alpha-Glucosidase inhibitory activity of the methanolic extract from Tournefortia hartwegiana: an anti-hyperglycemic agent

Tournefortia hartwegiana is a Mexican medicinal plant that is used for the treatment of diabetes, diarrhea and kidney pain. In a previous investigation, the methanolic extract of Tournefortia hartwegiana (METh) showed significant hypoglycemic and anti-diabetic properties on normoglycemic and alloxanized rats. In this context, the purpose of the present study was to establish one of the possible modes of action of METh to induce anti-diabetic activity. METh (310mg/kg) effect on alpha-glucosidase activity was investigated. METh intragastric administration was conducted to determine oral glucose tolerance test (OGTT), using different substrates: glucose, sucrose and maltose. The increase in plasma glucose level was significantly suppressed (P<0.05) by the extract after substrates administration. On the other hand, METh inhibited alpha-glucosidase activity in vitro, in a concentration-dependent manner (IC(50) of 3.16mg/mL). These results suggest that METh might exert its anti-diabetic effect by suppressing carbohydrate absorption from intestine, and thereby reducing the post-prandial increase of blood glucose. On the other hand, the bio-guided fractionation of this extract led to the isolation of: beta-sitosterol (1), stigmasterol (2), lupeol (3), ursolic acid (4), oleanolic acid (5), saccharose (6) and myo-inositol (7), using various chromatographic techniques.

Anti-diabetic effect on alloxanized and normoglycemic rats and some pharmacological evaluations of Tournefortia hartwegiana

The purpose of the present investigation was to assess the pharmacological properties of Tournefortia hartwegiana Steud (Boraginaceae), used in traditional medicine for the treatment of diabetes, diarrhea and kidney pain in Morelos, Mexico. Administration of methanol extract from aerial parts of Tournefortia hartwegiana (310 mg/kg body weight/day) for 10 days, to normoglycemic and alloxan-induced diabetic rats, significantly lowered their blood glucose levels (37 and 36%, respectively, p<0.05). The anti-diabetic and hypoglycemic activities due to the MeOH extract were similar to those produced by metformin at 120 mg/kg (positive control, p<0.05). In contrast, the hexane, dichloromethane and MeOH extracts from the same species showed no significant spasmolytic effect and did not have activity in antibacterial and Artemia salina toxicity bioassays.