Microplate Assay.
Compounds 1 and 2 were evaluated for AChE inhibition activity on 96-well microplates using Ellman’s method with a slight modification.
A mixture containing 100 µL of Tris buffer (pH 7.8), 20 µL of enzyme solution (0.5 U/mL in buffer), and 20 µL of sample diluted in 50% buffer-MeOH to give a range of concentration from 25 to 1600 µM was added to a microplate and incubated for 15 min at 37 ๐C.
Then 40 µL of 0.75 µM 5,5’-dithiobis(2-nitrobenzoic acid) was added, and the addition of 20 µL of 1.5 µM acetylthiocholine started the reaction.
On account of the hydrolysis of acetylthiocholine, yellow 5-thio-2-nitrobenzoate anion was generated, and the absorbance was recorded at a wavelength of 406 nm after incubation at 37 ๐C for 30 min.
Galanthamine was used as the positive control. The percentage inhibition was evaluated using the equation I(%) = [1-(Asample-Abackground) / Ablank] × 100%, where Asample is the absorbance of each test compound, Ablank is the absorbance of the blank without test compound, and Abackground is the absorbance of the background without enzyme.