Antiglycation activity of Vaccinium spp. (Ericaceae) from the Sam Vander Kloet collection for the treatment of type II diabetes

In this report, the inhibition of advanced glycation endproducts (AGEs) by extracts of leaves from a collection of six, mainly tropical, Vaccinium L. spp. (Ericaceae) was examined. Indigenous Peoples have used Vaccinium species to treat symptoms of type I and II diabetes. Sustained hyperglycaemia, often associated with diabetes, facilitates crosslinking of sugars with proteins, producing AGEs. AGEs are a therapeutic target since they are responsible for many diabetes symptoms and contribute to ageing and the development of atherosclerosis, kidney, vascular, and neurological diseases. Vaccinium barandanum S. Vidal, Vaccinium consanguineum Klotzsch, Vaccinium gaultheriifolium (Griff.) Hook. f. ex C.B. Clarke, Vaccinium poasanum Donn. Sm., Vaccinium tonkinense Dop, and Disterigma rimbachii (A.C. Sm.) Luteyn (outgroup) were collected from Sam Vander Kloet's common garden collection. Ethanolic extracts of leaves of these Vaccinium spp. were potent inhibitors of AGEs. Vaccinium and outgroup species extracts tested in an AGE inhibition assay demonstrated concentration dependent inhibition, with a half maximal inhibitory concentration (IC50) ranging from 4.2 to 16.2 mu g.mL(-1). Phenolic content ranged from 258 to 626 (mu g quercetin equivalents.mg extract(-1)). Activity and phenolic content show that these tropical accessions have a higher phenolic content (p < 0.001, t test) and AGE inhibition (p < 0.03, t test) than six temperate species from our collections in eastern North America. Significant relationships were found between IC50 and latitude of geographic origin.