Antihyperglycemic effects of the methanol leaf extract of Diaphananthe bidens in normoglycemic and streptozotocin–induced hyperglycemic rats

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Abstract
To evaluate the methanol leaf extract of Diaphanathe bidens (D. bidens) (AFZEL. EX SW) SCHLTR for antihyperglycemic activity in order to confirm it antidiabetic potential. D. bidens was extracted by cold maceration for 48 h and concentrated in vacuo to yield D. bidens extract (DBE). Hyperglycemia was induced by intraperitoneal administration of streptozotocin (75 mg/kg). Oral glucose tolerance test was done with 2 g/kg glucose load in normal rats. DBE (150, 300 and 600 mg/kg) was administered orally, while tolbutamide (100 mg/kg, p.o.) was used as the standard reference drug. Blood glucose levels determined using ACCUCHEK glucose auto-analyzer. The acute toxicity and phytochemical studies were also carried out. DBE (600 mg/kg) and tolbutamide (100 mg/kg) significantly (P<0.05, 0.005) reduced blood glucose levels of rats between 120 and 480 min post administration in normal rats. In the streptozotocin- induced hyperglycemic rats, DBE (150, 300, 600 mg/kg) caused significant (P<0.001) dose- and time- dependent reduction in the blood glucose levels by 1.7%, 22.8% and 43.4%, respectively at 480 min compared to the negative control group. DBE (600 mg/kg) reduced the blood glucose level of rats by 1.2% in the oral glucose tolerance test when compared with the normal saline treated group. The acute toxicity test showed that DBE was safe at the doses used and the phytochemical screening revealed the presence of saponins, steroids, tannins and terpernoids. D. bidens extract possess antihyperglycemic activity which may be mediated through pancreatic and extra-pancreatic pathways, thereby justifying it folkloric use.