Production and Characterization of Polyclonal Antibodies against the Bitter Sesquiterpene Lactones of Chicory (Cichorium intybus L.)

Polyclonal antisera against lactucin and lactucopicrin, two bitter-tasting principles of chicory (Cichorium intybus L.), were obtained after immunization of rabbits with KLH-lactucin and KLH-lactucopicrin conjugates, respectively. In competitive ELISA, the sera from KLH-lactucopicrinimmunized rabbits showed a very low cross-reactivity with other sesquiterpene lactones containing a guaiane skeleton, 0.5% with lactucin, 1% with a mixture of lactucin and 11β,13-dihydrolactucin, and 5% with 8-deoxylactucin and 11β,13-dihydro-8-deoxylactucin. The sera from rabbits immunized with KLH-lactucin showed 50% cross-reaction with 8-deoxylactucin and its 11β,13-dihydro derivative and only 0.4% cross-reaction with lactucopicrin. In competitive ELISAs, chicory extracts spiked with free sesquiterpene lactones showed an expected increase in inhibition level. These ELISAs seem useful in the assessment of chicory bitterness.