A Highly Convenient Synthesis of Hydroxytyrosol and Its Recovery from Agricultural Waste Waters

Abstract

Hydroxytyrosol, a polyphenol with very interesting antioxidant properties, which naturally occurs in virgin olive oil and mainly in olive oil mill waste waters, was synthesized by reducing 3, 4-dihydroxyphenylacetic acid with LiAlH(4) in tetrahydrofuran under refluxing for 2 h. The yield of reaction was 82.8%. The spectroscopic and HPLC data of the synthesized compound proved to coincide fully with those of a pure sample obtained by the chromatographic recovery from olive oil mill waste waters (yield = 91 mg/L). This synthetic method appears to be the most convenient compared with those reported in the literature and is more convenient than the chromatographic recovery. The tri- and diacetyl derivatives of the synthetic compound were also prepared for structure-bioactivity relationship studies. A brief discussion is given on the economical and ecological aspects regarding the production of hydroxytyrosol.

Use of Whole Cells ofPseudomonas aeruginosafor Synthesis of the Antioxidant Hydroxytyrosol via Conversion of Tyrosol

“…Its structure was established by means of spectroscopic techniques (mass spec- The MS and NMR analyses were performed using a spectrograph, Kratos apparatus type MS 25 magnetic sector, and a Geol apparatus, 270 MHz, respectively. These spectroscopic data agreed with those described by Capasso et al (9,10). The chemical structure of hydroxytyrosol is shown in Fig.…”

“…It has been proved that hydroxytyrosol, an orthodiphenol that occurs in olives and its derivatives, presents several interesting aspects for human health that would allow its potential application in food, as well as in the cosmetic and pharmaceutical industries (27,22). This polyphenolic compound is not commercially available (10). We investigated its production by microbial transformation using synthetic tyrosol as a precursor.…”

“…The method developed by Capasso et al (10) consisted of silica gel chromatography, C 8 reverse-phase chromatography, preparative TLC chromatography, and a crystallization technique. In that study, the researchers produced only 91 mg of pure hydroxytyrosol per liter of olive mill wastewater.…”

“…Chemical synthesis of hydroxytyrosol was performed by the reduction of 3,4-dihy-droxyphenyl acetic acid, followed by a chromatographic purification. The precursor is very expensive, and the method uses toxic reagents which must be removed (10). Hydroxytyrosol was produced from olive oil extraction by-products: (i) the liquid-solid waste of two-phase olive processing, alperujo, by hydrothermal treatment using acid or alkaline catalysts (7) and (ii) the liquid effluent generated from the three-phase olive oil extraction process by solvent extraction (9).…”

“…Several methods have been developed to produce it by means of chemical synthesis (10) through conversion of oleuropein (6), by enzymatic synthesis using tyrosinase as a biocatalyst (16), and by bench scale purification from olive mill wastewater (9). Recently, Bolanos et al (7) reported the production of hydroxytyrosol from the liquid-solid waste of two-phase olive processing, "alperujo," by hydrothermal treatment.…”