Chemical composition, antioxidant and alpha-Glucosidase-Inhibiting activities of the aqueous and hydroethanolic extracts of Vaccinium myrtillus Leaves

Vaccinium myrtillus (bilberry) leaf is traditionally used in southeastern Europe for the treatment of diabetes. In the present study, the ability of bilberry leaf extracts to inhibit carbohydrate-hydrolyzing enzymes and restore glutathione concentration in Hep G2 cells subjected to glucose-induced oxidative stress was investigated. A comprehensive analysis of the antioxidant activity of two bilberry leaf extracts was performed. The aqueous extract showed excellent total antioxidant and chelating activity. Its antioxidant activity in the beta-carotene-linoleic acid assay was very good, reaching the activity of the antioxidant standard BHA (93.4 +/- 2.3% vs. 95.1 +/- 2.4%, respectively). The hydroethanolic extract (ethanol/H2O, 8:2, v/v), on the other hand, was a better radical scavenger and Fe2+ reducing agent. Furthermore, the aqueous extract was able to efficiently increase glutathione concentration in Hep G2 cells subjected to glucose-induced oxidative stress and restore it to the levels observed in non-hyperglycaemic cells. The hydroethanolic extract strongly inhibited alpha-glucosidase, with the IC50 statistically equal to the antidiabetic drug acarbose (0.29 +/- 0.02 mg/mL vs. 0.50 +/- 0.01 mg/mL, respectively). Phytochemical analysis revealed the presence of quercetin and kaemferol derivatives, as well as chlorogenic and p-coumaric acid. The study results indicate that V. myrtillus leaf may have promising properties as a supporting therapy for diabetes.University of Zagrebinfo:eu-repo/semantics/publishedVersio

Effect of Betula pendula leaf extract on alpha-glucosidase and glutathione level in glucose-induced oxidative stress

B. pendula leaf is a common ingredient in traditional herbal combinations for treatment of diabetes in southeastern Europe. Present study investigated B. pendula ethanolic and aqueous extract as inhibitors of carbohydrate hydrolyzing enzymes, as well as their ability to restore glutathione concentration in Hep G2 cells subjected to glucose-induced oxidative stress. Phytochemical analysis revealed presence of rutin and other quercetin derivatives, as well as chlorogenic acid. In general, ethanolic extract was richer in phenolic substances than the aqueous extract. Furthermore, a comprehensive analysis of antioxidant activity of two extracts (determined by DPPH and ABTS radical scavenging activity, total antioxidant activity, and chelating activity as well as ferric-reducing antioxidant power) has shown that ethanolic extract was better radical scavenger and metal ion reductant. In addition, ethanolic extract effectively increased cellular glutathione levels caused by hyperglycemia and inhibited alpha-glucosidase with the activity comparable to that of acarbose. Therefore, in vitro research using B. pendula plant extracts has confirmed their antidiabetic properties