Extraction of nutraceuticals from milk thistle: I. Hot water extraction

Milk thistle contains compounds that display hepatoxic protection properties. We examined the batch extraction of silymarin compounds from milk thistle seed meal in 50, 70, 85, and 100°C water as a function of time. After 210 min of extraction at 100°C, the yield of taxifolin was 1.2 mg/g of seed, a 6.2-fold increase over the results obtained in a Soxhlet extraction with ethanol on pretreated (defatted) seeds. Similarly, the yield of silychristin was 5.0 mg/g of seed, a 3.8-fold increase. The yields of silybinin A and silybinin B were 1.8 and 3.3 mg/g of seed, respectively, or roughly 30% of the Soxhlet yield. 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 favored at 100°C.