title: Synthesis and Antioxidant Activity of Hydroxytyrosol Alkyl-Carbonate Derivatives.
abstract: Three procedures have been investigated for the isolation of tyrosol (1) and hydroxytyrosol (2) from a phenolic extract obtained from the solid residue of olive milling. These three methods, which facilitated the recovery of these phenols, were chemical or enzymatic acetylation, benzylation, and carbomethoxylation, and subsequent carbonylation or acetonation reactions. Several new lipophilic alkyl-carbonate derivatives of hydroxytyrosol have been synthesized, coupling the primary hydroxy group of this phenol, through a carbonate linker, using alcohols with different chain lengths. The antioxidant properties of these lipophilic derivatives have been evaluated by different methods and compared with free hydroxytyrosol (2) and also with the well-known antioxidants BHT and α-tocopherol. Three methods were used for the determination of this antioxidant activity: FRAP and ABTS assays, to test the antioxidant power in hydrophilic media, and the Rancimat test, to evaluate the antioxidant capacity in a lipophilic matrix. These new alkyl-carbonate derivatives of hydroxytyrosol enhanced the antioxidant activity of this natural phenol, with their antioxidant properties also being higher than those of the commercial antioxidants BHT and α-tocopherol. There was no clear influence of the side-chain length on the antioxidant properties of the alkyl-carbonate derivatives of 2, although the best results were achieved mainly by the compounds with a longer chain on the primary hydroxy group of this natural phenolic substance.
authors.affiliation: Departamento de Quimica Organica, Facultad de Ciencias, Universidad de Granada , Fuentenueva s/n, ES-18071 Granada, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Fernandez-Pastor
authors.affiliation: Centro "Venta del Llano" del Instituto Andaluz de Investigacion y Formacion Agraria, Pesquera, Agroalimentaria y de la Produccion Ecologica (IFAPA) , Mengibar, Jaén 23620, Spain.
authors.forename: Antonia
authors.initials: A
authors.lastname: Fernandez-Hernandez
authors.affiliation: Departamento de Quimica Organica, Facultad de Ciencias, Universidad de Granada , Fuentenueva s/n, ES-18071 Granada, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Rivas
authors.affiliation: Departamento de Quimica Organica, Facultad de Ciencias, Universidad de Granada , Fuentenueva s/n, ES-18071 Granada, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Martinez
authors.affiliation: Departamento de Quimica Organica, Facultad de Ciencias, Universidad de Granada , Fuentenueva s/n, ES-18071 Granada, Spain.
authors.forename: Andres
authors.initials: A
authors.lastname: Garcia-Granados
authors.affiliation: Departamento de Quimica Organica, Facultad de Ciencias, Universidad de Granada , Fuentenueva s/n, ES-18071 Granada, Spain.
authors.forename: Andres
authors.initials: A
authors.lastname: Parra
mesh_terms: D000975:Antioxidants / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D002254:Carbonates / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D015394:Molecular Structure; D031658:Olea / Q000737:chemistry*; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D024502:alpha-Tocopherol / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D002254:Carbonates; D010636:Phenols; C005975:3,4-dihydroxyphenylethanol; C011867:4-hydroxyphenylethanol; D024502:alpha-Tocopherol; D010626:Phenylethyl Alcohol