Table 4.

Inhibitory activity (IC₅₀) and selectivity index (SI) of the compounds investigated against AChE and BuChE.

Compound	IC50 (μM ± SD)/IC50 (µg/mL ± SD)		SI
	AChE IC50	BuChE IC50
Reserpine	1.7 ± 2.08 µM	2.8 ± 1.84 µM	1.65
Ajmalicine	3.5 ± 1.41 µM	5.44 ± 1.75 µM	1.55
R. serpentina extract	14 ± 3.62 µg/ml	22 ± 3.10 µg/ml	1.57
Donepzil	0.98 ± 1.20 µM	1 ± 2.89 µM	1.02

Regression analyses was used to determine IC₅₀ values were and expressed as the means ± SD of three replicate determinations. Selectivity index here is the AChE selectivity over BuChE defined as IC₅₀ BuChE/IC₅₀ AChE affinity ratio.