Saponins from the root of Bupleurum falcatum.

Three new saponins and nine known saponins were isolated from the dried roots of Bupleurum falcatum. On the basis of chemical and spectral analyses, the structures of new compounds, named 4''-O-acetylsaikosaponin d and hydroxysaikosaponins a and c, were established. In aqueous acidic conditions, saikosaponins a and d were converted into not only known compounds, saikosaponins b1 and b2, but also hydroxysaikosaponins a and d, respectively. Furthermore, quantitative analysis of the decoction of Bupleuri Radix itself by HPLC exhibited that it contained saikosaponins a, c and d, and hydroxysaikosaponins a, c and d.