Oligomeric procyanidins of French maritime pine bark extract (Pycnogenol®) effectively inhibit alpha-glucosidase

[Note: A step toward better understanding the identified ‘antidiabetic effects’ of supplementation with French maritime pine bark extract.] Journal: Diabetes Research and Clinical Practice. 2006. November 10. [Published online ahead of print.] Authors and affiliation: Schafer A, Hogger P. Universitat Wurzburg, Institut fur Pharmazie und Lebensmittelchemie, Wurzburg, Germany PMID: 17098323 The standardized maritime pine bark extract (Pycnogenol®) was reported to exert clinical anti-diabetic effects after peroral [by mouth] 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® are related to inhibition of alpha-glucosidase [enzymes that digest starches in food]. Therefore, we analyzed the inhibitory activity of Pycnogenol®, green tea extract, and acarbose towards alpha-glucosidase. Furthermore, we explored different fractions of Pycnogenol® 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® exhibited the most potent inhibition (IC(50) about 5mug/mL) on alpha-glucosidase compared to green tea extract (IC(50) about 20mug/mL) and acarbose (IC(50) about 1mg/mL). The inhibitory action of Pycnogenol® 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® observed in clinical trials with diabetic patients.

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