Antifeedant Activity of Some Pentacyclic Triterpene Acids and Their Fatty Acid Ester Analogues

Abstract
The 3-O-fatty acid ester derivatives (C12−C18) of two pentacyclic triterpenic acids, ursolic acid and oleanolic acid, were synthesized under mild esterification conditions in excellent yields (80−85%) and screened for their antifeedant activity, together with the parent acids, against the agricultural pest tobacco caterpillar larvae (Spodoptera litura F) in a no-choice laboratory study. The Urs-12-ene-28-carboxy-3β-octadecanoate and olean-12-ene-28-carboxy-3β-hexadecanoate were found to exhibit exceptionally potent antifeedant activities at 50 μg/cm2 concentration, even after 48 h. Keywords: Antifeedant activity; ursolic acid; oleanolic acid; fatty acid esters; tobacco caterpillar; Spodoptera litura