Inhibitory activity of thirty-one
ethanol extracts obtained from albedo, flavedo, seed and leaf parts of 17 cultivars of Citrus species from Turkey, the bark and leaves of Olea europaea L. from two locations (Turkey and Cyprus) as well as
caffeic acid and
hesperidin was tested against
acetylcholinesterase (AChE) and
butyrylcholinesterase (BChE), related to the pathogenesis of
Alzheimer's disease, using ELISA microtiter assays at 500 µg/mL.
Metal-chelating capacity of the extracts was also determined. BChE inhibitory effect of the Citrus sp. extracts was from (7.7±0.7) to (70.3±1.1) %, whereas they did not show any inhibition against AChE.
Cholinesterase inhibitory activity of the leaf and bark
ethanol extracts of O. europaea was very weak ((10.2±3.1) to (15.0±2.3) %). The extracts had either no or low
metal-chelating capacity at 500 µg/mL. HPTLC fingerprinting of the extracts, which indicated a similar
phytochemical pattern, was also done using the standards of
caffeic acid and
hesperidin with weak
cholinesterase inhibition. Among the screened extracts, the albedo extract of C. limon 'Interdonato', the flavedo extracts of 'Kara Limon' and 'Cyprus' cultivars and the seed extract of C. maxima appear to be promising as natural BChE inhibitors.