MAPT and Alzheimer disease: Ginsenoside Rd reduced OA-induced neurotoxicity and tau hyperphosphorylation in OA induced rat model (10 mg/kg) or in cultured cortical neurons (2.5 or 5 μM for 12 h) by enhancing the activities of protein phosphatase 2A (PP-2A) indicating that Rd might be a potential preventive drug candidate for AD and other tau pathology-related neuronal degenerative diseases [76].