Standardized Extract. Milk Thistle 175 mg per capsule. 90 Capsules. Derived from a purple flower, Milk Thistle helps maintain healthy liver functions. Milk Thistle contains antioxidant properties that help fight free radicals in the body. Free radicals may contribute to the premature aging of cells. Spring Valley's Milk Thistle is standardized to contain 80% Silymarin. This means that you can be assured of receiving a consistent level of active ingredients with each serving.