Antioxidant, hypoglycemic, and hepatoprotective effect of aqueous and ethyl acetate extract of carob honey in streptozotocin-induced diabetic rats

Aim: The aim of the study included the effect of aqueous extract (AE) and ethyl acetate extract (EAE) on blood sugar in diabetic rats and their effects on liver enzymes and lipid panel in control and diabetic rats. Furthermore, the antioxidant activity of the EAE was studied in vitro and compared with AE. Materials and Methods: Sugar and antioxidant content of AE and EAE were determined. In vitro antioxidant activity of AE and EAE was estimated by 2, 2-diphenyl-1-picrylhydrazyl and ABTS*+ radical scavenging assay, ferric-reducing antioxidant power assay, and total antioxidant assay. To study the effect of the extracts on blood glucose level (BGL), lipid profile, and liver function in non-diabetic and diabetic rats, five groups of six rats each were treated with distilled water, AE, EAE, glibenclamide (GLB), and sucrose for 8 days. Plasma glucose level (PGL), total cholesterol (TC), triglycerides (TG), transaminases (alanine transaminase [ALT] and aspartate transaminase [AST]), and alkaline phosphatase (ALP) were determined. The effect of the interventions on BGL after acute administration also was investigated. Diabetes was induced by streptozotocin injection. Results: EAE contains significantly lower content of fructose and glucose than AE (p<0.05), and it has no sucrose. AE and EAE exhibited a significant antioxidant activity and high antioxidant content; the antioxidant content was higher in AE than EAE (p<0.05). In diabetic rats, acute treatment by AE increased PGL, while EAE significantly lowered BGL as compared to the untreated diabetic rats. Both interventions significantly decreased BGL as compared to the sucrose treated group in diabetic rats (p<0.05). EAE was more potent than GLB. Sucrose caused 13% increment in BGL after 8 days of induction of diabetes, while AE caused only 1.3% increment. Daily treatment by EAE decreased significantly AST, ALT, ALP, and TC. EAE decreased significantly TC and TG level in diabetic rats in comparison to the untreated diabetic group. Conclusion: The study showed for the 1st time that EAE has more hypoglycemic effect than AE, and both extracts prevent the increment in BGL on day 8 after induction of diabetes observed in the control and sucrose treated group. EAE significantly ameliorated the lipid and liver function disorders induced by diabetes.