Anti-hyperglycemic Activity and Inhibition of Advanced Glycation End Products by Lonicera japonica Thunb. in Streptozotocin-induced Diabetic Rats

We investigated whether L. japonica Thunb. extract (LTE) has anti-hyperglycemic activity and/or inhibits the formation of advanced glycation end products (AGEs) in streptozotocin (STZ)-induced diabetic rats. LTE was examined for free-radical scavenging activity and α-glucosidase inhibitory effects, LTE strongly exhibited both activities, ED50 was 3.08 mg/mL, and IC50 was 1.348 mg/mL, respectively. The concentration of myo-inositol, which evaluates the insulin-mimetic activities of LTE was 2.24 g/100 g. These and other results suggest that LTE corrects intracellular myo-inositol deficiencies and improve insulin sensitivity. After STZ-induced diabetic rats freely ingested LTE for 12 weeks, glycoalbumin and blood glucose levels were reduced while serum biochemical profiles were improved. When tested in rat lens crystallins, 0.25% LTE inhibited Nε-(carboxymethyl) lysine formation by 17.7% when compared with the untreated groups. These results suggest that LTE ameliorates diabetes-induced abnormalities by an anti-hyperglycemic activities and inhibitory effects on the formation of AGEs.