Comment on the published data concerning the identification of biochanin A and prunetin by LC/ESI-MS.

Biochanin A is one of the most common phytoestrogens, occurring in high concentrations in soy and red clover, for instance, which shows a wide spectrum of biological activity. Prunetin is an isomer of biochanin A, and even though it is not very common, its structural relationship to the latter makes it interesting, regarding its biological activity. Nowadays, LC/ESI-MS methods are widely used for identification of natural compounds, including biochanin A and prunetin. However, we found that the published data concerning the identification of biochanin A and prunetin are sometimes disputable. Namely, the identification is based on the product ions which cannot be regarded as characteristic of biochanin A or prunetin. The reported retention times sometimes may be also disputable.