Contribution of fasting and postprandial glucose-lowering mechanisms to the acute hypoglycemic effect of traditionally used Eryngium cymosum F. Delaroche

Ethnopharmacological relevance: Eryngium cymosum F. Delaroche was detected as a traditional remedy against type 2 diabetes consumed by patients of Tlanchinol in the state of Hidalgo, Mexico. Aim of the study. Assessing the hypoglycemic effect and safety of the traditional extract of E. cymosum and relating it to key glucoselowering mechanisms both in fasting and postprandial state. Materials and methods: The aqueous extract of E. cymosum was subjected to HPLC analysis to identify its main components. Hyperglycaemic STZ-NA Wistar rats were administered with the extract to evaluate its effect on blood glucose levels and a possible dose-dependence. Afterward, it was evaluated in both pyruvate and maltose tolerance tests in STZ-NA rats to characterize its effect on gluconeogenesis and carbohydrate breakdown, two of the main mechanisms responsible for fasting and postprandial hyperglycaemia in type 2 diabetes patients. In addition, the inhibitory capacity of the extract was evaluated on key enzymes involved in gluconeogenesis and aglucosidases. Moreover, insulin concentrations were measured in normoglycemic rats in both conditions to establish a link between the hypoglycaemic effect of the extract with insulin release and functioning. Results: Caffeic acid (1), chlorogenic acid (2), and rosmarinic acid (3) were identified as the main constituents of the aqueous extract of E. cymosum, which exerted a hypoglycaemic effect in hyperglycaemic STZ-NA rats. It has a significant antihyperglycemic effect in the pyruvate tolerance test, and it was able to reduce the postprandial hyperglycaemia in maltose tolerance tests significantly. Moreover, it effectively reduced the activity of both gluconeogenic enzymes reaching almost 100% of inhibition, while it presented a modest 32% inhibition of aglucosidases. On the other hand, the extract decreased insulin levels after its oral administration in healthy rats in both nutritional states, without affecting normoglycemia in normal curves and reducing the postprandial peak in glucose load curves. Conclusions: The traditional consumed form of aerial parts of E. cymosum is safe and regulated glucose levels both in fasting and in postprandial state.