Potential application of Conyza canadensis (L) Cronquist in the management of diabetes: In vitro and in vivo evaluation

Purpose: To investigate the antihyperglycemic activity of Conyza canadensis via alpha-glucosidase inhibition in alloxan-induced diabetic mice. Methods: In vitro antidiabetic activity was investigated using alpha-glucosidase inhibition assay with acarbose (62.5, 125, 500 and 1000 mu g/ml) as the standard drug. Conyza canadensis crude extract (Cc.Cr) in doses of 10, 30, 100 and 300 mg/kg were administered daily as a single dose to alloxan-induced (200 mg/kg) diabetic mice (Balb/c), and its effect on fasting blood glucose levels and body weight were evaluated for 15 consecutive days; oral glucose tolerance test was conducted. Metformin (500 mg/kg) was used as a standard antidiabetic drug for comparison. Acute toxicity of Cc.Cr was also evaluated at doses of 3 and 5 g/kg. Results: Conyza canadensis crude extract (Cc.Cr) exhibited strong enzyme inhibition at concentrations (mu g/ml) of 1000 (74.78 +/- 0.92), 500(65.11 +/- 0.07), 250 (57.55 +/- 0.41), 125 (51.55 +/- 0.67) and 62.5 ( 44.00 +/- 0.57), with a median inhibitory concentration (IC50) of 107 mu/ml. Cc.Cr at all test doses (10 - 300 mg / kg) reduced fasting blood glucose levels in alloxan (200 mg/kg) - induced diabetic mice on days 5, 10 and 15 compared to the diabetic control group (p < 0.001). These effects were similar to those caused by the standard antidiabetic drug, metformin. Cc.Cr at all test doses also increased body weight of treated animals. The extract (300 mg/kg) significantly improved tolerance of oral glucose overload in mice, like metformin. The extract did not cause any mortality up to the maximum dose of 5 g/kg. Conclusion: The results reveal that Conyza canadensis possesses potent secondary metabolites which can cause inhibition of alpha-glucosidase. Moreover, the plant extract has the ability to reduce blood glucose level in diabetic animals and significantly improves oral glucose overload tolerance.