Mild photochemical synthesis of the antioxidant hydroxytyrosol via conversion of tyrosol.
Hydroxytyrosol, a naturally occurred orthodiphenolic antioxidant molecule found in olive oil and olive mill wastewaters, was obtained from the wet hydrogen peroxide photocatalytic oxidation of its monophenolic precursor tyrosol. The liquid-phase oxidation of tyrosol to hydroxytyrosol was performed by use of an iron-containing heterogeneous catalyst (Al-Fe)PILC with the assistance of UV irradiation at 254 nm and at room temperature. The spectroscopic and HPLC data of the synthesized compound proved to coincide fully with those of a pure sample obtained by continuous countercurrent extraction. This reaction was found to be light-induced. The hydroxytyrosol synthesis reaction reached its maximum yield of 64.36% under the optimized operating conditions of 3.6 mM tyrosol, 0.5 g L(-1) catalyst, and 10(-2) M H2O2 with the assistance of UV light. Increasing the initial hydrogen peroxide concentration more than 10(-2) M has a diminishing return on the reaction efficiency. Catalyst can be recuperated by means of filtration and then reused in a next run after regeneration since its activity did not significantly decrease (<10%). The reaction synthesis is operationally simple and could find application for industrial purposes.
Azabou
Samia
S
Laboratoire des BioProcédés, Centre de Biotechnologie de Sfax, BP K, Tunisia.
Najjar
Wahiba
W
Ghorbel
Abdelhamid
A
Sayadi
Sami
S
D000975:Antioxidants / Q000138:chemical synthesis* / Q000528:radiation effects; D002384:Catalysis; D007700:Kinetics; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism / Q000528:radiation effects; D010777:Photochemistry; D013816:Thermodynamics; D014466:Ultraviolet Rays
D000975:Antioxidants; C005975:3,4-dihydroxyphenylethanol; C011867:4-hydroxyphenylethanol; D010626:Phenylethyl Alcohol