MONOCLONAL-ANTIBODIES AGAINST THE BITTER SESQUITERPENE LACTONES, LACTUCIN AND LACTUCOPICRIN, FROM CHICORY (CICHORIUM-INTYBUS L)

Monoclonal antibodies (MAbs) against lactucin and lactucopicrin (two o f the bitter principles of chicory; Cichorium intybus L.) have been pr epared. In competitive ELISA, the sera from mice immunized with keyhol e limpet haemocyanin (KLH)-lactucin and KLH-lactucopicrin have been sc reened for cross-reactivity to various sesquiterpene lactones with a g uaiane skeleton that are present in chicory, such as lactucin, 8-deoxy lactucin, and their 11 beta,13-dihydro derivatives, and lactucopicrin. Mice showing low cross-reactivity were used to produce hybridomas tha t were screened for cross-reactivity in the same way. The screening re sulted in a lactucopicrin-specific hybridoma (no. 4H10) showing a low cross-reactivity (much less than 1%) for lactucin, 8-deoxylactucin and their 11 beta,13-dihydro derivatives. From KLH-lactucin immunized mic e, hybridoma no. 9F12 showed the best characteristics, i.e. 25% cross- reactivity to 8-deoxylactucin and its 11 beta,13-dihydro derivative, a nd a 10% cross-reactivity to lactucopicrin. The affinity constants of MAbs nos 9F12 and 4H10 were 2.2 x 10(4) and 2.8 x 10(5) M(-1) respecti vely. Chicory extracts spiked with free sesquiterpene lactones showed an inhibition level equal to the sum of the inhibition level of the ex tract and the level of sesquiterpene lactones added.