A comparative study of biomimetic oxidation of oregano essential oil by H2O2KHSO5 catalyzed by Fe (III) meso-tetraphenylporphyrin or Fe (III) phthalocyianine

Oregano (Origanum vulgare L.) is an aromatic plant very rich in essential o il which in turn is an important natural resource of thymol and carvacrol. These compounds can be transformed to more valuable thymoquinone. Herein, a comparative study is presented explaining the oregano essential oil oxidat ion applying potassium monopersulphate or hydrogen peroxide catalyzed by tw o different so-called biomimetic catalysts: Fe (III) meso-etraphenylporphyr in or Fe (III) phthalocyanine. Both are highly efficient catalysts in the p rocess of the KHSO5 oxidation of essential oil. A complete substrate conver sion was observed within 1h and the cocatalyst ammonium acetate did not inf luence the catalytic process. When H2O2 was used as oxidant, a relatively s lower conversion and lower reaction yield were observed and the presence of ammonium acetate affected the oxidation cycle with both catalysts. In conc lusion, the essential oil rich in thymol (47.6%) and carvacrol (25.1%) can be easily oxidized to oil containing thymoquinone (19.1-63.3%) as the main or as one of the main components. (C) 2001 Elsevier Science B.V. All rights reserved.