Identification of isoflavones in the roots of Pueraria lobata.

The isoflavones of the roots of Pueraria lobata (Willd.) Ohwi (Puerariae Radix) were investigated by high-performance liquid chromatography (HPLC) coupled to photodiode array (PDA) and to mass spectroscopy (MS) using atmospheric pressure chemical ionization (APCI) or electrospray ionization (ESI) in combination with collision-activated decomposition (CAD) (HPLC-APCI-CAD-MS or ESI-CAD-MS) for identification of glycosides and HPLC-APCI-CAD-MS for identification of aglycones. The major glycosides are derived from daidzein ( 9) and most are 8- C-glycosides. 3'-Hydroxypuerarin-4'- O-deoxyhexoside ( 2B) and 3'-methoxy-6''- O- D-xylosylpuerarin ( 6) were identified as new constituents. MS data were obtained for puerarin-4'- O- D-glucoside ( 1), 3'-hydroxypuerarin ( 2A), puerarin ( 3), 3'-methoxypuerarin ( 4), 6''- O- D-xylosylpuerarin ( 5), daidzin ( 7) and 3'-methoxydaidzin ( 8), which were previously characterized by NMR analysis. Isoflavones identified in Puerariae Radix comprise 3'-methoxydaidzein ( 10), genistein ( 12), daidzein-7- O-methyl ether ( 13A), 3'-methoxydaidzein-7- O-methyl ether or 3'-methoxyformononetin ( 13B) and biochanin A ( 15), while previous characterization of daidzein ( 9) and formononetin ( 14) was substantiated by MS data. The structure of compound 11 could not be established by MS techniques. The estrogenic activity was mainly located in the aglycone fraction.