Aureonitol Analogues and Orsellinic Acid Esters Isolated from Chaetomium elatum and Their Antineuroinflammatory Activity

Overexpression of various pro-inflammatory factors in microglial cells tends to induce neurodegenerative diseases, for which there is no effective therapy available. Aureonitol ( 1 ) and seven analogues, including six previously undescribed [elatumenol A–F ( 2 – 4, 6 – 8, respectively)], along with two new orsellinic acid esters [elatumone A and B ( 9 and 10 )], were isolated from Chaetomium elatum . The structures of the compounds were established through comprehensive analysis of spectroscopic data, including high-resolution mass spectra and one- and two-dimensional NMR, and absolute configurations determined by the Mosher method, dimolybdenum tetraacetate-induced circular dichroism, and theoretical calculations including electronic circular dichroism and NMR. Metabolites 3, 4, 7, and 8 exhibited antineuroinflammatory activity by attenuating the production of inflammatory mediators, such as nitric oxide, interleukin-6, interleukin-1β, tumor necrosis factor-α, and reactive oxygen species. Western blot results indicated 8 decreases the level of inducible nitric oxide synthase and cyclooxygenase-2 and suppresses the expression of Toll-like receptor 4 and nuclear factor kappa-B (NF-κB) as well as the phosphorylation of the inhibitor of NF-κB and p38 mitogen-activated protein kinases in lipopolysaccharide-activated BV-2 microglial cells.