Antifungal and new metabolites of Myrothecium sp. Z16, a fungus associated with white croaker Argyrosomus argentatus.

AIMS: Fungal infection is still a life-threatening risk for the immunocompromised population such as AIDS patients and those who receive treatments with immunosuppressors and/or frequent administrations of wide-spectrum antibiotics, which inevitably lead to the drug resistance and unbalanced microflora populations. The present work was accordingly performed to characterize more potent antifungal metabolites from various cultures of marine fungi residing in white croaker Argyrosomus argentatus. METHODS AND RESULTS: The three most common opportunistic human pathogens Candida albicans (CCCCM ID 00148), Aspergillus niger (CCCCM ACCC 30005) and Trichophyton rubrum (CCCCM ID 00001) were selected as test fungi. A total of 16 cultivable fungal strains were isolated from the variant tissues of Ar. argentatus collected from the Yellow Sea, followed by preliminary antifungal screenings of the EtOAc extracts of the corresponding cultures. As a result, the inhibition of the three target fungi, plus being allergic to isolators' skin, were discerned with the EtOAc extract of the fungus under the isolation number Z16 that was identified subsequently as Myrothecium sp. by a combination of morphological and 18S rDNA finger-typing characteristics. A follow-up bioassay fractionation of the EtOAc extract, in conjunction with spectral analyses [MS, (1)H-NMR, (13)C-NMR, distortionless enhancement by polarization transfer (DEPT), heteronuclear multiple quantum coherence (HMQC) and heteronuclear multiple bond resonance (HMBC)] wherever required, afforded eventually the characterization of a new acid (compound 1: 4,5-ditridecyl-octanedioic acid), three macrocyclic trichothecenes including roridin A (compound 2), verrucarin A (compound 3) and 8beta-acetoxy-roridin H (compound 4), (22E,24R)-cerevisterol (compound 5) and N-phenyl-beta-amino-naphthalene (compound 6). In vitro antifungal tests showed that the three trichothecenes were active against A. niger, T. rubrum and C. albicans with MICs of 31.25, 62.5 and 125 microg ml(-1) for compound 2, 250, 125 and 31.25 microg ml(-1) for compound 3 as well as 125, 62.5 and 125 microg ml(-1) for compound 4 respectively. The MICs of ketoconazole (co-assayed herewith as a positive reference) against A. niger, T. rubrum and C. albicans were 31.25, 250, 31.25 microg ml(-1) respectively. A preliminary structure-activity relationship of the antifungal trichothecenes was highlighted in brief. CONCLUSIONS: The present investigation demonstrated that marine fungus Myrothecium sp. Z16 associated with white croaker (Ar. argentatus), was an efficient producer of a new acid and antifungal trichothecenes, the latter presumably being also the allergic substances in the culture. SIGNIFICANCE AND IMPACT OF THE STUDY: The title marine fungus was investigated to be a resource of new aliphatic acid, and trichothecenes with potent antifungal and dermal toxic actions.

Aspergillus fumigatus CY018, an endophytic fungus in Cynodon dactylon as a versatile producer of new and bioactive metabolites.

Aspergillus fumigatus CY018 was recognized as an endophytic fungus for the first time in the leaf of Cynodon dactylon. By bioassay-guided fractionation, the EtOAc extract of a solid-matrix steady culture of this fungus afforded two new metabolites, named asperfumoid (1) and asperfumin (2), together with six known bioactive compounds including monomethylsulochrin, fumigaclavine C, fumitremorgin C, physcion, helvolic acid and 5alpha,8alpha-epidioxy-ergosta-6,22-diene-3beta-ol as well as other four known compounds ergosta-4,22-diene-3beta-ol, ergosterol, cyclo(Ala-Leu) and cyclo(Ala-Ile). Through detailed spectroscopic analyses including HRESI-MS, homo- and hetero-nuclear correlation NMR experiments (HMQC, COSY, NOESY and HMBC), the structures of asperfumoid and asperfumin were established to be spiro-(3-hydroxyl-2,6-dimethoxyl-2,5-diene-4-cyclohexone-(1,3')-5'-methoxyl-7'-methyl-(1'H, 2'H, 4'H)-quinoline-2',4'-dione) and 5-hydroxyl-2-(6-hydroxyl-2-methoxyl-4-methylbenzoyl)-3,6-dimethoxyl-benzoic methyl ester, respectively. All of the 12 isolates were subjected to in vitro bioactive assays against three human pathogenic fungi Candida albicans, Tricophyton rubrum and Aspergillus niger. As a result, asperfumoid, fumigaclavine C, fumitremorgin C, physcion and helvolic acid were shown to inhibit C. albicans with MICs of 75.0, 31.5, 62.5, 125.0 and 31.5 microg/mL, respectively.

Absolute configuration of keisslone, a new antimicrobial metabolite from Keissleriella sp. YS4108, a marine filamentous fungus.

In order to purify enough material for establishing the absolute stereochemistry of the new antifungal metabolite 3,6,8-trihydroxy-3-[3,5-dimethyl-2-oxo-3(E)-heptenyl]-2,3-dihydronaphthalen-1(4H)-one produced by Keissleriella sp., a marine filamentous fungus (strain number: YS 4108), a repeated growth and fractionation of the fungal culture was performed to give instead a new antimicrobial metabolite, keisslone (1), the structure of which was elucidated on the basis of spectral analyses including homo- and hetero-nuclear correlation NMR experiments (HMQC, COSY, NOESY and HMBC). The absolute configuration of metabolite 1 was determined mainly by its CD data and NOESY spectrum. The compound 1 was shown to be inhibitory against the human pathogenic fungi Candida albicans, Trichophyton rubrum and Aspergillus niger with MICs of 50, 70, 40 microg/mL, respectively. In order to purify enough material for establishing the absolute stereochemistry of the new antifungal metabolite 3,6,8-trihydroxy-3-[3,5-dimethyl-2-oxo-3(E)-heptenyl]-2,3-dihydronaphthalen-1(4 H)-one produced by Keissleriella sp., a marine filamentous fungus (strain number: YS 4108), a repeated growth and fractionation of the fungal culture was performed to give instead a new antimicrobial metabolite, keisslone (1), the structure of which was elucidated on the basis of spectral analyses including homo- and hetero-nuclear correlation NMR experiments (HMQC, COSY, NOESY and HMBC). The absolute configuration of metabolite 1 was determined mainly by its CD data and NOESY spectrum. The compound 1 was shown to be inhibitory against the human pathogenic fungi Candida albicans, Trichophyton rubrum and Aspergillus niger with MICs of 50, 70, 40 microg/mL, respectively.

Antifungal metabolite with a new carbon skeleton from Keissleriella sp. YS4108, a marine filamentous fungus.

In addition to four known metabolites (4-acetyl-6,8-dihydroxy-5-methylisocoumarin, 6,8-dihydroxy-3-methylisocoumarin, 6,8-dihydroxy-3,5,7-trimethylisocoumarin and 3,3'-oxy-(5-methyl)-phenol), bioassay-guided fractionation of the culture of Keissleriella sp., a marine filamentous fungus (strain number: YS 4108), afforded an antifungal metabolite with a new carbon skeleton whose structure was elucidated spectrometrically as 3,6,8-trihydroxy-3-[3,5-dimethyl-2-oxo-3(E)-heptenyl]-2,3-dihydronaphthalen-1(4H)-one. In vitro antifungal assays of all isolates revealed that the new metabolite and 3,3'-oxybis[5-methylphenol] were inhibitory to the growth of the human pathogenic fungi Candida albicans, Tricophyton rubrum and Aspergillus niger with MICs of the former being 40, 20 and 80 microg/ml, and those of the latter 10, 30 and 50 microg/ml, respectively.

Antifungal activity of Artemisia annua endophyte cultures against phytopathogenic fungi.

Artemisia annua, well recognized for its production of antimalarial drug artemisinin, is seldom attacked by any of phytopathogenic fungi, which could be partially associated with the presence of endophytes. Present investigation is aiming at disclosing whether the endophytes inside A. annua produce antifungal substances. A total of 39 endophytes were isolated and fermented, and the ferment broth was evaluated in vitro for the antifungal activity against crop-threatening fungi Gaeumannomyces graminis var. tritici, Rhizoctonia cerealis, Helminthosporium sativum, Fusarium graminearum, Gerlachia nivalis and Phytophthora capsici. These plant pathogens are still causing wheat take-all, sharp eyespot, common rot, scab, snow mould, and pepper phytophthora blight, respectively. Out of 39 endophytes investigated, 21 can produce in vitro substances that are inhibitory to all or a few of the tested phytopathogens whereas the rest yielded nothing active. Moreover, the most active broth of endophyte IV403 was extracted with EtOAc and n-butanol, and comparisons of the antifungal activity of the extracts indicated that the major active metabolites were EtOAc-extractable.

Metabolites of Colletotrichum gloeosporioides, an endophytic fungus in Artemisia mongolica.

A new antimicrobial metabolite, named colletotric acid (1), was isolated from a liquid culture of Colletotrichum gloeosporioides, an endophytic fungus colonized inside the stem of Artemisia mongolica. The structure was determined using spectroscopic methods (EIMS and FABMS,(1)H and (13)C NMR, (1)H-(1)H COSY, HMBC, and HMQC). Compound 1 inhibited the growth of Bacillus subtilis, Staphylococcusaureus, and Sarcina lutea with minimal inhibitory concentrations (MICs) of 25, 50, and 50 microg/mL, respectively, and the crop pathogenic fungus Helminthosporium sativum (MIC: 50 microg/mL).