Herpotrichones A and B, Two Intermolecular [4 + 2] Adducts with Anti-Neuroinflammatory Activity from a Herpotrichia Species

Herpotrichones A and B (1 and 2), two intermolecular [4 + 2] adducts with an unprecedented pentacyclic 6/6/6/6/3 skeleton, were isolated from Herpotrichia sp. SF09, an isopod-associated fungus, along with a new shunt product protrichone (3). Their structures were elucidated by the analysis of spectroscopic data, residual dipolar coupling (RDC)-based computer-assisted 3D structure elucidation (CASE-3D), and single-crystal X-ray diffraction in combination with electronic circular dichroism (ECD) calculations. Compounds 1 and 2 were assessed to be potent anti-neuroinflammatory agents in lipopolysaccharide (LPS)-induced BV-2 microglial cells with the half maximal inhibitory concentration (IC₅₀) values of 0.41 and 0.11 μM, respectively.