Dong-Dong Li

Novel 1,3,4-oxadiazole thioether derivatives targeting thymidylate synthase as dual anticancer/antimicrobial agents.

A series of novel 1,3,4-oxadiazole thioether derivatives (compounds 9-44) were designed and synthesized as potential inhibitors of thymidylate synthase (TS) and as anticancer agents. The in vitro anticancer activities of these compounds were evaluated against three cancer cell lines by the MTT method. Among all the designed compounds, compound 18 bearing a nitro substituent exhibited more potent in vitro anticancer activities with IC50 values of 0.7±0.2, 30.0±1.2, 18.3±1.4 μM, respectively, which was superior to the positive control. In the further study, it was identified as the most potent inhibitor against two kinds of TS protein (for human TS and Escherichia coli TS, IC50 values: 0.62 and 0.47 μM, respectively) in the TS inhibition assay in vitro and the most potent antibacterial agents with MIC (minimum inhibitory concentrations) of 1.56-3.13 μg/mL against the tested four bacterial strains. Molecular docking and 3D-QSAR study supported that compound 18 can be selected as dual antitumor/antibacterial candidate in the future study.

Synthesis and Antifungal Activity of Nicotinamide Derivatives as Succinate Dehydrogenase Inhibitors

Thirty-eight nicotinamide derivatives were designed and synthesized as potential succinate dehydrogenase inhibitors (SDHI) and precisely characterized by (1)H NMR, ESI-MS, and elemental analysis. The compounds were evaluated against two phytopathogenic fungi, Rhizoctonia solani and Sclerotinia sclerotiorum, by mycelia growth inhibition assay in vitro. Most of the compounds displayed moderate activity, in which, 3a-17 exhibited the most potent antifungal activity against R. solani and S. sclerotiorum with IC50 values of 15.8 and 20.3 μM, respectively, comparable to those of the commonly used fungicides boscalid and carbendazim. The structure-activity relationship (SAR) of nicotinamide derivatives demonstrated that the meta-position of aniline was a key position contributing to the antifungal activity. Inhibition activities against two fungal SDHs were tested and achieved the same tendency with the data acquired from in vitro antifungal assay. Significantly, 3a-17 was demonstrated to successfully suppress disease development in S. sclerotiorum infected cole in vivo. In the molecular docking simulation, sulfur and chlorine of 3a-17 were bound with PHE291 and PRO150 of the SDH homology model, respectively, which could explain the probable mechanism of action between the inhibitory and target protein.

Discovery of 6-substituted 4-anilinoquinazolines with dioxygenated rings as novel EGFR tyrosine kinase inhibitors

It had been reported that some dioxygenated rings fusing with the quinazoline scaffold could lead to new EGFR inhibitors. Based on this, several kinds of oxygenated alkane quinazoline derivatives were synthetized and evaluated as EGFR inhibitors. Their antiproliferative activities were tested against four cancer cell lines: A431, MCF-7, A549, and B16-F10. Most derivatives could counteract EGF-induced EGFR phosphorylation, and their potency was comparable to the reference compound Erlotinib. The size of the fused dioxygenated ring was crucial for the biological activity and the heptatomic ring derivative 19 showed potent in vitro inhibitory activity in the enzymatic assay as well as in the cellular assay.

Design and synthesis of thiazole derivatives as potent FabH inhibitors with antibacterial activity

Components of fatty acid biosynthetic pathway have been identified as attractive targets for the development of new antibacterial agents. Compounds of series A (4a-4 g) and series B (5a-5 g) were synthesized by the formation of an amine bond between aromatic acid and 4-phenylthiazol-2-amine or 4-(4-bromophenyl)thiazol-2-amine. These thiazole derivatives have evaluated as potent FabH inhibitors. Nineteen compounds (4b-4h, 4 k, 4 l, 5a-5h, 5k, 5l) are reported for the first time. Most of the synthesized compounds exhibited antibacterial activity in the MTT assay. The MIC value of these compounds ranged from 1.56 μg/mL to 100 μg/mL. Moreover, the tested compounds also showed FabH inhibition ability with IC50 value ranging from 5.8 μM to 48.1 μM. The IC50 values are near the MIC values. Compound 5f has exhibited the best antibacterial and Escherichia coli FabH inhibitory activity. Docking simulation and the QSAR study was conducted for learning about binding mode and the relationship between structure and activity.

Design, synthesis and insecticidal activities of N-(4-cyano-1-phenyl-1H-pyrazol-5-yl)-1,3-diphenyl-1H-pyrazole-4-carboxamide derivatives

Insect ryanodine receptor is one of the promising targets for the development of novel insecticides. In order to search for potent insecticides targeting the ryanodine receptor (RyR), a series of novel diphenyl-1H-pyrazole derivatives with cyano substituent were designed and synthesized. Their insecticidal activities against diamondback moth (Plutella xylostella) indicated that most of the compounds showed moderate to high activities at the four concentrations. Among these compounds, N-(4-cyano-1-(4-fluorophenyl)-1H-pyrazol-5-yl)-1-(4-fluorophenyl)-3-phenyl-1H-pyrazole-4-carboxamide (5g) showed 84% larvicidal activity against Plutella xylostella at the concentration of 0.1 mg L−1. Molecular docking showed the predicted binding mode between 5g and protein receptor, which could suggest that the title compounds were the possible activators of insect RyR.

Optimization of substituted 6-salicyl-4-anilinoquinazoline derivatives as dual EGFR/HER2 tyrosine kinase inhibitors.

4-Anilinoquinazolines as an important class of protein kinase inhibitor are widely investigated for epidermal growth factor receptor (EGFR) tyrosine kinase or epidermal growth factor receptor 2 (HER2) inhibition. A series of novel 6-salicyl-4-anilinoquinazoline derivatives 9–27 were prepared and evaluated for their EGFR/HER2 tyrosine kinase inhibitory activity as well as their antiproliferative properties on three variant cancer cell lines (A431, MCF-7, and A549). The bioassay results showed most of the designed compounds exhibited moderate to potent in vitro inhibitory activity in the enzymatic and cellular assays, of which compound 21 revealed the most potent dual EGFR/HER2 inhibitory activity, with IC50 values of 0.12 µM and 0.096 µM, respectively, comparable to the control compounds Erlotinib and Lapatinib. Furthermore, the kinase selectivity profile of 21 was accessed and demonstrated its good selectivity over the majority of the close kinase targets. Docking simulation was performed to position compound 21 into the EGFR/HER2 active site to determine the probable binding pose. These new findings along with molecular docking observations could provide an important basis for further development of compound 21 as a potent EGFR/HER2 dual kinase inhibitor.

Identification of novel B-RafV600E inhibitors employing FBDD strategy

Graphical abstract In this study, we utilized Fragment‐based Drug Design strategy to design and synthesize new B‐RafV600E antagonists whose potency was examined by a set of bioassays. Figure. No Caption available. ABSTRACT B‐Raf kinase is the key point in a main branch of mitogen‐activated protein kinase pathways and some of its mutations, such as the V600E mutation, lead to the persistent activation of ERK signaling and the trigger of severe diseases, including melanoma and other somatic cancers. Several potent drugs have been approved to treat B‐Raf‐related tumors, however, cases of resistance and relapse have been reported universally. Hence, differential scaffolds are in need to alleviate the scarcity of drugs and benefit the therapy of B‐Raf‐mutant cancers. Herein we report our recent work on the construction of novel B‐RafV600E inhibitors employing fragment‐based drug design strategy. In this research, we decomposed known inhibitors to fragments and rebuilt new candidates using these blocks according to the evaluation of their potential. Lead compounds were synthesized after selection by means of virtual screening and molecular dynamics validation. Afterwards, we tested the pharmacological efficiency of these entities both in vitro and in vivo utilizing A375 xenograft model. The results favored our rational design intention and hinted this new kind of inhibitors might be helpful in the further explorations of potent agents.

Design, synthesis, and evaluation of substituted 6-amide-4-anilinoquinazoline derivatives as c-Src inhibitors

The 4-anilinoquinazoline scaffold has been historically used for designing EGFR/VEGFR/HER2 inhibitors while it has not been reported widely for developing c-Src inhibitors. Thus, a series of novel 4-anilinoquinazoline derivatives grafting different amide moieties at the 6-position were designed and synthesized as potential inhibitors for c-Src. In this manuscript, all of the designed compounds were screened via molecular docking using Discovery Studio 3.5 software. As expected, the results of the docking study revealed that most of these targeted compounds possessed lower binding energy than the positive control Saracatinib. Subsequently, all of the screened compounds were synthesized and evaluated for their c-Src in vitro inhibitory activities and in vitro antiproliferation assays against four human cancer cells (A549, MCF-7, HepG-2, HeLa). Among these compounds, 24 exhibited the most potent inhibitory activity against c-Src kinase as well as at the cellular level, of which the IC50 value reached up to 2.9 nM, comparable to the positive compound Saracatinib. Kinase selectivity profile also demonstrated that compound 24 showed good selectivity over several close kinase targets. These results, along with relative 3D-QSAR study, could provide an important basis for further development of compound 24 as a potent tyrosine kinase inhibitor.

Novel Schiff-Base-Derived FabH Inhibitors with Dioxygenated Rings as Antibiotic Agents

Fatty acid biosynthesis plays a vital role in bacterial survival and several key enzymes involved in this biosynthetic pathway have been identified as attractive targets for the development of new antibacterial agents. Of these promising targets, β‐ketoacyl‐acyl carrier protein (ACP) synthase III (FabH) is the most attractive target that could trigger the initiation of fatty acid biosynthesis and is highly conserved among Gram‐positive and ‐negative bacteria. Designing small molecules with FabH inhibitory activity displays great significance for developing antibiotic agents, which should be highly selective, nontoxic and broad‐spectrum. In this manuscript, a series of novel Schiff base compounds were designed and synthesized, and their biological activities were evaluated as potential inhibitors. Among these 21 new compounds, (E)‐N‐((3,4‐dihydro‐2H‐benzo[b][1,4]dioxepin‐7‐yl)methylene)hexadecan‐1‐amine (10) showed the most potent antibacterial activity with a MIC value of 3.89–7.81 μM−1 against the tested bacterial strains and exhibited the most potent E. coli FabH inhibitory activity with an IC50 value of 1.6 μM. Docking simulation was performed to position compound 10 into the E. coli FabH active site to determine the probable binding conformation.

Synthesis and biological evaluation of 2-aryl-benzimidazole derivatives of dehydroabietic acid as novel tubulin polymerization inhibitors

A series of novel 2-aryl-benzimidazole derivatives of dehydroabietic acid were synthesized and characterized by IR, 1H NMR, 13C NMR, MS and elemental analyses. All the target compounds were evaluated for their in vitro cytotoxic activity against SMMC-7721, MDA-MB-231, HeLa and CT-26 cancer cell lines and the normal hepatocyte cell line QSG-7701 through MTT assays. Among them, compound 6j displayed the most potent cytotoxic activity with IC50 values of 0.08 ± 0.01, 0.19 ± 0.04, 0.23 ± 0.05 and 0.42 ± 0.07 μM, respectively, and substantially reduced cytotoxicity against QSG-7701 cells (5.82 ± 0.38 μM). The treatment of SMMC-7721 cells with compound 6j led to considerable inhibition of cell migration ability. The influence of compound 6j on cell cycle distribution was assessed on SMMC-7721 cells, exhibiting a cell cycle arrest at the G2/M phase. Moreover, tubulin polymerization assays and immunofluorescence assays elucidated that compound 6j could significantly inhibit tubulin polymerization and disrupt the intracellular microtubule network. A molecular docking study provided insight into the binding mode of compound 6j in the colchicine site of tubulin. In addition, compound 6j was found to induce apoptosis of SMMC-7721 cells, an increase of intracellular ROS level and a loss of mitochondrial membrane potential in a dose-dependent manner. These findings provided new molecular scaffolds for the further development of novel antitumor agents targeting tubulin polymerization.