Minor sesquiterpene lactones from Centaurea pullata and their antimicrobial activity

The aerial parts of Centaurea pullata afforded, in addition to the previously isolated sesquiterpene lactones, I 1 beta, 13dihydrocnicin and 11,13-dihydro-19-desoxycnicin, three minor sesquiterpene lactones, namely, anew germacranolide, 8(8 alpha(4-acetoxy-5-hydroxyangeloyl)-11 beta,13-dihydrocnicin, and two new eudesmanolides, 8 alpha-O-(4-hydroxy-2-methylenebutanoyloxy)-1 I,beta 13-dihydrosonchucarpolide and 8(alpha-O-(4-hydroxy-2-meth,yienebutanoyloxy)- I I P,13-dihydro-4epi-sonchucarpolide. The in vitro antimicrobial activity of all isolated sesquiterpene lactones was tested against six bacteria and eight fungal species, using a microdilution method. All compounds tested showed greater antibacterial and antifungal activities than the positive controls used.