ISOLATION AND IDENTIFICATION OF THE NATURAL ANTIOXIDANTS FROM ROSEMARINUS OFFICINALIS L.

摘要

A natural antioxidant with activity comparable to, or in some instances superior to, BHT was isolated from Rosemarinus officinalis L.. The antioxidant was found to be highly effective at a concentration of 0.02 - 0.005%. Addition of 0.005% of ascorbic acid further enhanced the antioxidant activity of the rosemary extract. The natural antioxidant thus prepared is a complex mixture of organic compounds. It was separated into 7 primary fractions with liquid chromatography, using silicic acid as the adsorbent and gradient elution. Fraction ranged from viscous liquids to crystalline solids were obtained. Each fraction showed a number of peaks when subjected to high performance liquid chromatography. They were therefore each rechromatographed to yield 16 subfractions. The two fractions with the greatest antioxidant activity were the 5 and 10% ether in hexane eluate. These two fractions were further fractionated by high performance liquid chromatography to yield pure fractions for structural identification. For this purpose, a modified procedure of the AOCS official method to evaluate the antioxidant properties of microgram quantities of subfractions was developed. Two crystalline compounds, carnosol and ursolic acid, were identified by IR, MS, and NMR spectroscopy. Carnosol was found to be an active antioxidant and ursolic acid was not. The third compound isolated from fraction five which has a good antioxidant activity was not identified yet.