In vitro studies of α-glucosidase inhibitors and antiradical constituents of Glandora diffusa (Lag.) D.C. Thomas infusion.

Glandora diffusa (Lag.) D.C. Thomas (Boraginaceae) is a species traditionally consumed as an infusion. The phenolic profile of its aqueous extract was assessed by HPLC-DAD-ESI/MS(n). Twenty-seven compounds were identified, comprising caffeic and p-coumaric acids, seventeen polymers of caffeic acid and eight 3-O-glycosylated flavonols. Caffeic, rosmarinic, and salvianolic acids were the most representative compounds, accounting for more than 75% of the phenolic fraction. The potential of G. diffusa aqueous extract to act as radical scavenger was assessed against DPPH(), superoxide and nitric oxide. A dose-dependent response was observed against all reactive species. Moreover, the extract showed promising results as inhibitor of α-glucosidase, being almost 9 times more effective than acarbose. Both activities are related with the presence of polyphenolic compounds. Therefore, the combination of α-glucosidase inhibition with its antiradical capacity opens a new perspective for the use of G. diffusa by patients with diabetes mellitus. As far as we know, this is the first study assessing the chemical composition and biological potential of G. diffusa. Our results can boost the consumption of G. diffusa species as an infusion or in food and pharmaceutical preparations.