Production of monoclonal antibodies against a major purgative component, sennoside B, their characterization and use in ELISA

For immunization, sennoside B was conjugated with bovine serum albumin. The hapten density in the antigen conjugate was determined to be 3 mol mol^-1 protein by matrix-assisted laser desorption-ionization TOF mass spectrometry. A hybridoma secreting monoclonal antibody against sennoside B was produced by fusing splenocytes from mouse immunized with the sennoside B conjugate and mouse myeloma cells. Weak cross-reactivities occurred with sennoside A which is a stereochemical isomer, and a monomer of sennoside B, rhein, but no cross-reactivity was observed with other related anthraquinones and phenolics. The range of the assay extended from 0.5 ng ml^-1 to 15 ng ml^-1 of sennoside B, and good correlation between ELISA and HPLC methods was obtained when crude extracts of rhubarb were analyzed.