Background: Endophytic fungi are considered a source of novel activities, compounds and biotechnological
processes with great and underexplored potential. The aims of this paper were: a) to evaluate the
antibiotic activity of mangrove endophytic fungi against the human pathogens Staphylococcus aureus,
Salmonela typhi and Escherichia coli and against the phytopathogen Xantomonas axonopodis citri; b) to
elucidate the structure of the antibiotic produced by the endophytic fungus Hypocrea virens strain 89(3),
using spectroscopic methods, mainly 1D and 2D NMR, as well as mass spectra and comparison with
previously published data.
Methods: The selection of the endophytic fungi producer of antibiotics was based on agar piece method.
The pure substance (viridiol) was obtained by carrying out biological tests with the extract and its fractions
against pathogenic bacteria (Escherichia coli), and this study was monitored by NMR spectroscopy.
Viridiol was isolated from the mangrove endophytic fungus H. virens, which was obtained from
branches of Avicennia nitida. The structure of the compound was elucidated by spectroscopic methods,
mainly 1D and 2D NMR spectroscopy and confirmed by mass spectrometry.
Results: In bioassays, compound viridiol showed antimicrobial activity against Escherichia coli, with an
MIC of 64 µg/ml. The antibiotic-producing strain was identified as H. virens using internal transcribed
spacer (ITS) sequence data. The spectroscopic methods employed were an efficient means of elucidating
the structure of antibiotic viridiol.
Conclusion: The isolation of a bioactive substance using 1H NMR monitoring was highly successful because
it showed step by step the spectral signals concerning the bioactive substance from crude extract
to pure substance. This is the first report of antimicrobial activity by viridiol against E. coli, a medically