Bioactivity-guided isolation of the antidiabetic principle in Pterocarpus Santalinoides leaf extract

Abstract Pterocarpus santalinoides is used in Nigerian ethnomedicine to treat diabetes mellitus. This study aimed to establish the antidiabetic property of the plant, and isolate and characterize its active principle. Dried and pulverized leaves (500 g) of P. santalinoides were extracted with 1.8 L of 80 % hydromethanol by cold maceration. The dried extract (10 g) was partitioned into n-hexane, ethyl acetate (EtOAc), n-butanol, and water. Antidiabetic activitiy-guided isolation by column chromatographic separation of the EtOAc soluble and purification of the sub-fractions by repeated preparative thin layer chromatography (pTLC) yielded a C-glycosyl flavonoid, identified as isovitexin. The chemical structure was elucidated based on high-resolution mass spectroscopy, 1D, and 2D nuclear magnetic resonance spectroscopic analyses. Alloxan-induced diabetic rat model was adopted for antidiabetic screening. The extract of P. santalinoides (100-200 mg/kg), fraction F4 (50 mg/kg), sub-fraction F4.3 (10 mg/kg), and the semi-purified compound F4.3.2 (5 mg/kg) significantly (p<0.05) reduced the fasting blood glucose of alloxan-induced diabetic rats, causing 48.4, 69.4, 57.7 and 64.5 % antidiabetic activity respectively, compared with > 68 % recorded in glibenclamide (2 mg/kg) control. These results reveal that isovitexin is the antidiabetic principle in P. santalinoides

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

OBJECTIVE@#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.@*METHODS@#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.@*RESULTS@#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.@*CONCLUSIONS@#D. bidens extract possess antihyperglycemic activity which may be mediated through pancreatic and extra-pancreatic pathways, thereby justifying it folkloric use.