Silybum marianum

Blessed Milk Thistle (Silybum marianum) is a milk thistle, a plant of the Asteraceae family. It is a fairly typical thistle with red to purple flowers and shiny pale green leaves with white veins. Originally a native of Southern Europe through to Asia, it is now found throughout the world. The medicinal parts of the plant are the ripe seeds.

It has a large number of other common names, such as Marian Thistle, Mary Thistle, Mediterranean Milk Thistle and Variegated Thistle.

Trade or commercial names under which this herb is sold include Silymarin, Milk Thistle Extract, Milk Thistle Super Complex, Milk Thistle Phytosome, Alcohol Free Milk Thistle Seed, Milk Thistle Plus, Silymarin Milk Thistle, Milk Thistle Power, Time Release Milk Thistle Power, and Thisilyn Standardized Milk Thistle Extract.

In herbalism, it is used in cases of liver diseases (cirrhosis, jaundice and hepatitis) and gallbladder disease, and is claimed to protect the liver against poisons. An AHRQ study of such claims in 2000 concluded that "clinical efficacy of milk thistle is not clearly established".

Its potent extract is used in medicine under the name silymarin. Another extract, silibinin or a derivative, is used against poisoning by amanitas, such as the Death Cap (Amanita phalloides) and the Fly Agaric (Amanita muscaria).

It has been widely introduced outside its natural range, for example into North America and Australia, where it is considered an invasive weed, and New Zealand.

The species has been found to be toxic to cattle and sheep. The plant contains potassium nitrate. When this is eaten by ruminants the bacteria in their stomachs breaks the chemical down producing a nitrite ion. This combines with hemoglobin to produce methaemoglobin which can't transport oxygen. The result is a form of oxygen deprivation. 

The extract is now also being used in a beverage called Rockstar Energy Drink as an energy enhancing agent.