| Abstract |
Oomycetes are eukaryotic microorganisms widely distributed in aquatic and terrestrial environments. Although they morphologically resemble fungi, they belong to the kingdom Stramenopila. Saprolegnia parasitica is an agriculturally and economically important oomycete and is well-known as a freshwater fish pathogen. Despite its significance, this organism has received little attention in natural product chemistry and is generally regarded as having limited secondary metabolite productivity. Nevertheless, oomycetes are known to produce small molecules that mediate interspecies and host communication and are therefore expected to generate secondary metabolites derived from components associated with the host and growth medium. Herein, we report the isolation, structural elucidation, and preliminary biological activities of parasitisterols A-C, newly identified 24,25-oxygenated cholestane-type triterpenes isolated from S. parasitica. These findings demonstrate that oomycetes represent an underexplored, yet promising, resource for natural product discovery.
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