Structure-Activity Relationship Studies on Derivatives of Eudesmanolides from Inula Helenium as Toxicants against Aedes Aegypti Larvae and Adults
DEPARTMENT OF AGRICULTURE STONEVILLE MS AGRICULTURE RESEARCH SERVICE
Pagination or Media Count:
An Aedes aegypti larval toxicity bioassay was performed on compounds representing many classes of natural compounds including polyacetylenes, phytosterols, flavonoids, sesquiterpenoids, and triterpenoids. Among these compounds, two eudesmanolides, alantolactone, and isoalantolactone showed larvicidal activities against Ae. aegypti and, therefore, were chosen for further structureactivity relationship study. In this study, structural modifications were performed on both alantolactone and isoalantolactone in an effort to understand the functional groups necessary for maintaining andor increasing its activity, and to possibly lead to more effective insect-control agents. All parent compounds and synthetic modification reaction products were evaluated for their toxic activities against Ae. aegypti larvae and adults. Structure modifications included epoxidations, reductions, catalytic hydrogenations, and Michael additions to the a,b-unsaturated lactones. None of the synthetic isomers synthesized and screened against Ae. aegypti larvae were more active than isoalantolactone itself which had an LC50 value of 10.0 mgml. This was not the case for analogs of alantolactone for which many of the analogs had larvicidal activities ranging from 12.4 to 69.9 mgml. In general, activity trends observed from Ae. aegypti larval screening were not consistent with observations from adulticidal screening. The propylamine Michael addition analog of alantolactone was the most active adulticide synthesized with an LC50 value of 1.07 mgmosquito. In addition, the crystal structures of both alantolactone and isoalantolactone were determined using CuKa radiation, which allowed their absolute configurations to be determined based on resonant scattering of the light atoms.