Inhibitory activity of nitric oxide synthase and peroxynitrite scavenging activity of extracts of Perilla frutescens

Abstract

Activated microglia by neuronal injury or inflammatory stimulation overproduce nitric oxide (NO) by inducible nitric oxide synthase (iNOS) and reactive oxygen species (ROS) such as superoxide anion, resulting in neurodegenerative diseases. The toxic peroxynitrite (ONOO-), the reaction product of NO and superoxide anion further contributes to oxidative neurotoxicity. We tried to evaluate the effects of two kinds of varieties of Perilla frutescens var japonica Hara on the NO production in lipopolysaccharide (LPS)-activated microglia. The perilla cultivars of Namcheondeulkkae (NC) and Boradeulkkae (BR) were developed by pure line from the local variety and by a cross between 'deulkkae' and 'chajogi', respectively. Spirit, hexane, chloroform and butanol fractions of the leaves of NC and BR inhibited the production of NO in LPS-activated microglia. The fractions of BR showed stronger activity than NC and the spirit extracts was the most potent in both cultivars. The solvent fractions of BR suppressed the expression of protein and mRNA of iNOS in LPS-activated microglial cells. Moreover, the extracts of NC and BR showed the activity of peroxynitrite scavenging in cell free bioassay system. These results imply that Namcheondeulkkae and Boradeulkkae might have neuroprotective activity through the inhibition of NO production by activated microglial cells and peroxynitrite scavenging activity.