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Olive oil microemulsions as a biomimetic medium for enzymatic studies: Oxidation of oleuropein
Author(s) -
Papadimitriou V.,
Sotiroudis T. G.,
Xenakis A.
Publication year - 2005
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-005-1075-4
Subject(s) - microemulsion , oleuropein , chemistry , lecithin , chromatography , organic chemistry , pulmonary surfactant , biochemistry , antioxidant
Microemulsions consisting of olive oil as the non‐polar solvent, lecithin as surfactant, 1‐propanol as cosurfactant, and water were prepared. The choice of the compositions of the microemulsions used was based on the pseudo‐ternary phase diagrams of the system determined at 30°C, for different weight ratios of lecithin/olive oil. Lecithin solubilization and water incorporation in these microemulsion systems was limited. Tyrosinase, an oxidizing enzyme present in olives, was successfully incorporated in the water core of these microemulsions. Enzymatic oxidation of oleuropein, the most abundant olive phenolic compound, in the restricted aqueous environment of olive oil microemulsions was studied. Formation of oleuropein oxidation products was followed spectrophotometrically at 30°C for several minutes. An absorption maximum was observed at 415 nm. When the enzymatic reaction was considered at different tyrosinase and oleuropein concentrations, a rapid inactivation of the enzyme was observed. Addition of l ‐proline as a coupling reactor did not succeed in preventing enzyme inactivation in the microemulsions, probably owing to substrate localization and product accumulation around the entrapped enzyme molecules in the micellar interface.