Azaphilones from an Endophytic sp. Prevent Neuronal Cell Death via Inhibition of MAPKs and Reduction of Bax/Bcl-2 Ratio.

Fourteen azaphilone-type polyketides (-), including nine new ones (- and -), were isolated from cultures of -associated sp. JVF17, and their structures were determined by spectroscopic analysis together with computational methods and chemical reactions. Neuroprotective effects of the isolated compounds were evaluated against glutamate-induced neurotoxicity. Treatment with compounds , , , and - increased cell viabilities of hippocampal neuronal cells damaged by glutamate, with compound being the most potent. Compound markedly decreased intracellular Ca and nuclear condensation levels. Mechanistically, molecular markers of apoptosis induced by treatment with glutamate, i.e., phosphorylation of MAPKs and elevated Bax/Bcl-2 expression ratio, were significantly lowered by compound . The azaphilones with an isoquinoline core structure were more active than those with pyranoquinones, but -substitution decreased the activity. This study, including the structure-activity relationship, indicates that the azaphilone scaffold is a promising lead toward the development of novel neuroprotective agents.