The effects of extraction techniques on the antioxidant potential of extracts of different parts of milk thistle (Silybum marianum L.)

摘要

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 alsoknown to be a source of biologically active compounds, as well as those with an antioxidant capacity. Theselection of the extraction parameters, such as type and concentration of extractant, and extraction time, havean 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 parametersof extraction on antioxidant capacity was also assessed.Materials and methods. The seeds, flowers and leaves were extracted using a Soxhlet apparatus, ultrasoundand shaking. 96% (v/v) and 70% (v/v) ethanol, concentrated methanol, acetone and petroleum ether wereapplied as solvents. The impact of the extraction time was also evaluated. The extracts were evaluated usingDPPH, 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 contentof Silybum marianum L. extracts. The solvent and an appropriately selected extraction method seem to beimportant factors in the effective isolation of active substances and could lead to the more effective application of this valuable plant material in different industries.