Phenolic acid profile and in vitro neurobiological effect of phlomis grandiflora H.S. Thompson var. Grandiflora

Abstract

Neurodegenerative diseases e.g. Alzheimer’s disease (AD) and Parkinson’s disease (PD) are on increase particularly among elderly population and the drugs available are only able to provide symptomatic treatment. Hence, an extensive research is still being conducted for developing new drugs toward these diseases. In the present study, we have focused on a Turkish medicinal plant, Phlomis grandiflora var. grandiflora (Lamiaceae) in order to assess its potential memory-enhancing effect. On this purpose, the methanol and ethanol extracts of the aerial parts of P. grandiflora var. grandiflora and the fractions (hexane, chloroform, ethyl acetate, and n-butanol) from the ethanol extract were subjected to several enzyme inhibitory assays including acetylcholinesterase (AChE), butyrylcholinesterase (BChE), which are related to AD treatment as well as tyrosinase (TYR) as a target for the treatment of PD toxicity. Among the tested extracts, only the chloroform fraction exerted a perceptible inhibition against BChE (59.38 ± 2.28%) at 200 µg/mL. The ethyl acetate and n-butanol fractions displayed clearly a stronger quenching activity (over 80%) against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) radicals, whereas all of them were observed with a lower activity (below 22%) against N,N-dimethyl-p-phenylendiamine (DMPD) radical. On the other hand, more polar extracts and fractions were the most active in ferric- (FRAP) and phosphomolibdenum-reducing antioxidant power (PRAP) assays, while the main extracts possessed a higher metal-chelation capacity. HPLC analysis on the ethanol and methanol extracts was shown to be rich in phenolic acids, although their quantity varied remarkably in these extracts. Our findings pointed out to the chloroform fraction with promising BChE-inhibitory effect