Mint extracts for potential management of Alzheimer's disease

Millions of people worldwide are affected by neurodegenerative disorders such as Alzheimer’s disease (AD). AD is a complex progressive disease, and many factors contribute to its development. These factors include oxidative stress, decreased levels of the neurotransmitter acetylcholine, neuroinflammation, abnormal protein accumulation and neuronal apoptosis. A declining capacity in cognition and memory is one of the signs of AD. Mint (Mentha, Lamiaceae) extracts possess antioxidant capacity and inhibit the activity of enzymes, such as acetylcholinesterase, histone deacetylase and β-secretase, associated with the development of AD. We investigated the neuroprotective activity of M. diemenica (Australian native slender mint) on hydrogen peroxide-induced apoptosis using human neuroblastoma (SH-SY5Y) as a neuronal cell model. Caspases are proteases that play an essential role in apoptotic cell death. Hence, caspase-3/7 activity was measured after exposing the cells to M. diemenica aqueous methanol (50% v/v) extract, then inducing oxidative damage and apoptosis using H2O2. To understand the role of the extract on the regulation of apoptosis, real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting were utilised. M. diemenica extract reduced caspase activity and the expression of the pro-apoptotic protein Bax, while it also enhanced the expression of the anti apoptotic protein Bcl-xL. M. diemenica is widespread in Australia and the First Nations people used it to treat stomach pain and menstrual disorders, and this study revealed for the first time that extracts of M. diemenica hold promise for suppressing apoptosis at the cellular level, making it a potential source of effective compounds for an AD therapeutic approach.