Inhibitory effect of ethanol extract of Magnolia officinalis and 4-O-methylhonokiol on memory impairment and neuronal toxicity induced by beta-amyloid

Abstract

The components of the herb Magnolia officinalis have exhibited antioxidant and neuroprotective activities. In this study, we investigated effects of ethanol extract of M. officinalis and its major component 4- O-methylhonokiol on memory dysfunction and neuronal cell damages caused by Aβ. Oral pretreatment of ethanol extract of M. officinalis (2.5, 5 and 10 mg/kg) and 4- O-methylhonokiol (1 mg/kg) into drinking water for 5 weeks suppressed the intraventricular treatment of Aβ 1–42 (0.5 μg/mouse, i.c.v.)-induced memory impairments. In addition, 4- O-methylhonokiol prevented the Aβ 1–42-induced apoptotic cell death as well as β-secretase expression. 4- O-methylhonokiol also inhibited H 2O 2 and Aβ 1–42-induced neurotoxicity in cultured neurons as well as PC12 cells by prevention of the reactive oxygen species generation. 4- O-methylhonokiol also directly inhibited β-secretase activity and Aβ fibrilization in vitro. Thus, ethanol extract of M. officinalis may be useful for prevention of the development or progression of AD, and 4- O-methylhonokiol may be a major active component.