Structure-activity aspects of 4 allergenic sesquiterpene lactones lacking the exocyclic alpha-methylene at the lactone ring.

4 sesquiterpene lactones lacking the exocyclic alpha-methylene at the lactone ring, but possessing further unsaturated centers such as a cyclopentenone ring or an epoxy group, were proved to be sensitizers in guinea pigs. Lack of substitution in the cyclopentenone ring and unsaturation in the side chains appear to be necessary prerequisites for nucleophilic attack. Our results suggest that to the estimated 650 potential sensitizing sesquiterpene lactones of the Compositae family, a further 50 sesquiterpene lactones should be added.