Identification and characterization of active compounds and their metabolites by high-performance liquid chromatography/Fourier transform ion cyclotron resonance mass spectrometry after oral administration of a herbal extract of Epimedium koreanum Nakai to rats.

Epimedium is an important traditional Chinese medicine that is widely used throughout China as a tonic, aphrodisiac, and antirheumatic medicine. Flavonoids are considered to be the active compounds in Epimedium. In the study reported here, high-performance liquid chromatography coupled with Fourier transform-ion cyclotron resonance mass spectrometry (HPLC/FTICR-MS) was developed to identify active compounds and their metabolites after oral administration of a herbal extract of Epimedium koreanum Nakai to rats, using parent mass list triggered data-dependent multiple-stage accurate mass analysis at a resolving power of 100 000 in the external calibration mode. Nine flavonoids were identified in rats. The chemical formulae with unsaturation numbers calculated from accurate m/z values of precursor and product ions were used to assign the structures of metabolites and the chemical sites of metabolism. The mass accuracies obtained for all full-scan MS and MS(n) spectra were within 3 ppm (<1 ppm in most cases). The majority of the metabolites identified have been previously reported, but three compounds were noted for the first time in rats. By contrasting the analytical results obtained from the herbal extract with those obtained from biological specimens, the profile of flavonoid biotransformation in Epimedium was obtained and the metabolic pathways of these components, in rats, are described. The results should be of use in targeting potential active ingredients in Epimedium.