Determination of Silymarin Flavonoids by HPLC and LC-MS and Investigation of Extraction Rate of Silymarin in Silybum marianum Fruits by Boiling Water

Abstract

A method has been developed for simultaneous separation and determination of seven important silymarin flavonoids by HPLC and LC-ESI/MS. The separation was completed on an ODS column using 1 % aqueous acetic acid solution and methanol as mobile phase with gradient elution. The methanol is better than acetonitrile as the organic modifier in mobile phase for separation of diastereomers of silybin (silybin A and silybin B) and diastereomers of isosilybin (isosilybin A and isosilybin B) was explained from the viewpoint of molecules interaction. The content of silybin and silymarin in Silybum marianum seed, defatted seed meal and standardized extract were determined with satisfactory recovery and precision. Furthermore, the extraction rate of silymarin flavonoids in Silybum marianum seed with boiling water was evaluated on the basis of the well-verified quantitative method. It is found that more polar flavonoids such as taxifolin and silychristin have good solution in water and the total extraction rates of seven times were more than 85 %, and the solubility of other silymarin flavonoids is relatively low, but the total extraction rates were all more than 30 % for seven times of extraction. The results of this study are in excellent agreement with those of batch extraction with hot water.