Yuan, T.; Wan, C.; Liu, K.; Seeram, N.P. New maplexins F-I and phenolic glycosides from red maple (Acer rubrum) bark. Tetrahedron, 2012, 68, 959-964.
Four new gallotannins, maplexins FeI (1e4), two new phenolic glycosides, rubrumosides AeB (5,6), and eleven known compounds were isolated from red maple (Acer rubrum) bark. Their structures were elucidated based on spectroscopic analysis. The maplexins contained three galloylated derivatives at-tached to different positions of 1,5-anhydro-glucitol and were 10e20 fold more potent a-glucosidase inhibitors than the clinical drug, Acarbose (IC 50 ¼7e16 vs 161 mM), in vitro. These results support previous data suggesting that gallotannins are the main contributors to the a-glucosidase inhibitory activities of maple plant part extracts and that three substituents on the 1,5-anhydro-glucitol moiety are important for activity.