Terresterol, a polyoxygenated lanostanoid, isolated from the oomycete Saprolegnia terrestris, and its innate immune-promoting activity

Oomycetes are widely spread eukaryotic microorganisms. However, there have only been a few reports on the secondary metabolites produced by them. In the course of screening for innate immune regulators from natural resources, we isolated a new polyoxygenated lanostanoid, terresterol (1), from the oomycetes Saprolegnia terrestris. Compounds bearing a 21,22,24,25-tetraoxygenated side chain similar to 1 have only been rarely described, and the isolation of such compounds shows that oomycetes are promising resources for natural product chemistry. In addition, terresterol (1) has potential to be used as a lead compound for novel immunostimulating agents against bacterial infections and as probe for the innate immune system.