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 qualit y of I. laevigata var. oldhami, a simple, rapid, and accurate high-performa nce liquid chrom-atographic (HPLC) method was developed for the assay of fo ur 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 w ith acetonitrile and 0.1% (v/v) phosphoric acid as the mobile phase. Ethylp araben was used as an internal standard and detected at 254 nm. Regression equations revealed good linear relationships (correlation coefficients: 0.9 998-0.9999) between the peak-area ratios of each constituent to ethylparabe n. The relative standard deviations of these six constituents ranged betwee n 0.56-3.04% (intra-day) and 0.79-4.39%(tinter-day). The contents of six co nstituents of I. laevigata var. oldhami in 7 crude drugs have been determin ed. This study also compared their constituents with those of similar folk herb s, I. chinensis and Taraxacum formosanum, commonly used as an adulterant, b y their HPLC chromatograms.