The neuroprotective effects of traditional oriental herbal medicines against β-amyloid-induced toxicity

Alzheimer's disease (AD) is the most common form of dementia among the elderly, causing progressive cognitive dysfunction, particularly memory loss. Recently, modulation of Aβ toxicity, which is one of the major potential causes of AD, by plant extracts is emerging as a possible therapeutic approach to control the onset of AD. Therefore, in the present study, the methanol extracts of 400 traditional oriental herbal medicines were tested for their abilities to protect PC12 rat pheochromocytoma cells against Aβ-induced toxicity. Our results identified 29 plant extracts that protected PC12 cells against Aβ insult, with ED50 values of less than 100 μg/mL. Among these extracts, those from Chaenomeles sinensis Koehne (Rosaceae), Ephedra sinica Stapf. (Ephedraceae), and Drynaria fortunei Smith (Polypodiaceae) exhibited the most promising neuroprotective effects, with ED50 values of less than 10 μg/mL. Their neuroprotective effects against Aβ insult were not fully explained by their participation in antioxidant pathways, as demonstrated by a free radical scavenging assay with DPPH. Therefore, the mechanisms and the major constituents behind the neuroprotective effects of these plant extracts warrant further study.