Paeoniae Radix, “Shaoyao” in Chinese and “Shakuyaku” in Japanese, the roots of Paeonia lactiflora PALLAS (Paeoni-

in Japanese, the roots of Paeonia lactiflora PALLAS (Paeoniaceae), is one of the well-known herbal drugs prescribed in traditional Chinese medicine (TCM) for the treatment of abdominal pain and stiffness of abdominal muscles. Meselhy and Hattori have reviewed the recent studies on peony roots in terms of chemical structure, biological activity, metabolism and pharmacokinetics. After the discovery of paeoniflorin (PF) having a unique cage-like pinane skeleton among the natural products, a series of such pinane type monoterpenes, including albiflorin (Alb), oxypaeoniflorin (OP) and benzoylpaeoniflorin (BP), were also isolated, and are suggested to be bioactive constituents of peony roots (Fig. 1). The concentration of PF in peony roots is also a representative quality control index authorized by the Japanese Pharmacopoeia (the 14th edition). Immunoassays using antibodies that can be polyclonal, monoclonal or recombinant are exquisite analytical techniques, and proved to be one of the most important contributions to medicine and fundamental life science research in the twentieth century. Since monoclonal antibodies (MAbs) are often considered superior to polyclonal antibodies because of their specificity to a single epitope, their homogeneous structure, and their ability to be mass-produced, we chose MAbs to apply to our immunoassay systems. In our ongoing study of the production of MAbs against naturally occurring bioactive compounds, we have raised MAbs against forskolin, solamargine, marijuana compounds, glycyrrhizin, ginsenoside Rb1 and Rg1, and have applied them to enzyme-linked immunosorbent assay (ELISA), affinity chromatography and immunostaining. Immunological approaches for the quantitative determination of PF and its metabolite using polyclonal antibodies were established by Yoshizaki and Hattori, respectively. However, since no success with MAbs against PF and Alb has been reported, we herein communicate the preparation of MAbs against PF and Alb, their characterization and the establishment of ELISA.