Mechanism of most of herbal used for diabetes mellitus treatment has not been well defined. This study was performed to investigate hypoglycemic effect of walnut leaf ( Juglans regia
), coriander leaf ( Coriandrum sativum
L.) or pomegranate seed ( Punica granatum
), and their possible role on pancreatic tissue. Diabetes mellitus was induced in 20 adult male Sprague Dawley
rats and the animals were divided into four groups; three of them fed a diet supplemented with about15 gram (60 g/ kg body weight /day) of mentioned plants for 15 days. The fourth diabetic untreated group (positive control) and a non-diabetic group (negative control) received standard diet. Blood glucose was measured every day and on the last day pancreases were isolated and stained with hematoxylin & eosin (H&E) and Gomeri aldehyde fuchsin (GAF). Histomorphology and following morphometric factors were studied; Volume density of β cells, volume density of islets, percent of β cells, number of islets per square centimeter and average area of islets. The results of this study indicate that only walnut leaf was able to reduce blood glucose significantly compared with diabetic untreated group (9.029vs. 14.358 mmol/l) (P<0.05). Hypercellularity of islets tissue, increased hyperchromic nucleus in pancreatic islets of this group was obvious. Density of islets in pancreatic tissue, percent of β cells and islets size increased significantly in this group in comparison with diabetic untreated group which may signify regeneration of islets or beta cells in group received walnut leaf (P<0.05).