Investigation on the hypoglycaemic effects of extracts of four Mexican medicinal plants in normal and alloxan-diabetic mice.

The hypoglycaemic activities of four water ethanol extracts (WEE) prepared from Bidens pilosa L., Salvia officinalis L., Psacalium peltatum H.B.K. (Cass) and Turnera diffusa Willd. were investigated in healthy and alloxan-diabetic mice. The WEE of S. officinalis significantly reduced the blood glucose of fasting normal mice 120 (15.7%) and 240 min (30.2%) after intraperitoneal administration (p < 0.05). The WEE of P. peltatum and B. pilosa also significantly diminished glycaemia in healthy mice at 240 min (19.6% and 13.8%, respectively). In mildly diabetic mice, the WEE of P. peltatum lowered the basal blood glucose level 120 (16%) and 240 min (54%) after intraperitoneal administration (p < 0.05 and p < 0.01, respectively). The WEE of B. pilosa and S. officinalis also significantly diminished the hyperglycaemia in mildly diabetic mice at 240 mins (32.6% and 22.7%, respectively). The administration of these three extracts to animals with severe hyperglycaemia did not cause a significant decrease. The WEE of T. diffusa did not show any hypoglycaemic activity. Thus, three of the WEE studied conserved the hypoglycaemic activity originally detected in the traditional preparations of the studied antidiabetic plants. It appears that these extracts require the presence of insulin to show hypoglycaemic activity.