Antihyperglycaemic effect of Coreopsis tinctoria aqueous extract in streptozotocin-induced glucose-intolerant rats

Coreopsis tinctoria Nutt. has been traditionally used in Portugal for the treatment of diabetes [1]. In a previous study we showed that marein was the main chalcone of the infusion and that a single administration of this extract has no effect on oral glucose tolerance in normal Wistar rats [2].

We now report the effect of C. tinctoria infusion on glucose intolerant Wistar rats. Glucose intolerance was induced by a single intraperitoneal injection of streptozotocin in saline solution (40mg/Kg b.w.). After one week, an Oral Glucose Tolerance Test (OGTT) was preformed and rats were considered intolerant when the fasted blood glucose was similar to normal rats (65±10,8mg/dl) but the AUC of glycemic curves (0 to 180min) were higher than those of normal rats (AUC=20048±1752 vs. AUC=25646±2499; p<0.05). Normal rats (Control 1) and glucose intolerant rats (Control 2) received vehicle solution; C.tinctoria aqueous extract at 100mg/Kg b.w. and C.tinctoria aqueous extract at 500mg/Kg b.w. were administered daily for 21 days using an intragastric tube. All animals were submitted to OGTT once a week for 3 weeks. The results show that after 3 weeks treatment with C. tinctoria extract (500mg containing 20mg of marein/Kg/day) the animals are no longer glucose-intolerant: AUC=20091±831 vs. AUC (Control 1)=19069±276, p>0.05 but vs. AUC (Control 2)=26248±1081, p<0.01). Conclusion: C. tinctoria aqueous extract is able to revert the streptozotocin-induced glucose-intolerance in rats after 3 weeks of treatment, possibly through an induction of β-pancreatic regeneration, but this hypothesis and the mechanism are under investigation.

Acknowledgements: Science and Technology Foundation, for the PhD grant

References: 1. D'Oliveira Feijão, R. (1973) Medicina pelas Plantas. Livraria Progresso Editora. Lisboa. 2. Dias, T. et al. (2007) PSE Congress, Helsinkii, B07.