Abstract
Background: Black rice bran contains bioactive compounds; previous studies have shown the ethanol extract of black rice bran (EEBRB) can decrease levels in diabetic rats.

Aims and Objective: To elucidate the mechanism of antidiabetic effect of EEBRB.

Materials and Methods: This research was carried out by setting a few parameters for antidiabetic. The effects of inhibition of the enzyme alpha-glucosidase performed with in vitro studies using the extracted enzyme of intestines of mice. A total of 5 mL alpha-glucosidase enzyme was incubated for 5 min with EEBRB 1 mL with a serial concentration in phosphate buffer pH 7.2. Enzyme inhibitory effect was determined by measuring the concentration of formed glucose with Lane–Eynon method. The insulin level and glucose-lowering activity were determined on rats induced by alloxan 150 mg/kg and treated with EEBRB. Treated rats for 28 days were sacrificed and were prepared for histopathological observation of pancreas.

Result: EEBRB was able to inhibit the activity of the enzyme a-glucosidase on glucose with IC50 values of 121 ± 12.3 mg%. The EEBRB extract dose of 100 mg/kg was able to decrease blood sugar levels to 151 ± 38.58 mg/dL. The level of insulin in diabetic rats administered by EEBRB dose of 50, 100, and 200 mg/kg was obtained 6.52 ± 5.94, 11.5 ± 3.5, and 15.20 ± 9.5 ng/mL, respectively. Meanwhile, histopathological observations showed an improvement on the pancreatic beta cells.

Conclusion: Antidiabetic mechanism of EEBRB is associated with increased insulin levels because of regeneration of pancreatic beta cells in diabetic rats.

Key words: Black Rice Bran; Antidiabetic; Insulin Level; Pancreatic Beta Cells