Oligomeric procyanidins of French maritime pine bark extract effectively inhibit alpha-glucosidase

Alternative Medicine Review, March, 2007

Schafer A, Hogger P. Diabetes Res Clin Pract 2006 Nov 10; [Epub ahead of print]

The standardized maritime pine bark extract (Pycnogenol) was reported to exert clinical anti-diabetic effects after peroral intake. However, an increased insulin secretion was not observed after administration of the extract to patients. Our aim was to elucidate whether the described clinical effects of Pycnogenol[R] are related to inhibition of alpha-glucosidase. Therefore, we analyzed the inhibitory activity of Pycnogenol[R], green tea extract and acarbose towards alpha-glucosidase. Furthermore, we explored different fractions of Pycnogenol[R] containing compounds of diverse molecular masses from polyphenolic monomers, dimers and higher oligomers to uncover which components exhibited the most pronounced inhibitory activity. We found that Pycnogenol[R] exhibited the most potent inhibition (IC(50) about 5[micro]g/mL) on alpha-glucosidase compared to green tea extract (IC(50) about 20 [micro]g/mL) and acarbose (IC(50) about 1mg/mL). The inhibitory action of Pycnogenol[R] was stronger in extract fractions containing higher procyanidin oligomers. The results obtained assign a novel, local effect to oligomeric procyanidins and contribute to the explanation of glucose-lowering effects of Pycnogenol[R] observed in clinical trials with diabetic patients.