were directly prepared in 30% methanol. The original standard mixture solution was prepared in 30% methanol with the concentrations of 233 g•mL1 for gallic acid, 290 g•mL1 for catechin, 100 gmL1 for epicatechin and 50 g•mL1 for IS. Then it was diluted with 30% methanol containing 50 g•mL1 IS to prepare standard mixture solutions at various concentration levels. The limits of detection (LOD) and quantification (LOQ) under the present chromatographic conditions were determined at a signal-to-noise ratio (S/N) of 3 and 10, respectively. All solutions were filtered prior to analysis through a 0.45 m membrane filter and injected three times into the HPLC. The calibration curve for each compound was constructed by plotting the peak area ratio of the compound to the IS as a function of the standard analyte concentration.