Extraction of Silymarin Compounds from Milk Thistle (Silybum Marianum) Seed Using Hot, Liquid Water as the Solvent

High value specialty chemicals are usually obtained from natural products by extracting with generally regarded as safe (GRAS) soh•ents. Because organic solvents are quite often used, high operating and disposal costs often occur. When compared to traditional solvents, water can be viewed as an interesting a/tentative because of its low operating and disposal costs. Milk thistle contains compounds (taxifolin, silychristin, silydianin, silybinin A and silybinin B) that display hepatoxic protection properties. This paper examines the batch extraction of silymarin compounds from milk thistle seed meal in 5(J'C, 7(J'C, 85"C and 1 OOooC water as a function of time. For taxifolin, silychristin, silybininA and silybinin B, extraction with 1 ()()' C water resulted in the highest yields. After 210 min of extraction at 1(J(J'C, the yield of taxifolin was 1.2 mg per g of seed, while the yields of silychristin, silybinin A and silybinin B were 5.0, 3. 7 and 6.5 mg per g of seed, respectively. The overall diffusion coefficients for the four compounds increased with temperature and ranged from 0.14 x 1 rt10 to 4 x1 rt m/sec, indicating that the diffusion coefficients could potentially be used for quantitative comparisons of extraction conditions. The ratios of the extracted compounds, and particularly the ratios at long extraction times, showed that the more polar compounds (taxifolin and silychristin) were preferentially extracted at 85"C, while the less polar silybinin was preferentially extracted at 1(J(J'C.