Optimization of microwave assisted extraction of bioactive flavonolignan - silybinin

In this paper, a novel method of microwave assisted extraction (MAE) used for the extraction of a potent hepatoprotective bioactive silybinin, as a main flavonolignan from Silybum marianum is presented.  The extracts were quantified for silybinin by HPLC. To prove the efficiency of the proposed MAE technique, it was compared with traditional methods like Soxhlet, maceration and stirring extraction. If the extraction yield obtained from MAE was to be considered as 100% performance level then, 12 h of Soxhlet extraction and 24 h of maceration and stirring extraction could attain 79.6%, 26.3% and 35% performance (in terms of extraction yield of silybinin) efficiency with high degree of reproducibility. The optimum extraction conditions were 600 W microwave power, 12 min extraction time (spread over two extraction cycles of 6 min each), 80% v/v ethanol as the extraction solvent, 20 min preleaching time and 25:1 (mL/gm) as the solvent to material loading ratio. A synergistic mechanism of heat and mass transfer was proposed to account for the accelerated extraction due to microwave.