title: Evidence of oleuropein degradation by olive leaf protein extract.
abstract: The enzymatic activity of raw protein olive leaf extract has been investigated in vivo, on olive leaf homogenate and, in vitro with pure oleuropein and other phenolic substrates. At least two types of enzymes were found to be involved in the degradation of endogenous oleuropein in olive leaves. As for the in vitro experiments, the presence of active polyphenoloxidase and β-glucosidase was determined by HPLC and UV-Visible spectroscopy. Interestingly, both the enzymatic activities were found to change during the storage of olive leaves. Specifically, the protein extracts obtained from fresh leaves showed the presence of both the enzymatic activities, because oleuropein depletion occurred simultaneously with the formation of the oleuropein aglycon, 3,4-DHPEA-EA. In comparison leaves subjected to the drying process showed a polyphenoloxidase activity leading exclusively to the formation of oxidation products responsible for the typical brown coloration of the reaction solution.
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DIAAA), University of Molise, Via De Sanctis, I-86100 Campobasso, Italy. Electronic address: antomac@unimol.it.
authors.forename: Antonella
authors.initials: A
authors.lastname: De Leonardis
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DIAAA), University of Molise, Via De Sanctis, I-86100 Campobasso, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Macciola
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DIAAA), University of Molise, Via De Sanctis, I-86100 Campobasso, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Cuomo
authors.affiliation: Department of Agricultural, Environmental and Food Sciences (DIAAA), University of Molise, Via De Sanctis, I-86100 Campobasso, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Lopez
mesh_terms: D004156:Catechol Oxidase / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D057888:Iridoid Glucosides; D039823:Iridoids / Q000737:chemistry*; D031658:Olea / Q000737:chemistry* / Q000201:enzymology; D010084:Oxidation-Reduction; D010936:Plant Extracts / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry / Q000201:enzymology; D010940:Plant Proteins / Q000737:chemistry*; D001617:beta-Glucosidase / Q000737:chemistry*
chemical_list: D057888:Iridoid Glucosides; D039823:Iridoids; D010936:Plant Extracts; D010940:Plant Proteins; C002769:oleuropein; D004156:Catechol Oxidase; D001617:beta-Glucosidase
keywords: Enzymes; Oleuropein; Olive leaf; Polyphenoloxidase; β-Glucosidase