Neuroprotective effect of ethanolic extract from Stewartia pseudocamellia leaves on H2O2-induced oxidative stress

This study was performed to evaluate the protective effect of ethanolic extract from Stewartia pseudocamellia leaves on H2O2-induced cytotoxicity in mouse hippocampal HT22 and human neuroblastoma MC-IXC cells. The 20% ethanolic extract from Stewartia pseudocamellia leaves (ESP) showed high total phenolic and flavonoid contents, with 243.89 mg of GAE/g and 81.21 mg of RE/g, respectively. The ESP presented considerable in vitro antioxidant activity, as evaluated by ABTS, DPPH radical scavenging activities, and malondialdehyde inhibitory effect. Furthermore, ESP exhibited significant inhibitory effects on α-glucosidase and acetylcholinesterase (AChE) activities. In addition, ESP increased cell viability and suppressed the production of intracellular reactive oxygen species on H2O2-induced cytotoxicity in HT22 and MC-IXC cells. ESP also decreased the expression levels of inflammatory proteins such as TLR4, MyD88 p-NF-κB, iNOS, and COX-2. Moreover, ESP regulated the expression levels of cholinergic enzymes and synaptic proteins such as AChE, ChAT, SYP, and PSD-95 in H2O2-induced HT22 cells. The bioactive compounds of ESP were identified as rutin through quantitative analysis using high-performance liquid chromatography (HPLC). Therefore, ESP could be used as valuable functional food material to improve oxidative stress-induced neurodegenerative diseases.