Analysis of flavonoids and coumarins in Ixeris laevigata var. Oldhami by HPLC

Tao-shang-tsao is the dried entire plant of Ixeris laevigata var. oldhami (Compositae) and a commonly used folk herb in Taiwan. To evaluate the quality of I. laevigata var. oldhami, a simple, rapid, and accurate high-performance liquid chrom-atographic (HPLC) method was developed for the assay of four flavonoids, apigenin, apigenin-7-O-glucoside, luteolin, and luteolin-7-O-glucoside, and two coumarins, esculetin and esculin. The present HPLC system uses an Inertsil ODS-2 column by gradient elution with acetonitrile and 0.1% (v/v) phosphoric acid as the mobile phase. Ethylparaben was used as an internal standard and detected at 254 nm. Regression equations revealed good linear relationships (correlation coefficients: 0.9998-0.9999) between the peak-area ratios of each constituent to ethylparaben. The relative standard deviations of these six constituents ranged between 0.56-3.04% (intra-day) and 0.79-4.39%(tinter-day). The contents of six constituents of I. laevigata var. oldhami in 7 crude drugs have been determined. This study also compared their constituents with those of similar folk herbs, I. chinensis and Taraxacum formosanum, commonly used as an adulterant, by their HPLC chromatograms.