Atividade antidiabética da Bauhinia Ungulata: papel dos inositóis componetes dos mediadores putativos da ação da insulina

Abstract

Bauhinia ungulata (“Mororo”) is a Caesalpiniaceae tree widely used in the popular medicine of Ceará, Brazil, as an hypoglicemiant agent. In this study, aqueous and ethanolic extracts from the leaves of this tree were evaluated in order to validate its reputed antidiabetic activity, to access its relative toxicity and to investigate inositols identified in this plant as possible active principies for the hypoglicemiante activity. The aqueous extract (AEBU)of B. ungulata was demonstrated to have hypoglicemiant activity by both oral and intravenous route. This extract was alsb show .to be devoidcd of overt toxicity by the oral route. The acute hypoglicemiant effect by intravenous or oral administration were quite reproduced by the inositols (D-chiro-inositol or pinitol) identified in AEBU in enough amounts to be responsible for the observed effects. The ethanolic extract was show to have a more potent hypoglicemiant effect than AEBU, maybe by its higher content of inositols. AEBU also protected euglycemic rats against an oral glucose overload in a similar fashion as did glibenclamide, a conventional antidiabetic drug. On the other hand, AEBU also provided a good glycemic control for STZ-diabetic rats after 3 weeks oral administration. This later effect was followed by ã better lipid profile with a lower atherogenic index. AEBU was also shown to have a direct ljipolipemiant effect in a nice model of dyslipidaemia induced by tiloxapol. To better approach its general safety the effects on the mean arterial blood pressure (MAP) were studied and AEBU was shown to have liypotensive activity by means of a direct vasodilatory action on rcsistancc vessels. This activity raises the possibilily of presence of a antihypertensive active principie is this plant. Furthermore, the antidiabetic, hypolipemiant and antihypertensive profile of AEBU is associated to a direct protective effect on the endothelial function that are decreased in the diabetic vessels. Additionaly, AEBU restored the decreased leveis of urinary D-quiro-inositol in diabetic rats towards to normal leveis, inducing a better insulin sensitivity profile. In conclusion, this is the first study to point a probable activity of a Bauhinia specie and to demonstrate its vasoprotective properties and action as a insulin sensitizer.