Inhibitory Effect of Ocimum gratissimum Leaf Extract on Postprandial Increase of Blood Glucose

The tea of Ocimum gratissimum (OG) leaves has been commonly consumed by people living in Ishigaki Island, Okinawa prefecture, Japan, and is considered to be effective for improving diabetes mellitus. In this study, we aimed to clarify the inhibitory potential of OG leaves extract (OG-ext) on gastrointestinal glucose absorption and to provide theoretical evidence for the anti-hyperglycemic effect of OG-ext. The increase of blood glucose after oral administration of alpha-starch and glucose in mice was suppressed by co-administration of OG-ext. An in vitro enzymatic assay suggested that amylase and maltase were inhibited weakly by the addition of OG-ext. In Caco-2 cells, a human intestinal epithelial model, the sodium-dependent glucose transporter (SGLT) 1-mediated uptake of fluorescence glucose analog was inhibited significantly by the addition of OG-ext in a concentration-dependent manner. These results indicate that the inhibitory effect on SGLT1 is one of the mechanisms of the anti-hyperglycemic effect of the tea of OG leaves.