The volatile constituents of rose, saffron and cardamom suppress the fibrillation of tau and not HEWL through the formation of non-toxic tau oligomers

Abstract

The formation of fibrillar structures of tau is correlated with taupathies including Alzheimer's disease (AD). This study has aimed to find ways to prevent tau fibril formation. Here, we used dietary compounds including cinnamon (CN), damask rose (Rose), saffron (Saf) and green cardamom (Car), to evaluate the effects of their volatile constituents, on hen egg white lysozyme (HEWL), as a model protein (commonly used for fibrillation studies), as well as the brain-related tau protein. The study was done using different spectroscopic techniques as well as SDS-PAGE, AFM and MTT assay. While the results suggested that the volatile constituents were unable to prevent HEWL fibril formation, most of the dietary compounds, in particular Saf, Rose and Car, were able to interfere with the mature fibril formation, by either maintaining the native form of tau or resulting in the entrapment of non-toxic oligomeric forms of tau. Moreover, the neurotoxicity analysis of tau samples on neuroblastoma SH-SY5Y cells indicated that tau treated with Saf, Rose and Car were the least toxic. Overall, the findings indicate that the potential therapeutic impacts of the volatile constituents of Rose, Car and in particular Saf, may demonstrate significant efficacy in addressing neurodegenerative diseases such as AD.