Allelochemical, Eudesmane-Type Sesquiterpenoids from Inula falconeri

We have identified through bioassay guided isolation an allelochemical, eudesmane-type sesquiterpeniod, 3 beta-caffeoxyl-beta 1,8 alpha-dihydroxyeudesm-4(15)-ene (1), from an endemic plant species growing in the Himalayas. In our search for the bioactive subfraction, the hexane one was highly significant, showing 100% inhibition of lettuce seed growth at 100 ppm while other subfractions (chloroform, ethyl acetate, butanol and water) exhibited inhibitory to stimulatory allelopathic effects. The bioactive hexane subfraction was subjected to chromatographic techniques, using lettuce seeds (Lactuca sativa) as indicator species to reveal the bioactive allelopathic fraction. This resulted in the isolation of compound 1, whose structure was elucidated through NMR techniques. The compound presented 92.34% inhibitory effect on the growth of lettuce at 500 ppm. Further field level experiments may help develop an environmentally friendly herbicide from this lead.