Discovery and antiparasitic activity of AZ960 as a Trypanosoma brucei ERK8 inhibitor

Human African trypanosomiasis (HAT) is a lethal, vector-borne disease caused by the parasite Trypanosoma brucei. Therapeutic strategies for this neglected tropical disease suffer from disadvantages such as toxicity, high cost, and emerging resistance. Therefore, new drugs with novel modes of action are needed. We screened cultured T. brucei against a focused kinase inhibitor library to identify promising bioactive compounds. Among the ten hits identified from the phenotypic screen, AZ960 emerged as the most promising compound with potent antiparasitic activity (IC₅₀ = 120 nM) and was shown to be a selective inhibitor of an essential gene product, T. brucei extracellular signal-regulated kinase 8 (TbERK8). We report that AZ960 has a K_i of 1.25 μM for TbERK8 and demonstrate its utility in establishing TbERK8 as a potentially druggable target in T. brucei.     

Identification and development of the 1,4-benzodiazepin-2-one and quinazoline-2,4-dione scaffolds as submicromolar inhibitors of HAT

A library of 1,4-benzodiazepines has been synthesised and evaluated for activity against Trypanosoma brucei, a causative parasite of Human African Trypanosomiasis (HAT). The most potent of these derivatives has an MIC value of 0.97 μM. Herein we report the design, synthesis and biological evaluation of the abovementioned compounds.     

Optimization of the electrophile of chloronitrobenzamide leads active against Trypanosoma brucei

We previously reported the phenylchloronitrobenzamides (PCNBs), a novel class of compounds active against the species of trypanosomes that cause Human African Trypanosomiasis (HAT). Herein, we explored the potential to adjust the reactivity of the electrophilic chloronitrobenzamide core. These studies identified compound 7d that potently inhibited the growth of trypanosomes (EC₅₀ = 120 nM for Trypanosoma b. brucei, 18 nM for Trypanosoma b. rhodesiense, and 38 nM for Trypanosoma b. gambiense) without significant cytotoxicity against mammalian cell lines (EC₅₀ > 25 μM for HepG2, HEK293, Raji, and BJ cell lines) and also had good stability in microsomal models (t_1/2 > 4 h in both human and mouse). Overall these properties indicate the compound 7d and its analogs are worth further exploration as potential leads for HAT.     

Design,synthesis, antiviral and cytostatic activity of ω-(1H-1,2,3-triazol-1-yl)(polyhydroxy)alkylphosphonates as acyclic nucleotide analogues

The efficient synthesis of a new series of polyhydroxylated dibenzyl ω-(1H-1,2,3-triazol-1-yl)alkylphosphonates as acyclic nucleotide analogues is described starting from dibenzyl ω-azido(polyhydroxy)alkylphosphonates and selected alkynes under microwave irradiation. Selected O,O-dibenzylphosphonate acyclonucleotides were transformed into the respective phosphonic acids. All compounds were evaluated in vitro for activity against a broad variety of DNA and RNA viruses and for cytostatic activity against murine leukemia L1210, human T-lymphocyte CEM and human cervix carcinoma HeLa cells. Compound (1S,2S)-16b exhibited antiviral activity against Influenza A H3N2 subtype (EC₅₀ = 20 μM—visual CPE score; EC₅₀ = 18 μM—MTS method; MCC >100 μM, CC₅₀ >100 μM) in Madin Darby canine kidney cell cultures (MDCK), and (1S,2S)-16k was active against vesicular stomatitis virus and respiratory syncytial virus in HeLa cells (EC₅₀ = 9 and 12 μM, respectively). Moreover, compound (1R,2S)-16l showed activity against both herpes simplex viruses (HSV-1, HSV-2) in HEL cell cultures (EC₅₀ = 2.9 and 4 μM, respectively) and feline herpes virus in CRFK cells (EC₅₀ = 4 μM) but at the same time it exhibited cytotoxicity toward uninfected cell (MCC ⩾ 4 μM). Several other compounds have been found to inhibit proliferation of L1210, CEM as well as HeLa cells with IC₅₀ in the 4–50 μM range. Among them compounds (1S,2S)- and (1R,2S)-16l were the most active (IC₅₀ in the 4–7 μM range).     

Synthesis of isothiazol-3-one derivatives as inhibitors of histone acetyltransferases (HATs)

High-throughput screening led to the identification of isothiazolones 1 and 2 as inhibitors of histone acetyltransferase (HAT) with IC50s of 3 μM and 5 μM, respectively. Analogues of these hit compounds with variations of the N-phenyl group, and with variety of substituents at C-4, C-5 of the thiazolone ring, were prepared and assayed for inhibition of the HAT enzyme PCAF. Potency is modestly favoured when the N-aryl group is electron deficient (4-pyridyl derivative 10 has IC₅₀ = 1.5 μM); alkyl substitution at C-4 has little effect, whilst similar substitution at C-5 causes a significant drop in potency. The ring–fused compound 38 has activity (IC₅₀ = 6.1 μM) to encourage further exploration of this bicyclic structure. The foregoing SAR is consistent with an inhibitory mechanism involving cleavage of the S–N bond of the isothiazolone ring by a catalytically important thiol residue.     

Membrane active chelators as novel anti-African trypanosome and anti-malarial drugs

Malaria (Plasmodium spp.) and human African trypanosomiasis (Trypanosoma brucei spp.) are vector borne, deadly parasitic diseases. While chemotherapeutic agents for both diseases are available, difficulty in disease eradication and development of drug resistance require that new therapies targeting unexplored pathways or exploiting novel modes of action be developed. Intracellular Plasmodium and extracellular Trypanosoma brucei may have unique and essential requirements for divalent metal ions, beyond that deemed physiological for the host. Membrane Active Chelators (MACs), biologically active only in a hydrophobic lipid environment, are able to bind metal ions at elevated non-physiological concentrations in the vicinity of cell membranes. A dose–response relationship study using validated viability assays revealed that two MAC drugs, DP-b99 and DP-460, were cytotoxic for these parasites in vitro. The 50% effective concentration (EC₅₀) values for DP-b99 and DP-460 were 87 μM and 39 μM for Trypanosoma brucei brucei and 21 μM and 28 μM for erythrocytic Plasmodium falciparum, respectively. Furthermore, drug potency was maintained for at least 24 h in serum containing medium at 37 °C. While the exact mechanism of action of MACs against intracellular malaria and extracellular African trypanosome parasites has yet to be determined, their potential as antiparasitic agents warrants further investigation.     

Synthesis and anti-parasitic activity of a novel quinolinone–chalcone series

A series of novel quinolinone–chalcone hybrids and analogues were designed, synthesized and their biological activity against the mammalian stages of Trypanosoma brucei and Leishmania infantum evaluated. Promising molecular scaffolds with significant microbicidal activity and low cytotoxicity were identified. Quinolinone–chalcone 10 exhibited anti-parasitic properties against both organisms, being the most potent anti-L. infantum agent of the entire series (IC₅₀ value of 1.3 ± 0.1 μM). Compounds 4 and 11 showed potency toward the intracellular, amastigote stage of L. infantum (IC₅₀ values of 2.1 ± 0.6 and 3.1 ± 1.05 μM, respectively). Promising trypanocidal compounds include 5 and 10 (IC₅₀ values of 2.6 ± 0.1 and 3.3 ± 0.1 μM, respectively) as well as 6 and 9 (both having IC₅₀ values of <5 μM). Chemical modifications on the quinolinone–chalcone scaffold were performed on selected compounds in order to investigate the influence of these structural features on antiparasitic activity.     

Synthesis and SAR study of 4,5-diaryl-1H-imidazole-2(3H)-thione derivatives,as potent 15-lipoxygenase inhibitors

A series of 4,5-diaryl-1H-imidazole-2(3H)-thione was synthesized and their inhibitory potency against soybean 15-lipoxygenase and free radical scavenging activities were determined. Compound 11 showed the best IC₅₀ for 15-LOX inhibition (IC₅₀ = 4.7 μM) and free radical scavenging activity (IC₅₀ = 14 μM). Methylation of SH at C₂ position of imidazole has dramatically decreased the 15-LOX inhibition and radical scavenging activity as it can be observed in the inactive compound 14 (IC₅₀ >250 μM). Structure activity similarity (SAS) showed that the most important chemical modification in this series was methylation of SH group and Docking studies revealed a proper orientation for SH group towards Fe core of the 15-LOX active site. Therefore it was concluded that iron chelating could be a possible mechanism for enzyme inhibition in this series of compounds.     

Inhibitory effect of novel tetrahydropyrimidine-2(1H)-thiones on melanogenesis

The series of imidazoldine-2-thiones 2 and tetrahydropyrimidine-2-thiones 3 were discovered as inhibitor of α-MSH-induced melanin production in melanoma B16 cells. The primary bioassay showed that 1-(4-ethylbenzyl)-tetrahydropyrimidine-2(1H)-thione 3e (>100% inhibition at 10 μM, IC₅₀ = 1.2 μM) and 1-(4-tert-butylbenzyl)-tetrahydropyrimidine-2(1H)-thione 3f (>100% inhibition at 10 μM, IC₅₀ = 0.76 μM) exhibited potent inhibitory effect against α-MSH-induced melanin production. Compounds 3 inhibit the biosynthesis of tyrosinase without affecting its catalytic activity in melanogenesis.     

Synthesis and biological evaluation of novel 2-(substituted phenylaminocarbonylmethylthio)-6-(2,6-dichlorobenzyl)-pyrimidin-4(3H)-ones as potent HIV-1 NNRTIs

A series of novel 2-(phenylaminocarbonylmethylthio)-6-(2,6-dichlorobenzyl)-pyrimidin-4(3H)-ones have been designed and synthesized. All of the new compounds were evaluated for their anti-HIV activities in MT-4 cells. Most of these new compounds showed moderate to potent activities against wild-type HIV-1 with an EC₅₀ ranging from 4.48 μM to 0.18 μM. Among them, 2-[(4-bromophenylamino)carbonylmethylthio]-6-(2,6-dichlorobenzyl)-5-methylpyrimidin-4(3H)-one 4b3 was identified as the most promising compound (EC₅₀ = 0.18 ± 0.06 μM, CC₅₀ >243.56 μM, SI >1326). The structure–activity relationship (SAR) of these new congeners is discussed.     

Antimycobacterial and herbicidal activity of ring-substituted 1-hydroxynaphthalene-2-carboxanilides

In this study, a series of 22 ring-substituted 1-hydroxynaphthalene-2-carboxanilides were prepared and characterized. Primary in vitro screening of the synthesized compounds was performed against Mycobacterium marinum, Mycobacterium kansasii and Mycobacterium smegmatis. The compounds were also tested for their activity related to inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. Most of tested compounds showed the antimycobacterial activity against the three strains comparable or higher than the standard isoniazid. N-(3-Fluorophenyl)-1-hydroxynaphthalene-2-carboxamide showed the highest biological activity (MIC = 28.4 μmol/L) against M. marinum, N-(4-fluorophenyl)-1-hydroxynaphthalene-2-carboxamide showed the highest biological activity (MIC = 14.2 μmol/L) against M. kansasii, and N-(4-bromophenyl)-1-hydroxynaphthalene-2-carboxamide expressed the highest biological activity (MIC = 46.7 μmol/L) against M. smegmatis. This compound and 1-hydroxy-N-(3-methylphenyl)naphthalene-2-carboxamide were the most active compounds against all three tested strains. The PET inhibition expressed by IC₅₀ value of the most active compound 1-hydroxy-N-(3-trifluoromethylphenyl)naphthalene-2-carboxamide was 5.3 μmol/L. The most effective compounds demonstrated insignificant toxicity against the human monocytic leukemia THP-1 cell line. For all compounds, structure–activity relationships are discussed.     

In vitro anti-rotavirus activity of polyphenol compounds isolated from the roots of Glycyrrhiza uralensis

We evaluated the ability of six polyphenols isolated from the roots of Glycyrrhiza uralensis to inactivate rotaviruses, specially G5P[7] and G8P[7]. Upon finding that all polyphenols possessed anti-rotavirus activity, we evaluated whether these properties were attributable to direct inhibition of the binding of rotavirus to cells and/or to inhibition of viral replication. Using the virucidal assay, we found that all six compounds directly inhibited rotavirus binding, with activity being dependent on the type of virus. The 50% effective inhibitory concentrations (EC₅₀) of the six compounds were 18.7–69.5 μM against G5P[7] and 14.7–88.1 μM against G8P[7], respectively. Five of the six compounds inhibited hemagglutination activity. Moreover, the CPE inhibition assay showed that five compounds inhibited viral replication with EC₅₀ values of 12.1–24.0 μM against G5P[7] and 12.0–42.0 μM against G8P[7], respectively. RT-PCR showed that the compounds suppressed viral RNA synthesis in TF-104 cells. Interestingly, the anti-rotavirus activities of four compounds were attributable to inhibition of both viral absorption and viral replication. These results suggest that compounds isolated from the roots of G. uralensis may be potent anti-rotavirus agents in vivo, acting by inhibiting both viral absorption and viral replication.     

Benzo[d]isothiazole 1,1-dioxide derivatives as dual functional inhibitors of 5-lipoxygenase and microsomal prostaglandin E2 synthase-1

A series of 6-nitro-3-(m-tolylamino) benzo[d]isothiazole 1,1-dioxide analogues were synthesized and evaluated for their inhibition activity against 5-lipoxygenase (5-LOX) and microsomal prostaglandin E₂ synthase (mPGES-1). These compounds can inhibit both enzymes with IC₅₀ values ranging from 0.15 to 23.6 μM. One of the most potential compounds, 3g, inhibits 5-LOX and mPGES-1 with IC₅₀ values of 0.6 μM, 2.1 μM, respectively.     

Synthesis and α-glucosidase inhibitory activity evaluation of N-substituted aminomethyl-β-d-glucopyranosides

A series of N-substituted 1-aminomethyl-β-d-glucopyranoside derivatives was prepared. These novel synthetic compounds were assessed in vitro for inhibitory activity against yeast α-glucosidase and both rat intestinal α-glucosidases maltase and sucrase. Most of the compounds displayed α-glucosidase inhibitory activity, with IC₅₀ values covering the wide range from 2.3 μM to 2.0 mM. Compounds 19a (IC₅₀ = 2.3 μM) and 19b (IC₅₀ = 5.6 μM) were identified as the most potent inhibitors for yeast α-glucosidase, while compounds 16 (IC₅₀ = 7.7 and 15.6 μM) and 19e (IC₅₀ = 5.1 and 10.4 μM) were the strongest inhibitors of rat intestinal maltase and sucrase. Analysis of the kinetics of enzyme inhibition indicated that 19e inhibited maltase and sucrase in a competitive manner. The results suggest that the aminomethyl-β-d-glucopyranoside moiety can mimic the substrates of α-glucosidase in the enzyme catalytic site, leading to competitive enzyme inhibition. Moreover, the nature of the N-substituent has considerable influence on inhibitory potency.     

Triazino indole–quinoline hybrid: A novel approach to antileishmanial agents

A novel series of 1,2,4-triazino-[5,6b]indole-3-thione covalently linked to 7-chloro-4-aminoquinoline have been synthesized and evaluated for their in vitro activity against extracellular promastigote and intracellular amastigote form of Leishmania donovani. Among all tested compounds, compounds 7a and 7b were found to be the most active with IC₅₀ values 1.11, 0.36 μM and selectivity index (SI) values 67, >1111, respectively, against amastigote form of L. donovani which is several folds more potent than the standard drugs, miltefosine (IC₅₀ = 8.10 μM, SI = 7) and sodium stibo-gluconate (IC₅₀ = 54.60 μM, SI ⩾ 7).     

Discovery,characterization and comparison of inhibitors of Bacillus anthracis and Staphylococcus aureus replicative DNA helicases

Antibacterial compounds with new mechanisms of action are needed for effective therapy against drug-resistant pathogens in the clinic and in biodefense. Screens for inhibitors of the essential replicative helicases of Bacillus anthracis and Staphylococcus aureus yielded 18 confirmed hits (IC₅₀ ? 25 μM). Several (5 of 18) of the inhibitors were also shown to inhibit DNA replication in permeabilized polA-deficient B. anthracis cells. One of the most potent inhibitors also displayed antibacterial activity (MIC ～5 μg/ml against a range of Gram-positive species including bacilli and staphylococci) together with good selectivity for bacterial versus mammalian cells (CC₅₀/MIC > 16) suitable for further optimization. This compound shares the bicyclic ring of the clinically proven aminocoumarin scaffold, but is not a gyrase inhibitor. It exhibits a mixed mode of helicase inhibition including a component of competitive inhibition with the DNA substrate (K_i = 8 μM) and is rapidly bactericidal at 4 × MIC.     

Antiplasmodial and leishmanicidal activity of biflavonoids from Indian Selaginella bryopteris

A series of eleven biflavonoids containing amentoflavone and hinokiflavone derivatives from the Indian medicinal herb Selaginella bryopteris has been investigated for their antiprotozoal activity using in vitro assays against the K1 strain of Plasmodium falciparum, Leishmania donovani, Trypanosoma brucei rhodesiense and Trypanosoma cruzi. The highest antiprotozoal activity was displayed by 7,4′,7″-tri-O-methylamentoflavone which exhibited an IC₅₀ of 0.26 μM. This compound showed no significant cytotoxicity (IC₅₀ > 150 μM) evaluated using L-6 cells. The strongest activity against Leishmania was detected for 2,3-dihydrohinokiflavone (IC₅₀ = 1.6 μM), whereas for Trypanosoma no significant activity was observed (IC₅₀ > 12.5 μg/mL for the extract). To evaluate the in vivo activity against Plasmodium of the most active compound, trimethylated amentoflavones were obtained by partial synthesis starting from amentoflavone. The synthesized mixture of trimethylated amentoflavones did not show activity in the Plasmodium berghei mouse model against female NMRI mice at 50 mg/kg.     

Pyridine sulfonamide as a small key organic molecule for the potential treatment of type-II diabetes mellitus and Alzheimer’s disease: In vitro studies against yeast α-glucosidase,acetylcholinesterase and butyrylcholinesterase

This paper presents the efficient high yield synthesis of novel pyridine 2,4,6-tricarbohydrazide derivatives (4a–4i) along with their α-glucosidase, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition activities. The enzymes inhibition results showed the potential of synthesized compounds in controlling both type-II diabetes mellitus and Alzheimer’s disease. In vitro biological investigations revealed that most of compounds were more active against yeast α-glucosidase than the reference compound acarbose (IC₅₀ 38.25 ± 0.12 μM). Among the tested series the compound 4c bearing 4-flouro benzyl group was noted to be the most active (IC₅₀ 25.6 ± 0.2 μM) against α-glucosidase, and it displayed weak inhibition activities against AChE and BChE. Compound 4a exhibited the most desired results against all three enzymes, as it was significantly active against all the three enzymes; α-glucosidase (IC₅₀ 32.2 ± 0.3 μM), AChE (IC₅₀ 50.2 ± 0.8 μM) and BChE (IC₅₀ 43.8 ± 0.8 μM). Due to the most favorable activity of 4a against the tested enzymes, for molecular modeling studies this compound was selected to investigate its pattern of interaction with α-glucosidase and AChE targets.