Experimental evaluation of a polyherbal formulation (Tetraherbs): antidiabetic efficacy in rats

Cinnamon ( Cinnamomum zeylanicum ), fenugreek ( Trigonella foenum-graecum ), shallot ( Allium hirtifolium Boiss), and clove ( Syzygium aromaticum ) are well-known and widely used medicinal plants in the world. There is some experimentally proven evidence demonstrated the beneficial effects of these herbs on metabolic disorders like diabetes. Despite the fact that there are limited studies in the field of herb-herb interactions, some of the diabetic patients prefer to use these herbs in a combination form. The aim of this study was to evaluate the possible effects of an equal mixture of these plants (named Tetraherbs) in streptozotocin (STZ)-induced diabetic rats. Severe diabetic rats (FBS above 350 mg/dL) were treated orally with ethanolic extracts of cinnamon (EEC), fenugreek (EEF), shallot (EES), and clove (EECL) separately at the dose of 75 mg/kg, or in equal combination formula (Tetraherbs) at doses of 100–300 mg/kg once per day for 28 days. At the end of the study, their effects on glucose levels, plasma lipids, liver enzymes activity, and histology of pancreas were evaluated. The blood glucose lowering activity, as well as pancreatic β cell regeneration of Tetraherbs, was significantly higher than the plants when they used separately. However, there was no significant difference in lipid-lowering and hepatoprotective potentials of the herbs whether used singly or in combination. In conclusion, the results of the present study provide evidence show combination form of the studied plants increased their glucose-lowering activity by positive interaction.