Neocosmospora  Neocosmospora is a genus of fungi in the family Nectriaceae. Bioassay-guided fractionation of a fungus "Neocosmospora" sp. resulted in the isolation of three new resorcylic acid lactones, neocosmosin A (2), neocosmosin B (3) and neocosmosin C (4). Three known resorcylic acid lactones, monocillin IV (1), monocillin II (5) and radicicol (6) were also isolated and identified, where compounds 4–6 show good binding affinity for the human opioid receptors. These findings have important implications for the potential psychoactive effects with this class of compounds.