Assessment of cholinesterase and tyrosinase inhibitory and antioxidant effects of Hypericum perforatum L. (St. John's wort)

Abstract

In the current study, in vitro neuroprotective effect of the ethyl acetate, methanol, and water extracts of Hypericum perforatum L growing in Turkey was investigated through testing against acetylcholinesterase and butyrylcholinesterase at 50, 100, and 200 mu g mL(-1), linked to Alzheimer's disease, and tyrosinase at 250 mu g mL(-1), related to Parkinson's disease. As neurodegeneration is strongly correlated with oxidative damage and metal accumulation, antioxidant activity of the extracts was determined by radical scavenging assays against 2,2-diphenyl-1-picrylhydrazyl (DPPH), N,N-dimethyl-p-phenylendiamine (DMPD), super oxide, and nitric oxide radicals, as well as metal-chelation capacity, ferric- (FRAP), and phosphomolibdenum-reducing antioxidant power (PRAP). Total phenol and flavonoid quantities of the extracts were also determined. The methanol extract showed the highest acetylcholinesterase inhibition (49.54 +/- 4.44%), while the ethyl acetate extract had the best inhibition towards butyrylcholinesterase (50.79 +/- 3.07%). Only the methanol extract showed low tyrosinase inhibition (19.21 +/- 1.44%). In the antioxidant assays, the methanol extract had a greater activity in general. (C) 2012 Elsevier B.V. All rights reserved.