Antifungal and antioomycete activities and modes of action of isobenzofuranones isolated from the endophytic fungus Hypoxylon anthochroum strain Gseg1.

Hypoxylon species are distributed worldwide and have been isolated from different habitats. The endophyte Hypoxylon anthochroum strain Gseg1 was isolated from healthy leaves of Gliricidia sepium. A chemical study of the culture medium and mycelium organic extracts of the endophytic fungus H. anthochroum Gseg1 led to the isolation of three known isobenzofuranones, 7-hydroxy-4,6-dimethyl-3H-isobenzofuran-1-one, 1, 7-methoxy-4,6-dimethyl-3H-isobenzofuran-1-one, 2, 6-formyl-4-methyl-7-methoxy-3H-isobenzofuran-1-one, 3, and one compound was isolated for the first time as a natural product, 7-methoxy-4-methyl-3H-isobenzofuran-1-one, 4. In addition, the chemical synthesis of 1 and 2, and a derivative, 7-methoxy-6-methyl-3H-isobenzofuran-1-one, 5, was performed. The isobenzofuranones showed antifungal and antioomycete activities. Compounds 1-5 inhibited the growth of Fusarium oxysporum, Alternaria alternata, Pythium aphanidermatum, and Phytophthora capsici, in addition, 1, 2 and 5 interrupted the respiration and caused electrolyte leakage due to cell membrane damage. Compound 2 was the most active, inhibiting the growth of the four microorganisms, affecting the respiration and increasing the relative conductivity due to electrolyte leakage. Compounds 1-4 also induce morphological changes in the plant pathogens' mycelia and hyphae. These compounds could be useful for the control of plant pathogenic fungi and oomycetes of agricultural relevance.

Volatile organic compounds from Hypoxylon anthochroum endophytic strains as postharvest mycofumigation alternative for cherry tomatoes.

The antifungal activity and chemical composition of the volatile organic compounds (VOCs) produced by four Hypoxylon anthochroum endophytic strains were analyzed. The bioactivity of the VOCs synthesized at different periods of incubation on rice medium was assessed, both in vivo and in vitro, against the phytopathogen Fusarium oxysporum. The in vivo effect was evaluated on cherry tomatoes, while the mechanism of action was determined in vitro analyzing the phytopathogen's growth, respiration and cell membrane permeability. In general, the VOCs from all strains and incubation periods significantly inhibited the growth of F. oxysporum on cherry tomatoes with percentages over 50%. They significantly inhibited the pathogen growth and respiration, and altered the cell membrane permeability and hyphal morphology. The chemical composition was analyzed after solid phase microextraction. In total, 36 VOCs were identified in the four strains, mainly sesquiterpenes and monoterpenes. Among the monoterpenes, eucalyptol had the highest fiber affinity (>60% area) in three of the four strains studied; thus, it could be considered as a chemical marker for H. antochroum. Chemical markers are important for the identification and differentiation of species. The H. anthochroum strains are potential mycofumigation agents against postharvest diseases caused by F. oxysporum.

Secondary metabolites of endophytic Xylaria species with potential applications in medicine and agriculture.

Fungal endophytes are important sources of bioactive secondary metabolites. The genus Xylaria Hill (ex Schrank, 1789, Xylariaceae) comprises various endophytic species associated to both vascular and non vascular plants. The secondary metabolites produced by Xylaria species include a variety of volatile and non-volatile compounds. Examples of the former are sesquiterpenoids, esters, and alcohols, among others; and of the latter we find terpenoids, cytochalasins, mellein, alkaloids, polyketides, and aromatic compounds. Some of these metabolites have shown potential activity as herbicides, fungicides, and insecticides; others possess antibacterial, antimalarial, and antifungal activities, or α-glucosidase inhibitory activity. Thus metabolites from Xylaria are promising compounds for applications in agriculture for plague control as biopesticides, and biocontrol agents; and in medicine, for example as drugs for the treatment of infectious and non-infectious diseases. This review seeks to show the great value of the secondary metabolites of Xylaria, particularly in the agriculture and medicine fields.

Antifungal Volatile Organic Compounds from the Endophyte Nodulisporium sp. Strain GS4d2II1a: a Qualitative Change in the Intraspecific and Interspecific Interactions with Pythium aphanidermatum.

This study demonstrates volatile organic compounds (VOCs) production as one of the defense mechanisms of the antagonistic endophyte Nodulisporium sp. GS4d2II1a, and the volatile changes in two times of the fungal growth; and, as result of its intra and interspecific interactions with the plant pathogen Pythium aphanidermatum. The antifungal activity of the volatile and diffusible metabolites was evaluated by means of three types of antagonism bioassays and by organic extract agar dilution. VOCs were obtained by gas chromatography coupled to mass spectrometry from 3- and 5-day Nodulisporium sp. cultures, as well as from its interspecific in vitro antagonistic interaction with the oomycete P. aphanidermatum, and its intraspecific Nodulisporium sp.-Nodulisporium sp. interaction. The GS4d2II1a strain completely inhibited the growth of two fungi and seven oomycetes by replacing their mycelia in simple antagonism bioassays and by producing in vitro volatile and diffusible metabolites that acted synergistically in multiple antagonism bioassays. Additionally, VOCs inhibited the growth of three oomycetes and one fungus in antagonism bioassays using divided plates. A total of 70 VOCs were detected, mainly including mono and sesquiterpenes, especially eucalyptol and limonene. Multiple correspondence analysis revealed four different volatile profiles, showing that volatiles changed with the fungus age and its intra and interspecific interactions. The metabolites produced by Nodulisporium sp. GS4d2II1a could be useful for biological control of fungal and oomycetes plant pathogens of economically important crops.