Acute effects of Fraxinus excelsior L. seed extract on postprandial glycemia and insulin secretion on healthy volunteers

Fraxinus excelsior L. (Family: Oleaceae) seeds are consumed as a food, condiment, and folk medicine. The seeds are traditionally used as a potent hypoglycemic agent, but no clinical evidence exists in as to this regard. We assessed the clinical efficacy and safety of the seed extract (FraxiPure™, Naturex), containing 6.8% of nuzhenide and 5.8% of GI3 (w/w), on plasma glucose and insulin levels against glucose (50 g) induced postprandial glycemia. Preselected dose (1.0 g) was used in a double blind, randomized, crossover, placebo (wheat bran) controlled study on 16 healthy volunteers. Each treatment was given immediately after a fasting blood glucose sample (0 min). Postprandial plasma glucose levels were estimated at 0, 15, 30, 45, 60, 90 and 120 min; and postprandial plasma insulin at 0, 30, 60, 90 and 120 min. The extract lowered the incremental postprandial plasma glucose concentration as compared to placebo at 45 min ( P = 0.06) and 120 min ( P = 0.07). It statistically ( P = 0.02) reduced the glycemic area under the blood glucose curve. The seed, also, induced a significant ( P = 0.002) secretion of insulin at 90 min after glucose administration. However, the insulinemic area under the blood insulin curve was not different than the placebo. No adverse events were reported. Our findings confirm the hypoglycemic action of Fraxinus excelsior L. seed extract. These promising results, thus, encourage conducting long-term clinical studies to further evaluate the efficacy and safety of Fraxinus excelsior L. seed extract in healthy and diabetic volunteers and also to explore the possible mechanism(s) of action.