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

<p>A series of 17 simple 1-(2,4-dihydroxyphenyl) ethanones were synthesised, and their structures characterised by <sup>1</sup>H, <sup>13</sup>C NMR and ESI-MS. Their <i>in vitro</i> antifungal activities were evaluated against five phytopathogenic fungi including <i>Glomerella cingulate</i>, <i>Botrytis cirerea</i>, <i>Fusarium graminearum</i>, <i>Curvularia lunata</i> and <i>Fusarium oxysporum</i> f. sp. <i>vasinfectum</i> by the mycelial growth inhibition assay. Compounds <b>2g</b> and <b>2h</b> exhibited broad-spectrum inhibitory activity against the mycelial growth of the tested pathogens with IC<sub>50</sub> values in the range of 16–36 μg/mL, and in particular being more active to <i>G. cingulate</i>, with IC<sub>50</sub> 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 <b>2g</b> and <b>2h</b> may be promising leads in the development of new antifungal agents.</p>