An unusual dimeric guaianolide with antiprotozoal activity and further sesquiterpene lactones from Eupatorium perfoliatum

► CH2Cl2 extract of E. perfoliatum is active against P. falciparum (IC50 = 2.7 μg/ml). ► Four guaianolides, one dimeric guaianolide, and two germacranolides were isolated. ► The dimer displays an unprecedented subunit linkage between C-14(A) and C-4(B). ► Except for euperfolitin, all STLs described here were hitherto unknown. ► Dimeric guaianolide is active against P. falciparum (IC50 = 2.0 μM, Sel. Ind. ≈ 8).