Evaluation of antioxidant properties of silymarin and its potential to inhibit peroxyl radicals in vitro.

Silymarin (milk thistle) has been used for centuries as a natural remedy for diseases of liver and biliary tract. The present study was carried out to evaluate the in vitro free radical scavenging activity and antioxidant properties of silymarin. Antioxidant properties of silymarin were evaluated by four methods: 1) FARP assay for total antioxidant capacity; 2) DPPH radical scavenging assay; 3) the inhibitory effect on RBC hemolysis induced by peroxyl radicals from APPH; 4) the inhibitory effect on plasma oxidation induced by Cu(2+). But total phenolic compound was evaluated by Folin-Ciocalteu method. Total polyphenol compounds of silymarin was 0.484+/-0.017 mg Gallic acid equivalent per mg in comparison to that of green tea which is 0.313+/-0.095. High Antioxidant properties and significant protective effect of silymarin were in a concentration dependent manner in all methods. Therefore, silymarin is a powerful antioxidant herbal drug which can protect biological systems against the oxidative stress. It is suggested that silymarin may be used in preventing free radical-related diseases as a dietary natural antioxidant supplement.