Abstract

Saprolegnia sp., a water mold causing significant economic losses in aquaculture, necessitates sustainable alternatives to chemical treatments. This study investigated the resinous exudate of Psoralea glandulosa and its derivatives as inhibitors of Saprolegnia parasitica and S. australis . Through in vitro assays and in silico molecular docking, the research aimed to determine the inhibitory efficacy and mechanism of action of these natural compounds. The results identified 3-hydroxybakuchiol (2) as the most potent agent. It demonstrated superior minimum inhibitory concentration (MIC) values of 50μg/mL against S. parasitica and 25μg/mL against S. australis , surpassing the commercial control, bronopol. Its minimum oomyceticidal concentration (MOC) was also confirmed at low levels (50–75μg/mL). Molecular docking analysis revealed that compound 2 has a high binding affinity for two crucial proteins in Saprolegnia: host-targeting protein 1 (Htp-1) and plasma membrane ATPase. These findings suggest that compound 2 acts as a potent dual inhibitor, with its free hydroxyl group being critical for its activity. This study positions 3-hydroxybakuchiol as a promising lead compound for developing new, safer, natural-based therapies to control saprolegniasis in the aquaculture industry.