Mannan changes induced by 3-methyl-5-aminoisoxazole-4-thiocyanate, a new azole derivative, on Epidermophyton floccosum

The synthetic and therapeutic expedition of isoxazole and its analogs

Isoxazole, constituting an important family of five-membered heterocycles with one oxygen atom and one nitrogen atom at adjacent positions is of immense importance because of its wide spectrum of biological activities and therapeutic potential. It is, therefore, of prime importance that the development of new synthetic strategies and designing of new isoxazole derivatives should be based on the most recent knowledge emerging from the latest research. This review is an endeavor to highlight the progress in the chemistry and biological activity of isoxazole derivatives which could provide a low-height flying bird's eye view of isoxazole derivatives to the medicinal chemists for the development of clinically viable drugs using this information.

3-Phenylisoxazolin-5-one: a redetermination

The structure of the title molecule, C9H7NO2, has been redetermined to improved precision and the H atoms located [Cannaset al.(1969).Acta Cryst.B25, 1050]. The five-membered ring is almost planar (r.m.s. deviation = 0.006 Å) and subtends a dihedral angle of 2.45 (6)° with the benzene ring. In the crystal, molecules form ribbons running parallel to thea-axis direction through a combination of C—H...N and C—H...O hydrogen bonds. `Stair-step' offset π–π stacking interactions are also observed.

A Multi-Target Approach toward the Development of Novel Candidates for Antidermatophytic Activity: Ultrastructural Evidence on α-Bisabolol-Treated Microsporum gypseum

Multi-target strategies are directed toward targets that are unrelated (or distantly related) and can create opportunities to address different pathologies. The antidermatophytic activities of nine natural skin lighteners: α-bisabolol, kojic acid, β-arbutin, azelaic acid, hydroquinone, nicotinamide, glycine, glutathione and ascorbyl tetraisopalmitate, were evaluated, in comparison with the known antifungal drug fluconazole, on nine dermatophytes responsible for the most common dermatomycoses: Microsporum gypseum, Microsporum canis, Trichophyton violaceum, Nannizzia cajetani, Trichophyton mentagrophytes, Epidermophyton floccosum, Arthroderma gypseum, Trichophyton rubrum and Trichophyton tonsurans. α-Bisabolol showed the best antifungal activity against all fungi and in particular; against M. gypseum. Further investigations were conducted on this fungus to evaluate the inhibition of spore germination and morphological changes induced by α-bisabolol by TEM.

Efficacy of some synthesized thiazoles against dermatophytes

Twelve thiazoles and their fused derivatives were tested for their antimicrobial activity against Trichophyton rubrum, T. terrestre, Epidermophyton floccosum, and Microsporum gypseum. Most of the synthesized compounds were inhibitory to the tested fungi. The most effective compound was 5-(4-ethoxybenzylidene-4,5-dihydro-4-oxothiazol-2-yl)-N,3-diphenylbut-2-namide (3c) followed by 2-(4-oxo-4,5-dihydrothiazol-2-yl)-3-phenyl-but-2-enoic acid-(3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophen-2-yl)-amide (2b). These compounds were more efficacious than terbinafine, the reference drug. The tested compounds caused variable reduction in the activity of keratinase of the dermatophytes, depending on the azole derivative and the test fungus. Thiazole derivatives (2b) and (3c) exhibited the highest efficacy in decreasing ergosterol biosynthesis of the tested dermatophytes. The treatment of guinea pigs with compound (3c) induced complete curing in the case of all the test dermatophytes 30days post-treatment. The percent curing for compounds (3c) and (2b) was better than the reference drug.

Stereospecific synthesis of new steroidal isoxazoles in dry media

An easy and fast procedure was developed for one-pot synthesis of steroidal isoxazoles starting from 23-acetylsapogenins derivatives in presence of P2O5/SiO2 in dry media under microwaves irradiation is described. Substrates of the 25S and 25R series were used as raw materials, establishing that this new methodology is applicable to both series.

Antidermatophytic activity of pyrazolo[3,4-c]isothiazoles: a preliminary approach on 4-chlorophenyl derivative for evaluation of mutagenic and clastogenic effects on bacteria and human chromosomes in vitro

The antifungal activity of eight pyrazolo[3,4-c]isothiazole derivatives was evaluated on five dermatophytes: three were of an anthropophilic species (i.e., Epidermophyton floccosum, Trichophyton rubrum, and Trichophyton tonsurans) and two were of a geophilic species (i.e., Microsporum gypseum and Nannizzia cajetani). The new compounds proved to be unlikely effective in inhibiting the growth of the different strains. In general, the fungi parasitic on man were more sensitive than the geophilic species. This fact can be positive for a possible practical-therapeutic utilization of this class of compounds. To verify their possible use against fungi of medical interest, the most interesting substance at low doses, 6-(4-chlorophenyl)-4-methyl-6H-pyrazolo[3,4-c]isothiazol-3-amine, was chosen to perform in vitro genotoxicity tests using the following: Salmonella/microsome test (SAL), sister chromatid excange test (SCE), cytokinesis-blocked micronucleus test (CBMN), and its improvement (Ara-C/CBMN). The compound showed no mutagenic activity at low doses, whereas at the highest dose (100 µg/mL), it caused a generalized cytotoxic effect. The high growth inhibition exerted on fungi at the lowest dose and the concomitant lack of genotoxicity, at least until the dose of 50 µg/mL, might suggest the compound as a safe candidate as an antidermatophytic substance.

Pyrazolo[3,4-c]isothiazole and isothiazolo[4,3-d]isoxazole derivatives as antifungal agents

CONTEXT

The diseases of plants and humans due to pathogenic fungi are increasing. Among the substances used to combat fungi, the azoles are of primary interest, both in agricultural field both in health. To avoid fungal resistance phenomena, the synthesis and tests of new derivatives are necessary.

OBJECTIVE

This article discusses the synthesis and the antifungal activity of pyrazolo[3,4-c]isothiazole and isothiazolo[4,3-d]isoxazole derivatives against three fungi that are pathogenic only for plants and two fungi that are opportunistic in humans and plants.

MATERIALS AND METHODS

The compounds were prepared starting from 2-cyano-3-ethoxy-2-butenethioamide. The antifungal activity of the compounds was determined by measuring the inhibition of growth of the fungi tested at 20, 50, and 100 µg/mL in comparison with the controls.

RESULTS

Results demonstrated that several compounds were able to control the mycelial growth of the tested fungi, even if they showed different sensitivity to the different azole-derivatives. In general Magnaporthe grisea (T.T. Hebert) Yaegashi & Udagawa was the most sensitive fungus, being blocked almost entirely by 4-chloro derivative even at 20 µg/mL, a concentration at which the reference commercial compound tricyclazole was nearly ineffective.

DISCUSSION AND CONCLUSION

These findings demonstrate that the pyrazolo[3,4-c]isothiazole derivatives have a wide spectrum of activity on phytopathogenic and opportunistic fungi. In particular the 4-chloro derivative seems to have a great potential as new product to combat M. grisea in the agricultural field.

A new fluorescent chemosensor for fluoride anion based on a pyrrole-isoxazole derivative

Molecules containing polarized NH fragments that behave as anion-binding motifs are widely used as receptors for recognition and sensing purposes in aprotic solvents. We present here a new example of a receptor, 3-amino-5-(4,5,6,7-tetrahydro-1H-indol-2-yl)isoxazole-4-carboxamide (receptor 1), which contains pyrrole, amide and amino subunits. This receptor shows both changes in its UV–vis absorption and fluorescence emission spectra upon the addition of F⁻, resulting in highly selectivity for fluoride detection over other anions, such as Cl⁻, Br⁻, I⁻, HSO₄⁻, H₂PO₄⁻ and AcO⁻ in CH₃CN. ¹H NMR titration, time-dependent density functional theory (TDDFT) calculations and other experiments confirm that the sensing process is brought about by deprotonation of the pyrrole-NH in receptor 1.

Three new species of Aspergillus from Amazonian forest soil (Ecuador)

From an undisturbed natural forest soil in Ecuador, three fungal strains of the genus Aspergillus were isolated. Based on molecular and morphological features they are described as three new species, named A. quitensis, A. amazonicus, and A. ecuadorensis.

Synthetic pyrazole derivatives as growth inhibitors of some phytopathogenic fungi

The present study was carried out to investigate the antifungal activity of pyrazole/isoxazole-3-carboxamido-4-carboxylic acids, 4-oxo-5-substituted pyrazolo[3,4-d]pyrimidine-6-thiones, and N-alkyl/aryl-N'-(4-carbethoxy-3-pyrazolyl)thioureas against Pythium ultimum, Botrytis cinerea, and Magnaporthe grisea. The results on growth inhibition showed differences in the sensitivity of the three fungi to the tested substances, and in general P. ultimum was shown to be the most sensitive. On all phytopathogens the best results within the pyrazole/isoxazolecarboxamide series are given by the compounds with the carboxamide and carboxylic groups in positions 3 and 4; the presence of these groups seems to be critical for biological activity in this series of compounds. Among the pyrazolopyrimidines the derivative supplied with the benzylic group was the most active on the three fungi and in particular against P. ultimum. Several compounds belonging to the thiourea series are able to inhibit selectively M. grisea at 50 and 10 microg mL(-1), doses at which the reference commercial compound tricyclazole had low or no effect.

Emerging antifungal azoles and effects on Magnaporthe grisea

Derivatives of pyrazolo[1,5-a][1, 3, 5]triazine-2,4-dione,pyrazolo[1,5-c][1, 3, 5]thiadiazine-2-one, pyrazolo[3,4-d][1, 3]thiazine-4-one, and pyrazolo[3,4-d][1, 3]thiazine-4-thione were screened for antifungal activity against the causal agent of rice blast disease, Magnaporthe grisea. The compounds were tested at doses ranging from 10 to 200mugml(-1), using the commercial fungicide tricyclazole as reference compound. All triazine derivatives inhibited the growth and pigmentation of the mycelia less effectively than tricyclazole. The thiadiazine derivatives proved to be more effective than their triazine counterparts, but only 4-(butylimino)-7-methylpyrazolo[1,5-c][1,3,5]thiadiazine-2-one (2h) and 4-(cyclohexylimino)-7-methylpyrazolo[1,5-c][1,3,5]thiadiazine-2-one (2j) were more effective than tricyclazole. Pyrazolo[3,4-d][1,3]thiazine-4-one derivatives were active only at the highest doses, whereas members of the pyrazolo[3,4-d][1,3]thiazine-4-thione series inhibited fungal growth at the lowest concentrations used, at which tricyclazole had no effect. A dose-dependent mechanism might be responsible for this effect, with lipophilicity as the governing factor. Within a given set, the presence of a cyclohexyl or an n-butyl group generally increased antifungal activity, with respect to both growth inhibition and cell de-pigmentation of the mycelium, suggesting that a higher lipophilicity might improve transport inside the cells. SEM and TEM of M. grisea hyphae showed that treatment with the most active substance (2h) caused significant ultrastructural effects, particularly on the endomembrane system, suggesting a mechanism of action similar to that of most azole fungicides. Dissimilarities were also observed, with no alterations of the cell wall evident. In conclusion, several compounds showed greater inhibition than tricyclazole, and therefore provide useful new chemistry for control of M. grisea infections.

Chicory extracts from Cichorium intybus L. as potential antifungals

In this work extracts from roots of the common vegetable Cichorium intybus L., highly appreciated for its bitter taste, were studied to investigate their possible biological activity on fungi from a variety of ecological environments: some are parasites on plants (phytopathogens) or of animals and humans (zoophilic and anthropophilic dermatophytes), others live on the soil and only seldom parasitize animals (geophilic dermatophytes). The extracts were ineffective on geophilic species and on tested phytopathogens, with the exception of Pythium ultimum, whereas they inhibited the growth of zoophilic and anthropophilic dermatophytes, in particular Trichophyton tonsurans var. sulfureum, whose treatment caused morphological anomalies, here observed by scanning electron microscopy. This behaviour is discussed on the basis of the presence in the chicory extract of the two main sesquiterpene lactones, 8-deoxylactucin and 11 beta,13-dihydrolactucin.

Synthesis and antifungal action of new tricyclazole analogues

Melanins are very important pigments for the survival and longevity of fungi, so their biosynthesis inhibition is a new biochemical target aiming at the discovery of selective fungicides. In this work is described the synthesis of new pyrazolo-thiazolo-triazole compounds, analogues of tricyclazole (a commercial antifungal product that acts by inhibiting melanin synthesis), and their biological activity was studied on some dermatophytes and phytopathogens. The compounds poorly inhibited the growth and pigmentation of fungi tested and were less efficient than tricyclazole. Electron microscopy on Botrytis cinerea showed that treatment with the most active compound caused abnormally thickened and stratified walls in fungi, whose ultrastructure was, in contrast, generally normal. The fungus treated with tricyclazole, on the other hand, appeared to be drastically altered, so as to become completely disorganized. These results suggest that the new azole compounds employ an action mechanism similar to that of other azoles, but dissimilar to that of tricyclazole.