Abstract: The natural product neurolenin D is isolated from Neurolaena lobata using continuous extraction, stirring over charcoal, flash column chromatography, and recrystallization. The secondary alcohol in this molecule is converted into a methane sulfonyl ester (mesylate) to generate a new molecule, neurolenin D mesylate. This previously unknown molecule has been tested for biological activity in assays for human toxicity, mutagenicity, and nematocidal potency. It is not toxic or mutagenic and demonstrates the ability to kill nematodes responsible for the neglected tropical disease lymphatic filariasis and is likely to have the same ability to kill other nematodes responsible for a wide range of diseases in humans, animals and plants. Additional esters of neurolenin D are claimed and procedures are outlined for their synthesis.