Biological evaluation and molecular docking of novel 1,3,4-thiadiazole-resorcinol conjugates as multifunctional cholinesterases inhibitors.

Two series of novel 1,3,4-thiadiazole-resorcinol conjugates were efficiently synthesized and evaluated as cholinesterases inhibitors. N-Butyl- and N-chlorophenyl-5-amino-1,3,4-thiadiazol-2-yl)benzene-1,3-diols were identified as the most promising compounds of low nanomolar activity against AChE (IC50 = 29-76 nM) and moderate activity against BuChE. The inhibition mechanism studies proved that the compounds are mixed type inhibitors. The docking simulations showed great affinity of the compounds for both enzymes. The modelled amine derivatives exhibited a similar arrangement in the catalytic anionic site of AChE similar to that of tacrine. The thiadiazole ring interacted with Trp84 and the phenyl groups created π-π stacking interactions with the residue - Phe330. The compounds showed better inhibition of the in vitro self-induced Aß (1-42) aggregation than that compared with curcumin as well as antioxidant properties similar to those of quercetin. They exhibited metal ion chelating properties, acceptable cytotoxicity in vitro and favourable ADMET profile determined in silico.

Differences in electrochemical response of prospective anticancer drugs IPBD and Cl-IPBD, doxorubicin and Vitamin C at plasmid modified glassy carbon.

For the comparison of the DNA interactions with drugs, two newly synthesized prospective anticancer drugs, 6-(1H-imidazo[4,5-b]phenasine-2-yl)benzene-1,3-diol (IPBD) and, its -Cl derivative (Cl-IPBD) have been compared with doxorubicin, a drug widely used in medicine, and with Vitamin C. These compounds were accumulated at a supercoiled scpUC19 plasmid layer formed on a glassy carbon electrode (GCE). Stability of the drug-plasmid/GCE layer was achieved by initial plasmid accumulation using prolonged potential cycling for ca. 200 min. from highly diluted scpUC19 solutions (8 pg/mL), followed by accumulation of the drugs from 1 µM - 50 µM. Electrochemical properties in terms of the redox potentials of the compounds and capacitative/resistive characteristics of the layers have been tested using, in sequence, four voltammetric methods: Square Wave (SWV), Differential Pulse (DPV) and Alternating Current (ACV) with phase detection 0° and 90°. Importantly, with progressive drug accumulation in the plasmid, for Cl-IPBD, but not for IPBD, an increase in peak (I) at -0.42 V vs. SCE was observed, while biological tests revealed a higher cytotoxic activity for Cl-IPBD vs. IPBD. Moreover, an additional redox signal of Cl-IPBD was observed with the compound reductive accumulation at the plasmid layer in the presence of Vitamin C.

Design, synthesis and biological evaluation of novel 1,3,4-thiadiazole derivatives as anti-glioblastoma agents targeting the AKT pathway.

In spite of progress in understanding biology of glioblastoma (GBM), this tumor remains incurable with a median survival rate of 15 months. Previous studies have shown that 2-(4-fluorophenyloamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole (FPDT) and 2-(3-chlorophenyloamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole (CPDT) diminished viability of cancer cell lines of different origin. In the current study, we have examined activity of these compounds in several GBM cell lines and patient-derived GBM cells. We have also designed, synthesized and evaluated anti-GBM activity of novel 1,3,4-thiadiazole derivatives containing additional Cl or CH2CH3 substitute at C5-position of 2,4-dihydroxyphenyl. The tested compounds presented a considerable cytotoxicity against all GBM cell lines examined as well as patient-derived GBM cells. They were 15-110 times more potent than temozolomide, the first-line chemotherapeutic agent for GBM. Notably, in anticancer concentrations three of the derivatives were not toxic to human astrocytes. FPDT appeared to be the most promising compound with IC50 values between 45 µM and 68 µM for GBM cells and >100 µM for astrocytes. It augmented activity of temozolomide and inhibited proliferation migration and invasion of GBM cells. Treatment with FPDT diminished phosphorylation level of GSK3ß and AKT. Pretreatment with PDGF-BB, an AKT activator, partially protected cells from death caused by FPDT, indicating that FPDT-mediated decrease in cell viability is causatively related to the inhibition of the AKT pathway.

ESIPT-Related Origin of Dual Fluorescence in the Selected Model 1,3,4-Thiadiazole Derivatives.

In our previous work, we discussed the emergence of the dual fluorescence phenomenon in selected compounds from the group of 1,3,4-thiadiazoles. The results obtained in a number of experimental studies, supported by [TD]DFT calculations, clearly indicated that the phenomenon of dual fluorescence stemmed from an overlap of several factors, including the correct conformation of the analyzed molecule and, very significantly in this context, aggregation effects. Where those two conditions were met, we could observe the phenomenon of intermolecular charge transfer (CT) and the emergence of electronic states responsible for long wave emissions. However, in light of the new studies presented in this paper, we were able, for the first time, to provide a specific theory for the effect of dual fluorescence observed in the analyzed group of 1,3,4-thiadiazoles. We present the results of spectroscopic measurements conducted for two selected analogues from the 1,3,4-thiadiazole group, both in polar and non-polar solvents, which clearly evidence (as we have already suspected in the past, albeit have not shown in publications to date) the possibility of processes related to emission from the tautomer formed in the process of excited state intramolecular proton transfer, which is responsible for the long-wavelength emissions observed in the selected analogues. The presented results obtained with the use of UV-Vis, fluorescence (stationary and time-resolved), FTIR, and Raman spectroscopy, as well as from calculations of dipole moment changes between the ground and excited state with the use of two derivatives with different structures of the resorcylic system, corroborated our standing hypothesis. At the same time, they excluded the presence of ground state keto forms of the analyzed analogues unless necessitated by the structure of the molecule itself. In this case, aggregation factors enhance the observed effects related to the dual fluorescence of the analyzed compounds (by way of AIE-aggregated induced emissions).

Biological Evaluation, Molecular Docking, and SAR Studies of Novel 2-(2,4-Dihydroxyphenyl)-1H- Benzimidazole Analogues.

In the present study, new 4-(1H-benzimidazol-2-yl)-benzene-1,3-diols, modified in both rings, have been synthesized and their efficacies as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors have been determined. The modified Ellman's spectrophotometric method was applied for the biological evaluation. The compounds showed strong (IC50 80-90 nM) AChE and moderate (IC50 5-0.2 µM) BuChE inhibition in vitro. Some compounds were effective toward AChE/BuChE, exhibiting high selectivity ratios versus BuChE, while the other compounds were active against both enzymes. The structure-activity relationships were discussed. The compounds inhibited also in vitro self-induced Aß(1-42) aggregation and exhibited antioxidant properties. The docking simulations showed that the benzimidazoles under consideration interact mainly with the catalytic site of AChE and mimic the binding mode of tacrine.

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 ß(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 ß(1→3) glucans and ß(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.

Spectroscopic Studies of Dual Fluorescence in 2-(4-Fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole: Effect of Molecular Aggregation in a Micellar System.

The article presents the results of spectroscopic studies focused on a selected compound from the 1,3,4-thiadiazole group-2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thia-diazole (FABT)-in a micellar system formed by Triton X-100, a non-ionic detergent. Fluorescence measurements revealed the phenomenon of dual fluorescence whose emergence is related to the particular molecular organisation of the compound, which depends both on the concentration of the detergent and, most of all, the concentration of the compound itself. Dual fluorescence of FABT in a micellar system was observed for the compound dissolved in a methanol aqueous system, i.e., an environment wherein the dual fluorescence of the compound had never been reported before. Based on the interpretation of UV-Vis electronic absorption, resonance light scattering (RLS), emission and excitation fluorescence spectra, as well as measurements of dynamic light scattering (DLS) and Principal Component Analysis (PCA), we were able to relate the occurrence of this effect to the process of molecular aggregation taking place between FABT molecules in the micellar system in question. Results of fluorescence spectra measurements and time-correlated single photon counting (TCSPC) indicate that dual fluorescence occurs at detergent concentrations necessary to form micellar systems, which in turn facilitate the process of aggregation of FABT molecules. The correlation between the observed fluorescence effects and the previous measurements performed for analogues from this group suggests the possibility of charge transfer (CT) within the range of detergent concentrations wherein the aforementioned fluorescence effects are observed. It ought to be emphasised that this type of fluorescence effects are relatively easy to induce, which predisposes this groups of fluorophores as ideal fluorescence probes in the context of biological samples.

Evaluation of the effect of 2-(2,4-dihydroxyphenyl)-4H-benzofuro[3,2-d][1,3]thiazin-4-one on colon cells and its anticancer potential.

In this paper, we present the biological effect of the newly synthesized 2-(2,4-dihydroxyphenyl)-4H-benzofuro[3,2-d][1,3]thiazin-4-one (DPBT) on human colon adenocarcinoma cell lines (HT-29 and LS180). Additionally, DPBT cytotoxicity was examined in human colon epithelial cells (CCD 841 CoTr) and human skin fibroblasts (HSF). The studies revealed a significant decrease in the proliferation of cancer cells after exposure to DPBT at concentrations in the range of 10-100 µM. Additionally, DPBT was not toxic to normal CCD 841 CoTr and HSF cells at concentrations that induced inhibition of cancer cell proliferation. The nature of the anti-proliferative action of DPBT in the cell cycle progression in colon cancer cells and the expression of proteins involved in this process were examined by flow cytometry and western blotting, respectively. The investigations demonstrated higher sensitivity of LS180 than HT-29 to the DPBT treatment. The anti-proliferative action of DPBT in LS180 was attributed to cell cycle arrest in the G1 phase via up-regulation of p27KIP1 and down-regulation of cyclin D1 and CDK4 proteins.

Spectroscopic and Theoretical Studies of Fluorescence Effects in 2-Methylamino-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole Induced by Molecular Aggregation.

The article presents the results of fluorescence analyses of 2-methylamino-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole (MDFT) in an aqueous environment. MDFT dissolved in aqueous solutions with a pH value in the range from 1 to 4.5 yielded an interesting effect of two clearly separated fluorescence emissions. In turn, a single fluorescence was observed in MDFT dissolved in water solutions with a pH value from 4.5 to 12. As it was suggested in the previous investigations of other 1,3,4-thiadiazole compounds, these effects may be associated with conformational changes in the structure of the analysed molecule accompanied by aggregation effects. Crystallographic data showed that the effect of the two separated fluorescence emissions occurred in a conformation with the -OH group in the resorcyl ring bound on the side of the sulphur atom from the 1,3,4-thiadiazole ring. The hypothesis of aggregation as the mechanism involved in the change in the spectral properties at low pH is supported by the results of (Time-Dependent) Density Functional Theory calculations. The possibility of rapid analysis of conformational changes with the fluorescence spectroscopy technique may be rather important outcome obtained from the spectroscopic studies presented in this article. Additionally, the presented results seem to be highly important as they can be easily observed in solutions and biologically important samples.

Spectroscopic Studies of Fluorescence Effects in Bioactive 4-(5-Heptyl-1,3,4-Thiadiazol-2-yl)Benzene-1,3-Diol and 4-(5-Methyl-1,3,4-Thiadiazol-2-yl)Benzene-1,3-Diol Molecules Induced by pH Changes in Aqueous Solutions.

This paper presents the results of stationary fluorescence spectroscopy and time-resolved spectroscopy analyses of two 1,3,4-thiadiazole analogues, i.e. 4-(5-methyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (C1) and 4-(5-heptyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (C7) in an aqueous medium containing different concentrations of hydrogen ions. An interesting dual florescence effect was observed when both compounds were dissolved in aqueous solutions at pH below 7 for C1 and 7.5 for C7. In turn, for C1 and C7 dissolved in water at pH higher than the physiological value (mentioned above), single fluorescence was only noted. Based on previous results of investigations of the selected 1,3,4-thiadiazole compounds, it was noted that the presented effects were associated with both conformational changes in the analysed molecules and charge transfer (CT) effects, which were influenced by the aggregation factor. However, in the case of C1 and C7, the dual fluorescence effects were visible in a higher energetic region (different than that observed in the 1,3,4-thiadiazoles studied previously). Measurements of the fluorescence lifetimes in a medium characterised by different concentrations of hydrogen ions revealed clear lengthening of the excited-state lifetime in a pH range at which dual fluorescence effects can be observed. An important finding of the investigations presented in this article is the fact that the spectroscopic effects observed not only are interesting from the cognitive point of view but also can help in development of an appropriate theoretical model of molecular interactions responsible for the dual fluorescence effects in the analysed 1,3,4-thiadiazoles. Furthermore, the study will clarify a broad range of biological and pharmaceutical applications of these compounds, which are more frequently used in clinical therapies. Graphical Abstract Upper left corner - C7 molecule at high pH, right upper corner - fluorescence emission spectrum for C7 dissolved in H2O at high pH (7-12) - single fluorescence. Bottom left corner - C7 molecule at low pH (1-7), lower right corner - fluorescence emission spectrum for C7 dissolved in water at low pH - two fluorescence emissions. The circles indicate the group related to dissociation of molecules at low and high pH and the additional long circles indicate C1 or a molecule with a shorter acyl chain.

Effect of Solvent Polarizability on the Keto/Enol Equilibrium of Selected Bioactive Molecules from the 1,3,4-Thiadiazole Group with a 2,4-Hydroxyphenyl Function.

Three novel 1,3,4-tiadiazole-derived compounds with biological-activity, i.e., 4-(5-(methylamino)-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (MDFT), 4-(5-(phenylamino)-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (PhATB), and 4-(5-(4-chlorophenylamino)-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (4-CIPhATB) were characterized with the use of several spectroscopic methods. Detailed UV-vis studies revealed keto/enol tautomerism of the examined compounds. The absorption spectra recorded in nonpolar solvents exhibited bands that were characteristic of keto tautomers, while in polar solvents the enol form is predominant. A number of spectra revealed the presence of both tautomeric forms in the solution. The keto/enol equilibria observed were both solvent- and temperature-dependent. The keto/enol equilibrium was also observed using FTIR spectroscopy. A detailed analysis of the spectroscopic data leads to a conclusion that the solvent-induced tautomerism of the selected compounds from the 1,3,4-thiadiazole group does not depend on the electric dipole moment of the solvent but more likely on its average electric polarizability. Additionally, a clear effect of the substituent present in the molecule on the tautomeric equilibrium in the selected 1,3,4-thiadiazole analogues was noted.

QSAR models of antiproliferative activity of imidazo[2,1-b][1,3,4]thiadiazoles in various cancer cell lines.

Imidazo[2,1-b][1,3,4]thiadiazoles have been recognized to possess antiproliferative potency towards a wide spectrum of cancer cell lines. QSAR investigations on a set of 42 di(tri)substituted imidazo[2,1-b][1,3,4]thiadiazoles were carried out to find the descriptors determining their biological potency. Three-variable equations were obtained by combinatorial protocols in multiple linear regression (CP MLR) for all three studied cancer cell lines. They showed that lipophilicity, electronic, and steric factors are decisive for the antiproliferative potency of compounds and indicate the important role of nitrogen atoms of imidazothiadiazole ring in the interactions with the molecular target. The best models gave high r squared values in the range from 0.887 to 0.924. They also have good predictive accuracy confirmed by the high value LOO cross-validation coefficient [Formula: see text] (from 0.842 to 0.904) and by the external validation quantities.

Molecular Organization of Dipalmitoylphosphatidylcholine Bilayers Containing Bioactive Compounds 4-(5-Heptyl-1,3,4-thiadiazol-2-yl) Benzene-1,3-diol and 4-(5-Methyl-1,3,4-thiadiazol-2-yl) Benzene-1,3-diols.

This article presents the results of spectroscopic studies of two compounds from the 1,3,4-thiadiazole group, that is, 4-(5-methyl-1,3,4-thiadiazole-2-yl)benzene-1,3-diol (C1) and 4-(5-heptyl-1,3,4-thiadiazole-2-yl)benzene-1,3-diol (C7), present at different molar concentrations in 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) liposome systems. In the case of both investigated compounds, fluorescence measurements revealed the presence of several emission bands, whose appearance is related to the molecular organization induced by changes in the phase transition in DPPC. On the basis of the interpretation of Fourier transform infrared spectra, we determined the molecular organization of the analyzed compounds in multilayers formed from DPPC and the 1,3,4-thiadiazoles. It was found that the compound with a longer alkyl substituent both occupied the lipid polar head region in the lipid multilayer and interacted with lipid hydrocarbon chains. In turn, the compound with a shorter alkyl substituent interacted more strongly with the membrane polar region. On the basis of the knowledge from previous investigations conducted using different solvents, the fluorescence effects observed were related to the phenomenon of molecular aggregation. The effects were strongly influenced by the structure of the compound and, primarily, by the type of the alkyl substituent used in the molecule. The substantial shortening of fluorescence lifetimes associated with the effect of long-wave emission (with a maximum at 505 nm) decay also confirms the model of aggregation effects in the analyzed systems. Similar effects can be very easily distinguished and associated with respective forms of the compounds in biologically relevant samples.

Solvent Effects on Molecular Aggregation in 4-(5-Heptyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol and 4-(5-Methyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol.

The article presents the results of spectroscopic studies of 4-(5-methyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (C1) and 4-(5-heptyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (C7) in organic solvent solutions. Depending on the concentration of the compound used, three bands were observed in the fluorescence emission spectra of the compounds in DMSO solutions. A single band was observed in methanol, propan-2-ol, or ethanol. The significantly shortened fluorescence lifetimes and the different shapes of circular dichroism (CD) spectra clearly indicate association of the fluorescence effects with the aggregation processes in the analyzed compounds. The differences in the course of the CD spectra also imply an effect of the substituent group structure on the molecule aggregation interactions. Therefore, it has been postulated that the occurrence of the different spectral forms induced by changes in the compound concentration may be related to the aggregation effects of C1 and C7 molecules, which are also induced by differences in the alkyl substituent structure.

Synthesis and antiproliferative activity of some N'-substituted 2,4-dihydroxybenzothiohydrazides.

The paper shows that new N'-substituted 2,4-dihydroxybenzocarbothiohydrazides are able to inhibit the in vitro proliferation of human tumor cell lines. The compounds were prepared by the reaction of sulfinylbis[(2,4-dihydroxyphenyl)methanethione] (STB) or its analogs with the hydrazines. The panel of N'-substitution included aryl, pyridinyl and pyrimidinyl rings. The highest antiproliferative activity for N'-(4-(4-chlorophenyl)-6-(trifluoromethyl)pyrimidin-2-yl)-5-ethyl-2,4-dihydroxybenzothiohydrazide (5b) was found. The antiproliferative potency of some compounds was similar to that of cisplatin. Analogs with the Et substituent on benzenediol moiety displayed higher potency than with the unsubstituted one. The influence of N'-substitution on antiproliferative activity of compounds was discussed.

New derivative of 2-(2,4-dihydroxyphenyl)thieno-1,3-thiazin-4-one (BChTT) elicits antiproliferative effect via p38-mediated cell cycle arrest in cancer cells.

2-(2,4-Dihydroxyphenyl)thieno-1,3-thiazin-4-ones are a group of new compounds with potential anticancer activity. This type of derivatives was poorly investigated in the area of synthesis and biological activities. In the present study the antiproliferative action of the most active derivative BChTT was described. The aim of biological evaluation was to investigate the ability of the compound to inhibit cancer cell proliferation and identify mechanism involved in its action on the molecular level. BChTT inhibited the proliferation of lung cancer A549, colon cancer HT-29 and glioma C6 cells in the concentration-dependent manner. It was not toxic to normal cells including skin fibroblasts, hepatocytes and oligodendrocytes in the antiproliferative concentrations. BChTT decreased the DNA synthesis in the treated cancer cells and induced cell cycle arrest in the G0/G1 phase. Moreover, the ability of the compound to activate p38 kinase and decrease cyclin D1 expression was estimated. Participation of p38 kinase in the antiproliferative action of the compound was confirmed by the analysis of BChTT activity in the cells with the p38 silenced gene. The obtained results may suggest the ability of the tested derivative to inhibit cancer cells proliferation by induction of p38-mediated cyclin D1 downregulation.

IN VITRO ANTIFUNGAL ACTIVITY OF 2,4-DIHYDROXY-N-(3-THIOXO-3H- 1,2,4-DITHIAZOL-5-YL)BENZENECARBOTHIOAMIDE.

An increase in infections due to non albicans species of Candida has been observed in the recent years. The aims of this study were to determine the antifungal activity of 2,4-dihydroxy-N-(3-thioxo-3H-l1,2,4-dithiazol-5-yl)benzenecarbothioamide (DNTDB) against C. albicans, non-C. albicans, dermatophytes, and molds and to evaluate the enzymatic activity of C. albicans strains. We used reference strans C. albicans 10231 ATCC, 200 C. albicans strains, 100 non-C. albicans, 19 dermatophyte strains, and 21 mold strains isolated from different ontocenoses from patients. DNTDB revealed a mean minimum inhibitory concentration (MIC) of 12.5 pg/mL against the reference C. albicans 10231 ATCC strain on Sabouraud agar (SA) and of 6.5 pg/mL on Roswell Park Memorial Institute (RPMI) medium. The mean MIC for C. albicans isolates was of 22.01 ± 7.5 µg/mL on SA, 17.8 ± 7.4 µg/mL on yeast nitrogen base (YNB), and 16.9 ± 7.9 µg/mL on RPMI medium. The mean MIC for non-C. albicans isolates was of 22.4 ± 12.4 µg/mL on SA, 18.2 ± 8.6 µg/mL on YNB and 15.2 ± 9.03 sg/mL on RPMI. Against Trichophyton mentagrophytes v. granulosum, the mean MIC was 10.9 ± 2.04 µg/mL after 5 days of incubation and 21.9 ± 3.8 µg/mL after 15 days, while Trichophyton mentagrophytes . inteiligitale showed a mean MIC of 13.3 ± 5.5 µg/mL and of 20.3 ± 6.1. µg/mL after the same incubation periods, respectively. DNTDB manifested a MIC over the test range of 25-100 µg/mL for molds after 5 days of incubation and inhibited the enzymatic activity of Candida strains. It seems, the new DNTDB demonstrates potential antifungal activity against yeast-like fungus strains, dermatophytes, and molds in vitro.

In Search of the Antimicrobial Potential of Benzimidazole Derivatives.

A broad series of 4,5,6,7-tetrahalogenated benzimidazoles and 4-(1H-benzimidazol-2-yl)-benzene-1,3-diol derivatives was tested against selected bacteria and fungi. For this study three plant pathogens Colletotrichum sp., Fusarium sp., and Sclerotinia sp., as well as Staphylococcus sp., Enterococcus sp., Escherichia sp., Enterobacter sp., Klebsiella spp. , and Candida spp. as human pathogens were used. MIC values and/or area of growth reduction method were applied in order to compare the activity of the synthesized compounds. From the presented set of 22 compounds, only 8, 16, 18 and 19 showed moderate to good inhibition against bacterial strains. Against Candida strains only compound 19 with three hydroxyl substituted benzene moiety presented high inhibition at nystatin level or lower.

SYNTHESIS AND BIOLOGICAL ACTIVITY OF NOVEL N,N-CYCLIC-2,4-DIHYDROXYTHIOBENZAMIDE DERIVATIVES.

A series of novel N,N-cyclic-2,4-dihydroxythiobenzamide derivatives is described. Test compounds were formed by the reaction of the commercially available reagents with sulfinylbis[(2,4-dihydroxyphenyl)methanethione] (STB). The chemical structures were confirmed by IR, 1H NMR, 13CNMR, EI-MS, and elemental analysis. For the estimation of potential activity in vitro, the MIC values against strains of Candida were determined. Antifungal properties of selected compounds under in vitro conditions against five phytopathogenic fungi were estimated. Furthermore, the antiproliferative activity against the HCV29T cancer cell lines has been studied. These compounds exhibited antiproliferative activity in the range of 33.98-10.51 µg/mL.