Anti-inflammatory and Neuroprotective α-Pyrones from a Marine-Derived Strain of the Fungus Arthrinium arundinis and Their Heterologous Expression.

Fungal linear polyketides, such as α-pyrones with a 6-alkenyl chain, have been a rich source of biologically active compounds. Two new ( 1 and 2 ) and four known ( 3 - 6 ) 6-alkenylpyrone polyketides were isolated from a marine-derived strain of the fungus Arthrinium arundinis . Their structures were determined based on extensive spectroscopic analysis. The biosynthetic gene cluster ( alt ) for alternapyrones was identified from A. arundinis ZSDS-F3 and validated by heterologous expression in Aspergillus nidulans A1145 ΔSTΔEM, which revealed that the cytochrome P450 monooxygenase Alt2' could convert the methyl group 26-CH 3 to a carboxyl group to produce 4 from 3 . Another cytochrome P450 monooxygenase, Alt3', catalyzed successive hydroxylation, epoxidation, and oxidation steps to produce 1 , 2 , 5 , and 6 from 4 . Alternapyrone G ( 1 ) not only suppressed M1 polarization in lipopolysaccharide (LPS)-stimulated BV2 microglia but also stimulated dendrite regeneration and neuronal survival after Aβ treatment, suggesting alternapyrone G may be utilized as a privileged scaffold for Alzheimer's disease drug discovery.