The use of immobilized capillary enzyme reactors (ICERs) and enzymes coated to 
magnetic beads ((NT or CT)-MB) for ligand screening has been adopted as a new 
technique of high throughput screening (HTS). In this work the selected target 
was the enzyme acetylcholinesterase (AChE), which acts on the central nervous 
system and is a validated target for the treatment of Alzheimer's disease, as 
well as for new insecticides. A new approach for the screening of plant extracts 
was developed based on the ligand fishing experiments and zonal chromatography. 
For that, the magnetic beads were used for the ligand fishing experiments and 
capillary bioreactors for the activity assays. The latter was employed also 
under non-linear conditions to determine the affinity constants of known 
ligands, for the first time, as well as for the active fished ligand.