Superior Quality European Milk Thistle Seed Extract. Source Naturals EUROPURE™ SILYMARIN contains a unique high quality European milk thistle seed extract. The milk thistle used for this silymarin extract is grown and processed according to strict European Union guidelines to meet our high standards of quality. Studies have shown that silymarin acts as a free radical scavenger to support the body's own antioxidant defense system. Preliminary research indicates that silymarin also stimulates RNA and DNA transcription in liver cells which supports protein synthesis and cellular regeneration.