Main content area

alpha-Glucosidase inhibitory action of natural acylated anthocyanins. 2. alpha-Glucosidase inhibition by isolated acylated anthocyanins

Matsui, T., Ueda, T., Oki, T., Sugita, K., Terahara, N., Matsumoto, K.
Journal of agricultural and food chemistry 2001 v.49 no.4 pp. 1952-1956
Ipomoea nil, pelargonidin, cyanidin, glucosides, roots, flowers, enzyme inhibitors, alpha-glucosidase, enzyme activity, small intestine, rats, assays, structure-activity relationships
Four diacylated pelargonidin (Pg: SOA-4 and SOA-6), cyanidin (Cy: YGM-3), and peonidin (Pn: YGM-6) 3-sophoroside-5-glucosides isolated from the red flowers of the morning glory, Pharbitis nil cv. Scarlett O'Hara (SOA), and the storage roots of purple sweet potato, Ipomoea batatas cv. Ayamurasaki (YGM), were subjected to an alpha-glucosidase (AGH) inhibitory assay, in which the assay was performed with the immobilized AGH (iAGH) system to mimic the membrane-bound AGH at the small intestine. As a result, the acylated anthocyanins showed strong maltase inhibitory activities with IC50 values of <200 micromolar, whereas no sucrase inhibition was observed. Of these, SOA-4 [Pg 3-O-(2-O-(6-O-(E-3-O-(beta-D-glucopyranosyl) caffeyl)-beta-D-glucopyranosyl)- 6-O-E-caffeyl-beta-D-glucopyranoside)- 5-O-beta-D-glucopyranoside] possessed the most potent maltase inhibitory activity (IC50 = 60 micromolar). As a result of a marked reduction of iAGH inhibitory activity by deacylating the anthocyanins, that is, Pg (or Cy or Pn) sophoroside-5-glucoside, acylation of anthocyanin with caffeic (Caf) or ferulic (Fer) acid was found to be important in the expression of iAGH (maltase) inhibition. In addition, the result that Pg-based anthocyanins showed the most potent maltase inhibition, with an IC50 value of 4.6 mM, and the effect being in the descending order of potency of Pg > Pn approximately equal Cy strongly suggested that no replacement at the 3'(5')-position of the aglycon B-ring may be essential for inhibiting iAGH action.