Butyrolactone V is a fungal metabolite that has been found in A. terreus and has antiprotozoal, antioxidant, and anticancer activities.1,2,3 It is active against the P. falciparum strain K1 (IC50 = 7.9 μg/ml) and L. amazonensis promastigotes (IC50 = 23.7 μM).2,1 Butyrolactone V (227 and 454.1 μM) is also active against adult S. mansoni worms.1 It scavenges 2,2-diphenyl-1-picrylhydrazyl and ABTS radicals with IC50 values of 20.7 and 3.7 μM, respectively, in cell-free assays.3 Butyrolactone V also inhibits proliferation of MDA-MB-231 and MCF-7 breast cancer cells (IC50s = 22.2 and 31.9 μM, respectively).1