Synthesis, enzyme inhibition, and molecular docking studies of a novel chalcone series bearing benzothiazole scaffold.

This study reports the facile synthesis of a novel series of benzothiazole-chalcones, in addition to their inhibitory profile on important metabolic enzymes including human carbonic anhydrases (hCA-I, hCA-II) and paraoxonase (PON-1). The inhibition parameters, IC50 (concentration for 50% inhibition) and Ki (dissociation constant) values, toward the title enzymes were determined for the studied compounds. As a result, IC50 values of hydratase activity were in the range 4.15-5.47 and 2.56-4.58 µM for hCA-I and hCA-II, respectively. At the same time, IC50 values of esterase activity were in the range 24.91-104.00 and 35.25-97.00 µM, while Ki values were in the range 14.43-59.66 and 26.65-73.34 µM for hCA-I and hCA-II, respectively. In addition, PON-1 enzyme inhibition results showed interesting inhibitory effects, with IC50 values between 13.28 and 16.68 µM. Finally, a comprehensive approach was established for the synthesized compounds based on theoretical calculations, which have been done using B3LYP, PBE0 theories and SVP, TVZP, TVZPP basis sets, followed by docking studies by which the outputs proved the harmonically flows with the experimental results.

Antimicrobial, Antiproliferative Effects and Docking Studies of Methoxy Group Enriched Coumarin-Chalcone Hybrids.

Methoxy group enriched eight coumarin-chalcone hybrid derivatives were synthesized. Antimicrobial/ antiproliferative activities were tested against eight human pathogenic microorganisms and four cancer cell lines (AGS, HepG2, MCF-7 and PC-3), respectively. Antimicrobial results showed that most of the compounds were almost more active than used standard antibiotics. Cytotoxicity results showed that 2,3,4-trimethoxyphenyl and thiophene containing structures have promising antiproliferative effects against AGS gastric cell lines with ∼5 µg/ml IC50 values. At the same time, 2,4-dimethoxyphenyl bearing derivative exhibited the lowest IC50 values against HepG2 (∼10 µg/ml) and PC-3 (∼5 µg/ml) cell lines. Particularly, the cell viabilities of MCF-7 cell lines were remarkably inhibited by all the compounds with lower IC50 values. Therefore, molecular docking studies between hybrid ligands and quinone reductase-2 enzyme (regulates in MCF-7 cancer cells) were performed. The results demonstrated that all the derivatives can smoothly interact with interested enzyme in agreement with the experimental results. Finally, ADME parameters were studied to reveal drug-likeness potentials of the coumarin-chalcone hybrids.

Singlet Exciton Fission and Associated Enthalpy Changes with a Covalently Linked Bichromophore Comprising TIPS-Pentacenes Held in an Open Conformation.

A covalently linked bichromophore, embracing 6,13-bis(triisopropylsilylethinyl)pentacene (TIPS-pentacene) terminals bridged by a rigid fluorene spacer, generates a relatively high yield (i.e., 65 ± 6%) of the spin-correlated, triplet biexciton upon illumination in toluene. Under the same conditions, the extent of fluorescence quenching relative to the parent TIPS-pentacene approaches 97% and is insensitive to temperature. The biexciton, having overall singlet spin multiplicity, undergoes internal conversion in competition to spin decorrelation. These latter processes occur on the relatively slow time scale of a hundred or so nanoseconds, possibly reflecting the restricted level of electronic communication between the terminals. Spin decorrelation leads to evolution of an independent triplet pair with an overall quantum yield of 0.50 ± 0.06 and a lifetime of 8 ± 2 µs in deaerated toluene. Photoacoustic calorimetry (PAC) indicates three separate enthalpy changes: a very fast step associated with intramolecular singlet exciton fission to form the correlated triplet biexciton, a fast step essentially reflecting spin decorrelation, and a slow step associated with relaxation of the independent triplet pair. Analysis of the PAC data, in conjunction with the transient absorption results, establishes excitation energies for both spin-correlated and independent triplet pairs. Polar solvent enhances both fluorescence quenching and triplet formation at the expense of radiationless decay while temperature effects have been recorded for all important intermediate species.

Pulse Radiolysis of TIPS-Pentacene and a Fluorene-bridged Bis(pentacene): Evidence for Intramolecular Singlet-Exciton Fission.

Exposing TIPS-pentacene in deaerated benzene to ionizing radiation generates a mixture of singlet- and triplet-excited states of the solute. The singlet undergoes radiative decay without spin conversion whereas the triplet undergoes radiationless decay on the microsecond time scale. The concentration of each species was established by dosimetry. The excited-singlet state is not observed on the nanosecond-time scale for a related fluorene-bridged bis(pentacene), but the triplet is present in high concentration. Failure to detect the excited-singlet state is attributed to fast intramolecular singlet-exciton fission (iSEF) which is found to produce two triplet species. A short-lived intermediate (τT = 145 ns) is identified as the species (T_T) having both pentacene units present as triplet states. The second transient is longer lived (τT = 7.5 µs) and is assigned to the corresponding species (T_G) with a single pentacene promoted to the triplet level. Dosimetry is used to conclude that iSEF partitions overwhelmingly in favor of T_G (70%) relative to T_T (25%). The total triplet yield from iSEF, therefore, is ca. 120% in this system, where the pentacene terminals are weakly coupled.

Exciton Migration and Surface Trapping for a Photonic Crystal Displaying Charge-Recombination Fluorescence.

A compact donor-acceptor molecular dyad has been synthesized by attaching an N,N-dimethylamino fragment to a naphthalic anhydride residue. The dyad shows fluorescence from an intramolecular charge-transfer state (i.e., charge-recombination fluorescence) in solution, with the photo-physical properties being strongly dependent on the solvent polarity. Similar emission is seen for single crystals of the target compound, the molecules being aligned head-to-head, although time-resolved emission profiles display dual-exponential kinetics. A second polymorph with the head-to-tail alignment also gives rise to two lifetimes that differ somewhat from those of the first structure, which are assigned to bulk and surface-bound molecules. Growing the crystal in the presence of Rhodamine B localizes the dye around the surface. Excitation of the crystal is followed by sub-ps exciton migration along the aligned stacks, with occasional crossing to adjacent stacks and trapping at the surface. Rhodamine B present at very low levels acts as the acceptor for excitons entering the surface layer. Crystals embedded in a polyester resin form an artificial light-harvesting antenna able to sensitize an amorphous silicon solar cell.

1-Amino-2-hydroxy-4-naphthalenesulfonic acid based Schiff bases or naphtho[1,2-d]oxazoles: selective synthesis and photophysical properties.

A series of Schiff base and naphtho[1,2-d]oxazole derivatives were selectively synthesized via condensation reaction of 1-amino-2-hydroxy-4-naphthalenesulfonic acid and benzaldehyde derivatives at same conditions. The synthesized compounds were then characterized by using (1)HNMR, (13)CNMR, FTIR spectroscopies and elemental analyses. It was seen that the Schiff bases generated in the presence of OH group at ortho position of benzaldehyde derivatives. However, the products were naphtho[1,2-d]oxazoles in other cases. Then, the synthesized compounds were photophysically investigated by UV absorption and fluorescence emission spectroscopies. As a result, these Schiff bases have shown long wavelength absorption (λ(max): 386 nm) and emission (λ(max): 429-437 nm) effect while synthesized naphtho[1,2-d]oxazole derivatives have a set of absorption (λ(max): about 296, 308, 320 nm) and emission maxima (λ(max): 378-395 nm) at lower wavelength.

In vitro inhibition effect of some chalcones on erythrocyte carbonic anhydrase I and II.

In this study, 4'-(phenylurenyl/thiourenyl)chalcones (14-25) were prepared from 4'-(phenylurenyl/thiourenyl)acetophenones and benzaldehyde derivatives by Claisen-Schmidt condensation. In vitro inhibition effects of chalcone derivatives on purified carbonic anhydrase I and carbonic anhydrase II were investigated by using the CO2 hydration method of Maren. The result showed that all the synthesized compounds inhibited the CA isoenzymes activity. 18 and 19 were found to be most active (IC50 = 25.41 µM and 23.06 µM) for hCA I, respectively. For hCA II, 24 is the most active compound (IC50 = 14.40 µM).

Evaluation of new chalcone derivatives as polyphenol oxidase inhibitors.

A newly series of 4-(phenylurenyl)chalcone (4a-j) and 4'-(phenylurenyl/thiourenyl)chalcone (9a-l) derivatives were synthesized and their inhibitory effects on the diphenolase activity of banana tyrosinase were evaluated. Tyrosinase has been purified from banana on an affinity gel comprised of Sepharose 4B-l-tyrosine-p-aminobenzoic acid. The result showed that 4a-j inhibited the PPO enzyme activity. Conversely, 9a-h and 9i-l showed activator effect on tyrosinase enzyme activity.

Synthesis, characterization and electrochemical behavior of some Ni(II), Cu(II), Co(II) and Cd(II) complexes of ONS type tridentate Schiff base ligand.

Tridentate Schiff base (H(2)L) ligand was synthesized via condensation of o-hydroxybenzaldehyde and 2-aminothiophenol. The metal complexes were prepared from reaction of the ligand with corresponding metal salts presence of substituted pyridine in two different solvents (MeOH or MeCN). The ligand and metal complexes were then characterized by using FTIR, TGA, (1)H NMR and (13)C NMR spectroscopies. The FTIR spectra showed that H(2)L was coordinated to the metal ions in tridentate manner with ONS donor sites of the azomethine N, deprotonated phenolic-OH and phenolic-SH. Furthermore, substituted pyridine was coordinated to the central metal atoms. The thermal behavior of the complexes was investigated by using TGA method and dissociations indicated that substituted pyridine and ligand were leaved from coordination. This coordination of the metal complexes was correlated by (1)H NMR and (13)C NMR. Finally, electrochemical behavior of the ligand and a Ni(II) complex were investigated.