Silymarin is an antihepatotoxic substance isolated from the fruits of silybum mariamum. Possibly due to their antioxidant and membrane stabilizing properties, the compounds was shown to protect various organs and cells against a number of insults (Kvasnicka et al., 2003). Among the main silymarin components, [silybin($SB_A,;SB_B$, isosilybin ($ISB_A,;ISB_B$) silydianin (SD) and silychristin (SC)], silybin is the major pharmacologically active compound. Korean Pharmaceutical Codex (2nd ed.) describes silybin as the main substance of Cardus Marianus extract as supportive treatment of chronic inflammatory liver disorders. The aim of this work was to analyze silybin from various preparations containing cardus marianus extract, nicotinamide, and riboflavin (CNR). Nine commercial products were tested using reversed-phase HPLC-PDA assay. The limits of detection and quantification were $0.2;{mu}g/ml$ and $1;{mu}g/ml$, respectively. Calibration curve showed a good linearity ($r^2$=1.00000) in the range of $1{sim}500;{mu}g/ml$ of silybin standard solutions.