Aralia has been reported to exhibit various pharmacological properties, including anti-inflammatory, antidiabetic and antioxidant activities. We performed in vitro and in vivo analyses on the neuroprotective effects of an ethanolic extract of the aerial parts of Aralia cordata Thunb. (Araliaceae). In cultured cortical neurons from rats, A. cordata (5-20 microg/mL) inhibited 100 muM hydrogen peroxide (H(2)O(2))-induced apoptotic neuronal death, elevation of intracellular calcium concentration ([Ca(2+)](i)) and generation of reactive oxygen species (ROS). Since oleanolic acid isolated from A. cordata also inhibited H(2)O(2)-induced neuronal death, increase in [Ca(2+)](i) and ROS generation in cultured cortical neurons, some of the neuroprotective effects of A. cordata might be attributable to this compound. In rats, A. cordata prevented cerebral ischemic injury induced by 3 h of middle cerebral artery occlusion, followed by 24 h of reperfusion. Ischemic infarct and edema volumes were significantly reduced in rats that received A. cordata (50 mg/kg, orally). These animals exhibited a corresponding improvement in neurological function and a reduction of neuronal death, as determined histologically from the cortex and hippocampal regions. It is possible that the anti-oxidative properties of A. cordata may be responsible for its neuroprotective effects against focal cerebral ischemic injury. In future, A. cordata might play a therapeutic role in the prevention and treatment of neurodegeneration in stroke.