Optimization of Two Eco-Friendly Extractions of Black Medick (Medicago lupulina L.) Phenols and Their Antioxidant, Cosmeceutical, α-Glucosidase and α-Amylase Inhibitory Properties.

Medicago lupulina is an ancient edible plant from the Fabaceae family. In this work, two eco-friendly methods for extraction of bioactive phenolics from M. lupulina were developed using mixtures of water with two non-toxic, skin- and environmentally-friendly polyol solvents: glycerol and polypropylene glycol. Ultrasound-assisted extractions were optimized using a Box-Behnken design. The independent variables were the concentration of organic solvent in water (X1), extraction temperature (X2) and time (X3), while the response was phenolic content. The optimum conditions for extraction of polyphenols were (X1, X2, X3): (45%, 70 °C, 60 min) and (10%, 80 °C, 60 min) for glycerol and polypropylene glycol extraction, respectively. The extracts prepared at optimum conditions were rich in phenolic compounds, mainly derivatives of apigenin, kaempferol, luteolin, quercetin, caffeic and ferulic acid, as well as coumestrol. Their cosmeceutical and antidiabetic activity was tested. Both extracts demonstrated notable antioxidant, anti-lipoxygenase and anti-α-amylase activity. In addition to those activities, the glycerol extract efficiently inhibited protein coagulation, elastase and α-glucosidase activity. Glycerol present in the extract displayed enzyme-inhibiting activity in several assays and supported the action of the bioactive constituents. Thus, the optimized glycerol extract is a desirable candidate for direct incorporation in antidiabetic food supplements and cosmeceutical products.

Chemical Composition, Antioxidant and α-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 ß-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 α-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.