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

Abstract

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 separation. Their structures have been confirmed by 1H NMR spectroscopy and unique mass fragmentation pattern. Curcumin-I, the major constituent has been converted to five alkyl ether derivatives, which have been tested along with the parent compounds and other extractives for insect growth inhibitory activity against Schistocerca gregaria and Dysdercus koenigii nymphs. At 20 µg per nymph, benzene extract and dibutyl curcumin-I were the most active (60% inhibition) against S gregaria, whereas at 50 µg per nymph these substances exhibited moderate growth-inhibitory activity (45%) against D koenigii 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 neem formulation. © 2000 Society of Chemical Industry