Comparison of Silymarin Extraction from Silybum marianum Using a Soxhlet Apparatus, Batch Parr, and Countercurrent Pressurized Hot Water Reactors

The extraction of phytochemicals using pressurized hot water extraction (PHWE) is promising because it is efficiently performed with an environmentally benign solvent, resulting in extracts that are devoid of organic solvent traces. For phytochemical extraction, PHWE is usually carried out with 110°C to 180°C water, which can unfortunately lead to product degradation. To reduce product degradation during PHWE, a countercurrent pressurized hot water reactor was designed, constructed and tested; the phytochemical system used to test the reactor was silymarin extracted from Silybum marianum (milk thistle) seed meal. Silymarin yields and product degradation from the countercurrent reactor were compared to ethanol-Soxhlet and batch pressurized hot water extractions. The ethanol-Soxhlet extraction produced the cleanest high-performance liquid chromatography (HPLC) chromatogram (minimal by-product formation) and the largest silymarin yield at 18.3 mg per g seed meal. The countercurrent reactor yielded 5.2 mg silymarin per g seed meal, and the batch reactor yielded 6.2 mg silymarin per g seed meal. However, the countercurrent reactor did not produce the degradation peaks that were produced in the batch reactor. Thus, the countercurrent reactor offers possible technology for environmentally benign extraction of phytochemicals without product degradation.