Two phytotoxic furan derivatives were isolated, together with the well-known fungal and plant phytotoxin tyrosol, from the culture filtrates of Stilbocrea macrostoma. This fungal pathogen isolated from Quercus brantii trees induced wood necrosis and decline symptoms on the host plant in Iran. The two furan derivatives, isolated for the first time from Stilbocrea macrostoma, were identified by spectroscopic methods (essentially 1 D and 2 D 1H and 13C NMR and ESIMS spectroscopy) as 5-hydroxymethylfuraldehyde and 2,5-dihydroxymethylfuran. The phytotoxic activity of the three metabolites was evaluated by leaf puncture assay on holm oak (Quercus ilex L.) and tomato (Lycopersicon esculentum L.) leaves. All compounds induced necrosis on holm oak leaves while very low toxicity was showed against tomato leaves. The two furan derivatives were more toxic than tyrosol and particularly 5-hydroxymethylfuraldehyde was the most phytotoxic compound.
