Evaluation of the antidiabetic and antioxidant potentials of methanolic leaf extract of Helianthus annuus L. on alloxan-induced hyperglycemic rats

Helianthus annuus (sunflower) is an annual plant native to America that possesses a large inflorescence. The present study evaluated the acute toxicity, antidiabetic, oral glucose tolerance test (OGTT), and antioxidant effects of methanol extract of H. annuus leaves using alloxan-induced diabetic rats. The extract at the dose range of 300–3,600 mg/kg was tolerated by the rats. The extract (150, 300, and 600 mg/kg) showed a significant (p < 0.05) dose- and time-dependent decrease in blood glucose level of alloxan-induced diabetic rats. There was no significant (p > 0.05) differences between the extract-treated groups and glibenclamide (2 mg/kg)-treated groups. At 6 h posttreatment, there was a significant (p < 0.05) decrease in blood glucose level at 600 mg/kg (66.74 %) extract compared with the negative control group (10 mg/kg distilled water). The OGTT in normoglycemic rat showed no significant (p > 0.05) difference in blood glucose level among the treatment groups. In diabetic OGTT, the blood glucose level of the extract (600 mg/kg)-treated group was significantly (p < 0.05) lower when compared to the that of the negative control group at 120 min post glucose load, but there was no significant (p > 0.05) difference between the extract- and glibenclamide (2 mg/kg)-treated groups. The extract produced a concentration-dependent increase in antioxidant activity. These findings suggest that H. annuus has potent antidiabetic and antioxidant activities and validate its folkloric use in traditional medicine for the treatment of diabetes mellitus. © 2013, Springer-Verlag London.