Natural products as sources of new fungicides (II): antiphytopathogenic activity of 2,4-dihydroxyphenyl ethanone derivatives.

A series of 17 simple 1-(2,4-dihydroxyphenyl) ethanones were synthesised, and their structures characterised by (1)H, (13)C NMR and ESI-MS. Their in vitro antifungal activities were evaluated against five phytopathogenic fungi including Glomerella cingulate, Botrytis cirerea, Fusarium graminearum, Curvularia lunata and Fusarium oxysporum f. sp. vasinfectum by the mycelial growth inhibition assay. Compounds 2g and 2h exhibited broad-spectrum inhibitory activity against the mycelial growth of the tested pathogens with IC50 values in the range of 16-36 μg/mL, and in particular being more active to G. cingulate, with IC50 values of 16.50 and 19.25 μg/mL, respectively, than the other pathogens. Preliminary SAR indicated that an α,β-unsaturated ketone unit of the alkyl chain of the compounds is the structure requirement for fungicidal action. The results suggested that 2g and 2h may be promising leads in the development of new antifungal agents.