Reaction of Alantolactone, an Allergenic Sesquiterpene Lactone, with some Amino Acids. Resultant Loss of Immunologic Reactivity

Abstract

A study of the reaction of a hapten, alantolactone, with some amino acids is reported. Previously, we have reported than an α-methylene group attached to the γ-lactone is the immunologic requisite of alantolactone and some other sesquiterpene lactones. Such a group is known to be capable of undergoing "Michael-type addition" with the sulfhydryl group of cysteine. We confirm this finding and report that alantolactone can also undergo addition with the imidazole group of histidine and with the ε-amino group of lysine, but not with the guanido group of arginine, the hydroxyl group of serine, or the thio ether function of methionine. We selected these amino acids for further study because of their nucleophilic side chain. Samples of alantolactone that have undergone such addition no longer produce allergic eczematous contact dermatitis, as measured by patch test.