The essential oil extracted by steam distillation from the capitula of Indian Tagetes patula, Asteraceae, was evaluated for its antifungal properties and analyzed by gas chromatography and gas chromatography-mass spectrometry. Thirty compounds were identified, representing 89.1% of the total detected. The main components were piperitone (24.74%), piperitenone (22.93%), terpinolene (7.8%), dihydro tagetone (4.91%), cis-tagetone (4.62%), limonene (4.52%), and allo-ocimene (3.66%). The oil exerted a good antifungal activity against two phytopathogenic fungi, Botrytis cinerea and Penicillium digitatum, providing complete growth inhibition at 10 microl/ml and 1.25 microl/ml, respectively. The contribution of the two main compounds, piperitone and piperitenone, to the antifungal efficacy was also evaluated and ultrastructural modifications in mycelia were observed via electron microscopy, evidencing large alterations in hyphal morphology and a multisite mechanism of action.

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.

Two series of new pyrazoles, namely six pyrazolo[1,5-a][1,3,5]triazine-2,4-dione and four pyrazolo[1,5-c][1,3,5]thiadiazine-2-one derivatives, were synthesized as potential inhibitors of the photosynthetic electron transport chain at the photosystem II level. The compounds were confirmed by 1H NMR, elemental, and IR analyses. Their biological activity was evaluated in vivo upon both the growth of blue-green algae and the photosynthetic oxygen evolution by eukaryotic algae and in vitro as the ability to interfere with light-driven reduction of ferricyanide by isolated spinach chloroplasts. Some compounds exhibited remarkable inhibitory properties, comparable to those of the reference commercial herbicides lenacil, diuron, and hexazinone. Results suggest that the substitution of triazine with thiadiazine ring may act as amplifier for herbicidal activity.

Methanol extract, obtained from Tagetes patula plant, was assayed against three phytopathogenic fungi: Botrytis cinerea, Fusarium moniliforme and Pythium ultimum. The antifungal activity was tested both in the dark and in the light, using two different lighting systems. The data showed that the extract proved to have a dose-dependent activity on all the fungi with a marked difference between treatments in the light than in the dark. Good growth inhibition was observed in fungi only when these were treated with the highest dose of the extract and irradiated, whereas the same dose gave only a modest inhibition when the experiment was conducted in the dark. At 5 and 10 microg/ml in the dark, growth increased. The results indicated that the presence of a luminous source enhances the antifungal activity, with small differences between UV-A and solar spectrum light. SEM and TEM observations on Pythium ultimum revealed that the Tagetes patula extract induced alterations on cell fungal membranes with a photoactivation mechanism possibly involving the production of free radicals and leading to a premature aging of the mycelium.

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.

No abstract

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

Protoanemonin, a component of Ranunculus bulbosus, was tested as an antifungal agent on selected strains of dermatophytes and yeasts. The minimum inhibitory concentrations ranged from 2.0 to 7.5 X 10(-4) M and the minimum lethal concentrations from 3.8 X 10(-4) M to greater than 1.0 X 10(-3) M. The most sensitive dermatophyte tested was Epidermophyton floccosum, and the most sensitive yeast Rhodotorula glutinis. The effects of different culture media and of light on the sensitivity of Rhodotorula glutinis to protoanemonin were also tested. Structural analogies between protoanemonin and other cytotoxic unsaturated lactones, and the reversal by the amino acid cysteine of the antifungal action suggest a possible mechanism of action.