Extraction of nutraceuticals from milk thistle: part II. Extraction with organic solvents

Seeds from milk thistle (Silybum marianum Gaert L.) contain flavanolignan and dihydroflavanol compounds that have interesting and important therapeutic activities. The recovery of these silymarin compounds generally involves a two-step defatting and extraction process using organic solvents. This study examined the batch, single-stage extraction of whole and defatted seeds using ethanol, methanol, acetonitrile, and acetone as the solvents. In extracting defatted milk thistle seeds with organic solvents, extraction with ethanol resulted in the highest silymarin yield, although some potential degradation was observed. The maximum yields of taxifolin, silychristin, silydianin, silybinin A, and silybinin B in ethanol were 0.6, 4.0, 0.4, 4.0, and 7.0 mg/g of defatted seed, respectively. However, if silybinin A were the diastereoisomer of choice, methanol would be the preferred extraction solvent because it yielded the highest silybinin A to silybinin B ratio. Interestingly, lipid removal is an important extraction step, because defatted material yields twice the silymarin concentration.