ANTI-MICROBIAL PROPERTIES AND POSSIBLE ROLE IN HOST-PATHOGEN INTERACTIONS OF PARTHENOLIDE, A SESQUITERPENE LACTONE ISOLATED FROM GLANDS OF CHRYSANTHEMUM-PARTHENIUM

Parthenolide (C15H20O3), a sesquiterpene lactone, was the major antimicrobial constituent of crude extracts obtained by dipping leaves or seeds of C. parthenium in chloroform. It was separated in pure form by TLC. Parthenolide was probably present in 2-lobed glands on both surfaces of leaves and between ridges on the seeds. Parthenolide inhibited growth of Gram-positive bacteria, yeasts and filamentous fungi in vitro. Gram-negative bacteria were unaffected. A number of the Gram-positive bacteria and yeasts were killed by parthenolide in nutrient broth, though the concentration required varied greatly with the species. Species of Bacillus without endospores were particularly sensitive. Filamentous fungi were relatively insensitive. Parthenolide reduced infection when added to spore-containing droplets of 2 facultative pathogens on chrysanthemum petals and bean leaves. Parthenolide was not phytotoxic except at very high concentrations, but crude extracts from C. parthenium leaves were strongly phytotoxic. The possible role of antimicrobial substances in glands in relation to defence of the plant against disease is discussed.