GA 2018

Milk thistle (Silybum marianum (L.) Gaertn., Asteraceae) fruit is a traditionally used hepatoprotective agent. Silymarin, a complex of flavonolignans, consisting of silybin A, silybin B, isosilybin A, isosilybin B and others, is considered to be the active component of this herb. In order to effectively extract the flavonolignans from milk thistle fruit, the ultrasonication-assisted extraction was carried out using water/glycerol as a non-toxic biodegradable solvent mixture. Firstly, for selection of independent variables that have the strongest influence on the silymarin extraction, the two-factor interaction model was used. Silymarin content was analyzed using the HPLC-DAD method. Analysis of variance (ANOVA) has shown that the most important extraction factors were glycerol concentration, temperature and extraction time. Subsequent Box Behnken analysis, performed by varying the selected factors, has shown that silymarin content was linearly dependent on time and temperature, as well as on their interaction. Glycerol concentration, on the other hand, influenced the extraction process as a quadratic factor. Numerical optimization has revealed that the best conditions for silymarin extraction were 40% glycerol, 80 °C and 60 min. The experimental silymarin content corresponded well with the expected one (105 microgg/mL vs. 102 microg/mL) thus confirming the validity of the quadratic model. The results indicate that the extraction using water/glycerol mixtures is an eco-friendly procedure for extraction of silymarin from milk thistle fruit.