Anti-neuroinflammatory effect of oxaline, isorhodoptilometrin, and 5-hydroxy-7-(2'-hydroxypropyl)-2-methyl-chromone obtained from the marine fungal strain Penicillium oxalicum CLC-MF05.

Penicillium is a rich source of bioactive compounds. Among all Penicillium species, Penicillium oxalicum has been reported to produce various types of secondary metabolites, including alkaloids, phenolics, and tetrahydroxanthone dimeric compounds, exhibiting many pharmacological effects, such as antiviral, antibacterial, and cytotoxic activities. Three secondary metabolites were isolated from a fermented culture of the sponge-associated fungal strain P. oxalicum CLC-MF05: oxaline (1), isorhodoptilometrin (2), and 5-hydroxy-7-(2'-hydroxypropyl)-2-methyl-chromone (3). Their chemical structures were identified by 1D and 2D NMR and high-resolution mass spectroscopic analyses and compared with previously reported data. All three compounds inhibited NO and PGE overproduction and iNOS and COX-2 overexpression in both LPS-stimulated BV2 and rat primary microglia. These metabolites also repressed mRNA expression of TNF-α, IL-1β, IL-6, and IL-12. Further, mechanistic studies revealed that the inhibitory actions of compounds 1-3 were regulated by the inactivation of the NF-κB and MAPK signaling pathways. Furthermore, inactivation of the TLR4/MyD88 pathway contributed to the anti-neuroinflammatory activity of these compounds. These results suggest that compounds 1-3 represent potential anti-inflammatory candidates for the treatment of neurodegenerative diseases; however, further investigation is needed.