Neuroprotection and free radical scavenging effects of Osmanthus fragrans

The ethanol extract of dried flowers Osmanthus fragrans (OFE) was assessed for free radical scavenging effects measured by the bleaching of the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical, scavenging of the hydroxyl anion, investigation of the ferric reducing/antioxidant power (FRAP) and lipid-peroxidation inhibition in rat tissues. OFE contained a high amount of total flavonoid and polyphenol. OFE presented the effects in the metal reducing power, FRAP assay with IC₅₀ values of 0.23 μg/ml, and 7.74 μg/ml, respectively. OFE presented similar activities toward the DPPH and hydroxyl anion scavenging ability with IC₅₀ values of 10 μg/ml. OFE with IC₅₀ values between 46 and 97 μg/ml inhibited lipid peroxidation initiated by ferrous chloride in rat brain, liver, heart and kidney mitochodrias. Moreover, the neuroprotective activity of OFE was investigated under different insults (glutamate, arachidonic acid, and 6-hydroxydopamine) in Wistar rat primary cortical neurons. OFE with EC₅₀ values between 66 and 165 μg/ml attenuated the neurotoxicity on MTT and LDH assays. In addition, the AKT protein expression of excitotoxicity and oxidative stress was displayed by western blotting analysis. OFE could up-regulate the glutamate and 6-OHDA decreased AKT expression. This is the first demonstration of the neuroprotective, free radical scavenging and anti-oxidative effects of O. fragrans.