(4Z)-Lachnophyllum Lactone, an Acetylenic Furanone from Conyza bonariensis, Identified for the First Time with Allelopathic Activity against Cuscuta campestris

Cuscuta species are obligate parasitic plants that infect the stems of a wide range of hosts including many crop and weed species causing severe agricultural problems. Using in vitro experiments to screen organic extracts prepared from fifteen autotrophic weed species found in agricultural fields infested with Cuscuta campestris, we have identified for the first time a strong phytotoxic activity in Conyza bonariensis extract against C. campestris. Additional pot experiments revealed that seven day-old Cuscuta seedlings had reduced capacity to coil and properly attach on Conyza plants, leading to reduced parasitic weed infection. Via activity-guided fractionation of Conyza extracts, we isolated and identified the acetylenic furanone (4Z)-lachnophyllum lactone as the major active component, with a concentration required to achieve reduction of 50% Cuscuta seedling growth (IC50) of 24.8 mu g/mL. The discovery of (4Z)-lachnophyllum lactone bioactivity could aid the development of efficient and sustainable management strategies for C. campestris, whose control is limited or non-existent.