Design,synthesis and biological evaluation of indeno[1,2-d]thiazole derivatives as potent histone deacetylase inhibitors

Novel indeno[1,2-d]thiazole hydroxamic acids were designed, synthesized, and evaluated for histone deacetylases (HDACs) inhibition and antiproliferative activities on tumor cell lines. Most of the tested compounds exhibited HDAC inhibition and antiproliferative activity against both MCF7 and HCT116 cells with GI₅₀ values in the sub-micromolar range. Among them, compound 6o showed good inhibitory activity against pan-HDAC with IC₅₀ value of 0.14 μM and significant growth inhibition on MCF7 and HCT116 cells with GI₅₀ values of 0.869 and 0.535 μM, respectively.     

Valproic acid induces three novel cytotoxic secondary metabolites in Diaporthe sp., an endophytic fungus from Datura inoxia Mill.

Addition of the valproic acid (histone deacetylases inhibitor) to a culture of an endophytic fungus Diaporthe sp. harbored from Datura inoxia significantly altered its secondary metabolic profile and resulted in the isolation of three novel compounds, identified as xylarolide A (1), diportharine A (2) and xylarolide B (3) along with one known compound xylarolide (4). The structures of all the compounds (1–4) were determined by detailed analysis of 1D and 2D NMR spectroscopic data. The relative configurations of compounds 1–3 were determined with the help of NOESY data and comparison of optical rotations with similar compounds with established stereochemistry. All the isolated compounds were screened for antibacterial, antioxidant and cytotoxic activities. Xylarolide A (1) and xylarolide (4) displayed significant growth inhibition of MIAPaCa-2 with an IC₅₀ of 20 and 32?µM respectively and against PC-3 with an IC₅₀ of 14 and 18?µM respectively. Moreover, compound 1 displayed significant DPPH scavenging activity with EC₅₀ of 10.3?µM using ascorbic acid as a positive control.     

Synthesis and biological evaluation of 2,4-disubstituted phthalazinones as Aurora kinase inhibitors

A series of 2,4-disubstituted phthalazinones were synthesized and their biological activities, including antiproliferation, inhibition against Aurora kinases and cell cycle effects were evaluated. Among them, N-cyclohexyl-4-((4-(1-methyl-1H-pyrazol-4-yl)-1-oxophthalazin-2(1H)-yl) methyl) benzamide (12c) exhibited the most potent antiproliferation against five carcinoma cell lines (HeLa, A549, HepG2, LoVo and HCT116 cells) with IC₅₀ values in range of 2.2–4.6?μM, while the IC₅₀ value of reference compound VX-680 was 8.5–15.3?μM. Moreover, Aurora kinase assays exhibited that compound 12c was potent inhibitor of AurA and AurB kinase with the IC₅₀ values were 118?±?8.1 and 80?±?4.2?nM, respectively. Molecular docking studies indicated that compound 12c forms better interaction with both AurA and AurB. Furthermore, compound 12c induced G2/M cell cycle arrest in HeLa cells by regulating protein levels of cyclinB1 and cdc2. These results suggested that 12c is a promising pan-Aurora kinase inhibitor for the potential treatment of cancer.     

The synthesis and evaluation of phenoxyacylhydroxamic acids as potential agents for Helicobacter pylori infections

Two series of ω-phenoxy contained acylhydroxamic acids as novel urease inhibitors were designed and synthesized. Biological activity evaluations revealed that ω-phenoxypropinoylhydroxamic acids were more active than phenoxyacetohydroxamic acids. Out of these compounds, 3-(3,4-dichlorophenoxy)propionylhydroxamic acid c24 showed significant potency against urease in both cell free extract (IC₅₀?=?0.061?±?0.003?μM) and intact cell (IC₅₀?=?0.89?±?0.05?μM), being over 450- and 120-fold more potent than the clinically prescribed urease inhibitor AHA, repectively. Non-linear fitting of experimental data (V-[S]) suggested a mixed-type inhibition mechanism and a dual site binding mode of these compounds.     

Identification of caffeoylquinic acid derivatives as natural protein tyrosine phosphatase 1B inhibitors from Artemisia princeps

Considerable attention has been paid to protein tyrosine phosphatase 1B (PTP1B) inhibitors as a potential therapy for diabetes, obesity, and cancer. Ten caffeoylquinic acid derivatives (1–10) from leaves of Artemisia princeps Pamp. (Asteraceae) were identified as natural PTP1B inhibitors. Among them, chlorogenic acid (3) showed the most potent inhibitory activity (IC₅₀ 11.1?μM). Compound 3 was demonstrated to be a noncompetitive inhibitor by a kinetic analysis. Molecular docking simulation suggested that compound 3 bound to the allosteric site of PTP1B. Furthermore, compound 3 showed remarkable selectivity against four homologous PTPs. According to these findings, compound 3 might be potentially valuable for further drug development.     

2-Substituted-1-(2-morpholinoethyl)-1H-naphtho[2,3-d]imidazole-4,9-diones: Design,synthesis and antiproliferative activity

Thirty-six of novel compounds 2-substituted-1-(2-morpholinoethyl)-1H-naphtho[2,3-d]imidazole-4,9-diones, bearing a N-(2-morpholinoethyl) group and a 2-substituted imidazole segment on a naphthoquinone skeleton, were designed, synthesized and tested as anticancer agents. Cytotoxicity was evaluated in vitro against three human cancer cell lines: human breast carcinoma cell line (MCF-7), human cervical carcinoma cell line (Hela), and human lung carcinoma cell line (A549); and one normal cell line: mouse fibroblast cell line (L929). Among them, the compound 2-(3-chloro-4-methoxyphenyl)-1-(2-morpholinoethyl)-1H-naphtho[2,3-d]imidazole-4,9-dione showed good antiproliferative activity against MCF-7, Hela and A549 (IC₅₀ values are equal to 10.6?μM, 8.3?μM and 4.3?μM respectively) and low cytotoxicity to L929 (IC₅₀ value is equal to 67.3?μM).     

Developing potential Helicobacter pylori urease inhibitors from novel oxoindoline derivatives: Synthesis,biological evaluation and in silico study

By recruiting the important moiety from Shikonin, a series of novel oxoindoline derivatives S1–S20 have been synthesized for inhibiting H. pylori urease. The most potent compound S18 displayed better activity (IC₅₀?=?0.71?μM; MIC?=?0.48?μM) than the positive controls AHA (IC₅₀?=?17.2?μM) and Metronidazole (MIC?=?31.3?μM). With low cytotoxicity, it showed considerable potential for further development. Docking simulation revealed the possible binding pattern of this series. 3D QSAR model was built to discuss SAR and give useful hints for future modification.     

Antibacterial endiandric acid derivatives from Beilschmiedia anacardioides

Three endiandric acid derivatives, beilschmiedic acids A, B and C were isolated from the stem bark of Beilschmiedia anacardioides together with the known β-sitosterol. Their structures were established by means of modern spectroscopic techniques. The relative configuration of compound 1 was determined by single crystal X-ray analysis. The antibacterial activities of compounds A,B,C were evaluated in vitro against five strains of microbes. Compound C showed strong activity against Bacillus subtilis, Micrococcus luteus and Streptococcus faecalis (MICs below 23 μM). This Compound was more active than the reference antibiotic ampicillin against B. subtilis and M. luteus.     

Synthesis,structure-activity relationships and preliminary mechanism study of N-benzylideneaniline derivatives as potential TLR2 inhibitors

Toll-like receptor 2 (TLR2) can recognize pathogen-associated molecular patterns to defense against invading organisms and has been represents an attractive therapeutic target. Until today, none TLR2 small molecule antagonist have been developed in clinical trial. Herein, we designed and synthesized 50?N-benzylideneaniline compounds with the help of CADD. And subsequent in vitro studies leading to the optimized compound SMU-A0B13 with most potent inhibitory activity to TLR2 (IC₅₀=18.21?±?0.87?μM). Preliminary mechanism studies indicated that this TLR2 inhibitor can work through the NF-κB signaling pathway with high specificity and low toxicity, and can also efficiently downregulate inflammatory cytokines, such as SEAP, TNF-α and NO in HEK-Blue hTLR2, human PBMC and Raw 264.7 cell lines. Additionally, the docking situation also indicate SMU-A0B13 can well bind to the TLR2-TIR (PDB: 1FYW) active domain, which probably explains the bioactivity.     

Leucoflavonine,a new bioactive racemic flavoalkaloid from the leaves of Leucosceptrum canum

A new flavoalkaloid racemate, leucoflavonine (1), together with its flavonoid precursor pectolinarigenin (2), was isolated from the leaves of Leucosceptrum canum collected from Tibet. Its structure was established by comprehensive spectroscopic analysis. Chrial separation of the enantiomers of 1 was achieved, and their absolute configurations were determined as S-(+)- and R-(?)-leucoflavonines ((+)-1a and (?)-1b) by comparison of their computational and experimental optical rotations. Biological assays indicated that both (+)-1a and (?)-1b exhibited inhibitory activity against acetylchlorinesterase (AChE) in vitro (IC₅₀?=?68.0?±?8.6 and 18.3?±?1.8?μM, respectively). Moreover, (?)-1b displayed cytotoxicity against human hepatoma cells HepG2 (IC₅₀?=?52.9?±?3.6?μM), and inhibited the production of interleukelin-2 (IL-2) in Jurkat cells (IC₅₀?=?16.5?±?0.9?μM), while (+)-1a showed no obvious activity in these assays.     

Callus induction and plant regeneration from anthers of Dendrocalamus latiflorus Munro

Bamboo varieties are very difficult to improve by traditional breeding methods. Here, we established an efficient plant-regeneration system for Dendrocalamus latiflorus (tropical giant bamboo) by anther culture. Culture conditions, especially the plant growth regulators required for callus induction and shoot differentiation, were optimized by orthogonal design. M8 medium supplemented with 5.37 μΜ α-naphthaleneacetic acid (NAA), 1.33 μM?N ⁶ -benzyladenine (BA), 110.17 μM phenylacetic acid (PAA), and a pretreatment time of 3 d produced the highest rate (5.08?±?0.61%) of callus induction. The maximum shoot differentiation rate reached 28.3?±?4.29% in M8 medium supplemented with 2.32 μM kinetin (KT), 8.89 μM BA, 1.08 μM NAA, and 110.17 μM PAA. The results of the ploidy level test showed that most of the regenerated plants were dodecaploid (96/100), a few were hexaploid (3/100), and one was triploid (1/100). The average chlorophyll content of dodecaploid lines was significantly higher than that of hexaploid lines. The present study provides an innovative method for bamboo ploidy breeding and a useful method for genetic improvement.     

Selective inhibition of β-N-acetylhexosaminidases by thioglycosyl–naphthalimide hybrid molecules

To develop selective inhibitors for β-N-acetylhexosaminidases which are involved in a myriad of physiological processes, a series of novel thioglycosyl–naphthalimide hybrid inhibitors were designed, synthesized and evaluated for inhibition activity against glycosyl hydrolase family 20 and 84 (GH20 and GH84) β-N-acetylhexosaminidases. These compounds which incorporate groups with varied sizes and lengths at the linker region between thioglycosyl moiety and naphthalimide moiety are designed to improve the selectivity and stacking interactions. The GH84 human O-GlcNAcase (hOGA) was sensitive to the subtle changes in the linker region and the optimal choice is a small size linker with six atoms length. And the GH20 insect β-N-acetylhexosaminidase OfHex1 could tolerate compounds with a hydrophobic bulky linker. Especially, the compound 5c (hOGA, K_i?=?3.46?μM; OfHex1, K_i?>?200?μM) and the compound 6f (hOGA, K_i?>?200?μM; OfHex1, K_i?=?21.81?μM) displayed high selectivity. The molecular docking results indicated that the inhibition mechanism was different between the two families due to their different structural characteristics beyond the active sites. These results provide some promising clues to improve selectivity of potent molecules against β-N-acetylhexosaminidases.     

Botryorhodines A-D, antifungal and cytotoxic depsidones from Botryosphaeria rhodina, an endophyte of the medicinal plant Bidens pilosa

An endophytic fungus (Botryosphaeria rhodina) was isolated from the stems of the medicinal plant Bidens pilosa (Asteraceae) that is known for its anti-inflammatory, antiseptic and antifungal effects. The ethyl acetate extract of the fungal isolate exhibits significant antifungal activity as well as potent cytotoxic and antiproliferative effects against several cancer cell lines. Activity-guided fractionation resulted in the isolation of a complex of four depsidones, botryorhodines A-D and the auxin indole carboxylic acid. Botryorhodine A and B show moderate to weak cytotoxic activities against HeLa cell lines with a CC₅₀ of 96.97 μM and 36.41 μM, respectively. In addition, they also show antifungal activity against a range of pathogenic fungi such as Aspergillus terreus (MIC 26.03 μM for botryorhodine A and 49.70 μM for B) and the plant pathogen Fusarium oxysporum (MIC 191.60 μM for botryorhodine A and 238.80 μM for B). A potential role of the endophyte in modulating fungal populations living within or attacking the host plant is discussed.     

Discovery of (E)-1-amino-4-phenylbut-3-en-2-ol derivatives as novel neuraminidase inhibitors

Neuraminidase has been considered as an important target for designing agents against influenza viruses. In a discovery of anti-influenza agents with epigoitrin as the initial lead compound, a series of 1-amino-2-alkanols were synthesized and biologically evaluated. The in vitro evaluation indicated that (E)-1-amino-4-phenylbut-3-en-2-ol (C1) had better inhibitory activities than 2-amino-1-arylethan-1-ol derivatives. To our surprise, sulfonation of C1 with 4-methoxybenzenesulfonyl chloride afforded more active inhibitor II with up to 6.4?μM IC₅₀ value against neuraminidase. Furthermore, docking of inhibitor II into the active site of NA found that the H atoms in both NH₂ and OH groups of inhibitor II were the key factors for potency. Molecular docking research did not explained very well the observed structure-activity relationship (SAR) from amino acid residue level, but also aided the discovery of (E)-1-amino-4-phenylbut-3-en-2-ol derivatives as novel and potent NA inhibitors.     

Identification of (4-(9H-fluoren-9-yl) piperazin-1-yl) methanone derivatives as falcipain 2 inhibitors active against Plasmodium falciparum cultures

Background

Falcipain 2 (FP-2) is the hemoglobin-degrading cysteine protease of Plasmodium falciparum most extensively targeted to develop novel antimalarials. However, no commercial antimalarial drugs based on FP-2 inhibition are available yet due to the low selectivity of most FP-2 inhibitors against the human cysteine proteases.

In silico and in vitro comparative activity of novel experimental derivatives against Leishmania major and Leishmania infantum promastigotes

This in silico and in vitro comparative study was designed to evaluate the effectiveness of some biurets (K1 to K8) and glucantime against Leishmania major and Leishmania infantum promastigotes. Overall, eight experimental ligands and glucantime were docked using AutoDock 4.3 program into the active sites of Leishmania major and Leishmania infantum pteridine reductase 1, which were modeled using homology modeling programs. The colorimetric MTT assay was used to find L. major and L. infantum promastigotes viability at different concentrations of biuret derivatives in a concentration and time-dependent manner and the obtained results were expressed as 50% and 90% of inhibitory concentration (IC₅₀ and IC₉₀). In silico method showed that out of eight experimental ligands, four compounds were more active on pteridine reductase 1. K3 was the most active against L. major promastigotes with an IC₅₀ of 6.8 μM and an IC₉₀ of 40.2 μM, whereas for L. infantum promastigotes was K8 with IC₅₀ of 7.8 μM. The phenylethyl derivative (K7) showed less toxicity (IC₅₀s > 60 μM) in both Leishmania strains. Glucantime displayed less growth inhibition in concentration of about 20 μM. In silico and especially docking results in a recent study were in accordance with the in vitro activity of these compounds in presented study and compound K3, K2 and K8 showed reasonable levels of selectivity for the Leishmania pteridine reductase 1.     

Bioassay-guided isolation of three anthelmintic compounds from Warburgia ugandensis Sprague subspecies ugandensis, and the mechanism of action of polygodial

Parasitic helminths continue to pose problems in human and veterinary medicine, as well as in agriculture. Resistance to current anthelmintics has prompted the search for new drugs. Anthelmintic metabolites from medicinal plants could be good anthelmintic drug candidates. However, the compounds active against nematodes have not been identified in most medicinal plants with anthelmintic activity. In this study, we aimed to identify the active compounds against helminths in Warburgia ugandensis Sprague subspecies ugandensis (Canellaceae) and study the underlying mechanism of action. A bioassay-guided isolation of anthelmintic compounds from the plant was performed using a Caenorhabditis elegans (C. elegans) test model with a WMicrotracker instrument to monitor motility. Three active compounds were purified and identified by nuclear magnetic resonance and high resolution MS: warburganal (IC₅₀: 28.2?±?8.6?μM), polygodial (IC₅₀: 13.1?±?5.3?μM) and alpha-linolenic acid (ALA, IC₅₀: 70.1?±?17.5?μM). A checkerboard assay for warburganal and ALA as well as polygodial and ALA showed a fractional inhibitory concentration index of 0.41 and 0.37, respectively, suggesting that polygodial and ALA, as well as warburganal and ALA, have a synergistic effect against nematodes. A preliminary structure–activity relationship study for polygodial showed that the α,β-unsaturated 1,4-dialdehyde structural motif is essential for the potent activity. None of a panel of C. elegans mutant strains, resistant against major anthelmintic drug classes, showed significant resistance to polygodial, implying that polygodial may block C. elegans motility through a mechanism which differs from that of currently marketed drugs. Further measurements showed that polygodial inhibits mitochondrial ATP synthesis of C. elegans in a dose-dependent manner (IC₅₀: 1.8?±?1.0?μM). Therefore, we believe that the underlying mechanism of action of polygodial is probably inhibition of mitochondrial ATP synthesis. In conclusion, polygodial could be a promising anthelmintic drug candidate worth considering for further development.     

Design,synthesis and evaluation against Mycobacterium tuberculosis of azole piperazine derivatives as dicyclotyrosine (cYY) mimics

Three series of azole piperazine derivatives that mimic dicyclotyrosine (cYY), the natural substrate of the essential Mycobacterium tuberculosis cytochrome P450 CYP121A1, were prepared and evaluated for binding affinity and inhibitory activity (MIC) against M. tuberculosis. Series A replaces one phenol group of cYY with a C3-imidazole moiety, series B includes a keto group on the hydrocarbon chain preceding the series A imidazole, whilst series C explores replacing the keto group of the piperidone ring of cYY with a CH₂-imidazole or CH₂-triazole moiety to enhance binding interaction with the heme of CYP121A1. The series displayed moderate to weak type II binding affinity for CYP121A1, with the exception of series B 10a, which displayed mixed type I binding. Of the three series, series C imidazole derivatives showed the best, although modest, inhibitory activity against M. tuberculosis (17d MIC?=?12.5?μg/mL, 17a 50?μg/mL). Crystal structures were determined for CYP121A1 bound to series A compounds 6a and 6b that show the imidazole groups positioned directly above the haem iron with binding between the haem iron and imidazole nitrogen of both compounds at a distance of 2.2?Å. A model generated from a 1.5?Å crystal structure of CYP121A1 in complex with compound 10a showed different binding modes in agreement with the heterogeneous binding observed. Although the crystal structures of 6a and 6b would indicate binding with CYP121A1, the binding assays themselves did not allow confirmation of CYP121A1 as the target.     

Rapid sporulation of Bacillus anthracis in a high iron, glucose-free medium

Spores are the infectious form of Bacillus anthracis (BA), causing cutaneous, inhalation and gastrointestinal anthrax. Because of the possible use of BA spores in a bioterrorism attack, there is considerable interest in studying spore biology. In the laboratory, however, it takes a number of days to prepare spores. Standard sporulation protocols, such as the use of ‘PA broth’, allow sporulation of BA to occur in 3 to 5 days. Another method employs growth of BA on plates in the dark for several days until they have efficiently sporulated. In efforts to determine the effect of iron on gene expression in BA, we grew BA Sterne strain 7702 in a minimal defined medium (CDM; Koppisch et al., 2005) with various concentrations of iron and glucose. As part of our initial observations, we monitored BA sporulation in CDM via light microscopy. In glucose-free CDM containing 1.5 mM Fe(NO₃)₃ (CDM-Fe), > 95% of the BA sporulated by 30 h; a far shorter time period than expected. We pursued this observation and we further characterized spores derived from PA and CDM-Fe media. Purified spores derived from PA or CDM-Fe had similar morphologies when viewed by light or electron microscopy, and were equally resistant to harsh conditions including heat (65 °C), ice and fresh 30% H₂O₂. Spore viability in long term cold storage in water was similar for the two spore preparations. Extracted spore coat proteins were evaluated by SDS-PAGE and silver staining, which revealed distinct protein profiles for PA and CDM-Fe spore coat extracts. ELISA assays were done to compare the interaction of the two spore preparations with rabbit antiserum raised against UV-killed Sterne strain 7702 spores prepared in PA medium. Spores from both media reacted identically with this antiserum. Finally, the interaction and fate of spores incubated with macrophages in vitro was very similar. In summary, BA spores induced in CDM-Fe or in PA medium are similar by several criteria, but show distinct extractable coat proteins. CDM-Fe liquid medium can be used for rapid production of BA spores, and could save considerable time in spore research studies.