Milk Thistle seed (Silybum marianum) has a long history of use. Although commonly referred to as a "seed," the plant part used is actually the "fruit." Recent studies have demonstrated the positive role of Milk Thistle extract and more specifically, one of its main active constituents silymarin, in supporting and protecting liver.Free Of Synthetic ingredients. Disclaimer These statements have not been evaluated by the FDA. These products are not intended to diagnose, treat, cure, or prevent any disease.