Bioassays. Butyrylcholinesterase inhibitory activity of the isolates
was evaluated according to Ellman and co-workers23 with some
modification using acetylthiocholine iodide (as substrate), cholinesterase
(from horse serum, EC 3.1.1.8), and galantamine hydrobromide from
Lycoris sp. Absorbance was read at 405 nm every 5 s for 2 min. The
IC50 is the concentration of inhibitor required to decrease enzyme
activity by 50% and was determined in triplicate. The data are shown
as mean ( standard deviation values