Methods are disclosed for the large-scale isolation of 98.5% pure Nimbin from Neem seeds. The ultimate product is obtained first from an alcoholic extraction with subsequent partitioning using chlorinated hydrocarbon solvents. A resulting partitioned layer, which is recovered and concentrated, is then stripped with a hydrocarbon solvent, distilled and cooled to ambient temperature. The resulting mass is mixed and washed in a second hydrocarbon solvent, after which the resulting solid is washed in methanol and treated with activated carbon to produce a crystalline, tasteless product having a melting point of approximately 210-212.degree. C.
