Novel gold(I) complexes with 5-phenyl-1,3,4-oxadiazole-2-thione and phosphine as potential anticancer and antileishmanial agents

Homo and heteromultimetallic complexes containing a group 8 transition metal and μ-diphosphine bridging ligands involved in anticancer research: A review

Herein, we present a comprehensive review focusing on synthetic strategies, detailed structural analysis, and anticancer activity investigations of complexes following the general formula [LnM(μ-diphosphine)M'Lm] where M = group 8 metal; M' = any transition metal; μ-diphosphine = bridging ligand; Ln and Lm = ligand spheres). Both homo- and heteromultimetallic complexes will be discussed in detail. We review in vitro, in vivo and in silico anticancer activity investigations, in an attempt to draw comparisons between the various complexes and derive structure-activity relationships (SAR). This review solely focuses on complexes falling under the general formula stated above that have been studied for their anticancer activities, other complexes falling into that scheme but which have not undergone anticancer testing are not included in this review. We compare the anticancer activities of these complexes to their mononuclear counterparts, and a positive control (cisplatin) when possible and present a summary of all existing data to date and attempt to draw some conclusions on the future development of these complexes.

Organogold(III)-dithiocarbamate compounds and their coordination analogues as anti-tumor and anti-leishmanial metallodrugs

The limited chemical stability of gold(III)-based compounds in physiological environment has been a challenge in drug discovery, and organometallic chemistry might provide the solution to overcome this issue. In this work, four novel cationic organogold(III)-dithiocarbamate complexes of general structure [(C^N)AuIIIDTC]PF6 (C1a - C4a, DTC = dithiocarbamate, L1 - L4, C^N = 2-anilinopyridine) are presented, and compared to their coordination gold(III)-dithiocarbamate analogues [AuIIIDTCCl2] (C1b - C4b), as potential anti-cancer and anti-leishmanial drugs. Most of the complexes effectively inhibited cancer cell growth, notably C3a presented anti-proliferative effect in the nanomolar range against breast cancer (MCF-7 and MDA-MB-231 cells with moderate selectivity. Pro-apoptotic studies on treated MCF-7 cells showed a high population of cells in early apoptosis. Reactivity studies of C3a towards model thiols (N-acetyl-L-cysteine) refer to a possible mode of action involving bonding between the organogold(III)-core and the thiolate. In the scope of neglected diseases, gold complexes are emerging as promising therapeutic alternatives against leishmaniasis. In this regard, all gold(III)-dithiocarbamate complexes presented anti-leishmanial activity against at least one Leishmania species. Complexes C1a, C4a, C1b, C4b were active against all tested parasites with IC50 values varying between 0.12 and 42 μM, and, overall, organometallic compounds presented more intriguing inhibition profiles. For C4a selectivity over 500-fold for L. braziliensis; even higher than the reference anti-leishmanial drug amphotericin B. Overall, our findings revealed that the organogold(III) moiety significantly amplified the anti-cancer and anti-leishmanial effects with respect to the coordination analogues; thus, showing the great potential of organometallic chemistry in metallodrug-based chemotherapy for cancer and leishmaniasis.

Next Generation Gold Drugs and Probes: Chemistry and Biomedical Applications

The gold drugs, gold sodium thiomalate (Myocrisin), aurothioglucose (Solganal), and the orally administered auranofin (Ridaura), are utilized in modern medicine for the treatment of inflammatory arthritis including rheumatoid and juvenile arthritis; however, new gold agents have been slow to enter the clinic. Repurposing of auranofin in different disease indications such as cancer, parasitic, and microbial infections in the clinic has provided impetus for the development of new gold complexes for biomedical applications based on unique mechanistic insights differentiated from auranofin. Various chemical methods for the preparation of physiologically stable gold complexes and associated mechanisms have been explored in biomedicine such as therapeutics or chemical probes. In this Review, we discuss the chemistry of next generation gold drugs, which encompasses oxidation states, geometry, ligands, coordination, and organometallic compounds for infectious diseases, cancer, inflammation, and as tools for chemical biology via gold-protein interactions. We will focus on the development of gold agents in biomedicine within the past decade. The Review provides readers with an accessible overview of the utility, development, and mechanism of action of gold-based small molecules to establish context and basis for the thriving resurgence of gold in medicine.

Preparation, cytotoxic activity and DNA interaction studies of new platinum(II) complexes with 1,10-phenanthroline and 5-alkyl-1,3,4-oxadiazol-2(3H)-thione derivatives

This work describes the synthesis, characterization and in vitro anticancer activity of two platinum(II) complexes of the type [Pt(L1)₂(1,10-phen)] 1 and [Pt(L2)₂(1,10-phen)] 2, where L1 = 5-heptyl-1,3,4-oxadiazole-2-(3H)-thione, L2 = 5-nonyl-1,3,4-oxadiazole-2-(3H)-thione and 1,10-phen = 1,10-phenanthroline. As to the structure of these complexes, the X-ray structural analysis of 1 indicates that the geometry around the platinum(II) ion is distorted square-planar, where two 5-alkyl-1,3,4-oxadiazol-2-thione derivatives coordinate a platinum(II) ion through the sulfur atom. A chelating bidentate phenanthroline molecule completes the coordination sphere. We tested these complexes in two breast cancer cell lines, namely, MCF-7 (a hormone responsive cancer cell) and MDA-MB-231 (triple negative breast cancer cell). In both cells, the most lipophilic platinum compound, complex 2, was more active than cisplatin, one of the most widely used anticancer drugs nowadays. DNA binding studies indicated that such complexes are able to bind to ct-DNA with K_b values of 10⁴ M^-1. According to data from dichroism circular and fluorescence spectroscopy, these complexes appear to bind to the DNA in a non-intercalative, probably via minor groove. Molecular docking followed by semiempirical simulations indicated that these complexes showed favorable interactions with the minor groove of the double helix of ct-DNA in an A-T rich region. Thereafter, flow cytometry analysis showed that complex 2 induced apoptosis and necrosis in MCF-7 cells.

Organometallic gold(I) and gold(III) complexes for lung cancer treatment

Metal compounds, especially gold complexes, have recently gained increasing attention as possible lung cancer therapeutics. Some gold complexes display not only excellent activity in cisplatin-sensitive lung cancer but also in cisplatin-resistant lung cancer, revealing promising prospects in the development of novel treatments for lung cancer. This review summarizes examples of anticancer gold(I) and gold (III) complexes for lung cancer treatment, including mechanisms of action and approaches adopted to improve their efficiency. Several excellent examples of gold complexes against lung cancer are highlighted.

Recent development of gold(I) and gold(III) complexes as therapeutic agents for cancer diseases

Metal complexes have demonstrated significant antitumor activities and platinum complexes are well established in the clinical application of cancer chemotherapy. However, the platinum-based treatment of different types of cancers is massively hampered by severe side effects and resistance development. Consequently, the development of novel metal-based drugs with different mechanism of action and pharmaceutical profile attracts modern medicinal chemists to design and synthesize novel metal-based agents. Among non-platinum anticancer drugs, gold complexes have gained considerable attention due to their significant antiproliferative potency and efficacy. In most situations, the gold complexes exhibit anticancer activities by targeting thioredoxin reductase (TrxR) or other thiol-rich proteins and enzymes and trigger cell death via reactive oxygen species (ROS). Interestingly, gold complexes were recently reported to elicit biochemical hallmarks of immunogenic cell death (ICD) as an ICD inducer. In this review, the recent progress of gold(I) and gold(III) complexes is comprehensively summarized, and their activities and mechanism of action are documented.

Novel N-(1H-Pyrazol-5-yl)nicotinamide Derivatives: Design, Synthesis and Antifungal Activity

To discover more effective antifungal agents, twenty N-(1H-pyrazol-5-yl)nicotinamide derivatives were designed, synthesized, and structurally confirmed by ¹ H-NMR, ¹³ C-NMR, and ESI-MS. All target compounds were evaluated for their antifungal activities by mycelia growth inhibition. Preliminary screening results displayed that many of these compounds had good fungicidal activity to S. sclerotiorum and V. mali. Compound B4 exhibited antifungal activity against S. sclerotiorum and V. mali with EC₅₀ values of 10.35 and 17.01 mg/L, respectively. The experiment in vivo identified that compound B4 was effective for suppressing rape sclerotinia rot caused by S. sclerotiorum at 50 mg/L. The molecular docking study and scanning electron microscopy preliminary clarified the possible antifungal mechanism of compound B4.

In vitro and in vivo Anti-leishmanial Potential of [Ag (PTA) 4 ]BF 4 and [Ag(HBPz 3 )(PPh 3 )] Silver Complexes

BACKGROUND

American tegumentary leishmaniasis is a parasitic disease known for being difficult to treat; therefore, the search for more effective therapeutic methods is necessary. The objective of this study was to evaluate the in vitro and in vivo antileishmanial activity of silver complexes [Ag(PTA)4]BF4 (Ag1) and [Ag(HBPz3)(PPh3)] (Ag2) against Leishmania (Leishmania) amazonensis [L. (L.) amazonensis] and Leishmania (Viannia) guyanensis.

METHODS

In vitro bioassays were performed to evaluate the activity of the complexes against promastigote and amastigote forms and evaluate their cytotoxicity. In vivo experiments were performed with hamsters (Mesocricetus auratus) infected and treated topically with two gels containing each metallic complex.

RESULTS

Both complexes reduced the number of viable parasites against the promastigote forms of L. (L.) amazonensis. Ag2 was mainly effective against the amastigote forms. The Ag2 complex did not present cellular cytotoxicity, and regarding the selectivity index, both complexes were considered acceptable, with Ag2 having the best selectivity index in murine peritoneal macrophages in relation to L. (L.) amazonensis. Ag2 showed better results in the topical treatment against infections caused by L. (L.) amazonensis, with a small reduction in the lesion volume after the 14th day of treatment and less parasitic load at the lesion site.

CONCLUSIONS

Ag2 was more effective than Ag1 against L. (L.) amazonensis.

Antileishmanial activity and insights into the mechanisms of action of symmetric Au(I) benzyl and aryl-N-heterocyclic carbenes

Leishmania amazonensis and L. braziliensis are the main etiological agents of the American Tegumentary Leishmaniasis (ATL). Taking into account the limited effectiveness and high toxicity of the current drug arsenal to treat ATL, novel options are urgently needed. Inspired by the fact that gold-based compounds are promising candidates for antileishmanial drugs, we studied the biological action of a systematic series of six (1)-(6) symmetric Au(I) benzyl and aryl-N-heterocyclic carbenes. All compounds were active at low micromolar concentrations with 50% effective concentrations ranging from 1.57 to 8.30 μM against Leishmania promastigotes. The mesityl derivative (3) proved to be the best candidate from this series, with a selectivity index ~13 against both species. The results suggest an effect of the steric and electronic parameters of the N-substituent in the activity. Intracellular infections were drastically reduced after 24h of (2)-(5) incubation in terms of infection rate and amastigote burden. Further investigations showed that our compounds induced significant parasites' morphological alterations and membrane permeability. Also, (3) and (6) were able to reduce the residual activity of three Leishmania recombinant cysteine proteases, known as possible targets for Au(I) complexes. Our promising results open the possibility of exploring gold complexes as leishmanicidal molecules to be further screened in in vivo models of infection.

Ni (II) detection by 2-amino-5-substituted-1,3,4-oxadiazole as a chemosensor using photo-physical method: Antifungal, antioxidant, DNA binding, and molecular docking studies

An oxadiazole derivative 2 was prepared by condensation reaction through cyclization of semicarbazone in the presence of bromine and the structural confirmation was supported by ¹ H and ¹³ C NMR, FT-IR spectroscopy, and LC-MS spectrometry. Its sensing ability was examined towards Ni²⁺ ion with binding constant 1.04 x 10⁵ over the other suitable metal cations (Ca²⁺ , Co²⁺ , Cr³⁺ , Ag⁺ , Pb²⁺ , Fe³⁺ , Mg²⁺ , and K⁺ ) by UV-visible and fluorescence spectroscopic studies and the minimum concentration of Ni²⁺ ion with LOD was found to be 9.4μM. Job's plot method gives the binding stoichiometry ratio of Ni²⁺ ion vs oxadiazole derivative 2 to be 2:1. Furthermore, the intercalative binding mode of oxadiazole derivative 2 with Calf Thymus DNA was supported by UV-Vis, fluorescence, viscosity, cyclic voltammetry, time-resolved fluorescence, and circular dichroism measurements. The molecular docking result gives the binding score for oxadiazole derivative 2 to be -6.5 kcal/mol, which further confirms the intercalative interaction. In addition, the anti-fungal activity of oxadiazole derivative 2 was also screened against fungal strains (C. albicans, C. glabrata, and C. tropicalis) by broth dilution and disc diffusion method. In the antioxidant studies, the oxadiazole derivative 2 showed potential scavenging activity against DPPH and H₂ O₂ free radicals.

Recent updates on Synthetic Strategies and Biological Potential of 1,3,4-oxadiazole: Review

Abstract:

Among the large variety of nitrogen and oxygen-containing heterocycles, 1,3,4-oxadiazole, the scaffold, has attracted considerable attention owing to its ability to show an extensive range of pharmacological actions. According to literature investigations, prepared 1,3,4-oxadiazole and its derivative are pharmacologically significant and consist of a variety of activities, such as anticonvulsant, anticancer, antioxidant, anti-inflammatory, antibacterial, antidiabetic, etc. These heterocyclics are formed mainly by the cyclization reactions of various reactants under diverse reaction circumstances. Therefore, significant efforts of organic chemists have been directed towards the synthesis of new drug candidates containing 1,3,4-oxadiazole subunits connected to an established potential pharmacophore to improve the efficacy and potency. This article aims to highlight recent publications on the various synthesis techniques of 1,3,4-oxadiazole and related compounds over the previous ten years (2011–2021). The purpose of this review is to help researchers by summarizing several synthetic strategies for synthesizing oxadiazole.

Multi-activity tetracoordinated pallado-oxadiazole thiones as anti-inflammatory, anti-Alzheimer, and anti-microbial agents: Structure, stability and bioactivity comparison with pallado-hydrazides

Herein, we report a comparative study based on structure, thermal and solution stability, and biopotency against lipoxygenase (LOX), butyrylcholinesterase (BChE) and microbes for Pd(II) compounds of N,O,S bearing 5-(C₅H₄XR)-1,3,4-oxadiazole-2-thiones (L') of type [PdL'Cl₂] (P'n) and N,O bearing respective hydrazides (L) of type trans-[PdL₂Cl₂] (Pn) {X = C, R = 4-I, 2-Br, 4-NO₂, 3-NO₂, 2-Cl, 3-Cl (n = 1-6, serially); X = N (n = 7)}. Spectral techniques (IR, EI-MS, NMR) and physicochemical evaluations successfully characterized the new compounds. The L' behaved as bidentate S-N donors bonded through exocyclic sulfur and N-3' nitrogen, while L acted as amino N donors. UV-vis (solution speciation) and thermal degradation profiles consistently confirmed the greater stability for P'n than Pn compounds. These compounds manifested varying degree in vitro potential to inhibit LOX, BChE and several bacteria and fungi, affected mainly by Pd(II) presence, M-L binding mode, nature and position of R, or halo groups electronegativity. Molecular docking with human 5-LOX and BChE further validated the respective experimental inhibition findings and explored several putative mechanistic interactions (H-bonding, π-stacking, π-alkyl, π-S, etc.) at the enzyme active sites. Pn generally offered superior antimicrobial and anti-LOX (anti-inflammatory) potential than respective P'n compounds, with P3/P'5, P(2,3,7)/P'3, and P6 being comparable, better and equivalent to ampicillin, nystatin and baicalein, the reference antibacterial, antifungal and anti-LOX drugs, respectively. Contrarily, the anti-BChE activity of P'n was found better than Pn compounds, showing P'2/P1 as the most promising anti-Alzheimer drug candidates. This study bares important structural and mechanistic aspects in optimizing antimicrobial, anti-inflammatory and anti-Alzheimer activities, highlighting some potential future pallado-drug candidates.

Auranofin: Past to Present, and repurposing

Auranofin (AF), a gold compound, has been used to treat rheumatoid arthritis (RA) for more than 40 years; however, its mechanism of action remains unknown. We revealed that AF inhibited the induction of proinflammatory proteins and their mRNAs by the inflammatory stimulants, cyclooxygenase-2 and inducible nitric oxide synthase, and their upstream regulator, NF-κB. AF also activated the proteins peroxyredoxin-1, Kelch-like ECH-associated protein 1, and NF-E2-related factor 2, and inhibited thioredoxin reductase, all of which are involved in oxidative or electrophilic stress under physiological conditions. Although the cell membrane was previously considered to be permeable to AF because of its hydrophobicity, the mechanisms responsible for transporting AF into and out of cells as well as its effects on the uptake and excretion of other drugs have not yet been elucidated. Antibodies for cytokines have recently been employed in the treatment of RA, which has had an impact on the use of AF. Trials to repurpose AF as a risk-controlled agent to treat cancers or infectious diseases, including severe acute respiratory syndrome coronavirus 2/coronavirus disease 2019, are ongoing. Novel gold compounds are also under development as anti-cancer and anti-infection agents.

Pegylation of phenothiazine – A synthetic route towards potent anticancer drugs

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Antitumor activity of two PEGylated phenotiazines was investigated

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The compounds showed cytotoxic activity against six tumor lines

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They inhibited the tumor growth in experimental mice

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The PEGylation improved the phenothiazine biocompatibility

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A synergistic effect of PEG and phenothiazine toward properties improvement was proved

Introduction

Cancer is a big challenge of the 21 century, whose defeat requires efficient antitumor drugs.

Objectives

The paper aims to investigate the synergistic effect of two structural building blocks, phenothiazine and poly(ethylene glycol), towards efficient antitumor drugs.

Methods

Two PEGylated phenothiazine derivatives were synthetized by attaching poly(ethylene glycol) of 550 Da to the nitrogen atom of phenothiazine by ether or ester linkage. Their antitumor activity has been investigated on five human tumour lines and a mouse tumor line as well, by determination of IC50. The in vivo toxicity was determined by measuring the LD50 in BALB/c mice by the sequential method and the in vivo antitumor potential was measured by the tumours growth test. The antitumor mechanism was investigated by complexation studies of zinc and magnesium ions characteristic to the farnesyltransferase enzyme, by studies of self-aggregation in the cells proximity and by investigation of the antitumor properties of the acid species resulted by enzymatic cleavage of the PEGylated derivatives.

Results

The two compounds showed antitumor activity, with IC50 against mouse colon carcinoma cell line comparable with that of the traditional antitumor drugs 5-Fluorouracil and doxorubicin. The phenothiazine PEGylation resulted in a significant toxicity diminishing, the LD50 in BALB/c mice increasing from 952.38 up to 1450 mg/kg, in phenothiazine equivalents. Both compounds inflicted a 92% inhibition of the tumour growth for doses much smaller than LD50. The investigation of the possible tumour inhibition mechanism suggested the nanoaggregate formation and the cleavage of ester bonds as key factors for the inhibition of cancer cell proliferation and biocompatibility improvement.

Conclusion

Phenothiazine and PEG building blocks have a synergetic effect working for both tumour growth inhibition and biocompatibility improvement. All these findings recommend the PEGylated phenothiazine derivatives as a valuable workbench for a next generation of antitumor drugs.

Metallodrugs for the Treatment of Trypanosomatid Diseases: Recent Advances and New Insights

Trypanosomatid parasites are responsible for many Neglected Tropical Diseases (NTDs). NTDs are a group of illnesses that prevail in low-income populations, such as in tropical and subtropical areas of Africa, Asia, and the Americas. The three major human diseases caused by trypanosomatids are African trypanosomiasis, Chagas disease and leishmaniasis. There are known drugs for the treatment of these diseases that are used extensively and are affordable; however, the use of these medicines is limited by several drawbacks such as the development of chemo-resistance, side effects such as cardiotoxicity, low selectivity, and others. Therefore, there is a need to develop new chemotherapeutic against these tropical parasitic diseases. Metal-based drugs against NTDs have been discussed over the years as alternative ways to overcome the difficulties presented by approved antiparasitic agents. The study of late transition metal-based drugs as chemotherapeutics is an exciting research field in chemistry, biology, and medicine due to the ability to develop multitarget antiparasitic agents. The evaluation of the late transition metal complexes for the treatment of trypanosomatid diseases is provided here, as well as some insights about their mechanism of action.

Antimicrobial Activity of 1,3,4-Oxadiazole Derivatives

The worldwide development of antimicrobial resistance forces scientists to search for new compounds to which microbes would be sensitive. Many new structures contain the 1,3,4-oxadiazole ring, which have shown various antimicrobial activity, e.g., antibacterial, antitubercular, antifungal, antiprotozoal and antiviral. In many publications, the activity of new compounds exceeds the activity of already known antibiotics and other antimicrobial agents, so their potential as new drugs is very promising. The review of active antimicrobial 1,3,4-oxadiazole derivatives is based on the literature from 2015 to 2021.

Potential of Gold Candidates against Human Colon Cancer

Development of novel metallodrugs with pharmacological profile plays a significant role in modern medicinal chemistry and drug design. Metal complexes have shown remarkable clinical results in current cancer therapy. Gold complexes have attained attention due to their high antiproliferative potential. Gold-based drugs are used for the treatment of rheumatoid arthritis. Gold-containing compounds with selective and specific targets are capable to assuage the symptoms of a range of human diseases. Gold (I) species with labile ligands (such as Cl in TEPAuCl) interact with isolated DNA; therefore, this biomolecule has been considered as a target for gold drugs. Gold (I) has a high affinity towards sulfur and selenium. Due to this, gold (I) drugs readily interact with cysteine or selenocysteine residue of the enzyme to form protein-gold(I) thiolate or protein-gold (I) selenolate complexes that lead to inhibition of the enzyme activity. Au(III) compounds due to their square-planner geometriesthe same as found in cisplatin, represent a good source for the development of anti-tumor agents. This article aims to review the most important applications of gold products in the treatment of human colon cancer and to analyze the complex interplay between gold and the human body.

A "Golden Age" for the discovery of new antileishmanial agents: Current status of leishmanicidal gold complexes and prospective targets beyond the trypanothione system

Leishmaniasis is one of the most neglected diseases worldwide and is considered a serious public health issue. The current therapeutic options have several disadvantages that make the search for new therapeutics urgent. Gold compounds are emerging as promising candidates based on encouraging in vitro and limited in vivo results for several Au^I and Au^III complexes. The antiparasitic mechanisms of these molecules remain only partially understood. However, a few studies have proposed the trypanothione redox system as a target, similar to the mammalian thioredoxin system, pointed out as the main target for several gold compounds with significant antitumor activity. In this review, we present the current status of the investigation and design of gold compounds directed at treating leishmaniasis. In addition, we explore potential targets in Leishmania parasites beyond the trypanothione system, taking into account previous studies and structure modulation performed for gold-based compounds.

1,3,4-Oxadiazole Containing Compounds As Therapeutic Targets For Cancer Therapy

BACKGROUND

Cancer is the first or second leading cause of premature death in 134 of 183 countries in the world. 1,3,4-Oxadiazoles are five memebered heterocyclic rings containing two nitrogen (two atoms) and oxygen (one atom). They show better thermal stability, metabolic stability, aqueous solubility and lower lipophilicity than the other isomeric oxadiazoles. They are important class of heterocycles present in many drug structures like Raltegravir, Furamizole Tidazosin, Nesapidil, Setileuton (MK-0633) and Zibotentan. Presence of this nucleus in the therapeutics has made them an indispensable anchor for drug design and development. Several 1,3,4-oxadiazoles are prepared and reported as anticancer agents by numerous scientists worldwide.

OBJECTIVES

The present review discusses the anticancer potentials together with the molecular targets of 1,3,4-oxadiazoles reported since 2010. The structure activity relationship (SAR) and molecular docking simulation on different targets have also been discussed herein. Some of the important cancer targets have also been explored.

METHODS

The most potent 1,3,4-oxadiazoles reported in literature was highlighted in the manuscript. The anticancer activity was reported in terms of growth percent (GP), percent growth inhibition (%GI), GI50, IC50, and LC50 and TGI.

RESULTS

1,3,4-Oxadiazoles are an important heterocyclic scaffolds with broad spectrum biological activities. They may be either mono substituted or disubstituted and act as an indispensable anchor for drug design and discovery due to their thermal stability together with low lipophilicity. They exhibited anticancer potentials and showed the inhibitions of various cancer targets.

CONCLUSION

The discussion outlined herein will proved to be a helpful and vital tool for medicinal chemists investigating and working with 1,3,4-oxadiazoles and anticancer research programs.

Comparing the Antileishmanial Activity of Gold(I) and Gold(III) Compounds in L. amazonensis and L. braziliensis in Vitro

A series of mononuclear coordination or organometallic AuI /AuIII complexes (1-9) have been comparatively studied in vitro for their antileishmanial activity against promastigotes and amastigotes, the clinically relevant parasite form, of Leishmania amazonensis and Leishmania braziliensis. One of the cationic AuI bis-N-heterocyclic carbenes (3) has low EC50 values (ca. 4 μM) in promastigotes cells and no toxicity in host macrophages. Together with two other AuIII complexes (6 and 7), the compound is also extremely effective in intracellular amastigotes from L. amazonensis. Initial mechanistic studies include an evaluation of the gold complexes' effect on L. amazonensis' plasma membrane integrity.

The anti-Zika virus and anti-tumoral activity of the citrus flavanone lipophilic naringenin-based compounds

Flavonoids are natural products widely recognized for their plurality of applications such as antiviral, antiproliferative, antitumor activities and, antioxidant properties. The flavanone naringenin is presented in citrus fruits and has been studied to combat recurrent diseases that still lack effective treatment. Research groups have been investing efforts to the development of new, safe and active candidates to combat these agents or conditions and despite good results recently reported against the Zika virus (ZIKV) and tumor cells, the use of citrus naringenin is limited due to its low bioavailability. Structural exchanges through functionalization, for example, attaching lipophilic groups instead of hydroxyl groups, can further enhance biological properties. Here, the synthesis and characterization of regioselective naringenin mono-7-O-ethers and both mono and di-fatty acid esters, structurally lipophilic ones were demonstrated. Finally, in vitro studies of anti-ZIKV action and antiproliferative activities against melanoma (B16-F10) and breast carcinoma (4T1) cells showed the ether derivatives were actives, with IC₅₀ ranging from 6.76, 18.5 and 22.6 μM to 28.53, 45.1 and 32.3 μM referring to ZIKV, B16-F10 and 4T1 cell lines, respectively. The lipophilic ethers present the ability to inhibit selectively ZIKV-replication in human cells and inhibitions. This class of modifications in flavonoid molecules could be further explore in the future development of specific anti-ZIKV compounds.

Preclinical Gold Complexes as Oral Drug Candidates to Treat Leishmaniasis Are Potent Trypanothione Reductase Inhibitors

The drugs currently used to treat leishmaniases have limitations concerning cost, efficacy, and safety, making the search for new therapeutic approaches urgent. We found that the gold(I)-derived complexes were active against L. infantum and L. braziliensis intracellular amastigotes with IC₅₀ values ranging from 0.5 to 5.5 μM. All gold(I) complexes were potent inhibitors of trypanothione reductase (TR), with enzyme IC₅₀ values ranging from 1 to 7.8 μM. Triethylphosphine-derived complexes enhanced reactive oxygen species (ROS) production and decreased mitochondrial respiration after 2 h of exposure, indicating that gold(I) complexes cause oxidative stress by direct ROS production, by causing mitochondrial damage or by impairing TR activity and thus accumulating ROS. There was no cross-resistance to antimony; in fact, SbR (antimony-resistant mutants) strains were hypersensitive to some of the complexes. BALB/c mice infected with luciferase-expressing L. braziliensis or L. amazonensis and treated orally with 12.5 mg/kg/day of AdT Et (3) or AdO Et (4) presented reduced lesion size and parasite burden, as revealed by bioimaging. The combination of (3) and miltefosine allowed for a 50% reduction in miltefosine treatment time. Complexes 3 and 4 presented favorable pharmacokinetic and toxicity profiles that encourage further drug development studies. Gold(I) complexes are promising antileishmanial agents, with a potential for therapeutic use, including in leishmaniasis caused by antimony-resistant parasites.

Harvesting greenish blue luminescence in gold(i) complexes and their application as promising bioactive molecules and cellular bioimaging agents

This work presents new gold materials as promising antitumoral and antibacterial agents and their potential use as luminescent probes for cellular bioimaging.

Synthesis and evaluation of some new 1,3,4-oxadiazoles bearing thiophene, thiazole, coumarin, pyridine and pyridazine derivatives as antiviral agents

In an attempt to produce heterocyclic compounds based on 1,3,4-oxadiazole derivatives with potential antiviral activity, synthesis of compound 1 [2-(5-thioxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)acetonitrile] was performed through the reaction of cyanoacetic acid hydrazide with carbon disulfide in alcoholic potassium hydroxide. Compound 1 has an activating methylene group, so it was directed toward some specific reactions. Thus, aryldiazonium chlorides reacted with compound 1 affording hydrazono derivatives 2a-c. Also, aromatic aldehydes reacted with compound 1 to produce compounds 3a,b. Furthermore, cyclic ketones were subjected to the synthesis of fused thiophene derivatives 4a,b via reaction with compound 1 in the presence of elemental sulfur. In addition, 1,3,4-oxadiazole derivative 1, when reacted with isothiocyanates, salicylaldehyde or 1,3-dicarbonyl compounds, formed thiazole derivatives 5a,b, coumarin derivative 6 and alkenyl derivatives 7a,b resp. Compound 7b underwent cyclization to afford pyridine derivative 8. Arylhydrazono derivatives 9a,b were produced through the reaction of compound 7a with aryldiazonium chlorides. Products 9a,b underwent cyclization to produce pyridazine derivatives 10a,b. Finally, 1,3,4-oxadiazole derivative 1 was directed toward reaction with hydrazine derivatives, bromoacetophenone and ethylchloroacetate affording compounds 11a,b, 12 and 13, resp. Fused thiophene derivatives 14a,b were produced via reaction of compounds 4a,b with a mixture of malononitrile and ethylorthoformate. Antiviral activity of the synthesized products showed that 5-(4-amino-3-ethyl-2-thioxo-2,3-dihydrothiazol-5-yl)-1,3,4-oxadiazole-2(3H)-thione (5a) and 5-(4-amino-3-phenyl-2-thioxo-2,3-dihydrothiazol-5-yl)-1,3,4-oxadiazole-2(3H)-thione (5b) acted as the most active agents against Feline herpes virus, Feline corona virus, Herpes simplex virus-1 and Herpes simplex virus-2, whereas compound 2-(5-(2-phenylhydrazono)-4,5-dihydro-1,3,4-oxadiazol-2-yl)acetonitrile (11b) was the most effective against Vaccinia virus, Herpes simplex virus (TK-KOS-ACVr), Coxsackie virus B4 and Vesicular stomatitis virus.

Synthesis and structure-activity relationships of carbohydrazides and 1,3,4-oxadiazole derivatives bearing an imidazolidine moiety against the yellow fever and dengue vector, Aedes aegypti

BACKGROUND

1,3,4-Oxadiazole and imidazolidine rings are important heterocyclic compounds exhibiting a variety of biological activities. In this study, novel compounds with oxadiazole and imidazolidine rings were synthesized from 3-(methylsulfonyl)-2-oxoimidazolidine-1-carbonyl chloride and screened for insecticidal activities. The proposed structures of the 17 synthesized compounds were confirmed using elemental analysis, infrared (IR), proton nuclear magnetic resonance (1 H-NMR), and mass spectroscopy.

RESULTS

None of the compounds showed larvicidal activity at the tested concentrations against first-instar Aedes aegypti larvae. However, nine compounds exhibited promising adulticidal activity, with mortality rates of ≥80% at 5 µg per mosquito. Further dose-response bioassays were undertaken to determine median lethal dose (LD50 ) values. Compounds 1, 2b, 2c, 2d, 2 g, 3b, 3c, 3 g, and 3 h were effective, with typical LD50 values of about 5 - 10 µg per mosquito against female Ae. aegypti. Compounds 2c (bearing a nitro group on the aromatic ring; LD50 = 2.80 ± 0.54 µg per mosquito) and 3 h (double halogen groups at 2,4 position on the phenyl ring; LD50 = 2.80 ± 0.54 µg per mosquito) were the most promising compounds.

CONCLUSION

Preliminary mode of action studies failed to show consistent evidence of either neurotoxic or mitochondria-directed effects. Further chemical synthesis within this series may lead to the development of new effective insecticides. © 2017 Society of Chemical Industry.

Synthesis of pyrazole acrylic acid based oxadiazole and amide derivatives as antimalarial and anticancer agents

Depravity of malaria in terms of morbidity and mortality in human beings makes it a major health issue in tropical and subtropical areas of the globe. Drug counterfeiting and non-adherence to the treatment regimen have significantly contributed to development and spread of multidrug resistance that has highlighted the need for development of novel and more efficient antimalarial drugs. Complexity associated with cancer disease and prevalence of diversified cell populations vindicates highly specific treatment options for treatment of cancer. Resistance to these anticancer agents has posed a great hindrance in successful treatment of cancer. Pondering this ongoing situation, it was speculated to develop novel compounds targeting malaria and cancer. Moving on the same aisle, we synthesized pyrazole acrylic acid based oxadiazole and amide derivatives using multi-step reaction pathways (6a-x; 6a'-h'). Schizont maturation inhibition assay was employed to determine antimalarial potential. Compound 6v emerged as the most potent antimalarial agent targeting falcipain-2 enzyme. Anticancer activity was done using sulforhodamine B assay. Compounds 6b' and 6g' demonstrated promising results against all the tested cell lines. Further, Microscopic view clearly indicated formation of apoptotic bodies, chromatin condensation, shrinkage of cells and bleb formation. Validation of the results was achieved using molecular docking studies. From the obtained results, it was observed that cyclization (oxadiazole) favored antimalarial activity while non-cyclized compounds (amides) emerged as better anticancer agents.

Synthesis, characterization, and antileishmanial activity of neutral N-heterocyclic carbenes gold(I) complexes

A series of five new mononuclear neutral gold(I) complexes containing N-heterocyclic carbenes (NHCs) was synthesized and fully characterized by spectroscopic methods. The X-ray structures of four complexes are presented. These gold(I) complexes together with four other neutral gold(I)-NHC complexes previously described were evaluated in vitro against Leishmania infantum promastigotes and axenic amastigotes. Moreover, their cytotoxicity was assessed on the murine macrophages J774A.1. Except one complex (10), eight gold(I)-NHC-Cl complexes show potent activity against the pathological relevant form of L. infantum amastigote with IC₅₀ in the low micromolar and submicromolar range and five of them exhibit a SI close to 10. The lead-complex 11 displays a very high and selective activity (IC₅₀ = 190 nM, SI = 40.29) and constitutes the best promising gold(I)-based drug of this series.