Novel terpene based 1,4,2-dioxazoles: Synthesis, characterization, molecular properties and screening against Entamoeba histolytica

Target analysis, occurrence and cytotoxicity of halogenated polyhydroxyphenols as emerging disinfection byproducts in drinking water

Halogenated aromatic disinfection byproducts (DBPs) in drinking water, such as halogenated phenols, have received widespread attention due to their high toxicity and ubiquitous occurrence in recent years. This study identified a group of emerging halogenated aromatic DBPs, known as halogenated polyhydroxyphenols (HPPs), and investigated their occurrence and cytotoxicity. We developed a highly sensitive solid-phase extraction ultra-performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS) method under multiple reaction monitoring (MRM) mode, with recoveries ranging from 86 to 115% and method detection limits (MDLs) ranging from 0.10 to 1.87 ng/L for the analysis of 15 HPPs. Eleven of these HPP DBPs were detected in collected drinking water samples using this method with detection frequencies ranging from 14 to 100% and a maximum concentration of 24 ng/L. The IC50 of the 15 HPPs in Chinese hamster ovary (CHO-K1) cells were ranged from 15.13 µM to 6.08×103 µM. The tested HPPs with -CHO substitution exhibited higher cytotoxicity compared to those with -COOH substitution. The TIC-Tox values of HPPs were calculated to be higher than those of HPs, indicating a potential necessity to pay attention to HPP DBPs. A quantitative structure-activity relationship (QSAR) model was developed for the cytotoxicity of HPPs, which was shown to be significantly associated with acid dissociation constant (pKa) and total valence connectivity (TVCon). To the best of our knowledge, this study reported the analysis, occurrence, and cytotoxicity of HPP DBPs in drinking water for the first time.

Gold-Catalyzed [4 + 1] Heterocyclization of Hydroxamic Acid and Nonactivated Alkyne: A Protocol to Construct 5-Methyl-1,4,2-dioxazole

A novel gold-catalyzed [4 + 1] heterocyclization of nonactivated alkyne and hydroxamic acid is developed for the regiospecific synthesis of 5-methyl-1,4,2-dioxazole, which is an important structural motif in various bioactive molecules. The current methodology is characterized by high efficiency, simple operation, mild reaction conditions, and good functional group compatibility. Moreover, gram-scale synthesis and synthetic application toward bioactive molecular skeletons have been realized.

Essential Oils and Terpenic Compounds as Potential Hits for Drugs against Amitochondriate Protists

The human anaerobic or microaerophilic protists Giardia duodenalis, Entamoeba histolytica, and Trichomonas vaginalis are classified as amitochondriate parasites, a group of unicellular organisms that lack canonical mitochondria organelles. These microorganisms suffered adaptations to survive in hostile microenvironments and together represent an increasing threat to public health in developing countries. Nevertheless, the current therapeutic drugs to manage the infections are scarce and often cause several side effects. Furthermore, refractory cases associated with the emergence of parasitic resistance are concerns that guide the search for new pharmacological targets and treatment alternatives. Herein, essential oils and terpenic compounds with activity against amitochondriate parasites with clinical relevance are summarized and insights into possible mechanisms of action are made. This review aims to contribute with future perspectives for research with these natural products as potential alternatives for the acquisition of new molecules for the treatment of amitochondriate protists.

Synthesis and Biological Evaluation of Benzo[b]thiophene Acylhydrazones as Antimicrobial Agents against Multidrug-Resistant Staphylococcus aureus

The benzo[b]thiophene nucleus and the acylhydrazone functional group were combined to prepare three new series of compounds for screening against Staphylococcus aureus. The reaction of substituted benzo[b]thiophene-2-carboxylic hydrazide and various aromatic or heteroaromatic aldehydes led to a collection of 26 final products with extensive structural diversification on the aromatic ring and on position 6 of the benzo[b]thiophene nucleus. The screening lead to the identification of eight hits, including (E)-6-chloro-N’-(pyridin-2-ylmethylene)benzo[b]thiophene-2-carbohydrazide (II.b), a non-cytotoxic derivative showing a minimal inhibitory concentration of 4 µg/mL on three S. aureus strains, among which were a reference classical strain and two clinically isolated strains resistant to methicillin and daptomycin, respectively.

Synthesis and SAR Study of Simple Aryl Oximes and Nitrofuranyl Derivatives with Potent Activity Against Mycobacterium tuberculosis

Background:

Oximes and nitrofuranyl derivatives are particularly important compounds in medicinal chemistry. Thus, many researchers have been reported to possess antibacterial, antiparasitic, insecticidal and fungicidal activities.

Methods:

In this work, we report the synthesis and the biological activity against Mycobacterium tuberculosis H37RV of a series of fifty aryl oximes, ArCH=N-OH, I, and eight nitrofuranyl compounds, 2-nitrofuranyl-X, II.

Results:

Among the oximes, I: Ar = 2-OH-4-OH, 42, and I: Ar = 5-nitrofuranyl, 46, possessed the best activity at 3.74 and 32.0 µM, respectively. Also, 46, the nitrofuran compounds, II; X = MeO, 55, and II: X = NHCH2Ph, 58, (14.6 and 12.6 µM, respectively), exhibited excellent biological activities and were non-cytotoxic.

Conclusion:

The compound 55 showed a selectivity index of 9.85. Further antibacterial tests were performed with compound 55 which was inactive against Enterococcus faecalis, Klebisiella pneumonae, Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhymurium and Shigella flexneri. This study adds important information to the rational design of new lead anti-TB drugs. Structure-activity Relationship (SAR) is reported.

Recent progress on the discovery of antiamoebic agents

A large number of protozoans infect humans but Entamoeba histolytica is the only organism responsible for causing amoebiasis, a deadly disease after malaria. Numerous heterocycle-based antiamoebic agents have been previously synthesized as E. histolytica inhibitors and while some of these agents have shown moderate activity, the search for a novel and ideal antiamoebic compound is still ongoing. In this digest Letter, we present the latest data on antiamoebic agents from 2011 to 2016 based on the different classes of heterocyclic agents.

Thienopyrimidine sulphonamide hybrids: design, synthesis, antiprotozoal activity and molecular docking studies

A series of hybrid compounds containing the thienopyrimidine scaffold with sulphonamide piperazine skeleton were synthesized and evaluated against K1 strain of Plasmodium falciparum and the HM1:1MSS strain of Entamoeba histolytica, respectively

New transition metal complexes containing imidazole rings endowed with potential antiamoebic activity

Imidazole-hydrazones were found to be better antiamoebic lead molecules compared to the standard drug metronidazole (MNZ). Chelation of these bioactive ligands with metals enhanced their activity profiles.

Design, synthesis and antibacterial potential of 5-(benzo[d][1,3]dioxol-5-yl)-3-tert-butyl-1-substituted-4,5-dihydropyrazoles

A series of 5-(benzo[d][1,3]dioxol-5-yl)-3-tert-butyl-1-substituted-4,5-dihydropyrazole derivatives 4a-e and 6a-g have been synthesized and spectrally characterized. The antibacterial activity of the novel candidates has been screened using the agar diffusion test. These compounds were endowed with high antibacterial activity against different Gram +ve and Gram -ve bacteria when compared with standard antibacterial drugs. In the light of zone of inhibition and MIC results, Sarcina and Staphylococcus aureus are the most sensitive bacteria where pyrrolidinomethanone derivative 4e showed MICs at 80 and 110 nM, respectively. While hydroxypiperidinoethanone derivative 6c showed MIC at 90 nM for Sarcina.