Diversity of antimicrobial pyrenophorol derivatives from an endophytic fungus, Phoma sp.

Pyrenophorol (1) and (-)-dihydropyrenophorin (3), two known macrodiolides, were isolated together with four new analogues (2, 4-6) and three ring-opened derivatives (7-9) from Phoma sp., an endophytic fungus isolated from Lycium intricatum from Gomera. The structures of the new compounds were elucidated by detailed spectroscopic analysis, comparison with reported data, and chemical interconversion. The absolute configurations were determined by chemical correlations and a modified Mosher's method. The diversity of these seven newly discovered metabolites not only extends the pyrenophorol macrocyclic family, but also gives insight into the biosynthetic interconnections, in particular by isolation of the open-chain precursors. Preliminary studies showed antimicrobial activity of these compounds against the fungus Microbotryum violaceum, the alga Chlorella fusca, and the bacteria Escherichia coli and Bacillus megaterium. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).