(-)-Myrtenal ((1R)-(-)-Myrtenal; orally; 80 mg/kg/day for 28 days) reveals decreased the levels of plasma glucose, improved the plasma insulin levels, up-regulation of IRS2, Akt and GLUT2 in liver and IRS2, Akt and GLUT4 protein expression in skeletal muscle in diabetic rats induced by single intraperitoneal injection of Streptozotocin (STZ) (40 mg/kg bw).