Abstract
High-throughput screening of the NatureBank marine extract library (n = 7616) using a phenotypic assay for the parasitic nematode Haemonchus contortus identified an active extract derived from the Australian marine sponge Citronia sp. Bioassay-guided fractionation of the CH2Cl2/MeOH extract from Citronia sp. resulted in the purification of two known hexachlorinated peptides, dysidenin (1) and dysideathiazole (2). Compound 1 inhibited the growth/development of H. contortus larvae and induced multiple phenotypic changes, including a lethal evisceration (Evi) phenotype and/or somatic cell and tissue destruction. This is the first report of anthelmintic activity for these rare and unique polychlorinated peptides.