Anti-amnesic activity screening of the seed ethanol extracts of Turkish Paeonia taxa by in vitro methods

The genus Paeonia L. (Paeoniaceae), known as „şakayik, ayi gülü, bocur, etc.“ in Turkey, was recorded to be used in Chinese traditional medicine against amnesia. Paeonia species were recorded in Turkey, which is the most important gene center worldwide for this genus. Consequently, the ethanol extracts of the defatted seeds of 7 Paeonia taxa; (P. arietina Anders., P. daurica Andrews, P. mascula Miller subsp. bodurii N. Özhatay, P. cf. mascula L. (Mill.) subsp. mascula, P. peregrina Miller, P. tenuifolia L., and P.×kayae N. Özhatay) were screened against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), linked to Alzheimer's disease and tyrosinase (TYRO), connected to Parkinson's disease using ELISA microplate reader. As amnesia is a neurodegenerative situation associated with oxidative damage, antioxidant activity of the extracts was also measured by radical scavenging activity tests against 2,2-diphenyl-1-picrylhydrazyl (DPPH), N,N-dimethyl-p-phenylendiamine (DMPD), and nitric oxide (NO) as well as metal-chelation capacity and ferric-reducing antioxidant power (FRAP) tests. Total phenol and flavonoid contents were determined spectrophotometrically. All of the extracts strongly inhibited AChE (85.69±0.58% –96.68±0.44%), BChE (73.34±1.92% –98.87±1.08%), and TYRO (60.50±1.68% –76.16±0.30%) at 200µg mL^-1. The extracts displayed scavenging activity below 40% against DPPH and DMPD radicals, whereas they were not able to quench NO. They exhibited moderate FRAP values and very low metal-chelation capacity.

As conclusion, our findings reveal that Paeonia species possess potent anti-amnesic activity in vitro via enzyme inhibition associated with neurodegeneration. The present study confirms the claimed utilization of the plant against amnesia in traditional medicine.