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Context: Otostegia persica Boiss (Lamiaceae) contains antioxidant agents and is used in traditional medicine for treatment of diabetes mellitus complications. Objectives: The acute antihyperglycemic, antilipid peroxidation, and insulin secretory activities of methanol extract of O. persica aerial parts were investigated. Materials and methods: The extract [200, 300, 400 mg/kg body weight (b.w.)] was given orally to rats and glucose (2 g/kg b.w. orally) was administered 30 min later. Glucose and insulin serum levels were measured before and 30, 60, 120, and 240 min after administration of the test samples in normal and diabetic rats. The in vitro insulin secretory activity of extract was evaluated in C187 pancreatic β-cells and its antilipid peroxidation effect was determined by measuring malondialdehyde (MDA) and glutathione (GSH) levels in rat livers after 240 min. The identification of the major phytoconstituents of the extract was carried out using gas chromatography-mass spectrometry. Results: The extract (300 mg/kg b.w.) significantly decreased the serum glucose level in diabetic rats at 1 h (494 ± 13.4 vs. 426 ± 12.9), 2 h (472.8 ± 17.8 vs. 396 ± 22), and 4 h (438.8 ± 25 vs. 346 ± 19) after treatment. Accordingly, the serum insulin level increased at the same times. The extract significantly increased glucose-induced insulin secretion in C187 β-cells. Moreover, the extract significantly decreased MDA and increased GSH levels in the liver of diabetic rats. Phytochemical analysis revealed thymol as the major phytoconstituent in the extract. Discussion and conclusion: O. persica shoot extract has antihyperglycemic, antilipid peroxidation, and insulin secretory properties. [ABSTRACT FROM AUTHOR]