Antioxidant and α-glucosidase inhibitory activities of Maple (Acer Spp.) bark extracts

Maple (Acer) species have long been used as a source for maple syrup. In recent years, there has been a strong interest in investigating maple plant parts as a source of biologically active natural products. Recent phytochemical studies of sugar and red maple bark extracts have revealed the presence of a number of phenolics, including the new gallotannins, maplexins A-I, which exhibit strong α-glucosidase inhibitory activities. The present study focused on the polyphenolic content, antioxidant and α-glucosidase inhibitory activities of bark extracts of five maple species growing in the north eastern region of the United States: A. saccharum (sugar maple), A. rubrum (red maple), A. platanoides (Norway maple), A. saccharinum (silver maple), and A. pseudoplatanus (sycamore maple). There was a direct correlation between polyphenol content and antioxidant activity, with the red maple bark extract showing the strongest antioxidant activity and sycamore maple showing the weakest activity. In the α-glucosidase inhibitory assay, the red maple bark extract showed the best activity, consistent with the presence of maplexins.