Alkaline Methanolysis and Octylamine Addition Products of Dehydrocostus Lactone Isolated from Echinops kebericho Root

Dehydrocostus lactone is biosynthesized in Saussurea lappa (commonly known as costus), Echinops kebericho, and E. amplexicaulis. Since reports described the compound as a bioactive metabolite, many analogues were synthesized to evaluate the structure-activity relationship. In this study, two new analogues of the active principle were synthesized to compare their mycelial growth inhibition potential against two plant pathogens, namely, Fusarium species causing root rot/wilt of faba bean and Phytophthora infestans triggering potato late blight in Ethiopia. Structural changes at the lactone ring of the synthesized compounds led to a decrease in growth inhibition diameter, which describes the role of the α-methylene-γ-lactone moiety in determining the observed bioactivity. The chemical structures of the two new compounds are elucidated using spectroscopic analysis and reported for the first time.