Obtaining of the antioxidants by supercritical fluid extraction

One of the important trends in the food industry today is demand for natural antioxidants from plant material. Synthetic antioxidants such as butylated hydroxytoluene (BHT), and butylated hydroxyanisole (BHA) are now being replaced by the natural antioxidants because of theirs possible toxicity and as they may act as promoters of carcinogens. The natural antioxidants may show equivalent or higher antioxidant activity than the endogenous or the synthetic antioxidants. Thus, great effort is being devoted to the search for alternative and cheap sources of natural antioxidants, as well as to the development of efficient and selective extraction techniques. The supercritical fluid extraction (SFE) with carbon dioxide is considered to be the most suitable method for producing natural antioxidants for the use in food industry. The supercritical extract does not contain residual organic solvents as in conventional extraction processes, which makes these products suitable for use in food, cosmetic and pharmaceutical industry. The recovery of antioxidants from plant sources involves many problematic aspects: choice of an adequate source (in terms of availability, cost, difference in phenolic content with variety and season); selection of the optimal recovery procedure (in terms of yield, simplicity, industrial application, cost); chemical analysis of extracts (for optimization purposes a fast colorimetric method is more preferable than a chromatographic one); evaluation of the antioxidant power (preferably by the different assay methods). The paper presents information about different operational methods for SFE of bioactive compounds from natural sources. It also includes the various reports on the antioxidant activity of the supercritical extracts from Lamiaceae herbs, in comparison with the activity of the synthetic antioxidants and the extracts from Lamiaceae herbs obtained by the conventional methods