Effects of 50% Ethanol Extract from Rosemary (Rosmarinus officinalis) on α‐Glucosidase Inhibitory Activity and the Elevation of Plasma Glucose Level in Rats, and Its Active Compound

Abstract

Rosemary (Rosmarinus officinalis) extract with 50% ethanol remarkably inhibited rat intestinal αglucosidase (sucrase) activity when compared with 31 different herbs and spices (aqueous and 50% ethanol aqueous extracts). Rosemary-distilled extract obtained from 50% ethanol extract by evaporation inhibited α-glucosidase activity in the reaction with both maltose and sucrose. Maltose or sucrose was orally administered, with or without rosemary-distilled extract, to mice at a dose of 20 mg/mouse. A postprandial elevation in plasma glucose levels 30 min after administration of maltose or sucrose plus the distilled extract was significantly suppressed compared with glucose levels in mice that did not receive the distilled extract. A 0.01% aqueous solution of rosemary-distilled extract supplied as drinking water to streptozotocin (STZ)-induced diabetic mice significantly suppressed an increase in plasma glucose levels 4 d after injection of STZ. It was also shown that a 0.01% aqueous solution of the distilled extract inhibited α-glucosidase (maltase and sucrase) in the small intestine of STZ-induced diabetic mice. An active compound with IC 50 values of 290 μg/mL (maltase inhibitory activity) and 150 μg/mL (sucrase inhibitory activity) was isolated and identified to be 5,7,3 ,4 -tetrahydroxy flavone (luteolin). These results suggested that rosemary extract might be a beneficial food material in the prevention of diabetes and obesity.

Rosmarinic acid modulates the antioxidant status and protects pancreatic tissues from glucolipotoxicity mediated oxidative stress in high-fat diet: streptozotocin-induced diabetic rats.

“…10 Schematic overview of the mechanism of action of rosmarinic acid during HFD-STZ-induced experimental diabetes mellitus in rats the condition which is reversed upon oral administration of RA. These data indicate the beneficial effects of RA in preventing the diabetic complications which is supported by the previous studies which demonstrates that RA extract regulates glucose metabolism in rats [49].…”

Physiological investigations on the effect of olive and rosemary leaves extracts in male rats exposed to thioacetamide

“…Moreover, recent study reported that rosemary leaves lead to regeneration of the b-cells of the pancreas and potentiating of insulin secretion from surviving b-cells, which indicates that rosemary leaves decrease blood glucose level by stimulating insulin secretion from the remnant b-cells or regenerated b-cells (Alnahdi, 2012). Furthermore, the reduction of fasting blood glucose may be due to that rosemary leaves might inhibit the intestinal absorption of glucose by inhibition of intestinal amylase enzyme or a-glucosidase enzyme (McCue and Shetty, 2004;Koga et al, 2006).…”

In vivo assessment of antidiabetic and antioxidant activities of rosemary (Rosmarinus officinalis) in alloxan-diabetic rabbits

“…by the inhibition of endogenous glucose production (Eddouks et al, 2003) or by the inhibition of intestinal glucose absorption (Platel and Srinivasan, 1997). In a previous study, it has been suggested that 50% ethanol extract of Rosmarinus officinalis, in part, due to intestinal ␣-glucosidase (AGc) inhibitory activity of its active compound might play a role in controlling dietary glucose uptake in the small intestinal track (Koga et al, 2006).…”