Comparative study of the hepatoprotective effect of silymarin and silybin on isolated rat hepatocytes

The flavonoid silymarin and its main active component silybin have been used in the treatment of toxic liver diseases. In order to evaluate the hepatoprotective potency of both these compounds, their effects on the viability, lipid peroxidation and reduced glutathione (GSH) depletion induced by allyl alcohol (AA) and tert-butyl hydroperoxide (t-BuOOH) in suspensions of isolated hepatocytes were investigated. Cells were preincubated for 30 min with silymarin and silybin before the addition of AA or t-BuOOH. Samples were taken after 1-2 hr of incubation. Cell death, after 2 hr of incubation with 0.2 mm AA, was prevented by 0.01 mm silymarin; however, 2 mm silybin was required to give comparable protection. The presence of silymarin reduced AA-induced lipid peroxidation by more than 90%, whereas silybin was much less effective. The near-complete depletion of intracellular GSH by AA was restored in a dose-dependent manner by silymarin, but silybin did not have this effect. Protection by silymarin against the toxic effects of t-BuOOH was less pronounced than that against AA. In conclusion, silymarin was much more effective than silybin in preventing the toxic effects induced by two pro-oxidant toxins, AA and t-BuOOH.