CE Method with Partial Filling Techniques for Screening of Xanthine Oxidase Inhibitor in Traditional Chinese Medicine

A combination of electrophoretically mediated microanalysis (EMMA) methodology with a partial filling technique was developed for screening of xanthine oxidase (XOD) inhibitors in substances used in traditional Chinese medicine (TCM). In order to achieve sufficient separation, a micellar electrokinetic chromatography (MEKC) method was employed for the separation. The enzyme activity was determined by the quantification of the peak area of the product, uric acid (UA), at 295 nm. Enzyme inhibition can be read out directly from the reduced peak area of UA in comparison to a reference electropherogram obtained in the absence of any inhibitor. The method was validated using a commercially available XOD inhibitor, 4-aminopyrazolo3,4-d]pyrimidine, and the IC₅₀ value was determined to be 29.90 ± 0.26 μM. Fifteen natural extracts from TCM were screened, and Cortex Phellodendri (the dried bark of Phellodendron chinense) extract was found to be positive for XOD inhibition.