Evidence of oleuropein degradation by olive leaf protein extract. (15th May 2015)

• Record Type: Journal Article
• Authors: De Leonardis, Antonella; Macciola, Vincenzo; Cuomo, Francesca; Lopez, Francesco
• Is Part Of: Food chemistry. Volume 175(2015)
• Page Start: 568
• Page End: 574
• Publication Date: 2015-05-15
• Subjects: 3, 4-DHPEA-EA aldehydic form of oleuropein aglycon -- DL dried leaves -- FL fresh leaves -- p-NPG p-nitrophenyl-β-d-glucopyronoside -- p-NP p-nitrophenol -- PPO polyphenoloxidase -- RPE-FL raw protein extract from fresh leaves -- RPE-DL raw protein extract from dried leaves; Enzymes -- β-Glucosidase -- Olive leaf -- Oleuropein -- Polyphenoloxidase; Food -- Analysis -- Periodicals; Food -- Composition -- Periodicals; 664
• DOI: 10.1016/j.foodchem.2014.12.016
• Languages: English
• ISSNs: 0308-8146

Abstract

Abstract : Graphical abstract: Highlights: Naturally occurring enzymes in olive leaf were investigated. Hydrolytic (β-glucosidase) and oxidative (polyphenoloxidase) activities were detected. Enzymatic activity changed during olive leaf storage. An inhibitory effect of hydroxytyrosol on polyphenoloxidase activity was demonstrated. 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.