Structure-Activity Relationship of Natural Dihydrochalcones and Chalcones, and Their Respective Oxyalkylated Derivatives as Anti- Saprolegnia Agents.

Saprolegnia sp. is a pathogenic oomycete responsible for severe economic losses in aquaculture. To date, there is no treatment for its control that is effective and does not pose a threat to the environment and human health. In this research, two dihydrochalcones 1 and 2 , and three chalcones 3 - 5 , isolated from the resinous plant Adesmia balsamica , as well as their synthesized oxyalkylated derivatives 6 - 29 already reported and a new synthesized series of oxyalkylchalcones 30 - 35 , were evaluated for their anti- saprolegnia activity and structure-activity relationship as potential control and treatment agents for strains of Saprolegnia parasitica and S. australis . Among the molecules tested, natural 2',4'-dihydroxychalcone ( 3 ) and new oxyalkylchalcone 34 were the most potent anti saprolegnia agents against both strains, even with better results than the commercial control bronopol. On the other hand, the structure-activity relationship study indicates that the contributions of steric and electrostatic fields are important to enhance the activity of the compounds, thus the presence of bulky substituents favors the activity.