In the present investigation, the study results revealed that the ethanol extract fraction of A. Mexicana L. efficiently inhibits the enzyme, α-amylase in a similar manner like that of acarbose, a standard drug. The IC50 values of both are 27.83 μg/ml and 36.93 μg/ml respectively. Inhibition of α-amylase assay of ethanol fraction suggest that one of the mechanisms by which A. Mexicana L. might be exhibiting their antidiabetic properties probably by inhibition of α-amylase activity leading to decrease of the rate of starch digestion, thus preventing sudden hyperglycaemia after intake of a starch in turn reduction of formation of glucose and consequently decrease in absorption of glucose. This investigation reported that the ethanol extract of A. Mexicana L. leaves shows effective α-amylase inhibitory activity.