Neuroprotective effect from stem bark extracts of Knema laurina against H2O2- and Aβ1-42-induced cell death in human SH-SY5Y cells

The stem bark extracts of Knema laurina inhibited the hydrogen peroxide (H2O2)- and aggregated amyloid -peptide 1-42 length (A(1-42))-induced cell death in differentiated SH-SY5Y cells. Exposure of 250M H2O2 or 20M A(1-42) to the cells for 24h reduced 50% of cell viability. Pretreatment of cells with ethyl acetate extract (EAE) or n-butanol extract (BE) at 300g/mL and then exposure to H2O2 protected the cells against the neurotoxic effects of H2O2. Besides, methanolic extract (ME) at 1 and 10g/mL exerted neuroprotective effect on A(1-42)-induced toxicity to the cells. These results showed that EAE, BE and ME exhibited neuroprotective activities against H2O2- and A(1-42)-induced cell death. Flavonoids (3-6) and -sitosterol glucoside (8) were isolated from the EAE. Compound 1 was isolated from hexane extract, and compounds 2 and 7 were isolated from dichloromethane extract. All these observations provide the possible evidence for contribution in the neuroprotective effects.