[show abstract][hide abstract] ABSTRACT: Secondary metabolites produced by endophytic microorganisms can provide benefits to host plants, such as stimulating growth and enhancing the plant's resistance toward biotic and abiotic factors. During its life, a host plant may be inhabited by many species of endophytes within a restrictive environment. This condition can stimulate secondary metabolite production that improves microbial competition and may consequently affect both the neighboring microorganisms and the host plant. The interactions between the endophytes that co-habit the same host plant have been studied. However, the effect of these interactions on the host plant has remained neglected. When using mixed microbial cultures, we found that the endophytic fungus Alternaria tenuissima significantly increased the production of some polyketides, including antifungal stemphyperylenol in response to the endophytic Nigrospora sphaerica. Biological activity assays revealed that stemphyperylenol can cause cytotoxic effects against N. sphaerica, although no phytotoxicity was observed in the host plant Smallanthus sonchifolius, even at concentrations much higher than those toxic to the fungus. The polyketides produced by A. tenuissima may be important for the ecological relationships between endophyte-endophyte and endophytes-host plants in the natural environment.
Journal of Chemical Ecology 10/2013; · 2.46 Impact Factor
[show abstract][hide abstract] ABSTRACT: Smallanthus sonchifolius is a traditional Andean plant which has been cultured mainly in Brazil, Japan and New Zealand due to its medicinal properties. A study of the endophytic fungi associated to the plant was carried out in order to characterize new cytotoxic agents. Thirty two fungal strains were isolated and submitted to cultivation and extraction producing 186 extracts. Of these, 12% displayed moderate to high cytotoxic activities and were considered promising anticancer compound sources. The ethyl acetate fractions of Nigrospora sphaerica and Phoma betae liquid fermentations contained the synergistic compounds 8-hydroxy-6-methoxy-3-methylisocoumarin and (22E,24R)-ergosta-4,6,8(14),22-tetraen-3-one which are potential compounds for drug discovery. Another isolated compound, pimara-7,15-dien-3-beta-ol diterpene is being characterized for the first time through a detailed spectroscopic analysis including GC/MS, homo- and hetero-nuclear correlated NMR experiments (HMQC, HMBC, COSY and NOEdiff) along with its optical rotation.
Journal of Basic Microbiology 10/2008; 49(2):142-51. · 1.20 Impact Factor