[2-(2,4-Dihydroxyphenyl)-1,3,4-thiadiazole analogues: antifungal activity in vitro against Candida species]

Synthesis, biological and molecular modelling for 1,3,4-thiadiazole sulfonyl thioureas: bacterial and fungal activity

Some substituted thioureas (6a-i) containing a 1,3,4-thiadiazole ring were synthesized by the reaction of the corresponding substituted 2-amino-1,3,4-thiadiazoles 3a-i with p-toluenesulfonyl isocyanate in a one-pot procedure. The antibacterial and antifungal activities of these sulfonyl thioureas were estimated using a minimum inhibitory concentration protocol. Almost all the thioureas exhibited remarkable antimicrobial activity. Amongst the studied compounds, thioureas 6a, 6c, 6h, and 6i were better inhibitors against the bacterium S. aureus, with MIC values of 0.78-3.125 μg mL-1. These compounds were also tested for their inhibition against S. aureus enzymes, including enzymes of DNA gyrase, DNA topoisomerase IV (Topo IV), and dihydrofolate reductase. Amongst the compounds, 6h was a strong inhibitor, with IC50 values of 1.22, 53.78, and 0.23, respectively. Induced fit docking calculations were performed to observe the binding efficiency and steric interactions of these compounds. The obtained results showed that compound 6h was compatible with the active sites of S. aureus DNA gyrase 2XCS. This ligand interacted with residues ASP1083 (chain D), MET1121 (chain B), ARG1122 (chain D), and also with HOH2035, HOH2089, HOH2110, HOH2162. Molecular dynamics simulation in a water solvent system showed that the active interactions with residues ASP083 and MET1121 (chain B), along with ASP1083, MET1121, and ARG1122 (chain D), played an important role in stabilizing complex 6h/2XCS in the active pocket.

Structural Features of 1,3,4-Thiadiazole-Derived Ligands and Their Zn(II) and Cu(II) Complexes Which Demonstrate Synergistic Antibacterial Effects with Kanamycin

Classical synthetic protocols were applied for the isolation of three novel 1,3,4-thiadiazole derivatives which were then complexed with the biologically important Cu(II) and Zn(II) ions. All free ligands and their corresponding complexes were characterized using a number of spectroscopic techniques including Ultraviolet-visible (UV–vis), Fluorescence, Infrared (FT-IR), tandem liquid chromatography-mass (LC-MS), X-ray diffraction (XRD), and Nuclear Magnetic Resonance (NMR) spectroscopy (¹H, ¹³C, HSQC, HMBC). The results obtained are consistent with the formation of dihydrate complexes, in which the chelation of the metal ion occurs via one of the thiadiazole nitrogen atoms and the deprotonated hydroxyl group of the neighboring resorcynyl moiety. The Zn(II) complexes utilize a 1:1 ligand–metal ratio, while in the Cu(II) complexes the ligand–metal ratio is 2:1. Although the antibacterial testing identified moderate activity of the compounds against the tested bacterial strains and additionally modest antioxidant activity, a strong synergistic antibacterial effect against Staphylococcus aureus, using concomitant treatment of thiadiazole derivatives with the commercial antibiotic kanamycin, was observed. The most active thiadiazole derivative demonstrated a minimal inhibitory concentration (MIC) of 500 μg/mL while it was 125 μg/mL in the presence of kanamycin. Moreover, in the presence of few thiadiazole derivatives the MIC value of kanamycin decreased from 0.39 μg/mL to 0.5 μg/mL. The antioxidant activity (IC₅₀) of the most active thiadiazole derivative was determined as 0.13 mM which was nearly three-fold lower compared to that of TROLOX (0.5 mM).

Antifungal effects of a 1,3,4-thiadiazole derivative determined by cytochemical and vibrational spectroscopic studies

Compounds belonging to the group of 5-substituted 4-(1,3,4-thiadiazol-2-yl) benzene-1,3-diols exhibit a broad spectrum of biological activity, including antibacterial, antifungal, and anticancer properties. The mechanism of the antifungal activity of compounds from this group has not been described to date. Among the large group of 5-substituted 4-(1,3,4-thiadiazol-2-yl) benzene-1,3-diol derivatives, the compound 4-(5-methyl-1,3,4-thiadiazole-2-yl) benzene-1,3-diol, abbreviated as C1, was revealed to be one of the most active agents against pathogenic fungi, simultaneously with the lowest toxicity to human cells. The C1 compound is a potent antifungal agent against different Candida species, including isolates resistant to azoles, and molds, with MIC100 values ranging from 8 to 96 μg/ml. The antifungal activity of the C1 compound involves disruption of the cell wall biogenesis, as evidenced by the inability of cells treated with C1 to maintain their characteristic cell shape, increase in size, form giant cells and flocculate. C1-treated cells were also unable to withstand internal turgor pressure causing protoplast material to leak out, exhibited reduced osmotic resistance and formed buds that were not covered with chitin. Disturbances in the chitin septum in the neck region of budding cells was observed, as well as an uneven distribution of chitin and β(1→3) glucan, and increased sensitivity to substances interacting with wall polymerization. The ATR-FTIR spectral shifts in cell walls extracted from C. albicans cells treated with the C1 compound suggested weakened interactions between the molecules of β(1→3) glucans and β(1→6) glucans, which may be the cause of impaired cell wall integrity. Significant spectral changes in the C1-treated cells were also observed in bands characteristic for chitin. The C1 compound did not affect the ergosterol content in Candida cells. Given the low cytotoxicity of the C1 compound to normal human dermal fibroblasts (NHDF), it is possible to use this compound as a therapeutic agent in the treatment of surface and gastrointestinal tract mycoses.

Synergistic antifungal interactions of amphotericin B with 4-(5-methyl-1,3,4-thiadiazole-2-yl) benzene-1,3-diol

Amphotericin B (AmB) is a very potent antifungal drug with very rare resistance among clinical isolates. Treatment with the AmB formulations available currently is associated with severe side effects. A promising strategy to minimize the toxicity of AmB is reducing its dose by combination therapy with other antifungals, showing synergistic interactions. Therefore, substances that display synergistic interactions with AmB are still being searched for. Screening tests carried out on several dozen of synthetic 1,3,4-thiadiazole derivatives allowed selection of a compound called 4-(5-methyl-1,3,4-thiadiazole-2-yl) benzene-1,3-diol (abbreviated as C1), which shows strong synergistic interaction with AmB and low toxicity towards human cells. The aim of the present study was to investigate the type of in vitro antifungal interactions of the C1 compound with AmB against fungal clinical isolates differing in susceptibility. The results presented in the present paper indicate that the C1 derivative shows strong synergistic interaction with AmB, which allows the use of a dozen to several dozen times lower AmB concentration necessary for 100% inhibition of the growth of pathogenic fungi in vitro. Synergistic interactions were noted for all tested strains, including strains with reduced sensitivity to AmB and azole-resistant isolates. These observations give hope for the possibility of application of the AmB - C1 combinatory therapy in the treatment of fungal infections.

Crystal structure of tetra-μ-acetato-bis-[(5-amino-2-methyl-sulfanyl-1,3,4-thia-diazole-κN 1)copper(II)]

The reaction of 2-methyl-thio-5-amino-1,3,4-thia-diazole (Me-SNTD; C3H5N3S2) with copper(II) acetate monohydrate [Cu(OAc)2·H2O; C4H8CuO5] resulted in the formation of the title binuclear compound, [Cu2(C2H3O2)4(C3H5N3S2)2] or [Cu2(OAc)4(Me-SNTD)2]. The structure has triclinic (P ) symmetry with a crystallographic inversion centre located at the midpoint of the line connecting the Cu atoms in the dimer. These two Cu atoms of the dimer [Cu⋯Cu = 2.6727 (6) Å] are held together by four carboxyl-ate groups. Each Cu atom is further coordinated to the N atom of an Me-SNTD mol-ecule and exhibits a Jahn-Teller-distorted octa-hedral geometry. The dimers are connected into infinite chains by hydrogen bonds between the NH (Me-SNTD) and the carboxyl-ate groups of neighbouring mol-ecules, generating an R 2 2(12) ring motif. The mol-ecules are further linked by C-H⋯π inter-actions between the thia-diazole rings and the methyl groups of the acetate units.

2-Amino-1,3,4-thiadiazole as a potential scaffold for promising antimicrobial agents

Pathogenic microorganisms are causative agents for different types of serious and even lethal infectious diseases. Despite advancements in medication, bacterial and fungal infections continue to be a growing problem in health care. As more and more bacteria become resistant to antibiotics used in therapy and an increasing number of invasive fungal species become resistant to current antifungal medications, there is considerable interest in the development of new compounds with antimicrobial activity. The compounds containing a heterocyclic ring play an important role among organic compounds with biological activity used as drugs in human and veterinary medicine or as insecticides and pesticides in agriculture. Thiadiazoles belong to the classes of nitrogen-sulfur heterocycles with extensive application as structural units of biologically active molecules and as useful intermediates in medicinal chemistry. The potency of the thiadiazole nucleus is demonstrated by the drugs currently used. 1,3,4-Thiadiazoles and some of their derivatives are extensively studied because of their broad spectrum of pharmacological activities. The aim of this review was to highlight the main antimicrobial properties exhibited by derivatives possessing 2-amino-1,3,4-thiadiazole moiety. Many of the reported 2-amino-1,3,4-thiadiazole derivatives can be considered as lead compounds for drug synthesis, and several of them have demonstrated higher antimicrobial activity in comparison to standard drugs. Furthermore, taking into account the reactivity of the amine group in the derivatization process, 2-amino-1,3,4-thiadiazole moiety may be a good scaffold for future pharmacologically active 1,3,4-thiadiazole derivatives.

Synthesis of Oxadiazole-Thiadiazole Hybrids and Their Anticandidal Activity

In the field of infection management, it is a major challenge to discover a potent and safe antifungal agent due to the emergence of resistant strains. Hence, the goal of this paper is to design and synthesize novel oxadiazole-thiadiazole hybrid compounds (6a-6s) and evaluate their antifungal activity. The structures of synthesized compounds were elucidated by various methods including FT-IR, ¹H-NMR, ¹³C-NMR and HR-MS spectral data. Compounds were tested against four Candida species by broth microdilution assay. Compounds 6e, 6k and 6r, bearing a nitro group, showed significant antifungal activity against all fungi with minimum inhibitory concentration (MIC) in the range of 0.78-3.12 µg/mL. These compounds were also screened for their in vitro cytotoxic effects by MTT assay and detected as nontoxic at their active concentrations against Candida strains. To examine the effects of these compounds on ergosterol biosynthesis, the LC-MS-MS method, which is based on quantification of ergosterol level in C. krusei, was carried out. Finally, the most active molecule (6e) was docked in the active site of the lanosterol 14α-demethylase enzyme, and it was determined that there is a strong interaction between the compound and enzyme.

Design, synthesis, and biological evaluation of new series of 2-amido-1,3,4-thiadiazole derivatives as cytotoxic agents

A series of novel 1,3,4-thiadiazole derivatives bearing an amide moiety were designed, synthesized, and evaluated for their in vitro antitumor activities against HL-60, SKOV-3 and MOLT-4 human tumor cell lines by MTT assay. Ethyl 2-((5-(4-methoxybenzamido)-1,3,4-thiadiazol-2-yl)thio)acetate (5f) showed the best inhibitory effect against SKOV-3 cells, with an IC50 value of 19.5 μm. In addition, the acridine orange/ethidium bromide staining assay in SKOV-3 cells suggested that the cytotoxic activity of 5f occurs via apoptosis.

Synthesis, characterization, antimicrobial, and pharmacological evaluation of some 2, 5-disubstituted sulfonyl amino 1,3,4-oxadiazole and 2-amino-disubstituted 1,3,4-thiadiazole derivatives

The presence of heterocyclic structures in diverse types of compounds, this is strongly indicative of the profound effect like structure exerts on physiologic activity, and recognition of this is abundantly reflected in efforts to find useful synthetic drugs. The search for better pharmacological active drug and the importance of disubstituted 1,3,4-oxadiazole and 1,3,4-thiadiazole as active pharmacophores, prompted us to design, synthesize, characterize, and evaluate a series of differently substituted sulfonyl amino 1,3,4-oxadiazole and 1,3,4-thiadiazole for their potential antimicrobial, analgesic and antiinflammatory activity, respectively. New sulfonyl amino 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives were synthesized by intramolecular cyclization of thiosemicarbazide in alkaline medium. Reactions were carried out by the reaction between aromatic carbonyl halide and thiosemicarbazide.

A convenient four-component one-pot synthesis of 2-amino-1,3,4-thiadiazoles in water

A novel four-component one-pot approach for the synthesis of 2-amino-1,3,4-thiadiazoles from primary amines, carbon disulfide, hydrazine, and acyl chlorides has been developed. A series of 5-substituted-2-amino-1,3,4-thiadiazoles were synthesized in medium-to-good yields utilizing this newly developed method.

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.