Silymarin is an extract from the milk thistle plant. Research that appeared in Hepatology (2010;51(6):1912–1921) looked at its effect on the hepatitis C virus. The researchers grew liver cells in the laboratory (in vitro) and infected them with the hepatitis C virus. Samples of the cells were then treated with either silymarin or standard hepatitis C treatment. Silymarin prevented the virus from entering the liver cells. It also interfered with the life cycle, interfering with production of RNA and protein in the virus. Silymarin stopped the virus from spreadding cell-to cell.