Natural products as sources of new fungicides (III): Antifungal activity of 2,4-dihydroxy-5-methylacetophenone derivatives

A series of new 2,4-dihydroxy-5-methylacetophenone 2 derivatives were synthesized, and characterized by (1)H, (13)C NMR and ESI-MS. Their Antifungal activities were evaluated in vitro against five important plant Fungal pathogens including Cytospora sp., Glomerella cingulate, Pyricularia oryzaecar, Botrytis cinerea and Alternaria solani by the mycelial growth inhibitory rate assay. Compounds 2b-d, 2g and 2h displayed a broad-spectrum activity. The logP value of these active compounds is ranging from 1.71 to 2.54. Especially, isopropyl ketone 2g (logP 2.27) was found to be the most active to the tested organisms with IC50 values of 17.28-32.32 μg/mL. The results suggest that compound 2g might be a promising candidate in the development of new agrochemical Antifungal agents. Preliminary structure-activity relationship (SAR) studies of the acetophenone derivatives are also discussed.