Postprandial hyperglycemia plays an important role in the development of type 2 diabetes. Inhibition of alpha-amylase was led to a delay in breaks down of starch and glycogen and prevented a rapid rise in blood sugar. Alpha-amylase was isolated by gel filtration chromatography Sephadex G-75 from bovine pancreas. Then, total methanolic extracts of plants were prepared and [IC.sub.50] values of extracts on alpha-amylase were obtained and compared with acarbose [IC.sub.50]. The polyphenolic content of extracts and antioxidant capacity were determined by Folin-Ciocalteu test and DPPH test, respectively. The specific activity of alpha-amylase was 48.2 U/mg. For inhibition of alpha-amylase, [IC.sub.50] values of H. persicum, Z. jujuba, and acarbose were 307, 827, and 113 [micro]g/ml, respectively. For inhibition of DPPH radical, [IC.sub.50] values of extracts were 235 and 701 [micro]g/ml. Total phenolic contents of methanol extracts were 73.8 [+ or -] 3.2 and 44.2 [+ or -] 1.8 [micro]g tannic acid equivalent/mg extract. Acarbose causes gastrointestinal symptoms and liver toxicity, but H. persicum and Z. jujuba decrease these side effects and prevent gastrointestinal disorders. Due to the high polyphenolic content and antioxidant capacity of these plants and significant inhibitory effect of the plants on alpha-amylase, these plants can be proposed for treatment of diabetic patients.