Thirteen gallic acid derivatives including five new gallotannins, named maplexins A–E, were isolated from red maple (Acer rubrum) stems. The compounds were identified by spectral analyses. The maplexins varied in number and location of galloyl groups attached to 1,5-anhydro-d-glucitol. The isolates were evaluated for a-glucosidase inhibitory and antioxidant activities. Maplexin E, the first compound identified with three galloyl groups linked to three different positions of 1,5-anhydro-d-glucitol, was 20 fold more potent than the a-glucosidase inhibitory drug, Acarbose (IC50 = 8 vs 160 µM). Structure–activity related studies suggested that both number and position of galloyls attached to 1,5-anhydro-d-glucitol were important for a-glucosidase inhibition.Graphical abstractThirteen gallic acid derivatives, including five new gallotannins, 2, 3, 5, 6, 9, assigned the common names of maplexins A–E, respectively, were isolated from red maple stems. The isolates were evaluated for a-glucosidase inhibitory and antioxidant activities in vitro. [The original abstract for this article contains an image that cannot be displayed here. Please click on the link below to read the full abstract and article.]
