Selective leishmanicidal effect of 1,3,4-thiadiazole derivatives and possible mechanism of action against Leishmania species

Synthesis, molecular docking, and molecular dynamic simulation studies of new 1,3,4-thiadiazole derivatives as potential apoptosis inducers in A549 lung cancer cell line

1,3,4-Thiadiazoles are structures that are bioisosteres of 1,3,4-oxadiazole and pyrimidine ring, which are found in the structure of many drugs and anticancer active newly studied derivatives. In the past, high effect profiles have been observed in many molecules created, based on the anticancer effects of the 2-amino-1,3,4-thiadiazole (NSC 4728) molecule and acetazolamide molecules. Focusing on these molecules and evaluating them in terms of mechanistic effects, twelve new N-[5-((3,5-dichlorophenoxy) methyl]-1,3,4-thiadiazole derivatives (3a-3i) were synthesized and their biological activities were investigated in lung cancer cells. The anticancer effects of the compounds were evaluated on the A549 and L929 cell lines. Compound 3f, namely 2-[(5-chlorobenzotiyazol-2-yl)thio]-N-[5-[(3,5-dichlorophenoxy)methyl]-1,3,4-thiadiazol-2-yl]acetamide, showed better activity than cisplatin, exhibiting high inhibitory potency (IC50: <0.98 μg/mL) and selectivity against A549 cell line even at the lowest concentration tested. Compounds 3c, 3f, and 3h with the lowest IC50 values of the compounds exhibited an excellent percentage of apoptosis between 72.48 and 91.95% compared to cisplatin. The caspase-3 activation and mitochondrial membrane potential change of the aforementioned three compounds were also studied. Moreover, matrix metalloproteinase-9 (MMP-9) inhibition potential of all final compounds was also investigated and IC50 values for compounds 3b and 3g were identified as 154.23 and 107.28 µM. Molecular docking and molecular dynamic simulation studies for MMP-9 enzyme inhibition were realized on these compounds and the nitrogen atoms of amide and thiadiazole moieties' ascertained that they play a key role in chelating with Zn metal, at the same time, (thio)ether moieties allow conformational change resulting in the ligand can make more stable contacts.Communicated by Ramaswamy H. Sarma.

In Vitro Antileishmanial and Antischistosomal Activities of Anemonin Isolated from the Fresh Leaves of Ranunculus multifidus Forsk

Leishmaniasis and schistosomiasis are neglected tropical diseases (NTDs) infecting the world’s poorest populations. Effectiveness of the current antileishmanial and antischistosomal therapies are significantly declining, which calls for an urgent need of new effective and safe drugs. In Ethiopia fresh leaves of Ranunculus multifidus Forsk. are traditionally used for the treatment of various ailments including leishmaniasis and eradication of intestinal worms. In the current study, anemonin isolated from the fresh leaves of R. multifidus was assessed for its in vitro antileishmanial and antischistosomal activities. Anemonin was isolated from the hydro-distilled extract of the leaves of R. multifidus. Antileishmanial activity was assessed on clinical isolates of the promastigote and amastigote forms of Leishmania aethiopica and L. donovani clinical isolates. Resazurin reduction assay was used to determine antipromastigote activity, while macrophages were employed for antiamastigote and cytotoxicity assays. Antischistosomal assays were performed against adult Schistosoma mansoni and newly transformed schistosomules (NTS). Anemonin displayed significant antileishmanial activity with IC₅₀ values of 1.33 nM and 1.58 nM against promastigotes and 1.24 nM and 1.91 nM against amastigotes of L. aethiopica and L. donovani, respectively. It also showed moderate activity against adult S. mansoni and NTS (49% activity against adult S. mansoni at 10 µM and 41% activity against NTS at 1 µM). The results obtained in this investigation indicate that anemonin has the potential to be used as a template for designing novel antileishmanial and antischistosomal pharmacophores.

1,3-Thiazine, 1,2,3,4-Dithiadiazole, and Thiohydrazide Derivatives Affect Lipid Bilayer Properties and Ion-Permeable Pores Induced by Antifungals

Over the past decade, thiazines, thiadiazoles, and thiohydrazides have attracted increasing attention due to their sedative, antimicrobial, antiviral, antifungal, and antitumor activities. The clinical efficacy of such drugs, as well as the possibility of developing resistance to antimicrobials, will depend on addressing a number of fundamental problems, including the role of membrane lipids during their interaction with plasma membranes. The effects of the eight 1,3- thiazine-, 1,2,3,4- dithiadiazole-, and thiohydrazide-related compounds on the physical properties of model lipid membranes and the effects on reconstituted ion channels induced by the polyene macrolide antimycotic nystatin and antifungal cyclic lipopeptides syringomycin E and fengycin were observed. We found that among the tested agents, the fluorine-containing compound N′-(3,5-difluorophenyl)-benzenecarbothiohydrazide (C6) was the most effective at increasing the electric barrier for anion permeation into the hydrophobic region of the membrane and reducing the conductance of anion-permeable syringomycin pores. A decrease in the membrane boundary potential with C6 adsorption also facilitated the immersion of positively charged syringomycin molecules into the lipid bilayer and increases the pore-forming ability of the lipopeptide. Using differential scanning microcalorimetry, we showed that C6 led to disordering of membrane lipids, possibly by potentiating positive curvature stress. Therefore, we used C6 as an agonist of antifungals forming the pores that are sensitive to membrane curvature stress and lipid packing, i.e., nystatin and fengycin. The dramatic increase in transmembrane current induced by syringomycin E, nystatin, and fengycin upon C6 treatment suggests its potential in combination therapy for treating invasive fungal infections.

A Survey on Inhibitory Effect of Whole-Body Extraction and Secretions of Lucilia sericata's Larvae on Leishmania major In vitro

Background:

Leishmaniasis is a skin disease caused by Leishmania parasite. Despite being self-limiting, must be treated. Available drugs have side effects and drug resistance has also been seen.

Materials and Methods:

Maggot debridement therapy (MDT) is using sterile fly larvae (maggots) of blow flies (Lucilia sericata) for the treatment of different types of tissue wounds. Larvae have excreted and secreted substances that have been proved to have antimicrobial effects, in addition to the some other specifications.

Results:

In this study, the anti-leishmanial effects of extracts and secretions of sterile second- and third-instar larvae of L. sericata on the growth of Leishmania major promastigotes and amastigotes in the J774 macrophages have been evaluated in vitro.

Conclusion:

The results showed that extracts and secretions had almost the same leishmaniocidal effect on promastigotes and intracellular amastigotes without cytotoxic effect on macrophages.

Novel 5-(nitrothiophene-2-yl)-1,3,4-Thiadiazole Derivatives: Synthesis and Antileishmanial Activity against promastigote stage of Leishmania major

In this study, a series of novel compounds based on 5-(5-nitrothiophene-2-yl)-1,3,4-thiadiazole possessing (het) aryl thio pendant at C-2 position of thiadiazole ring is developed and evaluated as antileishmanial agents using MTT colorimetric assay. 10 New compounds containing aryl and heteroaryl derivatives, started from thiophene-2-carbaldehyde in five steps, were synthesized in good to excellent yields and characterized by ¹H-NMR, ¹³C-NMR, and IR spectroscopy. Through the compounds 6a-j, methylimidazole containing derivative 6e was recognized as the most active compound against L. major promastigotes exhibiting IC₅₀ values of 11.2µg/mL and 7.1µg/mL after 24 and 48 h, respectively. This compound is > 4 fold more effective than Glucantime as a standard drug (IC₅₀ = 50 µg/mL after 24 h and 25 µg/mL after 48 h).

Essential and nonessential metal effects on extracellular Leishmania amazonensis in vitro

Protozoan parasites like Leishmania amazonensis are excellent models to test the effects of new drugs against a functional molecular arsenal used to establish successfully an infection in the vertebrate host, where they invade the cells of the monocytic system. However, little is known about the influence of metal ions on the cellular functionality of the infective forms of L. amazonensis. In the present work, we show that ZnCl₂ (an essential metal to cellular metabolism) did not induce drastic effects on the survival of the promastigote under the conditions tested. However, incubation of ZnCl₂ prior to subsequent treatment with CdCl₂ and HgCl₂ led to a drastic toxic effect on parasite survival in vitro. Nonessential metals such as CdCl₂ and HgCl₂ promoted a drastic effect on parasite survival progressively with increasing dose and time of exposure. Notably, HgCl₂ produced an effective elimination of the parasite in doses/time smaller than the CdCl₂. This toxic action induced in the parasite a high condensation of the nuclear heterochromatin, besides the absence or de-structuring of functional organelles such as glycosomes, acidocalcisomes, and mitochondria in the cytoplasm. Our results suggest that promastigotes of L. amazonensis are sensitive to the toxic activity of nonessential metals, and that this activity increases when parasites are previously exposed to Zn. To summarize, toxic effects of the tested metals are dose and time dependent and can be used as a study model to better understand the functionality of the molecular arsenal responsible for the parasitism.

Leishmanicidal Activity of Isoselenocyanate Derivatives

Conventional chemotherapy against leishmaniasis includes agents exhibiting considerable toxicity. In addition, reports of drug resistance are not uncommon. Thus, safe and effective therapies are urgently needed. Isoselenocyanate compounds have recently been identified with potential antitumor activity. It is well known that some antitumor agents demonstrate effects against Leishmania In this study, the in vitro leishmanicidal activities of several organo-selenium and organo-sulfur compounds were tested against Leishmania major and Leishmania amazonensis parasites, using promastigotes and intracellular amastigote forms. The cytotoxicity of these agents was measured in murine peritoneal macrophages and their selectivity indexes were calculated. One of the tested compounds, the isoselenocyanate derivative NISC-6, showed selectivity indexes 2- and 10-fold higher than those of the reference drug amphotericin B when evaluated in L. amazonensis and L. major, respectively. The American strain (L. amazonensis) was less sensitive to NISC-6 than L. major, showing a trend similar to that observed previously for amphotericin B. In addition, we also observed that NISC-6 significantly reduced the number of amastigotes per infected macrophage. On the other hand, we showed that NISC-6 decreases expression levels of Leishmania genes involved in the cell cycle, such as topoisomerase-2 (TOP-2), PCNA, and MCM4, therefore contributing to its leishmanicidal activity. The effect of this compound on cell cycle progression was confirmed by flow cytometry. We observed a significant increase of cells in the G₁ phase and a dramatic reduction of cells in the S phase compared to untreated cells. Altogether, our data suggest that the isoselenocyanate NISC-6 may be a promising candidate for new drug development against leishmaniasis.

Promising antileishmanial activity of novel imidazole antifungal drug luliconazole against Leishmania major: In vitro and in silico studies

OBJECTIVES

Pentavalent antimonials have been used for the treatment of leishmaniasis for over 70 years, however they are limited by their toxicity. Unfortunately, the efficacy of first-line drugs for the treatment of leishmaniasis has decreased and resistance is noticeable. Luliconazole is a new azole with unique effects on fungi that has not yet been tested on Leishmania parasites.

METHODS

In this study, the cytotoxicity and antileishmanial activity of luliconazole were evaluated in vitro against promastigotes and intracellular amastigotes of Leishmania major. The docking simulation with the target enzyme, sterol 14α-demethylase (CYP51) was performed using AutoDock 4.2 program.

RESULTS

The IC₅₀ (concentration of test compound required for 50% inhibition) against promastigotes revealed that luliconazole (IC₅₀=0.19μM) has greater potency than ketoconazole (KET), meglumine antimoniate (MA) and amphotericin B (AmB) (IC₅₀ values of 135, 538 and 2.52μM, respectively). Against the amastigote stage, luliconazole at a concentration of 0.07μM decreased the mean infection rate and the mean number of amastigotes per macrophage more effectively than MA (P<0.004) and KET (P<0.043), but there was no difference compared with AmB (P>0.05). A docking study of luliconazole with the cytochrome P450 enzyme sterol 14α-demethylase (CYP51) revealed that this azole drug can properly interact with the target enzyme in Leishmania mainly via coordination with heme and multiple hydrophobic interactions.

CONCLUSION

These results show the potent activity of luliconazole at extremely low concentrations against L. major. It may therefore be considered as a new candidate for treatment of leishmaniasis in the near future.

Nanoemulsions containing a synthetic chalcone as an alternative for treating cutaneous leshmaniasis: optimization using a full factorial design

Nanoemulsions are drug delivery systems that may increase the penetration of lipophilic compounds through the skin, enhancing their topical effect. Chalcones are compounds of low water solubility that have been described as promising molecules for the treatment of cutaneous leishmaniasis (CL). In this context, the aim of this work was to optimize the development of a nanoemulsion containing a synthetic chalcone for CL treatment using a 2(2) full factorial design. The formulations were prepared by spontaneous emulsification and the experimental design studied the influence of two independent variables (type of surfactant - soybean lecithin or sorbitan monooleate and type of co-surfactants - polysorbate 20 or polysorbate 80) on the physicochemical characteristics of the nanoemulsions, as well as on the skin permeation/retention of the synthetic chalcone in porcine skin. In order to evaluate the stability of the systems, the antileishmanial assay was performed against Leishmania amazonensis 24 hours and 60 days after the preparation of the nanoemulsions. The formulation composed of soybean lecithin and polysorbate 20 presented suitable physicochemical characteristics (droplet size 171.9 nm; polydispersity index 0.14; zeta potential -39.43 mV; pH 5.16; and viscosity 2.00 cP), drug content (91.09%) and the highest retention in dermis (3.03 µg·g(-1)) - the main response of interest - confirmed by confocal microscopy. This formulation also presented better stability of leishmanicidal activity in vitro against L. amazonensis amastigote forms (half maximal inhibitory concentration value 0.32±0.05 µM), which confirmed the potential of the nanoemulsion soybean lecithin and polysorbate 20 for CL treatment.

Multicomponent domino reactions of hydrazinecarbodithioates: concise access to 3-substituted 5-thiol-1,3,4-thiadiazolines

Two classes of addition/cycloaddition cascade reactions of hydrazinecarbodithioate (1) have been developed under mild reaction conditions. Reaction of hydrazinecarbodithioate (1) with formaldehyde solution (2) and propiolic acid (3) gives 3-propargyl-5-thiol-2,3-dihydro-1,3,4-thiadiazoles (5) via a decarboxylative coupling/cycloaddition domino sequence. When propiolic acid (3) is switched to phenyl boronic acid (4), a petasis/cycloaddition domino reaction is instead observed, in which 3-benzyl-5-thiol-2,3-dihydro-1,3,4-thiadiazoles (6) are obtained. Both these reactions show a wide range of functional-group compatibility for propiolic acids and aryl boronic acids, and give the corresponding products in moderate to good yields.

Antileishmanial activity evaluation of adunchalcone, a new prenylated dihydrochalcone from Piper aduncum L

Bioactivity-guided fractionation of EtOH extract from the leaves of Piper aduncum L. (Piperaceae) afforded a new dihydrochalcone, named adunchalcone. Its structure was elucidated on the basis of their spectroscopic data, primarily NMR and MS. Adunchalcone was evaluated against promastigote forms of Leishmania (L.) amazonensis, L. (V.) braziliensis, L. (V.) shawi, and L. (L.) chagasi and displayed 50% effective concentrations (EC50) of 11.03, 26.70, and 11.26 μM, as well as selective indexes of 4.86, 2.01, 4.76 and 0.50, respectively. This compound was also tested against intracellular forms of L. (L.) amazonensis, displaying weak activity, in comparison to reference drug amphotericin B. However, despite reduced effect of adunchalcone against amastigotes of L. (L.) amazonensis, this work opens the perspective to use this particular molecule as a scaffold for the design of novel and selective drug candidates for neglected diseases, mainly leishmaniasis.

1,3,4-thiadiazole and its derivatives: a review on recent progress in biological activities

The 1,3,4-thiadiazole nucleus is one of the most important and well-known heterocyclic nuclei, which is a common and integral feature of a variety of natural products and medicinal agents. Thiadiazole nucleus is present as a core structural component in an array of drug categories such as antimicrobial, anti-inflammatory, analgesic, antiepileptic, antiviral, antineoplastic, and antitubercular agents. The broad and potent activity of thiadiazole and their derivatives has established them as pharmacologically significant scaffolds. In this study, an attempt has been made with recent research findings on this nucleus, to review the structural modifications on different thiadiazole derivatives for various pharmacological activities.

Leishmanicidal activity of two naphthoquinones against Leishmania donovani

Here we studied ability of two naphthoquinones to inhibit Leishmania growth (2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (TR 001) and 2,3-dibromo-1,4-naphthoquinone (TR 002). TR 001 was more efficient than TR 002 in inducing killing of promastigotes and intracellular amastigotes. These values compare well to those obtained with the standard first-line antileishmanial agent sodium stibogluconate (SSG). TR 001 also induced significantly more nitric oxide (NO) production than TR 002 or SSG. Taken together, these data show that TR 001 and TR 002 could be promising new drugs for treatment of visceral leishmaniasis.

Novel immunomodulatory function of 1,3,4-thiadiazole derivatives with leishmanicidal activity

OBJECTIVES

Previously, some nitroheteroaryl-1,3,4-thiadiazole derivatives were identified to have potent activity against Leishmania sp. The present aim was to complete the in vitro analysis, thereby investigating the in vivo efficiency of the analogues 15a, 21a and 21b against infected BALB/c mice.

METHODS

Following parasite inoculation and intraperitoneal drug administration (5 and 20 mg/kg/day) for 5 days, the course and size of cutaneous lesions, histopathology of the liver, parasite loads in the spleen through limiting dilution assay as well as spleen cell activation assays through cytokine secretion profiles were studied in BALB/c mice, over a period of 23 and 30 days post-drug injections.

RESULTS

The analogues significantly decreased lesion size and progression of infection in the liver and spleen, and were associated with granuloma formation, which correlates with disease regression in the liver of murine hosts. Moreover, the analogues had immunomodulatory effects, stimulating interferon-γ expression and suppressing interleukin-10 and interleukin-5 production, favouring type-1 immune responses and resolution of the parasitic infection.

CONCLUSIONS

Our results highlight marked differences between the responses of key anatomical organs to the thiadiazole derivatives in comparison with the current antileishmanial drug, meglumine antimoniate. The in vivo observations provide further evidence on the efficiency of the compounds for Leishmania treatment. The immunomodulatory function plays an essential role in enhancing cell-mediated immunity for complete clearance of the pathogen.

Synthesis of new 2-naphthyl ethers and their protective activities against DNA damage induced by bleomycin-iron

The reaction of 2-naphthaloxyacetic acid with thiosemicarbazide in the presence of phosphoryl chloride, followed by treatment with phenacylbromides, led to the formation of imidazo[2,1-b][1,3,4]thiadiazoles 3a-c. 2-(Naphthalen-3-yloxy)acetohydrazide 4 on treatment with ethyl 2-(2-arylhydrazono)-3-oxobutanoates (5a-c), 2-methoxymethylene)malononitrile, or ethyl 2-cyano-3,3-bis(methylthio)acrylate led to the formation of substituted pyrazoles 6-8. The reaction of the hydrazide 4 with hydrazonoyl chlorides 9a-c and 1,2,4,5-benzene tetracarboxylic-1,2:4,5-dianhydride produced bis-diazo compounds 10a-c and dimide 11 respectively. All new compounds were tested for their protective activity against DNA damage induced by bleomycin-iron complex. Compound 2 showed the greatest protection against DNA damage, thus diminishing chromogen formation between the damaged DNA and thiobarbituric acid.