A Conserved Hydrogen-Bonding Network of P2 bis-Tetrahydrofuran-Containing HIV-1 Protease Inhibitors (PIs) with a Protease Active-Site Amino Acid Backbone Aids in Their Activity against PI-Resistant HIV

In the present study, GRL008, a novel nonpeptidic human immunodeficiency virus type 1 (HIV-1) protease inhibitor (PI), and darunavir (DRV), both of which contain a P2-bis-tetrahydrofuranyl urethane (bis-THF) moiety, were found to exert potent antiviral activity (50% effective concentrations [EC₅₀s], 0.029 and 0.002 μM, respectively) against a multidrug-resistant clinical isolate of HIV-1 (HIV_A02) compared to ritonavir (RTV; EC₅₀, >1.0 μM) and tipranavir (TPV; EC₅₀, 0.364 μM). Additionally, GRL008 showed potent antiviral activity against an HIV-1 variant selected in the presence of DRV over 20 passages (HIV_DRV^R_P20), with a 2.6-fold increase in its EC₅₀ (0.097 μM) compared to its corresponding EC₅₀ (0.038 μM) against wild-type HIV-1_NL4-3 (HIV_WT). Based on X-ray crystallographic analysis, both GRL008 and DRV showed strong hydrogen bonds (H-bonds) with the backbone-amide nitrogen/carbonyl oxygen atoms of conserved active-site amino acids G27, D29, D30, and D30′ of HIV_A02 protease (PR_A02) and wild-type PR in their corresponding crystal structures, while TPV lacked H-bonds with G27 and D30′ due to an absence of polar groups. The P2′ thiazolyl moiety of RTV showed two conformations in the crystal structure of the PR_A02-RTV complex, one of which showed loss of contacts in the S2′ binding pocket of PR_A02, supporting RTV''s compromised antiviral activity (EC₅₀, >1 μM). Thus, the conserved H-bonding network of P2-bis-THF-containing GRL008 with the backbone of G27, D29, D30, and D30′ most likely contributes to its persistently greater antiviral activity against HIV_WT, HIV_A02, and HIV_DRV^R_P20.     

An Amphipathic Undecapeptide with All d-Amino Acids Shows Promising Activity against Colistin-Resistant Strains of Acinetobacter baumannii and a Dual Mode of Action

Multiple strains of Acinetobacter baumannii have developed multidrug resistance (MDR), leaving colistin as the only effective treatment. The cecropin-α–melittin hybrid BP100 (KKLFKKILKYL-NH₂) and its analogs have previously shown activity against a wide array of plant and human pathogens. In this study, we investigated the in vitro antibacterial activities of 18 BP100 analogs (four known and 14 new) against the MDR A. baumannii strain ATCC BAA-1605, as well as against a number of other clinically relevant human pathogens. Selected peptides were further evaluated against strains of A. baumannii that acquired resistance to colistin due to mutations of the lpxC, lpxD, pmrA, and pmrB genes. The novel analogue BP214 showed antimicrobial activity at 1 to 2 μM and a hemolytic 50% effective concentration (EC₅₀) of >150 μM. The lower activity of its enantiomer suggests a dual, specific and nonspecific mode of action. Interestingly, colistin behaved antagonistically to BP214 when pmrAB and lpxC mutants were challenged.     

GRL-04810 and GRL-05010, Difluoride-Containing Nonpeptidic HIV-1 Protease Inhibitors (PIs) That Inhibit the Replication of Multi-PI-Resistant HIV-1 In Vitro and Possess Favorable Lipophilicity That May Allow Blood-Brain Barrier Penetration

We designed, synthesized, and identified two novel nonpeptidic human immunodeficiency virus type 1 (HIV-1) protease inhibitors (PIs), GRL-04810 and GRL-05010, containing the structure-based designed privileged cyclic ether-derived nonpeptide P2 ligand, bis-tetrahydrofuranylurethane (bis-THF), and a difluoride moiety, both of which are active against the laboratory strain HIV-1_LAI (50% effective concentrations [EC₅₀s], 0.0008 and 0.003 μM, respectively) with minimal cytotoxicity (50% cytotoxic concentrations [CC₅₀s], 17.5 and 37.0 μM, respectively, in CD4⁺ MT-2 cells). The two compounds were active against multi-PI-resistant clinical HIV-1 variants isolated from patients who had no response to various antiviral regimens. GRL-04810 and GRL-05010 also blocked the infectivity and replication of each of the HIV-1_NL4-3 variants selected by up to 5 μM lopinavir (EC₅₀s, 0.03 and 0.03 μM, respectively) and atazanavir (EC₅₀s, 0.02 and 0.04 μM, respectively). Moreover, they were active against darunavir (DRV)-resistant variants (EC₅₀ in 0.03 to 0.034 μM range for GRL-04810 and 0.026 to 0.043 μM for GRL-05010), while DRV had EC₅₀s between 0.02 and 0.174 μM. GRL-04810 had a favorable lipophilicity profile as determined with the partition (log P) and distribution (log D) coefficients of −0.14 and −0.29, respectively. The in vitro blood-brain barrier (BBB) permeability assay revealed that GRL-04810 and GRL-05010 may have a greater advantage in terms of crossing the BBB than the currently available PIs, with apparent penetration indexes of 47.8 × 10⁻⁶ and 61.8 × 10⁻⁶ cm/s, respectively. The present data demonstrate that GRL-04810 and GRL-05010 exert efficient activity against a wide spectrum of HIV-1 variants in vitro and suggest that two fluorine atoms added to their bis-THF moieties may well enhance their penetration across the BBB.     

Anti-inflammatory and antioxidant activities of flavonoids from the flowers of Hosta plantaginea

Hosta plantaginea was a traditional Chinese medicinal plant used to treat inflammation-related diseases with little scientific validation. Twelve flavonoids, including two new compounds namely plantanones A (1) and B (2), were isolated from the flowers of Hosta plantaginea. Their structures were elucidated by NMR and HRMS as well as comparison with literature data. All of the isolated compounds showed significant inhibitory activities against ovine COX-1 and COX-2 at a concentration of 50 μM, with inhibition ratios from 53.00% to 80.55% for COX-1 and from 52.19% to 66.29% for COX-2. Further detailed testing showed that compounds 1, 2, 4 and 12 inhibited the COX-1 and COX-2 enzymes with IC₅₀ values 12.90–33.37 μM and 38.32–46.16 μM, respectively. Moreover, the antioxidant effects of these isolates against DPPH free radical-scavenging were also evaluated in vitro, and a tight structure-activity relationship was discussed. Our results suggested that the anti-inflammatory and antioxidant activities of H. plantaginea flowers are partly attributed to these flavonoids.

Twelve flavonoids, including two new compounds namely plantanones A (1) and B (2), were isolated from the flowers of Hosta plantaginea.     

Semi-synthetic puwainaphycin/minutissamide cyclic lipopeptides with improved antifungal activity and limited cytotoxicity

Microbial cyclic lipopeptides are an important class of antifungal compounds with applications in pharmacology and biotechnology. However, the cytotoxicity of many cyclic lipopeptides limits their potential as antifungal drugs. Here we present a structure–activity relationship study on the puwainaphycin/minutissamide (PUW/MIN) family of cyclic lipopeptides isolated from cyanobacteria. PUWs/MINs with variable fatty acid chain lengths differed in the dynamic of their cytotoxic effect despite their similar IC₅₀ after 48 hours (2.8 μM for MIN A and 3.2 μM for PUW F). Furthermore, they exhibited different antifungal potency with the lowest MIC values obtained for MIN A and PUW F against the facultative human pathogen Aspergillus fumigatus (37 μM) and the plant pathogen Alternaria alternata (0.6 μM), respectively. We used a Grignard-reaction with alkylmagnesium halides to lengthen the lipopeptide FA moiety as well as the Steglich esterification on the free hydroxyl substituents to prepare semi-synthetic lipopeptide variants possessing multiple fatty acid tails. Cyclic lipopeptides with extended and branched FA tails showed improved strain-specific antifungal activity against A. fumigatus (MIC = 0.5–3.8 μM) and A. alternata (MIC = 0.1–0.5 μM), but with partial retention of the cytotoxic effect (∼10–20 μM). However, lipopeptides with esterified free hydroxyl groups possessed substantially higher antifungal potencies, especially against A. alternata (MIC = 0.2–0.6 μM), and greatly reduced or abolished cytotoxic activity (>20 μM). Our findings pave the way for a generation of semi-synthetic variants of lipopeptides with improved and selective antifungal activities.

Both the substitution of free hydroxyl substituents and extending/branching of the fatty acid moiety improved the antifungal potency and limits the cytotoxicity of cyanobacterial cyclic lipopeptides puwainaphycin/minutissamides.     

4-Amino Bis-Pyridinium Derivatives as Novel Antileishmanial Agents

The antileishmanial activity of a series of bis-pyridinium derivatives that are analogues of pentamidine have been investigated, and all compounds assayed were found to display activity against promastigotes and intracellular amastigotes of Leishmania donovani and Leishmania major, with 50% effective concentrations (EC₅₀s) lower than 1 μM in most cases. The majority of compounds showed similar behavior in both Leishmania species, being slightly more active against L. major amastigotes. However, compound VGP-106 {1,1′-(biphenyl-4,4′-diylmethylene)bis[4-(4-bromo-N-methylanilino)pyridinium] dibromide} exhibited significantly higher activity against L. donovani amastigotes (EC₅₀, 0.86 ± 0.46 μM) with a lower toxicity in THP-1 cells (EC₅₀, 206.54 ± 9.89 μM). As such, VGP-106 was chosen as a representative compound to further elucidate the mode of action of this family of inhibitors in promastigote forms of L. donovani. We have determined that uptake of VGP-106 in Leishmania is a temperature-independent process, suggesting that the compound crosses the parasite membrane by diffusion. Transmission electron microscopy analysis showed a severe mitochondrial swelling in parasites treated with compound VGP-106, which induces hyperpolarization of the mitochondrial membrane potential and a significant decrease of intracellular free ATP levels due to the inhibition of ATP synthesis. Additionally, we have confirmed that VGP-106 induces mitochondrial ROS production and an increase in intracellular Ca²⁺ levels. All these molecular events can activate the apoptotic process in Leishmania; however, propidium iodide assays gave no indication of DNA fragmentation. These results underline the potency of compound VGP-106, which may represent a new avenue for the development of novel antileishmanial compounds.     

Discovery of quinolone derivatives as antimycobacterial agents

Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis), is an important public health issue. Current first-line drugs administered to TB patients have been in use for over 40 years, whereas second-line drugs display strong side effects and poor compliance. Additionally, designing effective regimens to treat patients infected with multi- and extremely-drug-resistant (MDR and XDR) strains of TB is challenging. In this report, we screened our compound library and identified compound 1 with antituberculosis activity and a minimal inhibitory concentration (MIC) against M. tuberculosis of 20 μg mL⁻¹. Structure optimization and the structure–activity relationship of 1 as the lead compound enabled the design and synthesis of a series of quinolone derivatives, 6a1–6a2, 6b1–6b36, 6c1, 6d1–6d14, 7a1–7a2, 7b1–7b2, 7c1, 8a1–8a5, 9a1–9a4 and 10a1–10a6. These compounds were evaluated in vitro for anti-tubercular activity against the M. tuberculosis H₃₇Rv strain. Among them, compounds 6b6, 6b12 and 6b21 exhibited MIC values in the range of 1.2–3 μg mL⁻¹ and showed excellent activity against the tested MDR-TB strain (MIC: 3, 2.9 and 0.9 μg mL⁻¹, respectively). All three compounds were non-toxic toward A549 and Vero cells (>100 and >50 μg mL⁻¹, respectively). In addition, an antibacterial spectrum test carried out using compound 6b21 showed that this compound specifically inhibits M. tuberculosis. These can serve as a new starting point for the development of anti-TB agents with therapeutic potential.

6b21: MIC against M. tb H₃₇Rv = 1.2 μg mL⁻¹, MIC against drug-resistant strains = 0.9 μg mL⁻¹, solubility = 132 μg mL⁻¹, non-cytotoxicity.     

Synthesis and biological evaluation of novel artemisone–piperazine–tetronamide hybrids

For the first time, six novel artemisone–piperazine–tetronamide hybrids (12a–f) were efficiently synthesised from dihydroartemisinin (DHA) and investigated for their in vitro cytotoxicity against some human cancer cells and benign cells. All the targets showed good cytotoxic activity in vitro. Hybrid 12a exhibited much better inhibitory activity against human liver cancer cell line SMMC-7721 (IC₅₀ = 0.03 ± 0.04 μM for 24 h) than the parent DHA (IC₅₀ > 0.7 μM), and two references, vincristine (VCR; IC₅₀ = 0.27 ± 0.03 μM) & cytosine arabinoside (ARA; IC₅₀ = 0.63 ± 0.04 μM). Furthermore, hybrid 12a had low toxicity against human benign liver cell line LO2 (IC₅₀ = 0.70 ± 0.02 μM for 24 h) compared with VCR, ARA, and DHA in vitro. Moreover, the inhibitory activity of hybrid 12a was obviously enhanced when human liver cancer cell line MHCC97H absorbed Fe²⁺in vitro.

Six novel artemisone–piperazine–tetronamide hybrids were efficiently synthesised and investigated for their cytotoxicity against some human cancer cells.     

Cembrane-type diterpenoids from the gum resin of Boswellia carterii and their biological activities

Eight new cembrane-type diterpenoids, boscartins AH–AK (1–8), along with two known ones (9-10), were isolated from the gum resin of Boswellia carterii. Compounds 1–3 were characteristic of high oxidation assignable to three epoxy groups, while compounds 4–8 were characteristic of two epoxy groups. Spectroscopic examination was used to elucidate their structures. All isolates were evaluated for antiproliferative activity against HCT-116 human colon cancer cells, anti-inflammatory activity against nitric oxide (NO) production, and hepatoprotective activity in vitro. All of them showed weak antiproliferative activity (IC₅₀ > 100 μM), 8 exhibited potent inhibitory effects on NO production (IC₅₀ of 14.8 μM), with the others showing weak anti-inflammatory activity (IC₅₀ > 30 μM), and 1 exhibited more potent hepatoprotective activity than the positive control, bicyclol, at 10 μM against the damage induced by paracetamol in HepG2 cells.

Cembrane-type diterpenoids from the gum resin of Boswellia carterii.     

Chemical composition,nutraceuticals characterization,NMR confirmation of squalene and antioxidant activities of Basella rubra L. seed oil

Basella rubra (Malabar spinach) is a commonly consumed green leafy vegetable in southern parts of India. The chemical composition, nutraceuticals characterization, squalene Nuclear Magnetic Resonance (NMR), in vitro antioxidant activities and cytotoxicity of B. rubra seed oil (33.08%) was investigated. Gas chromatography-mass spectrometry (GC/MS) analysis revealed the presence of palmitic (27.21 μmol%), oleic (33.83 μmol%) and linoleic acid (26.02 μmol%) with a total of 64.38 μmol% unsaturated fatty acids respectively. HPLC nutraceutical characterization showed a major constituent of gallic acid (11.23 mg%), γ-tocopherols (17.74 mg%), cycloartenylferulate (1.7 mg%), and squalene (1 g%). Squalene was further recovered (98%), purified (99.9%), and confirmed through ¹H and ¹³C NMR. The in vitro antioxidant activities recorded by using 2,2-diphenyl-1-picrylhydrazyl (EC₅₀ = 6 mg mL⁻¹), ferric reducing antioxidant power (361.85 mM of Trolox Eq./100 g) and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (EC₅₀ = 56.19 mg mL⁻¹) scavenging activity. In vitro cytotoxicity assessed on 3T3-L1 showed good cell survival without any toxicity (upto 400 μg mL⁻¹). B. rubra seed oil has proven nutraceuticals and antioxidant potentials with least toxicity which can be recommended for functional foods applications.

Basella rubra (Malabar spinach) is a commonly consumed green leafy vegetable in southern parts of India.     

In Vitro and In Vivo Trypanosomicidal Action of Novel Arylimidamides against Trypanosoma cruzi

Arylimidamides (AIAs) have been shown to have considerable biological activity against intracellular pathogens, including Trypanosoma cruzi, which causes Chagas disease. In the present study, the activities of 12 novel bis-AIAs and 2 mono-AIAs against different strains of T. cruzi in vitro and in vivo were analyzed. The most active was m-terphenyl bis-AIA (35DAP073), which had a 50% effective concentration (EC₅₀) of 0.5 μM for trypomastigotes (Y strain), which made it 26-fold more effective than benznidazole (Bz; 13 μM). It was also active against the Colombiana strain (EC₅₀ = 3.8 μM). Analysis of the activity against intracellular forms of the Tulahuen strain showed that this bis-AIA (EC₅₀ = 0.04 μM) was about 100-fold more active than Bz (2 μM). The trypanocidal effect was dissociated from the ability to trigger intracellular lipid bodies within host cells, detected by oil red labeling. Both an active compound (35DAP073) and an inactive compound (26SMB060) displayed similar activation profiles. Due to their high selectivity indexes, two AIAs (35DAP073 and 35DAP081) were moved to in vivo studies, but because of the results of acute toxicity assays, 35DAP081 was excluded from the subsequent tests. The findings obtained with 35DAP073 treatment of infections caused by the Y strain revealed that 2 days of therapy induced a dose-dependent action, leading to 96 to 46% reductions in the level of parasitemia. However, the administration of 10 daily doses in animals infected with the Colombiana strain resulted in toxicity, preventing longer periods of treatment. The activity of the combination of 0.5 mg/kg of body weight/day 35DAP073 with 100 mg/kg/day Bz for 10 consecutive days was then assayed. Treatment with the combination resulted in the suppression of parasitemia, the elimination of neurological toxic effects, and survival of 100% of the animals. Quantitative PCR showed a considerable reduction in the parasite load (60%) compared to that achieved with Bz or the amidine alone. Our results support further investigations of this class with the aim of developing novel alternatives for the treatment of Chagas disease.     

Human Cytomegalovirus Resistance to Deoxyribosylindole Nucleosides Maps to a Transversion Mutation in the Terminase Subunit-Encoding Gene UL89

Human cytomegalovirus (HCMV) infection can cause severe illnesses, including encephalopathy and mental retardation, in immunocompromised and immunologically immature patients. Current pharmacotherapies for treating systemic HCMV infections include ganciclovir, cidofovir, and foscarnet. However, long-term administration of these agents can result in serious adverse effects (myelosuppression and/or nephrotoxicity) and the development of viral strains with reduced susceptibility to drugs. The deoxyribosylindole (indole) nucleosides demonstrate a 20-fold greater activity in vitro (the drug concentration at which 50% of the number of plaques was reduced with the presence of drug compared to the number in the absence of drug [EC₅₀] = 0.34 μM) than ganciclovir (EC₅₀ = 7.4 μM) without any observed increase in cytotoxicity. Based on structural similarity to the benzimidazole nucleosides, we hypothesize that the indole nucleosides target the HCMV terminase, an enzyme responsible for packaging viral DNA into capsids and cleaving the DNA into genome-length units. To test this hypothesis, an indole nucleoside-resistant HCMV strain was isolated, the open reading frames of the genes that encode the viral terminase were sequenced, and a G766C mutation in exon 1 of UL89 was identified; this mutation resulted in an E256Q change in the amino acid sequence of the corresponding protein. An HCMV wild-type strain, engineered with this mutation to confirm resistance, demonstrated an 18-fold decrease in susceptibility to the indole nucleosides (EC₅₀ = 3.1 ± 0.7 μM) compared to that of wild-type virus (EC₅₀ = 0.17 ± 0.04 μM). Interestingly, this mutation did not confer resistance to the benzimidazole nucleosides (EC₅₀ for wild-type HCMV = 0.25 ± 0.04 μM, EC₅₀ for HCMV pUL89 E256Q = 0.23 ± 0.04 μM). We conclude, therefore, that the G766C mutation that results in the E256Q substitution is unique for indole nucleoside resistance and distinct from previously discovered substitutions that confer both indole and benzimidazole nucleoside resistance (D344E and A355T).     

In Vitro and In Vivo Inhibition of Murine Gamma Herpesvirus 68 Replication by Selected Antiviral Agents

We have evaluated the susceptibility of the murine gamma herpesvirus 68 (MHV-68) to a variety of antiviral agents. The acyclic nucleoside phosphonate analogs cidofovir [(S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine], (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA), and adefovir [9-(2-phosphonylmethoxyethyl)adenine] efficiently inhibited the replication of the virus in Vero cells (50% effective concentrations [EC₅₀s], 0.008, 0.06, and 2.2 μg/ml, respectively). Acyclovir, ganciclovir, and brivudin [(E)-5-(2-bromovinyl)-2′-deoxyuridine] had equipotent activities (EC₅₀s, 1.5 to 8 μg/ml), whereas foscarnet and penciclovir were less effective (EC₅₀s, 23 and ≥30 μg/ml, respectively). The novel N-7-substituted nucleoside analog S2242 [7-(1,3-dihydroxy-2-propoxymethyl)purine] inhibited MHV-68 replication by 50% at 0.2 μg/ml. The susceptibilities of MHV-68 and Epstein-Barr virus (EBV) to cidofovir, HPMPA, adefovir, and acyclovir were found to be comparable. However, for penciclovir, ganciclovir, brivudin, and S2242, major differences in the sensitivity of MHV-68 and EBV were observed, suggesting that MHV-68 is not always an optimal surrogate for the study of antiviral strategies for EBV. When evaluated with a model for lethal MHV-68 infections in mice with severe combined immunodeficiency, cidofovir proved to be very efficient in protecting against virus-induced mortality (100% survival at 50 days postinfection), whereas acyclovir, brivudin, and adefovir had little or no effect.     

A Novel Tricyclic Ligand-Containing Nonpeptidic HIV-1 Protease Inhibitor,GRL-0739, Effectively Inhibits the Replication of Multidrug-Resistant HIV-1 Variants and Has a Desirable Central Nervous System Penetration Property In Vitro

We report here that GRL-0739, a novel nonpeptidic HIV-1 protease inhibitor containing a tricycle (cyclohexyl-bis-tetrahydrofuranylurethane [THF]) and a sulfonamide isostere, is highly active against laboratory HIV-1 strains and primary clinical isolates (50% effective concentration [EC₅₀], 0.0019 to 0.0036 μM), with minimal cytotoxicity (50% cytotoxic concentration [CC₅₀], 21.0 μM). GRL-0739 blocked the infectivity and replication of HIV-1_NL4-3 variants selected by concentrations of up to 5 μM ritonavir or atazanavir (EC₅₀, 0.035 to 0.058 μM). GRL-0739 was also highly active against multidrug-resistant clinical HIV-1 variants isolated from patients who no longer responded to existing antiviral regimens after long-term antiretroviral therapy, as well as against the HIV-2_ROD variant. The development of resistance against GRL-0739 was substantially delayed compared to that of amprenavir (APV). The effects of the nonspecific binding of human serum proteins on the anti-HIV-1 activity of GRL-0739 were insignificant. In addition, GRL-0739 showed a desirable central nervous system (CNS) penetration property, as assessed using a novel in vitro blood-brain barrier model. Molecular modeling demonstrated that the tricyclic ring and methoxybenzene of GRL-0739 have a larger surface and make greater van der Waals contacts with protease than in the case of darunavir. The present data demonstrate that GRL-0739 has desirable features as a compound with good CNS-penetrating capability for treating patients infected with wild-type and/or multidrug-resistant HIV-1 variants and that the newly generated cyclohexyl-bis-THF moiety with methoxybenzene confers highly desirable anti-HIV-1 potency in the design of novel protease inhibitors with greater CNS penetration profiles.     

Structural transformation of methasterone with Cunninghamella blakesleeana and Macrophomina phaseolina

An anabolic-androgenic synthetic steroidal drug, methasterone (1) was transformed by two fungi, Cunninghamella blakesleeana and Macrophimina phaseclina. A total of six transformed products, 6β,7β,17β-trihydroxy-2α,17α-dimethyl-5α-androstane-3-one (2), 6β,7α,17β-trihydroxy-2α,17α-dimethyl-5α-androstane-3-one (3), 6α,17β-dihydroxy-2α,17α-dimethyl-5α-androstane-3,7-dione (4), 3β,6β,17β-trihydroxy-2α,17α-dimethyl-5α-androstane-7-one (5), 7α,17β-dihydroxy-2α,17α-dimethyl-5α-androstane-3-one (6), and 6β,9α,17β-trihydroxy-2α,17α-dimethyl-5α-androstane-3-one (7) were synthesized. Among those, compounds 2–5, and 7 were identified as new transformed products. MS, NMR, and other spectroscopic techniques were performed for the characterization of all compounds. Substrate 1 (IC₅₀ = 23.9 ± 0.2 μg mL⁻¹) showed a remarkable anti-inflammatory activity against nitric oxide (NO) production, in comparison to standard LNMMA (IC₅₀ = 24.2 ± 0.8 μg mL⁻¹). Whereas, its metabolites 2, and 7 showed moderate inhibition with IC₅₀ values of 38.1 ± 0.5 μg mL⁻¹, and 40.2 ± 3.3 μg mL⁻¹, respectively. Moreover, substrate 1 was found to be cytotoxic for the human normal cell line (BJ) with an IC₅₀ of 8.01 ± 0.52 μg mL⁻¹, while metabolites 2–7 were identified as non-cytotoxic. Compounds 1–7 showed no cytotoxicity against MCF-7 (breast cancer), NCI-H460 (lung cancer), and HeLa (cervical cancer) cell lines.

Fungal transformation of methasterone resulted in six products (2–7). 2–5, and 7 were identified as new. Substrate 1 showed remarkable anti-inflammatory activity but was cytotoxic. Products 2 and 7 showed moderate activity but were non-cytotoxic.     

Quinoline-triazole hybrids inhibit falcipain-2 and arrest the development of Plasmodium falciparum at the trophozoite stage

Falcipain-2 (FP2) is a papain family cysteine protease and a key member of the hemoglobin degradation pathway, a process that is required at erythrocytic stages of Plasmodium falciparum to obtain amino acids. In this study, we report a set of 10 quinoline-triazole-based compounds (T1–T10) which exhibit a good binding affinity for FP2, inhibit its catalytic activity at micromolar concentrations and thereby arrest the parasite growth. Compounds T4 and T7 inhibited FP2 with IC₅₀ values of 16.16 μM and 25.64 μM respectively. Both the compounds T4 and T7 arrested the development of P. falciparum at the trophozoite stage with an EC₅₀ value 21.89 μM and 49.88 μM. These compounds also showed morphological and food-vacuole abnormalities like E-64, a known inhibitor of FP2. Our results thus identify the quinoline-triazole-based compounds as a probable starting point for the design of FP2 inhibitors and they should be further investigated as potential antimalarial agents.

The present study involves development of novel quinoline triazole-containing cysteine protease inhibitors which arrest the development of P. falciparum at the trophozoite stage.     

Novel derivatives of eugenol as potent anti-inflammatory agents via PPARγ agonism: rational design,synthesis, analysis,PPARγ protein binding assay and computational studies

Eugenol is a natural product abundantly found in clove buds known for its pharmacological activities such as anti-inflammatory, antidiabetic, antioxidant, and anticancer activities. It is well known from the literature that peroxisome proliferator-activated receptors (PPARγ) have been reported to regulate inflammatory responses. In this backdrop, we rationally designed semi-synthetic derivatives of eugenol with the aid of computational studies, and synthesized, purified, and analyzed four eugenol derivatives as PPARγ agonists. Compounds were screened for PPARγ protein binding by time-resolved fluorescence (TR-FRET) assay. The biochemical assay results were favorable for 1C which exhibited significant binding affinity with an IC₅₀ value of 10.65 μM as compared to the standard pioglitazone with an IC₅₀ value of 1.052 μM. In addition to the protein binding studies, as a functional assay, the synthesized eugenol derivatives were screened for in vitro anti-inflammatory activity at concentrations ranging from 6.25 μM to 400 μM. Among the four compounds tested 1C shows reasonably good anti-inflammatory activity with an IC₅₀ value of 133.8 μM compared to a standard diclofenac sodium IC₅₀ value of 54.32 μM. Structure–activity relationships are derived based on computational studies. Additionally, molecular dynamics simulations were performed to examine the stability of the protein–ligand complex, the dynamic behavior, and the binding affinity of newly synthesized molecules. Altogether, we identified novel eugenol derivatives as potential anti-inflammatory agents via PPARγ agonism.

Rational design, synthesis, analysis, PPARγ protein binding assay and computational studies of novel eugenol derivatives.     

Discovery of mercaptopropanamide-substituted aryl tetrazoles as new broad-spectrum metallo-β-lactamase inhibitors

β-Lactam antibiotic resistance mediated by metallo-β-lactamases (MBL) has threatened global public health. There are currently no available inhibitors of MBLs for clinical use. We previously reported the ruthenium-catalyzed meta-selective C–H nitration synthesis method, leading to some meta-mercaptopropanamide substituted aryl tetrazoles as new potent MBL inhibitors. Here, we described the structure–activity relationship of meta- and ortho-mercaptopropanamide substituted aryl tetrazoles with clinically relevant MBLs. The resulting most potent compound 13a showed IC₅₀ values of 0.044 μM, 0.396 μM and 0.71 μM against VIM-2, NDM-1 and IMP-1 MBL, respectively. Crystallographic analysis revealed that 13a chelated to active site zinc ions via the thiol group and interacted with the catalytically important residues Asn233 and Tyr67, providing further structural information for the development of thiol based MBL inhibitors.

Compound 13a showed IC₅₀ values of 0.044 μM, 0.396 μM and 0.71 μM against VIM-2, NDM-1 and IMP-1 MBL, respectively. It binds to chelates via active site zinc ions and forms interactions with residues on the L1 and L3 loops of VIM-2.     

Thymol derivatives with antibacterial and cytotoxic activity from the aerial parts of Ageratina adenophora

Three new thymol derivatives, 7-formyl-9-isobutyryloxy-8-hydroxythymol (1), 7,9-di-isobutyryloxy-8,10-dehydrothymol (2) and 2α-methoxyl-3β-methyl-6-methylol-2,3-dihydrobenzofuran (3), along with five known ones (4–8), were isolated from the aerial parts of the invasive plant Ageratina adenophora. Their structures were elucidated by extensive spectroscopic analysis and they were all isolated from the aerial part of A. adenophora for the first time. These compounds, except 8, selectively showed in vitro antimicrobial activity against three Gram-(+) and two Gram-(−) bacterial strains. In particular, compounds 1 and 5 showed notable in vitro antimicrobial activity against all five bacterial strains with IC₅₀ values ranging from 3.9 to 15.6 μg mL⁻¹, as compared to reference compound kanamycin sulfate with a MIC value 1.9–3.9 μg mL⁻¹. Compounds 1 and 5 were further revealed to show in vitro cytotoxic activity against three tested human tumor (MCF-7, NCI-H460 and HeLa) cell lines, with IC₅₀ values ranging from 7.45 to 28.63 μM. Compounds 7 and 8 selectively showed slight but detectable in vitro cytotoxicity toward MCF-7 and NCI-H460 cell lines, with IC₅₀ values 44.65–83.19 μM. No cytotoxic effects were detected in the bioassay of the other four thymol derivatives. The present results provide new data to support that the aerial parts of A. adenophora are a rich source of bioactive chemicals valuable in medicinal applications.

Eight thymol derivatives including three new ones (1–3) were obtained from the aerial parts of Ageratina adenophora, with most of them, in particular 1 and 5, showing notable in vitro antimicrobial and cytotoxic activity.     

Results from the Solithromycin International Surveillance Program (2014)

Solithromycin, a fourth-generation macrolide (a fluoroketolide with enhanced activity against macrolide-resistant bacteria due to interaction with three ribosomal sites) and the first fluoroketolide, was tested against a 2014 collection of 6,115 isolates, including Streptococcus pneumoniae (1,713 isolates), Haemophilus influenzae (1,308), Moraxella catarrhalis (577), Staphylococcus aureus (1,024), and beta-hemolytic streptococci (1,493), by reference broth microdilution methods. The geographic samples included 2,748 isolates from the United States, 2,536 from Europe, 386 from Latin America, and 445 from the Asia-Pacific region. Solithromycin was observed to be very active against S. pneumoniae (MIC_50/90, 0.008/0.12 μg/ml), demonstrating 2-fold greater activity than telithromycin (MIC_50/90, 0.015/0.25 μg/ml) and 16- to >256-fold greater activity than azithromycin (MIC_50/90, 0.12/>32 μg/ml), with all strains being inhibited at a solithromycin MIC of ≤1 μg/ml. Against H. influenzae, solithromycin showed potency identical to that of telithromycin (MIC_50/90, 1/2 μg/ml), and both of these compounds were 2-fold less active than azithromycin (MIC_50/90, 0.5/1 μg/ml). All but one of the M. catarrhalis isolates were inhibited by solithromycin at ≤0.25 μg/ml. Solithromycin inhibited 85.3% of S. aureus isolates at ≤1 μg/ml, and its activity was lower against methicillin-resistant (MIC_50/90, 0.06/>32 μg/ml) than against methicillin-susceptible (MIC_50/90, 0.06/0.06 μg/ml) isolates. Little variation in solithromycin activity was observed by geographic region for the species tested. Solithromycin was very active against beta-hemolytic streptococci (MIC_50/90, 0.015/0.03 μg/ml), and all isolates were inhibited at MIC values of ≤0.5 μg/ml. In conclusion, solithromycin demonstrated potent activity against global and contemporary (2014) pathogens that represent the major causes of community-acquired bacterial pneumonia. These data support the continued clinical development of solithromycin for the treatment of this important indication.