Neuroprotective effect of compounds isolated from Euonymus alatus on glutamate-induced oxidative stress in HT22 hippocampal cells

Background: Euonymus alatus is used to treat diabetes in China. It is also known to have antioxidant and anti-inflammatory effects. Objectives: In this study, we isolated 10 compounds from E. alatus and confirmed that compounds whether protected neuroral cell (HT22) against glutamate induced toxicity. Materials and Methods: The n -hexane fraction of E. alatus was significantly protected HT22 cells injured by the excitotoxic amino acid, L-glutamate. We isolated ten compounds from n-hexane fraction of E. alatus , and they were identified as moretenone (1), moretenol (2), friedelanol (3), lupenone (4), β-sitosterol (5), betulin (6), undecanoic acid, 1,2-phenylene ester (7), glycerol 1-tetracosanoate (8), methyl hydrogen tetradecanedioate (9), and 10,13-nonadecadienoic acid, methyl ester (10) by spectroscopic data such as UV, IR, NMR, Mass spectroscopy. Results: Their neuroprotective activity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Betulin (6) and methyl hydrogen tetradecanedioate (9) had significant neuroprotective activity against glutamate-injured HT22 cells. Furthermore, reactive oxygen species level and intracellular Ca2+ was decresed by betulin (6) and methyl hydrogen tetradecanedioate (9) and these compounds increased mitochondrial membrane potential, total glutathione (GSH) level, GSH reductase activity and GSH peroxidase activity. Conclusion: Our results suggest that betulin (6) and methyl hydrogen tetradecanedioate (9) significantly protect HT22 cells against glutamate-induced oxidative stress, through anti-oxidative activities.