Abstract: We measured infrared spectra of nine raw herbs of Euphorbia L. distributed in Shaanxi Province by Fourier Transform Infrared(FTIR) spectrometer, and analyzed the secondary derivative infrared spectra in 1 800-400  cm^-1. By principal component analysis of the second derivative spectra, the first two principal components accounted for 77.04%, which reflected the most information of the original spectrum and could be used for identifying nine Euphorbia species. The scattered score distributive diagram and cluster analysis based on the first two principal components showed that nine raw herbs of Euphorbia L. can be divided into three classes, E.kansui was one class, E.lathylris was the other class, and E.humifusa, E.lunulata, E.pekinensis, E.hylonama, E.jolkini, E.esula and E.helioscopia fell into another class. Our result is similar to that by morphological classification, and FTIR spectroscopy combined with principal component analysis and cluster analysis could provide evidence for the taxonomic study of Euphorbia.

Key words: Euphorbia L., FTIR spectrum, secondary derivative infrared spectrum, taxonomic significance