thymine conjugate by the reaction between chitosan and thymine-1-yl-acetic acid followed by acylation. The synthesized conjugate was characterized by FTIR, XRD, (1)H NMR, TGA and SEM. The microbiological screening results demonstrated the antimicrobial activity of the conjugate against bacteria viz., Escherichia coli, Staphylococcus aureus, and fungi viz., Aspergillus niger. The chitosan-thymine conjugate also inhibited (p<0.05) the proliferation of human liver cancer cells (HepG2) in a dose-dependent manner but had no cellular toxicity in non-cancerous mouse embryonal fibroblast cells (NIH 3T3). Thus, the chitosan-nucleobase conjugate may open a new perspective in biomedical applications.     

Combretoxazolones: synthesis, cytotoxicity and antitumor activity.

Two series of combretoxazolones including 3,4-diaryloxazolones (6) and 4,5-diaryloxazolones (7) were synthesized and evaluated for cytotoxicity and antitumor activity. Both series showed strong cytotoxicities against a variety of tumor cell lines. Compound 6g exhibited a significant antitumor activity in BDF1 mice bearing B16 murine melanoma cells with inhibition rates of 67 and 61% at 100 and 30 mg/kg/day, respectively.     

Synthesis, characterization, antitumor activity of pluronic mimicking copolymer micelles conjugated with doxorubicin via acid-cleavable linkage

Pluronic mimicking poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer having multiple hydroxyl groups in the PPO middle segment (core-functionalized Pluronic: CF-PLU) was synthesized for conjugation of doxorubicin (DOX). DOX was conjugated on the multiple hydroxyl groups of CF-PLU via an acid-labile hydrazone linkage (CF-PLU-DOX). In aqueous solution, CF-PLU-DOX copolymers self-assembled to form a core/shell-type micelle structure consisting of a hydrophobic DOX-conjugated PPO core and a hydrophilic PEO shell layer. The conjugated DOX from CF-PLU-DOX micelles was released out more rapidly at pH 5 than pH 7.4, indicating that the hydrazone linkage was cleaved under acidic condition. CF-PLU-DOX micelles exhibited greatly enhanced cytotoxicity for MCF-7 human breast cancer cells compared to naked DOX, while CF-PLU copolymer itself showed extremely low cytotoxicity. Flow cytometry analysis revealed that the extent of cellular uptake for CF-PLU-DOX micelles was greater than free DOX. Confocal image analysis also showed that CF-PLU-DOX micelles had a quite different intracellular distribution profile from free DOX. CF-PLU-DOX micelles were mainly distributed in the cytoplasm, endosomal/lysosomal vesicles, and nucleus, while free DOX was localized mainly within the nucleus, suggesting that CF-PLU-DOX micellar formulation might be advantageously used for overcoming the multidrug resistance (MDR) effect, which gradually develops in many tumor cells during repeated drug administration.     

Palladium(II) complexes of quinolinylaminophosphonates: synthesis, structural characterization, antitumor and antimicrobial activity

Three types of palladium(II) halide complexes of quinolinylaminophosphonates have been synthesized and studied. Diethyl and dibutyl [α-anilino-(quinolin-2-ylmethyl)]phosphonates (L1, L2) act as N,N-chelate ligands through the quinoline and aniline nitrogens giving complexes cis-[Pd(L1/L2)X₂] (X═Cl, Br) (1-4). Their 3-substituted analogues [α-anilino-(quinolin-3-ylmethyl)]phosphonates (L3, L4) form dihalidopalladium complexes trans-[Pd(L3/L4)₂X₂] (5-8), with trans N-bonded ligand molecules only through the quinoline nitrogen. Dialkyl [α-(quinolin-3-ylamino)-N-benzyl]phosphonates (L5, L6) give tetrahalidodipalladium complexes [Pd₂(L5/L6)₃X₄] (9-12), containing one bridging and two terminal ligand molecules. The bridging molecule is bonded to the both palladium atoms, one through the quinoline and the other through the aminoquinoline nitrogen, whereas terminal ligand molecules are coordinated each only to one palladium via the quinoline nitrogen. Each palladium ion is also bonded to two halide ions in a trans square-planar fashion. The new complexes were identified and characterized by elemental analyses and by IR, UV-visible, ¹H, ¹³C and ³¹P nuclear magnetic resonance and ESI-mass spectroscopic studies. The crystal structures of complexes 1-4 and 6 were determined by X-ray structure analysis. The antitumor activity of complexes in vitro was investigated on several human tumor cell lines and the highest activity with cell growth inhibitory effects in the low micromolar range was observed for dipalladium complexes 11 and 12 derived from dibutyl ester L6. The antimicrobial properties in vitro of ligands and their complexes were studied using a wide spectrum of bacterial and fungal strains. No specific activity was noted. Only ligands L3 and L4 and tetrahalidodipalladium complexes 9 and 11 show poor activities against some Gram positive bacteria.     

New homocamptothecins: synthesis, antitumor activity, and molecular modeling

Homocamptothecins (hCPTs) represent a class of new emerging antitumor agents, which contains a seven-membered beta-hydroxylactone in place of the conventional six-membered alpha-hydroxylactone ring (E ring) of camptothecins. Some novel 7-substituted hCPTs were designed and synthesized based on a newly developed synthetic route which couples ring A with ring C, E and D. Most of the synthesized compounds exhibit very high cytotoxic activity on tumor cell line A549. Some compounds, such as 9b, 9l, and 9y, show broad in vitro antitumor spectrum and are more potent than topotecan. Three-dimensional quantitative structure-activity relationship (3D-QSAR) methods, CoMFA and CoMSIA, were applied to explain the structure-activity relationship (SAR) of the synthesized compounds. Furthermore, molecular docking was used to clarify the binding mode of the synthesized compounds to human DNA topoisomerase I. The important hydrophobic, base-pair stacking, and hydrogen-bonding interactions were observed between the hCPT derivatives and their receptor. The results from molecular modeling will guide the design of novel hCPTs with higher antitumor activity.     

Macrocyclic complexes: synthesis,characterization, antitumor and DNA binding studies

Abstract

The present paper deals with the synthesis of novel macrocyclic complexes of the type [MLX]X, where [(M?=?Co(II) (1), and Ni(II) (2) X?=?(Cl₂)]. The complexes are synthesized by the reaction of ligand(L)diquinolineno[1,3,7,9]tetraazacyclododecine-7,15-ethane(14H,16H)-benzene with the corresponding metal salts. The synthesized complexes are thoroughly characterized by elemental analysis, FT-IR, ¹H-NMR, Mass and electronic spectra. The complexes (1) and (2) were evaluated for in vitro cytotoxicity against human breast adenocarcinoma cell (MCF-7). MTT cytotoxicity studies shows both the complexes are most effective. The binding properties of these complexes with calf thymus-DNA were studied by absorption, emission spectra, viscosity measurements, and thermal denaturation studies. On binding to CT-DNA, the absorption spectrum undergoes bathochromic and hypochromic shifts. The absorption spectral results indicate that the intrinsic binding constant (K_b) are 4.8?×?10⁵?M^?1 for (1) and 3.9?×?10⁵?M^?1 for (2) respectively, suggesting that complex (1) binds more strongly to CT-DNA than complex (2). The viscosity measurement results revealed the viscosity of sonicated rod like DNA fragments increased when the complex was added to the solution of CT-DNA. The synthesized ligand and its metal complexes are screened for antibacterial and antifungal activities.     

Amino acids derived benzoxazepines: Design,synthesis and antitumor activity

Two series of new benzoxazepines substituted with different alkyl amino ethyl chains were synthesized comprising synthetic steps of inter and intramolecular Mitsunobu reaction, lithium aluminium hydride (LAH) reduction, debenzylation, bimolecular nucleophilic substitution (S_N2) reaction. The present study investigates the effect of a tyrosine-based benzoxazepine derivative in human breast cancer cells MCF-7 and MDA-MB-231 and in breast cancer animal model. The anti-proliferative effect of 15a on MCF-7 cells was associated with G1 cell-cycle arrest. This G1 growth arrest was followed by apoptosis as 15a dose dependently increased phosphatidylserine exposure, PARP cleavage and DNA fragmentation that are hallmarks of apoptotic cell death. Interestingly, 15a activated components of both intrinsic and extrinsic pathways of apoptosis characterized by activation of caspase-8 and -9, mitochondrial membrane depolarization and increase in Bax/Bcl2 ratio. However, use of selective caspase inhibitors revealed that the caspase-8-dependent pathway is the major contributor to 15a-induced apoptosis. Compound 15a also significantly reduced the growth of MCF-7 xenograft tumors in athymic nude mice. Together, 15a could serve as a base for the development of a new group of effective breast cancer therapeutics.     

PAMAM dendrimer-based multifunctional conjugate for cancer therapy: synthesis, characterization, and functionality

Poly(amidoamine) (PAMAM) dendrimer-based multifunctional cancer therapeutic conjugates have been designed and synthesized. The primary amino groups on the surface of the generation 5 (G5) PAMAM dendrimer were neutralized through partial acetylation, providing enhanced solubility of the dendrimer (in conjugation of FITC (fluorescein isothiocyanate)) and preventing nonspecific targeting interactions (in vitro and in vivo) during delivery. The functional molecules fluorescein isothiocyanate (FITC, an imaging agent), folic acid (FA, targets overexpressed folate receptors on specific cancer cells), and paclitaxel (taxol, a chemotherapeutic drug) were conjugated to the remaining nonacetylated primary amino groups. The appropriate control dendrimer conjugates have been synthesized as well. Characterization of the G5 PAMAM dendrimer and its nanosize conjugates, including the molecular weight and number of primary amine groups, has been determined by multiple analytical methods such as gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (NMR), potentiometric titration, high-performance liquid chromatography (HPLC), and UV spectroscopy. These multifunctional dendrimer conjugates have been tested in vitro for targeted delivery of chemotherapeutic and imaging agents to specific cancer cells. We present here the synthesis, characterization, and functionality of these dendrimer conjugates.     

Design, synthesis, and antitumor activity of new bis-aminomethylnaphthalenes

A new series of bis-aminomethylnaphthalenes were synthesized in satisfactory overall yield, through a simple synthetic strategy using reductive amination. The DNA binding properties of these compounds have been examined and compared to those of reference drugs using an UV spectroscopy method. The compounds were evaluated for their in vitro anticancer activity and some of them were studied in vivo. Compound 15 exhibited remarkable antitumor activity and represents a novel template for anticancer chemotherapy and can serve as a new lead compound.     

Synthesis and antitumor activity of arginine–glucosamine conjugate

Using d-glucosamine hydrochloride (GlcNH₂·HCl) as starting material, a new amino acid sugar conjugate, arginine–glucosamine (Arg–GlcNH₂), was synthesized and characterized by infrared spectroscopy, ¹³C NMR and element analysis. Its cytotoxicity in vitro was evaluated by MTT assay. The inhibition ratio against human hepatoma cell SMMC-7721 was higher than that of GlcNH₂·HCl. This effect was accompanied by a marked increase in the proportion of S cells as analyzed by flow cytometry. In addition, SMMC-7721 cells treated with Arg–GlcNH₂ resulted in the induction of apoptosis as assayed qualitatively by agarose gel electrophoresis. The manner of Arg–GlcNH₂ cytocidal activity was concluded to be apoptosis.     

Design, synthesis, and antitumor activity of bile acid-polyamine-nucleoside conjugates

A series of bile acid-polyamine amides conjugated with 3'-azido-3'-deoxythymidine (AZT) as potential antitumor prodrugs in the form of phosphoramidates were synthesized in good yields and their antitumor activities were assayed against two human cancer cells in vitro: cervix cancer HeLa cells and renal cancer 7860 cells. The improved antitumor activity probably derived from the enhanced delivery efficiency of AZT due to bile acid-polyamine conjugates.     

Structure and antitumor activity of polysaccharides from the micelles of Aspergillus oryzae

Three polysaccharide fractions active against mammary gland adenocarcinoma Ca-755 in mice but inactive against sarcoma C-180 were isolated from Aspergillus oryzae strain 5214. The main fraction, extracted from the mycelium by cold dilute alkali in the presence of sodium borohydride, was shown to be linear (1----3)-a-D-glucopyranan (pseudonigeran) according to 13C NMR spectroscopy, partial acid hydrolysis and periodate oxidation data.     

Synthesis, characterization, and antitumor activity of 5-iodouracil complexes.

Complexes of 5-iodouracil (5IU) with Mn(II), Co(II), Cu(II), Zn(II), and Cd(II) ions have been prepared, characterized, and subjected to a screening system for evaluation of antitumor activity against Sarcoma-180 (S-180) and L 929 tumor cells. The complexes were characterized by their elemental analysis, infrared spectra, electronic spectra, magnetic measurements, and powder x-ray diffraction. The antitumor activity results indicate that some complexes have good antitumor activity both in vivo and in vitro against S-180 and L 929 tumor cells.     

Synthesis and preliminary antitumor activity evaluation of a DHA and doxorubicin conjugate

A conjugate of DHA and doxorubicin (DHA-Dox) was synthesized, and its antitumor activity was evaluated in vitro against L1210 leukemia cells and in experimental animal tumor models including L1210 leukemia and B16 melanoma. DHA-Dox showed a greatly improved antitumor efficacy compared to free doxorubicin.     

Long-circulating near-infrared fluorescence core-cross-linked polymeric micelles: synthesis, characterization, and dual nuclear/optical imaging

We report the synthesis of PEG-coated, core-cross-linked polymeric micelles (CCPMs) derived from an amine-terminated amphiphilic block copolymer, poly(PEG-methacrylate)-b-poly(triethoxysilyl propylmethacrylate). The block copolymer self-assembled to form micellar nanoparticles, and a Cy-7-like near-infrared fluorescence (NIRF) dye was entrapped in the core bearing reactive ethoxysilane functional groups through a subsequent sol-gel process. The fluorescent signal of CCPMs on the molar basis was 16-fold brighter than that of Cy7. With an average diameter of 24 +/- 8.9 nm, CCPMs exhibited a prolonged blood half-life (t1/2,alpha = 1.25 h; t1/2,beta = 46.18 h) and moderate uptake by the mononuclear phagocytic system. Significant accumulation of CCPMs in human breast tumor xenografts allowed noninvasive monitoring of the uptake kinetics with both NIRF optical and gamma imaging techniques. Our data suggest that Cy7-entrapped CCPM nanoparticles are suitable for NIRF imaging of solid tumors and have potential applications in the imaging of tumor-associated molecular markers.     

Hydrophobically modified hydroxyethyl starch: synthesis, characterization, and aqueous self-assembly into nano-sized polymeric micelles and vesicles

Hydroxyethyl starch (HES) is a water soluble semisynthetic polysaccharide that is used as a plasma volume expander and cryoprotectant. In order to produce a fully biodegradable amphiphilic polymer, HES was esterified with lauric, palmitic, and stearic acids under mild reaction conditions using dicyclohexyl carbodiimide (DCC) and dimethylaminopyridine (DMAP). The molar substitution of the acyl chains (MSfatty acid) was determined with 1H NMR spectroscopy, while the conformational state of the hydrocarbon chains in the graft copolymer was determined using Raman spectroscopy. Furthermore, the aqueous self-assembly of the modified polymer was studied using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Results show the formation of 20 to 30 nm micelles, and 250 to 350 nm polymeric vesicles. Electron spin resonance (ESR) spectroscopy was used to study the microenvironment of a hydrophobic spin probe loaded inside the formed nanodispersion. It was possible to identify the location of the probe and its distribution between the micelles and vesicles. Finally, the hydrophobically modified HES might find use as a potential drug carrier, warranting the future investigation of its ability to encapsulate and deliver drug candidates.     

Asymmetric synthesis and antitumor activity of cycloalkanin.

Cycloalkanin was accessible by a practical and efficient asymmetric synthesis. The chiral center of the target is introduced via an asymmetric C-arylation of chiral aldehyde in high de. The synthesized cycloalkanin was shown to be significantly active against P388 cell line as assayed by in vitro MIT method.     

Resveratrol-based cinnamic ester hybrids: synthesis,characterization, and anti-inflammatory activity

Twenty-three novel resveratrol-based cinnamic ester hybrids were designed and synthesized. All the compounds were evaluated for their anti-inflammatory activity using RAW264.7 cells. Among them, compound D15 was found to be the most potent one in inhibiting NO production in LPS-stimulated RAW264.7 cells. The further study indicated that compound D15 could suppress expression of proteins iNOS, COX-2, p-p65, and p-IκB LPS-induced. Immunofluorescence further revealed compound D15 could reduce activation p65 in nuclei. All the results indicated that the anti-inflammatory activity of title compound may partly due to its inhibitory effect on the NF-κB signaling pathway.     

Synthesis, characterization, and antitumor activity of new chloroethylamine platinum complexes.

A series of cis-bis-(2-chloroethylamine)platinum(II) and platinum(IV) complexes were synthesized and characterized by elemental analysis, IR, and 1H and 195Pt NMR spectroscopic techniques. Complexes were tested in vitro against murine L1210 leukemia and human ovarian A2780 cell lines and in vivo against the L1210 leukemia model. Some of these complexes showed excellent antitumor activity in both systems. However, all were inactive against cisplatin-resistant A2780/CP cells.