Synthetic Studies toward 5,6,7,3',4'-Monomethoxytetrahydroxyflavones: Synthesis of Pedalitin.

During the synthetic studies toward 5,6,7,3',4'-monomethoxytetrahydroxyflavones, a concise pedalitin synthesis procedure was achieved. As previously reported, 6-hydroxy-2,3,4-trimethoxyacetophenone was prepared by Friedel-Crafts acylation of 1,4-dihydroxy-2,6-dimethoxybenzene with boron trifluoride diethyl etherate in acetic acid. When aldol condensation of 6-hydroxy-2,3,4-trimethoxyacetophenone 2b with vanillin was performed in basic conditions, it produced 2'-hydroxychalcone 3b, and, surprisingly, along with 3-hydroxyflavone 4 in a considerable amount. We propose that this oxidative cyclization is presumably due to the contribution of a quinone methide, likely to be subjected to aerobic oxidation. The chalcone was then subjected to oxidative cyclization with iodine in dimethyl sulfoxide to afford flavone 5 in good yield. To our delight, serial demethylation of the three methoxy groups at the 5-, 6-, and 3'-positions of 5 proceeded smoothly to produce pedalitin 1, under hydrogen bromide solution (30% in acetic acid). The crystal structures of 3-hydroxyflavone 4 and pedalitin tetraacetate 6 were unambiguously determined by X-ray crystallography.

Structural Requirements of 1-(2-Pyridinyl)-5-pyrazolones for Disproportionation of Boronic Acids.

We observed an unusual formation of four-coordinate boron(III) complexes from the reaction of 1-(2-pyridinyl)-5-pyrazolone derivatives with arylboronic acids in the basic media. The exact mechanism is not clear; however, the use of unprotected boronic acid and the presence of a bidentate ligand appeared to be the key structural requirements for the transformation. The results suggest that base-promoted disproportionation of arylboronic acid with the assistance of the [N,O]-bidentate ligation of 1-(2-pyridinyl)-5-pyrazolone should take place and facilitate the formation of pyrazole diarylborinate. Experiments to obtain a deeper understanding of its mechanism are currently underway.

Antimicrobial activity of IDD-B40 against drug-resistant Mycobacterium tuberculosis.

The emergence of multi-drug resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis creates the urgency for new anti-tuberculosis drugs to improve the efficiency of current tuberculosis treatment. In the search for a new potential tuberculosis drug, we synthesized an isoindole based chemical library and screened a potential candidate with significant anti-tuberculosis activity. The compound named 2-hydroxy-4-(4-nitro-1,3-dioxoisoindolin-2-yl) benzoic acid (IDD-B40) showed strong activity against all the tested drug-susceptible and drug-resistant strains of M. tuberculosis, with the 50% minimum inhibitory concentrations (MIC50) of 0.39 µg/ml both in culture broth and inside Raw 264.7 cells. Also, IDD-B40, in combination with rifampicin, exhibited a direct synergistic effect against both XDR and H37Rv M. tuberculosis. Besides, IDD-B40 showed a better post-antibiotic effect (PAE) than did some first-line drugs and showed no significant cytotoxicity to any cell line tested, with a selectivity index of ≥ 128. Although IDD-B40 showed a result similar to isoniazid in the preliminary mycolic acid inhibition assay, it did not exhibit any effect against other mycolic acid-producing nontuberculous mycobacterial strains (NTM), and different non-mycobacterial pathogenic strains, so further studies are required to confirm the mode of action of IDD-B40. Considering its results against M. tuberculosis, IDD-B40 is a potential anti-tuberculosis drug candidate. However, further studies are required to evaluate its potential in vivo effect and therapeutic potential.

Synthesis and activity of BNF15 against drug-resistant Mycobacterium tuberculosis.

Aim: Tuberculosis is the leading cause of mortality among infectious diseases worldwide. Finding a new competent anti tubercular therapy is essential. Materials & methods: We screened thousands of compounds and evaluated their efficacy against Mycobacterium tuberculosis. Results: Initially, 2-nitronaphtho[2,3-b]benzofuran-6,11-dione was active against M. tuberculosis. Next, among 15 newly synthesized derivatives, BNF15 showed promising effect against all drug-sensitive and drug-resistant M. tuberculosis (MIC: 0.02-0.78 µg/ml). BNF15 effectively killed intracellular M. tuberculosis and nontuberculous mycobacteria. BNF15 exhibited a prolonged post antibiotic effect superior to isoniazid, streptomycin, and ethambutol and synergistic interaction with rifampicin. In acute oral toxicity test, BNF15 did not show toxic effect at a concentration up to 2000 mg/kg. Conclusion: These results highlight the perspective of BNF15 to treat drug-resistant M. tuberculosis.

Pharmacokinetic Study of NADPH Oxidase Inhibitor Ewha-18278, a Pyrazole Derivative.

In a previous study, the specific NOX1/2/4 inhibitor Ewha-18278 was confirmed as a possible treatment for osteoporosis both in vitro and in vivo. Here, we investigated the pharmacokinetics (PK) of the compound by intravenous (IV) and oral administrations to rats. Dimethyl sulfoxide (DMSO)-based and diazepam injection-based formulations were used to dissolve the compound. In the latter formulation applicable to humans, the changes in PK parameters were monitored at two different concentrations (1 mg/mL and 2 mg/mL). The area under the plasma concentration-time curve from zero time to infinity (AUCinf) of Ewha-18278 was highest in the DMSO-based formulation (2 mg/mL). Also, the concentration was increased 1.6-fold at the low concentration of the diazepam injection-based formulation compared to the high concentration. There was no statistical significance in the AUCinf of the compound between DMSO-based formulation (2 mg/mL) and diazepam injection-based formulation (1 mg/mL). These results suggest that Ewha-18278 can be delivered to humans by both IV and oral routes. In addition, the diazepam injection-based formulation of Ewha-18278 appears to be a suitable candidate for dosage development for future toxicity test and clinical trial.

In vitro activity of DNF-3 against drug-resistant Mycobacterium tuberculosis.

Due to the emergence of multidrug-resistant and extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis, new antituberculosis drugs are urgently required to improve the efficacy of current tuberculosis (TB) treatment. To achieve this goal, ca. 1000 chemical compounds were screened for potential antimycobacterial activity, among which methyl 5-(2-diethylaminoethoxy)-7,12-dioxo-7,12 dihydrodinaphtho[1,2-b;2',3'-d]furan-6-carboxylate (DNF-3) showed strong activity against all of the tested drug-susceptible and -resistant M. tuberculosis strains, with 50% minimum inhibitory concentrations (MIC50 values) of 0.02-0.39 µg/mL both in culture broth and within murine RAW 264.7 macrophage cells. When DNF-3 was used in combination with rifampicin or streptomycin, it exhibited direct synergy against XDR-TB and an additive effect against M. tuberculosis H37Rv. DNF-3 displayed a long post-antibiotic effect (PAE) that was comparable with rifampicin but was superior to isoniazid, streptomycin and ethambutol. Importantly, DNF-3 showed no cytotoxicity to any cell line tested, with a selectivity index (SI) of >32. DNF-3 was also active against 27 nontuberculous mycobacteria (NTM) strains, Staphylococcus spp. and Streptococcus spp. Taken together, these results indicate that DNF-3 is a promising new candidate drug for treating TB. Further studies are warranted to establish the in vivo effect and therapeutic potential of DNF-3.

Identification of quinone analogues as potential inhibitors of picornavirus 3C protease in vitro.

Picornaviruses are non-enveloped viruses that represent a large family of positive-sense single-stranded RNA viruses including a number of causative agents of many human and animal diseases such as coxsackievirus B3 (CVB3) and rhinoviruses (HRV). In this study, we performed a high-throughput screening of a compound library composed of ∼6000 small molecules in search of potential picornavirus 3C protease (3Cpro) inhibitors. As results, we identified quinone analogues that effectively inhibited both CVB3 3Cpro and HRV 3Cpro with IC50 values in low micromolar range. Together with predicted binding modes of these compounds to the active site of the viral protease, it is implied that structural features of these non-peptidic inhibitors may act as useful scaffold for further anti-picornavirus drug design and development.

Acute, subchronic oral toxicity, toxicokinetics, and genotoxicity studies of DFC-2, an antitubercular drug candidate.

The infectious disease tuberculosis remains a serious global health issue and is responsible for nearly 1.8 million deaths every year. In our previous study, DFC-2 was confirmed to show anti-tubercular activity against drug-susceptible and drug-resistant strains of Mycobacterium tuberculosis. To support the safety-in-use of DFC-2 as an anti-tubercular drug, DFC-2 was tested via single- and 28-day repeated-dose oral toxicity study and mutagenicity assays. In the oral toxicity study, a single oral dose of DFC-2 at 2000 mg/kg did not produce deaths or abnormal lesions in the internal organs of rats. The results of a 28-day orally repeated dose of DFC-2 did not show treatment-related deaths or obvious toxicity symptoms in the animals treated with a dose of 300 mg/kg/day during the experimental period. Therefore, the no-observed-adverse-effect level (NOAEL) of DFC-2 was determined as 300 mg/kg/day for both male and female rats. In addition, DFC-2 showed no genetic toxicity in in vitro bacterial reverse mutation test, in vitro chromosomal aberration test, and in vivo mouse bone marrow micronucleus formation test. These results indicate that DFC-2 is a promising anti-tubercular drug candidate with a favorable safety profile.

In Vitro Effect of DFC-2 on Mycolic Acid Biosynthesis in Mycobacterium tuberculosis.

DFC-2, a methyl 5-[2-(dimethylamino)ethoxy]-7,12-dioxo-7,12-dihydrodinaphtho[1,2-b:2',3'-d]furan-6-carboxylate, is reported to have antitubercular effects against Mycobacterium tuberculosis. At concentrations ranging from 0.19 to 0.39 µg/ml, DFC-2 inhibited both drug-susceptible and -resistant strains of M. tuberculosis. Microarray analyses were employed to gain insights into the molecular mechanisms of DFC-2's action in M. tuberculosis. The most affected functional gene category was "lipid biosynthesis," which is involved in mycolic acid synthesis. The decrease in transcription of genes related to mycolic acid synthesis was confirmed by RT-PCR. Furthermore, we found that DFC-2 triggered a reduction in mycolic acid levels, showing a similar pattern to that of mycolic acid synthesis inhibitor isoniazid. These results may explain how this compound kills mycobacteria efficiently by inhibiting mycolic acid synthesis.

One-pot synthesis of four-coordinate boron(III) complexes by the ligand-promoted organic group migration between boronic acids.

Multidisciplinary applications of four-coordinate boron(III) complexes make them very attractive and challenging research field in chemistry, biology and material sciences. The dual role played by boron atom in stabilising the chelate ligand and enhancing the π-conjugation makes them very useful as luminescent materials for organic electronics and photonics, and sensing and imaging probes for biomedical purposes. The conventional methods involve the use of diarylborinic acids or anhydrides and triaryl boranes, which are made from organometallic reagents. The strong nucleophilicity of these reagents limits the peripheral modifications onto the boron cores. Here, we report a metal-free one-pot synthesis of four-coordinate organoborons using boronic acids, which represents the first instance of ligand assisted organic group migration between boronic acids. A tetrahedral boron 'ate' complex capable of transferring an organic group to the adjacent sp2 boron within a boronic anhydride intermediate is proposed and preliminary mechanistic studies by MALDI-TOF and 11B NMR support this proposal. The products are available from a series of N,O-, N,N- and O,O-bidentate ligands upon a wide array of boronic acids. We anticipate that this reaction will impact the way of producing the four-coordinate organoborons, and propel a new discovery of such materials for optoelectronic and biomedical applications.

Naphthofuroquinone derivatives show strong antimycobacterial activities against drug-resistant Mycobacteria.

Tuberculosis, one of the world's major health problems, has become more serious due to the emergence of multi-drug resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis (MTB). In this study, we performed three anti-MTB assays to evaluate the anti-mycobacterial activity of naphthofuroquinone derivatives against drug-resistant MTB. Among them, methyl 5-[2-(dimethylamino)ethoxy]-7,12-dioxo-7,12-dihydrodinaphtho[1,2-b:2',3'-d]furan-6-carboxylate (DFC2) exhibited strong anti-mycobacterial activity against MTB H37Ra, H37Rv and four drug-resistant MTB strains. The MIC of DFC2 ranged from 0.19-0.39 µg/ml to 0.78-1.56 µg/ml against all tested MTB strains. Moreover, DFC2 showed low cytotoxicity against fibroblast cells (L929) at concentrations 10-40-fold higher than their MICs. The IC50 value of DFC2 against L929 cells was 15.218 µg/ml. In addition, DFC2 reduced the number of intracellular M. tuberculosis in macrophages in a dose-dependent manner. Taken together, our results indicate DFC2 to be promising new candidate agents for the treatment of tuberculosis.

Identification of a novel cellulose-binding domain within the endo-ß-1,4-xylanase KRICT PX-3 from Paenibacillus terrae HPL-003.

The model 3-D structure of xylanase KRICT PX3 (JF320814) identified by DNA sequence analysis revealed a catalytic domain and CBM4-9 which functions as a xylan binding domain (XBD). To identify its role in xylan hydrolysis, six expression plasmids were constructed encoding the N-terminal CBM plus the catalytic domain or different glycosyl hydrolases, and the biochemical properties of the recombinant enzymes were compared to the original structure of PX3 xylanase. All six of the recombinant xylanases with the addition of CBM in the pIVEX-GST expression vector showed no improved PX3 hydrolytic activity. However, the absence of the CBM domain resulted in a decrement of 40% in thermostability, movement of the optimal temperature from 55°C to 45°C, alteration of the optimal pH range from 5-10 to 6-8, and reduction of the enzymatic activity to one-second under the same condition, respectively. The putative XBD in PX3 comprises a new N-terminal domain homologous to the catalytic thermostabilizing domains from other xylanases. Analysis of the main products released from xylan indicate that the recombinant enzymes act as endo-1,4-ß-xylanases but differ in their hydrolysis of xylan from beech wood, birch wood, and oat spelt.

Small molecules that allosterically inhibit p21-activated kinase activity by binding to the regulatory p21-binding domain.

p21-activated kinases (PAKs) are key regulators of actin dynamics, cell proliferation and cell survival. Deregulation of PAK activity contributes to the pathogenesis of various human diseases, including cancer and neurological disorders. Using an ELISA-based screening protocol, we identified naphtho(hydro)quinone-based small molecules that allosterically inhibit PAK activity. These molecules interfere with the interactions between the p21-binding domain (PBD) of PAK1 and Rho GTPases by binding to the PBD. Importantly, they inhibit the activity of full-length PAKs and are selective for PAK1 and PAK3 in vitro and in living cells. These compounds may potentially be useful for determining the details of the PAK signaling pathway and may also be used as lead molecules in the development of more selective and potent PAK inhibitors.

A novel pyrazole derivative protects from ovariectomy-induced osteoporosis through the inhibition of NADPH oxidase.

Osteoclast cells (OCs) are differentiated from bone marrow-derived macrophages (BMMs) by activation of receptor activator of nuclear factor κB (NF-κB) ligand (RANKL). Activation of NADPH oxidase (Nox) isozymes is involved in RANKL-dependent OC differentiation, implicating Nox isozymes as therapeutic targets for treatment of osteoporosis. Here, we show that a novel pyrazole derivative, Ewha-18278 has high inhibitory potency on Nox isozymes. Blocking the activity of Nox with Ewha-18278 inhibited the responses of BMMs to RANKL, including reactive oxygen species (ROS) generation, activation of mitogen-activated protein (MAP) kinases and NF-κB, and OC differentiation. To evaluate the anti-osteoporotic function of Ewha-18278, the derivative was applied to estrogen-deficient ovariectomized (OVX) ddY mice. Oral administration of Ewha-18278 (10 mg/kg/daily, 4 weeks) into the mice recovered bone mineral density, trabecular bone volume, trabecular bone length, number and thickness, compared to control OVX ddY mice. Moreover, treatment of OVX ddY mice with Ewha-18278 increased bone strength by increasing cortical bone thickness. We provide that Ewha-18278 displayed Nox inhibition and blocked the RANKL-dependent cell signaling cascade leading to reduced differentiation of OCs. Our results implicate Ewha-18278 as a novel therapeutic agent for the treatment of osteoporosis.

Triazolyl phenyl disulfides: 8-Amino-7-oxononanoate synthase inhibitors as potential herbicides.

The chemical validation of a potential herbicide target was investigated with 8-amino-7-oxononanoate synthase (AONS, also known as 7-keto-8-aminopelargonate synthase, KAPAS) and triazolyl phenyl disulfide derivatives in vitro and in vivo. AONS activity was completely inhibited by these synthesized compounds, with an IC50 of 48 to 592µM in vitro. Forty five-day old Arabidopsis thaliana plants were completely killed by representative compound KHG23844 {N-(2-fluorophenyl)-3-(phenyldisulphanyl)-1H-1,2,4-triazole-1-carboxamide} at the application rate of 250gha(-1) of foliar treatment in greenhouse conditions. Foliar application of 1000gha(-1) KHG23844 induced 2.3-fold higher l-alanine accumulation in the treated A. thaliana plants. Foliar supplement of 1mM biotin at 1 and 2days before KHG23844 application effectively recovered the growth inhibition of A. thaliana plant treated with KHG23844. The results strongly suggested that representative compound KHG23844 and its derivatives are potential AONS inhibitors.

6-trifluoromethyl-2-thiouracil possesses anti-Toxoplasma gondii effect in vitro and in vivo with low hepatotoxicity.

Since pyrimethamine, the general therapeutic drug for toxoplasmosis, presents several adverse side effects, the need to develop and evaluate new drugs for the condition is critical. In this study, anti-Toxoplasma gondii activities of 3-[{2-((E)-furan-2-ylmethylene)hydrazinyl}methylene]-1,3-dihydroindol-2-one (ATT-5126) and 6-trifluoromethyl-2-thiouracil (KH-0562) were evaluated in vitro using a 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay and in vivo by measuring amount of the tachyzoites in mice ascites. Biochemical parameters such as lipid peroxidation (LPO), glutathione (GSH), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were also evaluated in livers of mice at 4 days post-infection. As a result, the ATT-5126 and KH-0562 showed anti-T. gondii activity in vitro. Treatment of ATT-5126 or KH-0562 decreased the amount of tachyzoites in T. gondii infected ICR mice. The relative weight of liver and spleen increased by T. gondii infection were decreased by treatment of ATT-5126 or KH-0562. The levels of LPO, ALT and AST, which are biochemical parameters involved in liver injury, were also significantly recovered by treatment of ATT-5126 or KH-0562 (p<0.05). In particular, the recovered levels by KH-0562 were similar to those of pyrimethamine-treated group (p<0.05). However, the level of GSH, which is an antioxidant indicator, showed insignificant statistics. The results suggest that KH-0562 show anti-T. gondii activities in vitro and in vivo with low hepatotoxicity. Therefore, KH-0562 may be a useful candidate for treating T. gondii infection.

A new bi-modular endo-ß-1,4-xylanase KRICT PX-3 from whole genome sequence of Paenibacillus terrae HPL-003.

A new bi-modular, wide pH spectrum and highly active xylanase KRICT PX3 (JF320814) isolated from Paenibacillus terrae HPL-003 (KCTC11987BP) has been cloned and expressed in Escherichia coli. Purified recombinant xylanase KRICT PX-3 (1,620 bp, 540aa, NCBI accession number JF320814) showed highly active at 55°C in pH 4.0-11.0, and stability for at least 24h at 50°C, and exhibited Km and Vmax of 0.2mg/mL and 153.8 U/mg on birchwood xylan. Most common ions did not affect the enzyme activity at 1mM concentration. This enzyme could belong to glycoside hydrolase family 10 because hydrolyzed glucuronoxylan and arabinoxylan substrate to xylobiose, xylotriose, and some traces of xylose as hydrolysis products. Model 3-D structure was composed of two domains, the catalytic domain of a (ß/α)8 barrel fold while the small domain probably functions as a xylan binding domain, and the two domains are connected by a flexible linker peptide (PPLAIEKDIPSL). However, sequence alignment between xylan-binding module in this xylanase KRICT PX3 and CBM22 showed 21% of identity and 35% of similarity. This xylanase structure showed a distinctive group of enzyme cluster separately from the rest of GH10 xylanases, and seems to constitute a new type of xylanases.

Genome sequence of Paenibacillus terrae HPL-003, a xylanase-producing bacterium isolated from soil found in forest residue.

This article reports on the full genome sequence of Paenibacillus terrae HPL-003, which is a gram-positive, endospore-forming, xylanase-producing bacterium isolated from soil found in forest residue on Gara Mountain. The strain HPL-003 contains 6,083,395 bp with a G+C content of 46.77 mol%, 2,633 protein-coding genes, and 117 structural RNAs.

A facile synthesis of highly functionalized 4-arylcoumarins via Kostanecki reactions mediated by DBU.

An efficient synthesis of 4-arylcoumarins has been accomplished via Kostanecki reactions of 2-hydroxybenzophenones with acetic anhydride employing DBU at ambient temperature. Using the same strategy, several 2-acyloxybenzophenone derivatives were readily converted to 3,4-difunctionalized coumarins. This protocol offers a notable improvement in reaction conditions for coumarin synthesis and takes advantage of its synthetic capability, especially for highly functionalized 4-arylcoumarins with structural diversity.

[5-Hydroxy-3-phenyl-1-(pyridin-2-yl)pyrazol-5-olato]diphenylboron.

In the title compound, C(26)H(20)BN(3)O, the B atom has tetra-hedral geometry and is linked to two phenyl rings, the O atom of the hy-droxy-pyrazole ring and the N atom of the pyridinyl ring. A six-membered BOCNCN ring forms by coordination of the B atom and the pyridinyl N atom. The BOCNCN ring has an envelope conformation [dihedral angle = 36.7 (1)° between the planar ring atoms and the flap] with the B atom out of the plane. In the 1-(2-pyridin-yl)-3-phenyl-5-hy-droxy-pyrazole group, the pyridinyl ring, the phenyl ring and the pyrazole ring are almost coplanar: the pyrazole ring makes a dihedral angle of 9.56 (8)° with the pyridinyl ring and 17.68 (7)° with the phenyl ring. The crystal structure is stabilized by π-π stacking inter-actions involving the pyridinyl and pyrazole rings of centrosymmetrically related mol-ecules, with ring centroid separations of 3.54 (5) Å.