Crocus sativus, Olea Europea and Salvia spp: Role in Neuroprotection against H2O2 and Aβ-peptide Induced Cell Toxicity

Neurotoxicity belongs to the leading factors inducing neurodegeneration-related diseases, such as Alzheimer’s (AD) and Parkinson’s disease. In particular, accumulation of β-amyloid proteins in the brain, a hallmark in AD, induces oxidative stress and neurotoxicity. The use of antioxidants in AD is not sufficiently effective and other pharmacological approaches tested failed to cure, prevent or retard the progression of the disease. Clinical studies indicated that several medicinal plants display beneficial effects by improving memory and cognitive functions of patients with mild and moderate AD. In this study, the potential antioxidant and neuroprotective properties of Olea europea, Crocus sativus and Salvia spp extracts, as well as their main active compounds on cell viability was evaluated using an in vitro model of AD, the differentiated human SH-SY5Y neuroblastoma cells to cholinergic neurons. Their effects were assessed against the H2O2- and β-amyloid- induced cell toxicity using the MTS test. Current findings indicated that Salvia fruticosa, S. officinalis, S. argentea leaf extracts and the active compounds, oleuropein, trans-crocin-3 and -4 display significant dose-dependent antioxidant and neuroprotective properties. It is of note though that the total phenolic fragment of Olea europea leaf extract includes several toxic compounds, such as oleocanthal, that markedly reduce cell viability and exacerbate the H2O2- and Aβ-induced cell toxicity. In addition, the Crocus sativus hydrophilic and diethyl ether extracts and all their active compounds tested markedly increased the H2O2-induced cell toxicity. In conclusion, the medicinal plants tested contain several compounds displaying dose-dependent effects against H2O2- and Aβ-induced neurotoxicity and could be used in AD, but they also contain several neurotoxic agents.