The effects of different combinations of plant extracts and traditional Chinese medicine on hydrogen peroxide- and thapsigargin-induced neurotoxicity

Abstract

Oxidative stress and endoplasmic reticulum (ER) stress have been known as some of the significant causes of neuronal cell death in many neurodegenerative diseases. Agents that can attenuate these stresses are believed to have neuroprotective effects. Allium fistulosum has been shown to have antioxidant and antimicrobial activities (Chang et al., 2016). The root extract of Clitoria ternatea has been found to improve memory in the chronic cerebral hypoperfusion rat model (Damodaran et al., 2018). Hibiscus sabdariffa aqueous extract has been shown to have protective effects against acute cerebral ischaemia (Owoeye and Gabriel 2017). Sterculia lychnophora has been reported to have neuroprotective effects against hydrogen peroxide-induced toxicity (Wang et al., 2013) while its activity against ER stress has not yet been studied. Traditional Chinese medicine is usually formulated as a complex of herbs which may have synergistic effects for a disease (Zhou et al., 2016). In the present study, the effects of different combinations of extracts of Allium fistulosum, Clitoria ternatea, Hibiscus sabdariffa and Sterculia lychnophora against hydrogen peroxide- and thapsigargin-induced neuronal cell death were studied. The extracts were prepared by dissolving the powder of ground dried Allium fistulosum, Clitoria ternatea, Hibiscus sabdariffa and Sterculia lychnophora in absolute ethanol and insolubles were filtered out by 0.22 micro-meter membrane filter. Undifferentiated SH-SY5Y cells were pre-treated with a single or multiple plant extracts for 24 hours in DMEM supplemented with 2% fetal bovine serum. Following the removal of the extracts, SH-SY5Y cells were treated with 400 micro-molar of hydrogen peroxide or 0.5 micro-molar of thapsigargin for 24 hours in DMEM supplemented with 2% fetal bovine serum. Results indicated that there were differential effects of the extracts against hydrogen peroxide- and thapsigargin-induced cytotoxicity, implying that the combined applications of these herbal extracts may have different effects on neuronal cell death induced by oxidative stress and ER stress.