Toshiro Ibuka

Structure-antimicrobial activity relationships among the sesquiterpene lactones and related compounds

Abstract Thirty-six sesquiterpene lactones and related compounds were evaluated for antimicrobial activity against six strains of bacteria. The results obtained show that the beta unsubstituted cyclopentenone ring moiety contributes to moderate antimicrobial activity against Gram positive bacteria. The corresponding saturated compounds gave a more than ten-fold decrease in activity. The significant antimicrobial activity appears to be independent of the presence or absence of an α-methylene-γ-lactone moiety. A more than ten-fold diminution in antimicrobial activity was also observed when the beta position of the cyclopentenone ring was substituted. A similar result was found when the beta unsubstituted enone system was present in a six-membered ring. Enhanced activity was obtained by esterification of the hydroxyl group of helenalin as well as epoxidation of mexicanin-A.