Isolation, characterization and insect growth inhibitory activity of majorturmeric constituents and their derivatives against Schistocerca gregaria (Forsk) and Dysdercus koenigii (Walk)

Curcuminoids, the major colouring constituents of Curcuma longa (turmeric) rhizome powder, comprise mainly three closely related curcumins (I, II and III). A simple method has been devised for their efficient extraction and s eparation. Their structures have been confirmed by H-1 NMR spectroscopy and unique mass fragmentation pattern. Curcumin-I, the major constituent has b een converted to five alkyl ether derivatives, which have been tested along with the parent compounds and other extractives for insect growth inhibito ry activity against Schistocerca gregaria and Dysdercus koenigii nymphs. At 20 mug per nymph, benzene extract and dibutyl curcumin-I were the most act ive (60% inhibition) against S gregaria, whereas at 50 mug per nymph these substances exhibited moderate growth-inhibitory activity (45%) against D ko enigii nymphs. At these concentrations, turmeric oil caused 50-60% nymphal mortality in both test insects. The insect control activity of most of the turmeric products was comparable to or better than that of a commercial nee m formulation. (C) 2000 Society of Chemical Industry.