Antidiabetic, Antihypertensive and Antioxidant Properties of Grapevine Leaf Extracts Obtained by Ultrasound, Microwave Assisted, and Classical Solvent Extraction; [Antidiabetische, blutdrucksenkende und antioxidative Eigenschaften von Extrakten aus Weinrebenblättern, die mit Hilfe von Ultraschall, mikrowellenunterstützter und klassischer Lösungsmittelextraktion gewonnen werden]

Grapevine leaves are consumed as a food in Mediterranean countries. At the same time, it is a byproduct of the wine industry. Antioxidant, antihypertensive and antidiabetic properties of grapevine leaves after ultrasound-assisted extraction (UAE), microwave assisted extraction (MAE) and classical solvent extraction (CSE) were evaluated and compared by using water and methanol as solvent. DPPH radical scavenging activity, total phenolic content (TPC), total antioxidant capacity (TEAC), metal chelating activity, ACE inhibitory activity and α‑glucosidase inhibitory activity of grapevine leaves extracts were determined. The highest values of grapevine leave extracts for antioxidant properties; DPPH (61.60%), TPC (910.18 mg GAE g−1), TEAC (6.23 µg Trolox mg−1) and metal chelating activity (IC50; 3.18 mg mL−1) were obtained from UAE when the methanol was used extracting solvent. However antihypertensive activity (13.68%) and antidiabetic activity (83.00%) values obtained from MAE by using water as a solvent were relatively highest. The effectiveness of UAE, MAE and CSE methods in terms of antioxidant, antihypertensive and antidiabetic properties of grapevine leaves were significantly (p < 0.05) different from each other. This differences depending on the solvent used. © 2018, Springer-Verlag GmbH Deutschland, ein Teil von Springer Nature.