Identification and determination of aesculin and aesculetin in ash barks by capillary zone electrophoresis

Summary A capillary zone electrophoresis method for identification and determination of aesculin and aesculetin has been established using borate-phosphate buffer containing 30% ethanol with on-column UV detection. A detailed investigation of the influence of changes in borate concentration, pH, applied voltage, temperature and organic modifier was then carried out. For both aesculin and aesculetin, a linear plot of migration time (MT) against borate concentration was obtained, and lnmeasured peak area (MA)] and lnMT both gave linear plots against ln(applied voltage) with correlation coefficient r>0.999, which also resulted in a linear correlation between MA and MT (r≥0.9998) under varied voltage. Ethanol as organic modifier to the background electrolytes helped in separating aesculin and aesculetin from other components in ash barks. The reproducibility with relative standard deviation in MT and in normalized peak area(NA) and linearity based on NA against concentration were evaluated. Finally, the method was successfully applied to monitor the quality of different ash barks and to compare the effect of sample preparation on content of bioactive components in ash bark. Results indicate that CZE promises to be applicable to quality control of traditional Chinese medicines containing aesculin and aesculetin.