Antidiabetic Effect of Spearmint in Streptozotocin-Induced Diabetic Rats

Mentha spicata is a medicinal plant with several beneficial effects on health. The objective of this study was to evaluate the antidiabetic effect of this plant in the experimental diabetic state.

In this work, the effect of Mentha spicata (L.) (M. spicata) aerial part aqueous extract (A.P.A.E) at a dose of 20 mg/kg body weight on blood glucose levels has been demonstrated in normal and streptozotocin (STZ) diabetic rats. Additionally, a preliminary phytochemical screening for various bioactive constituents was realized and a dosage of polyphenols and flavonoid has been done. Moreover, the histopathological changes in liver and pancreas have been evaluated both in normal and STZ diabetic rats. The effect of M. spicata aqueous extract to improve glucose tolerance in normal rats was also evaluated.

In normal rats, both a single and repeated administration of the A.P.A.E (20 mg/kg) had not shown a significant reduction in blood glucose levels. However, repeated oral administration of M. spicata aqueous extract showed a significant blood glucose lowering effect (p<0.0001) in STZ diabetic rats. The blood glucose lowering activity of A.P.A.E was comparable to glibenclamide treatment at the dose used. Also, a histopathological study has showed the better act of M. spicata in pancreas and liver. Moreover, the oral glucose tolerance test demonstrated the ability of the aqueous extract (20 mg/kg) to improve the increase in blood glucose levels in normal treated rats. In the current study, no significant changes in body weight in normal and STZ rats have been shown. In addition, the preliminary phytochemical screening of M. spicata A.P.A.E. showed the presence of several beneficial compounds including polyphenols, flavonoids, anthraquinones, tannins, saponins, sterol, glucides, glycosides, terpenoids and reducing sugars. Furthermore, the result of dosage of some bioactive compounds present in this plant showed an important value of polyphenol (424.37±43.93 mg EAG) and showed also a non-negligible content of flavonoid. (9.74 ±0.39 mg EQ/g of extract).

In conclusion, aqueous M. spicata extract exhibits an interesting antidiabetic effect in streptozotocin rats.