THE EFFECTS OF EXTRACTION TECHNIQUES ON THE ANTIOXIDANT POTENTIAL OF EXTRACTS OF DIFFERENT PARTS OF MILK THISTLE (SILYBUM MARIANUM L.)

Background. Extracts of milk thistle, particularly from seeds, are used as a valuable source of natural antioxidants in different industries, for example pharmaceutical and cosmetic. The leaves and flowers are also known to be a source of biologically active compounds, as well as those with an antioxidant capacity. The selection of the extraction parameters, such as type and concentration of extractant, and extraction time, have an impact on the antioxidant capacity of the obtained extracts. The aim of this study was to evaluate the antioxidant activities of extracts obtained using different parts of raw material. The impact of different parameters of extraction on antioxidant capacity was also assessed. Materials and methods. The seeds, flowers and leaves were extracted using a Soxhlet apparatus, ultrasound and shaking. 96% (v/v) and 70% (v/v) ethanol, concentrated methanol, acetone and petroleum ether were applied as solvents. The impact of the extraction time was also evaluated. The extracts were evaluated using DPPH, ABTS, FRAP and Folin-Ciocalteu techniques. Results. The obtained extracts, except for the samples in petroleum ether, showed the antioxidant capacity. Soxhlet extraction, especially that which uses ethanol, methanol and acetone, seems to be a valuable extraction method. Conclusion. To sum up, many factors could affect the antioxidant capacity and the total polyphenol content of Silybum marianum L. extracts. The solvent and an appropriately selected extraction method seem to be important factors in the effective isolation of active substances and could lead to the more effective application of this valuable plant material in different industries.