Microwave-Assisted Extraction of Olive Leaf from Five Italian Cultivars: Effects of Harvest-Time and Extraction Conditions on Phenolic Compounds and <i>In Vitro</i> Antioxidant Properties

The aim of this study was to determine the total phenolic content (TPC), flavonoids (TFC), composition, and in vitro antioxidant activity olive leaf extract five cultivars (Caiazzana, Frantoio, Leccino, Ortice, Coratina) from Campania Region (Italy) during three harvest-times (March, June, November). Different microwave powers, treatment-times, solvents (methanol, ethanol, water) different proportions were tested. Our results show that TPC is not affected by MAE conditions but cultivar harvest-time. Instead, TFC also depends on solvent used; with EtOH:H2O (70:30) MetOH:H2O (80:20) giving higher yields than H2O alone. Caiazzana Coratina harvested March showed highest compared other cultivars, they particularly rich oleuropein. These activity, as indicated DPPH hemolysis tests. In conclusion, harvest time influence polyphenol flavonoid leaf.