Monoclonal Antibodies from Rubia cordifolia Against Antitumor Cyclohexapeptide Deoxybouvardin and Their Use in Immunoassay

An immunoassay system was established for the estimation of the quantity of an antitumor cyclohexapeptide, deoxybouvardin (RA-V) from Bouvardia ternifolia (Cav.) Schlecht, Rubia cordifolia L., and R. akane Nakai (Rubiaceae). First, RA-V was converted into a protein conjugate to make it an effective antigen. In the conjugate the molecular ratio between RA-V and the carrier protein was 5.9:1. The splenocytes from the mouse immunized with the conjugate were then fused with mouse myeloma cells to produce hybridoma, secreting monoclonal antibodies (MAbs) against RA-V. Two clones were isolated, one producing MAb IgG₁ and the other MAb IgG_2b, both having a κ light chain. The resultant MAbs were evaluated for their sensitivity and cross-reactivity.