Milbemycin D is a minor member of a complex family of macrocyclic lactones that contain a characteristic spiroketal group produced from the fermentation of soil bacterium S. hygroscopicus subsp. aureolacrimosus. It potentiates glutamate and GABA-gated chloride channel opening (EC50 = 89 nM) and has been used as a nematocide and insecticide.
