*3.6. Effects of L-Dopa and M. pruriens Seed Aqueous Extract on the Acetylcholinesterase Enzyme Activity*

The effect of L-dopa and *M. pruriens* seed extract on acetylcholinesterase activity was investigated by the Ellman method, in which thiocholine produced by AChE reacted with 5, 5 -dithiobis(2-nitrobenzoic acid) to form a colorimetric product. The enzyme activity of the control without reaction with samples was 2.29 Units/L. One unit of AchE is the amount of enzyme that catalyzes the production of 1.0 μmole of tricholine per minute at pH 8.0 at room temperature. L-dopa was found to increase the activity of the acetylcholinesterase enzyme in a dose-dependent manner, whereas *M. pruriens* seed extract showed inhibitory activity against the acetylcholinesterase enzyme. Figure 4 demonstrated a kinetic curve plotted between the absorbance of the Ellman reaction product and time. The slopes of each plot were further used to calculate the AChE activity. The AChE activity increased with increasing concentrations of L-dopa (Figure 5). At the highest concentration of L-dopa (5 mg/mL), the AChE activity was activated up to 213%. In contrast, M. pruriens seed extract showed enzymatic inhibitory activity. The AChE inhibitory activity of *M. pruriens* seed extract was found to be 52.61% at an L-dopa equivalent concentration of 0.05 mg/mL. However, at the higher dose, the enzyme inhibitory effect was considerably lower to 11.02% at an L-dopa equivalent concentration of 3.5 mg/mL. This result was probably due to a higher concentration of L-dopa present in the extract.

**Figure 4.** Plots of average O.D. readings subtracted from the mean blank (no enzyme) of each time point from its respective mean sample time points vs. time in the presence of (**A**) L-dopa and (**B**) *M. pruriens* seed extract.

(**B**)

**Figure 5.** Acetylcholinesterase activity in the presence of (**A**) synthetic L-dopa and (**B**) *M. pruriens* seed aqueous extract.
