ORIGINAL PAPER Antihyperglycemic and antioxidative potential of Matricaria chamomilla L. in streptozotocin-induced diabetic rats Mustafa Cemek Æ Sadık Kag ˘a Æ Nejdet S ¸ ims ¸ek Æ Mehmet Emin Bu ¨yu ¨ kokurog ˘lu Æ Muhsin Konuk Received: 1 October 2007 / Accepted: 17 December 2007 Ó The Japanese Society of Pharmacognosy and Springer 2008 Abstract Plants with antidiabetic activities provide important sources for the development of new drugs in the treatment of diabetes mellitus. In the present study, we investigated possible antihyperglycemic and antioxidative activities of the aerial part of the Matricaria chamomilla L. ethanolic extract (MCE) in streptozotocin (STZ; 70 mg/kg, i.p.)-induced diabetic rats. The following groups were assigned; sham (did not receive any substance), STZ + distilled water (control), STZ + 5 mg/kg gliben- clamide, STZ + 20 mg/kg MCE, STZ + 50 mg/kg MCE, STZ + 100 mg/kg MCE. Diabetic rats were treated for 14 days by gavage. Postprandial blood glucose levels, mal- ondialdehyde, reduced glutathione (GSH), nitrate, nitrite, ascorbic acid, retinol, b-carotene, superoxide dismutase, and catalase levels were measured, and immunohisto- chemical studies were performed in all of the groups. The obtained data showed that STZ resulted in oxidative stress and affected the antioxidant status. Treatment with different doses of MCE significantly reduced postprandial hyperglycemia and oxidative stress, and augmented the antioxidant system. In histological investigations, MCE treatment protected the majority of the pancreatic islet cells, with respect to the control group. As a result, MCE exhibited significant antihyperglycemic effect and pro- tected b-cells in STZ-diabetic rats, in a dose-dependent manner, and diminished the hyperglycemia-related oxida- tive stress. Keywords Streptozotocin  Diabetes  Oxidative stress  Antioxidant  Pancreas  Immunohistochemistry Introduction Diabetes mellitus (DM) is a chronic and major endocrine disorder caused by inherited and/or acquired deficiency in the production of insulin by the pancreas, or by the inef- fectiveness of the insulin produced. It is a growing health problem in most countries and its incidence is considered to be high (4–5%) all over the world. Chronic hyperglycemia causes complications linked to diabetes, such as heart dis- ease, retinopathy, kidney disease, and neuropathy. It is also a common cause of chronic morbidity and disability among the working population in the world. Several drugs, such as sulfonylureas, metaformin, and a-glucosidase inhibitors, are used presently to reduce the hyperglycemia. In spite of the use of many hypoglycemic agents, diabetes and its linked complications are still an important medical prob- lem. All of these drugs also have limited efficacy and certain adverse effects, such as causing hypoglycemia at higher doses, liver problems, lactic acidosis, and diarrhea [1]. The formation of reactive oxygen species (ROS) is involved in the etiology and pathogenesis of diabetes and M. Cemek  S. Kag ˘a Department of Chemistry (Biochemistry Division), Faculty of Sciences and Arts, Afyon Kocatepe University, Afyonkarahisar, Turkey N. S ¸ ims ¸ek Department of Histology and Embriyology, Faculty of Veterinary Medicine, Atatu ¨rk University, Erzurum, Turkey M. E. Bu ¨yu ¨kokurog ˘lu (&) Department of Pharmacology, Faculty of Medicine, Afyon Kocatepe University, Ali Cetinkaya Kampusu, Izmir yolu 9. km, 03200 Afyonkarahisar, Turkey e-mail: memin@aku.edu.tr M. Konuk Department of Biology, Faculty of Sciences and Arts, Afyon Kocatepe University, Afyonkarahisar, Turkey 123 J Nat Med DOI 10.1007/s11418-008-0228-1