Angelicae Sinensis Radix, Danggui in Chinese, is an important traditional Chinese medicine derived from the roots ofAngelica sinensis （Oliv.） Diels. HPLC-ESI-MSn was applied to analyze the chemical constituents in the methanol extract ofDanggui. A total of 24 compounds were identified or tentatively characterized based on their UV and mass spectra, containing11 phenolic compounds, 12 phthalides and 1 amino acid. Three dicaffeoylquinic acids, 5-feruoylquinic acid and ferulic acidhexoside were detected in A. sinensis for the first time. According to Chinese medicine theories, the three parts of Danggui（Guitou, Guishen, Guiwei） have different therapeutic effects and their substantial evidence has not been clearly elucidatedyet. In the present study, the chemical compositions of different parts of Danggui were investigated by using the establishedHPLC method. The result indicated that the content of tryptophan was getting lower and the contents of low polarity constituentslike phthalides trended to get higher from Guitou to Guiwei. This might partly explain the therapeutic effects of differentparts of Danggui.
The fragmentation behavior of isoflavones was studied using electrospray ionization-ion trap-time of flight mass spectrometry （ESI-IT-TOF-MSn）. It was found that the isoflavone glycoside bond was easily broken. The fragmentation occurred mostly on the C-ring, and the fragment ions of A^1,3＋ produced by the RDA cracking will predict the hydroxylation replacement on A-ring or B-ring. In addition, four carbonyl groups on the C-ring were fragmented through neutral loss of 28 （-CO）. A and B-rings primarily lose substituents which including a neutral losses of 32 （-CH3OH）, 16 （-CH4）, or 16 （-O）, and 18 （-H2O）. A-ring in the presence of adjacent hydroxylation, also easily made to be a neutral losses of 28 （-CO） or 18 （-H20）. It is likewise common to see methoxy replaced with a neutral losses of 16 （-CH4） or 32 （-CHaOH） in B-ring, also the hydroxylation on benzene ring can occasionally results with the neutral loss of 28 （-CO）.
