Potential neuroprotective activity of Mentha longifolia L. in aluminum chloride-induced rat model of Alzheimer's disease.

Alzheimer's disease (AD) is an irreversible neurodegenerative disorder manifested by cognitive deterioration where the available treatments failed to delay its progression. The objective of this study was to investigate the neuroprotective activity in an aluminum chloride (AlCl3 )-induced AD in vivo model and phytochemical profile of the traditional Egyptian herb Mentha longifolia (Ml). Male albino rats were injected with Ml fractions and essential oil for 15 days followed by AlCl3 for 30 days. Oxidative stress and neuroinflammatory markers were measured namely: malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide (NO), and nuclear factor-κB (NF-κB). Furthermore, cholinesterase activity was tested and analysis of brain neurotransmitters using HPLC was performed. Results showed that methylene chloride and ethyl acetate fractions were able to reverse the AlCl3 mediated MDA increase, GSH decrease and exhibited anticholinesterase activity. EaFr reversed the increased levels of NF-κB and NO. Ml fractions and oil counteracted the AlCl3 effect on brain neurotransmitters. Forty metabolites were tentatively characterized in the bioactive fractions using UPLC-PDA-ESI-MS. 5,6,4'-trihydroxy-3',7,8-trimethoxy flavone was isolated from Ml as a first report, in addition to 5,6-dihydroxy-3',4',7,8-tetramethoxy flavone and rosmarinic acid. These findings suggest that Ml is a promising nutraceutical and source of lead compounds halting AD progression. PRACTICAL APPLICATIONS: The results presented in this paper unravels the neuroprotective effect of Mentha longifolia fractions and oil by acting as anti-inflammatory, antioxidant agents, and regulating the levels of neurotransmitters. This provides basic knowledge for the development of Ml as a source of lead compounds and a promising food supplement protective against Alzheimer's disease.