This research project studied the effect of ethanolic leaf extract of Dialium guineense Willd (Fabaceae) on oral glucose tolerance in mice and alloxan-induced diabetic female rats.
The ethanolic leaf extract was prepared by marcerating 500g of the dried, milled leaves of D. guineense in 3L of 96% ethanol in a suitable sized plastic bucket/bowl (with cover) for five days with intermittent stirring (at least once a day) using a glass rod. Then the extract was filtered using Whatsman No.1 filter papers into several evaporating dishes and dried over a regulated water bath at 50°C. The extract was then scrapped into universal glass bottles, labeled and stored in a deep freezer until when needed.
Oral acute toxicity study was conducted by treating four groups of overnight fasted mice with Normal saline (control), 2, 4 and 8g/kg body weight of the ethanol extract respectively.
Oral Glucose Tolerance Test study was conducted on five groups of overnight fasted mice with Normal saline (Normal control), Glibenclamide 5mg/kg, 100, 200 and 400mg/kg body weight of the ethanol extract respectively. One hour after administering the drugs, all the mice were given oral glucose solution at a loading dose of 2g/kg b.wt.
For the Alloxan-induced diabetic model, diabetes was induced on 40 female albino rats with a single intraperitoneal dose of Alloxan monohydrate 150mg/kg for 72 hours. Rats with fasting blood glucose levels >200mg/dL (Diabetic rats) were selected and divided into five groups and then a total of six groups was formed and were respectively treated with:
Group1: Normal saline 2ml/kg b.wt (NONDIABETIC) control,
Group2: Glibenclamide 5mg/kg b.wt, Group3: Ethanol extract 100mg/kg b.wt
Group4: Ethanol extract 200mg/kg b.wt
Group5:Ethanol extract 400mg/kg b.wt; and
Group6: DIABETIC control also received Normal saline 2ml/kg b.wt.
The drugs were administered once daily for 14 days.
Freshly prepared laboratory reagents were used in all the qualitative phytochemical tests. The results were analyzed by two-way anova using SPSS version 17 and Post-Hoc Duncan.
The results showed that the anti-diabetic potential of the ethanol extract was significant at (P= 0.027) with the 400mg/kg dose of the extract reducing FBGLs of alloxan-induced diabetic female rats from 530mg/dL to 79.5mg/dL within 24 hours compared to the hypoglycaemic potential of glibenclamide (496.30 – 116mg/dL ) within 24 hours. The extract also suppressed post-prandial induced hyperglycaemia following a heavy glucose meal in normoglycaemic mice. Percentage glycaemic reduction showed that the anti-diabetic activity of the extract was non-dose dependent. The 400mg/kg appear to be more effective in acute phase of hyperglycaemia; the 100mg/kg dose, on prolonged anti-diabetic treatment while the 200mg/kg appear to be the intermediary. Acute toxicity study indicates that the oral LD50 of the ethanol extract could be above 8g/kg body weight of mice; as no mortality was recorded for up to 72 hours post-dose. Preliminary weight assessment showed that the ethanol extract induced a weight loss of 6.2-11.5% on the diabetic female rats compared to glibenclamide (13.5%) as at the end of 14 days anti-diabetic treatment whereas a weight gain of 16.40% was observed for the untreated diabetic rats. Heamatological assay, showed that the extract demonstrated a significant inhibition of hyperglycaemia-induced glycoxylation of haemoglobin as the free, non-glycoxylated haemoglobin concentrations of the ethanol extract treated rats [100mg/kg (12.4mg/dL), 200mg/kg (10.5mg/dL) and 400mg/kg (11.85mg/dL)]; Normal control (11.9mg/dL) and glibenclamide (9.3mg/dL) were higher than that of the untreated diabetic rats (3.85g/dL). Phytochemical screening of the crude ethanolic leaf extract of D. guineense Willd, showed the presence of alkaloids, flavonoids, tannins, phlobatannins, cardiac glycosides, steroids and saponins.
From the results of this study, it can be concluded that the ethanolic leaf extract of D. guineense Willd; may be a potent source of yet-to-be discovered drugs of plant origin for the prevention and therapy of diabetes.
