Neuroprotective and anti-inflammatory effects of flavonoids isolated from Rhus verniciflua in neuronal HT22 and microglial BV2 cell lines

The neuroprotective and anti-inflammatory activities of the methanolic extract of Rhus verniciflua Stokes (Anacardiaceae) were investigated with mouse hippocampal and microglial cells. Bioactivity-guided isolation yielded 10 flavonoids including fustin (1), fisetin (2), sulfuretin (3), butein (4), butin (5), eriodictyol (6), morin hydrate (7), quercetin (8), kaempferol (9) and isoliquiritigenin (10). Among the isolated flavonoids, compounds 2-5 significantly protected the murine hippocampal HT22 cells against glutamate-induced neurotoxicity and attenuated reactive oxygen species (ROS) generations. In addition, these flavonoids significantly maintained antioxidative defense systems preserving the activities of superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GSH-Px) and the content of glutathione (GSH) decreased by glutamate insult. These compounds also showed significant inhibitory effects on LPS-induced nitric oxide (NO) production in BV2 cells. Especially, compound 4 dose-dependently suppressed the expression of both inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). These results suggest that these flavonoids possess therapeutic potentials as a multipotent agent against neurodegenerative diseases related to oxidative stress and pathological inflammatory responses.