Chemical analysis of Eriocaulon buergerianum and adulterating species by high-performance liquid chromatography with diode array detection and electrospray ionization tandem mass spectrometry.

Eriocaulon buergerianum Koern. is the botanical source for the Chinese herbal medicine Gu-Jing-Cao. Other Eriocaulon species are also used as the same herb in local areas and are difficult to be differentiated. In order to improve the quality control of Gu-Jing-Cao, chemical constituents of E. buergerianum and adulterating species were analyzed by high-performance liquid chromatography with diode array detection and electrospray ionization tandem mass spectrometry (HPLC-DAD-ESI-MS(n)). The 70% methanol extracts were separated on a Zorbax SB-C(18) column and eluted with acetonitrile-water (each containing 0.1% formic acid). The compounds were identified by ion-trap mass spectrometry in both positive and negative ion modes. From E. buergerianum, E. faberi, E. sexangulare and E. cinereum, a total of 72 compounds were characterized, including 37 flavonols, 6 flavones, 4 isoflavones, 6 xanthones, 14 naphthopyranones, 3 phenolic acids, and 2 other flavonoids. Chemical variation of these four species were studied at three tiers, HPLC fingerprinting, quantitation of six major flavonoids, and semi-quantitative analysis of all characterized compounds, in combination with principal component analysis. E. buergerianum contained abundant flavonols and naphthopyranones, with minor flavones and xanthones; E. cinereum contained abundant isoflavones and flavones, together with few naphthopyranones; E. sexangulare was rich in flavones; and E. faberi contained abundant xanthones. Based on the above chemical analysis, E. buergerianum could be explicitly differentiated from the adulterating species, and the botanical species of 13 commercial batches of Gu-Jing-Cao were identified correctly. This is the first report on comprehensive chemical analysis of Eriocaulon species.