The potential of compounds isolated from Xylaria spp. as antifungal agents against anthracnose

ABSTRACT Anthracnose is a crop disease usually caused by fungi in the genus Colletotrichum or Gloeosporium. These are considered one of the main pathogens, causing significant economic losses, such as in peppers and guarana. The current forms of control include the use of resistant cultivars, sanitary pruning and fungicides. However, even with the use of some methods of controlling these cultures, the crops are not free of anthracnose. Additionally, excessive application of fungicides increases the resistance of pathogens to agrochemicals and cause harm to human health and the environment. In order to find natural antifungal agents against guarana anthracnose, endophytic fungi were isolated from Amazon guarana. The compounds piliformic acid and cytochalasin D were isolated by chromatographic techniques from two Xylaria spp., guided by assays with Colletotrichum gloeosporioides. The isolated compounds were identified by spectrometric techniques, as NMR and mass spectrometry. This is the first report that piliformic acid and cytochalasin D have antifungal activity against C. gloeosporioides with MIC 2.92 and 2.46 µmol mL-1 respectively. Captan and difenoconazole were included as positive controls (MIC 16.63 and 0.02 µmol mL-1, respectively). Thus, Xylaria species presented a biotechnological potential and production of different active compounds which might be promising against anthracnose disease.

Antifungal activity of Gallesia integrifolia fruit essential oil

ABSTRACT Gallesia integrifolia (Phytolaccaceae) is native to Brazil and has a strong alliaceous odor. The objective of this study was to identify the chemical composition of G. integrifolia fruit essential oil and evaluate fungicidal activity against the main food-borne diseases and food spoilage fungi. The essential oil was extracted by hydrodistillation and identified by GC-MS. From 35 identified compounds, 68% belonged to the organosulfur class. The major compounds were dimethyl trisulfide (15.49%), 2,8-dithianonane (52.63%) and lenthionine (14.69%). The utilized fungi were Aspergillus fumigatus, Aspergillus niger, Aspergillus ochraceus, Aspergillus versicolor, Penicillium funiculosum, Penicillium ochrochloron, Penicillium verrucosum var. cyclopium, and Trichoderma viride. Minimal fungicidal concentration for the essential oil varied from 0.02 to 0.18 mg/mL and bifonazole and ketoconazole controls ranged from 0.20 to 3.50 mg/mL. The lower concentration of the essential oil was able to control P. ochrochloron, A. fumigatus, A. versicolor, A. ochraceus and T. viride. This study shows a high fungicidal activity of G. integrifolia fruit essential oil and can support future applications by reducing the use of synthetic fungicides.

Efficacy of Origanum essential oils for inhibition of potentially pathogenic fungi / Eficácia de Origanum óleos essenciais para a inibição de fungos potencialmente patogênicos

This study aimed to assess the efficacy of O. vulgare L. and O. majorana L. essential oil in inhibiting the growth and survival of potentially pathogenic fungal strains and also sought to evaluate the possible mechanisms involved in the establishment of the antifungal property of the tested essential oils through assays of osmotic stability and morphogenesis. Test strains included in this study were Candida albicans ATCC 7645, C. tropicalis LM-14, C. krusei LM-09, Cryptococcus neoformans FGF-5, Aspergillus flavus LM-02, A. fumigatus IPP-21, T. rubrum ATCC 28184, T. mentagrophytes LM-64, Microsporum gypseum ATCC 184, M. canis LM-36 and Cladosporium herbarium ATCC 26362. O. vulgare essential oil presented a MIC value of 80 µL/mL, while for O. majorana this was 160 µL/mL. C. krusei LM-09 was the only strain resistant to all assayed concentrations of both essential oils. O. vulgare and O. majorana essential oil at their MIC values provided a cidal effect against C. albicans ATCC 7645 after 4 h of exposure. O. vulgare essential oil at 80 µL/mL exhibited 100 percent inhibition of the radial mycelia growth of T. rubrum ATCC 28184 and M. canis LM-36 for 14 days. Assayed fungus strain protected by sorbitol (osmo-protectant agent) grew in media containing higher concentrations of O. vulgare and O. majorana essential oil in comparison to media without sorbitol, suggesting some specificity of these essential oils for targeting cell wall in the fungi cell. Main morphological changes observed under light microscopy provided by the essential oil of O. vulgare in A. flavus LM-02 were decreased conidiation, leakage of cytoplasm, loss of pigmentation and disrupted cell structure indicating fungal wall degeneration. These results suggest that essential oils from Origanum could be regarded as a potential antifungal compound for controlling the growth of pathogen fungi and the occurrence of mycoses.

O objetivo deste estudo foi observar a eficácia do óleo essencial de O. vulgare L. e O. majorana L. na inibição do crescimento e sobrevivência de cepas de fungos potencialmente patogênicas, bem como avaliar os possíveis mecanismos envolvidos no estabelecimento da propriedade antifúngica dos óleos essenciais testados através do ensaio de estabilidade osmótica e morfogênese. As cepas fúngicas utilizadas neste estudo foram Candida albicans ATCC 7645, C. tropicalis LM-14, C. krusei LM-09, Cryptococcus neoformans FGF-5, Aspergillus flavus LM-02, A. fumigatus IPP-21, T. rubrum ATCC 28184, T. mentagrophytes LM-64, Microsporum gypseum ATCC 184, M. canis LM-36 e Cladosporium herbarium ATCC 26362. O óleo essencial de O. vulgare apresentou valor de CIM de 80 µL/mL, enquanto o óleo essencial de O. majorana apresentou valor de CIM de 160 µL/mL. C. krusei LM-09 apresentou-se como a única cepa resistente a todas as concentrações ensaiadas de ambos os óleos essenciais. Os óleos essenciais testados quando ensaiadas em seu valor de CIM causaram um efeito fungicida contra C. albicans ATCC 7645 após 4 h de exposição. O óleo essencial de O. vulgare na concentração de 80 µL/mL exibiu uma total inibição do crescimento micelial radial de T. rubrum ATCC 28184 e M. canis LM-36 ao longo de 14 dias. As cepas fúngicas ensaiadas quando tratadas com sorbitol (agente osmo-protetor) foram capazes de crescer em meio adicionado de mais altas concentrações dos óleos essenciais quando comparados ao meio não adicionado de sorbitol, sugerindo especificidade destes produtos a parede celular como alvo na célula fúngica. As principais alterações causadas pelo óleo essencial de O. vulgare sobre a morfologia de A. flavus LM-02 foram diminuída conidiação, perda de citoplasma, perda de pigmentação e ruptura da estrutura celular indicando degeneração da parede celular fúngica. Estes resultados sugerem que óleos essenciais de espécies de Origanum poderiam ser considerados como potenciais antifúngicos para ...

Persistence and degradation of metalaxyl, mancozeb fungicides and its metabolite ethylenethiourea in soils.

The degradation pattern of metalaxyl, mancozeb and its metabolite ethylenethiourea (ETU) residues indicated a close correspondence to first order exponential degradation kinetics in soils. Degradation of fungicides in soils was predominantly biological as well as chemical in nature. Slower degradation ofmetalaxyl was noticed in the soils and their half-life values were higher than mancozeb and ETU as evident by wide range of half-life values from 41.24 to 165.11 days. In case of metalaxyl, Hiriyur soil was found to be superior in degrading the metalaxyl. Lower persistence of mancozeb and ETU was observed in soils resulting in rapid rate of degradation at smaller half-life values as compared to metalaxyl indicating the faster degradation of mancozeb and ETU. In mancozeb applied soils, the ETU formation was increased up to 30 days of incubation and thereafter it declined. Amongsoils, degradation of either mancozeb or ETU is not influenced by soil types. However, mancozeb persistence was higher in Hiriyur soils than Chettalli and Bangalore soils.

Properties of a new fungal ß-Galactosidase with potential application in the dairy industry

ß-Galactosidase or ß-D-galactohydrolase (EC.3.2.1.23) is an important enzyme industrially used for the hydrolysis of lactose from milk and milk whey for several applications. Lately, the importance of this enzyme was enhanced by its galactosyltransferase activity, which is responsible for the synthesis of transgalctosylated oligosaccharides (TOS) that act as functional foods, with several beneficial effects on consumers. Penicillium simplicissimum, a strain isolated from soil, when grown in semi-solid medium showed good productivity of ß-galactosidase with galactosyltransferase activity. The optimum pH for hydrolysis was in 4.0-4.6 range and the optimum pH for galactosyltransferase activity was in the 6.0-7.0 range. The optimum temperature for hydrolysis and transferase activity was 55-60§C and 50§C, respectively, and the enzyme showed high thermostability for the hydrolytic activity. The enzyme showed a potential for several industrial applications such as removal of 67 (per cent) of the lactose from milk and 84 (per cent) of the lactose from milk whey when incubated at their original pH (4.5 and 6.34, respectively) under optimum temperature conditions. When incubated with a 40 (per cent) lactose solution in 150 mM McIlvaine buffer, pH 4.5, at 55§C the enzyme converted 86.5 (per cent) of the lactose to its component monosaccharides. When incubated with a 60 (per cent) lactose solution in the same buffer but at pH 6.5 and 50§C, the enzyme can synthetize up to 30.5 (per cent) TOS, with 39.5 (per cent) lactose and 30 (per cent) monosaccharides remaining in the preparation.