Normal phase HPLC profiling of the acetylcholinesterase activity in apolar plant extracts

Among nineteen evaluated Clusiaceous species, one stem bark CH2Cl2 crude extract was selected based on a significant inhibition of acetylcholinesterase (AChE) using the micro-dilution Ellman\u27s method [1]. A normal phase HPLC profiling with micro-fractionation of this extract provided discrete fractions every 20 seconds. In order to obtain a comprehensive profiling of AChE activity all microfractions were tested [2] in dilution assay (Ellman) as well as by bioautography (the Fast Blue B salt method). Furthermore the potency of inhibition was evaluated both by keeping the genuine concentration within the extract and after normalisation to a standard concentration level. From the active fractions five pure compounds were isolated and identified. The different methods of sample preparation and biological evaluation associated with normal-phase micro-fractionation of plant extracts are critically discussed