|Abstract:||In this graduate work, we determined the optimal solvent to obtain a maximum efficiency of extraction of antioxidative compounds from biological material. In order to obtain extracts of alfalfa, we used conventional extraction, Soxhlet extraction and extraction with supercritical fluid (CO2) on the pilot device (UHDE). As the solvent for conventional extractions we used 100% hexane, a mixture of acetone: water (0: 1, 1: 3, 1: 1, 3: 1, 1: 0) (V:V) and a mixture of ethanol: water (1: 0, 1: 3, 1: 1, 3: 1, 1: 0) (V:V).
With the spectrophotometric methods we determined in extracts antioxidant activity, total phenolic content and the content of proanthocyanidins. The antioxidant activity was presented as % of inhibition, where was measured the absorbance of the sample and the reference solution. As the most effective solvent, by which the obtained extract give the highest antioxidant activity, has proved to be 100% ethanol. The concentrations of total phenolic content and proanthocyanidins are provided per gram of extract as well as per gram of material.
Alfalfa contains beside the antioxidant constituents vitamin D. Since vitamin D is fat-soluble component, we used as extraction solvent hexane and supercritical fluid (CO2). Vitamin D is found in nature in very low concentrations, so we have to use appropriate analytical methods which can detect components also in the ng. Analysis of vitamin D was therefore performed with LC-MS (MS) analytical technique. The results of these analyzes showed the presence of vitamin D2, which the highest level is in the extract obtained with 100% acetone and amounts to 39.22 ng / g of material. For the detection of vitamin D was required saponification, as the analysis of extracts made without saponification give poor results because of the difficulty of detecting in such low concentrations. |