Larvicidal activity of turmerone-rich essential oils of Curcuma longa leaf and rhizome from Nigeria on Anopheles gambiae

The essential oils from the leaves and rhizomes of Curcuma longa L. (Zingiberaceae) were subjected to larvicidal toxicity studies on Anopheles gambiae, the malaria vector. The leaf essential oils were obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry, respectively. The rhizome oil was much more toxic to the mosquito larvae, exhibiting 100% mortality at 0.125 mg/mL with an LC50 of 0.017 mg/mL. The leaf had absolute mortality at 0.500 mg/mL with an LC50 of 0.029 mg/mL. The observed toxicities were also found to be concentration dependent. The oils were found to be composed mainly of turmerones, with the major components in the leaf volatile oil being ar-turmerone (63.4%), α-turmerone (13.7%), and β-turmerone (12.6%). ar-Turmerone (44.4%), β-turmerone (26.5%), and α-turmerone (20.8% were the main components in the rhizome. Both oils displayed overwhelming activities compared with the reference compound N,N-Diethyl-m-toluamid (DEET) which had an LC50 value of 1.09 mg/mL. The turmerone composition, especially the combination of α-turmerone and β-turmerome constituents in the oils, may be responsible for the observed larvicidal toxicities of both essential oils. The essential oils from the leaf and rhizome of this plant may find use as a source of malaria vector control agents. © 2008 Informa Healthcare USA, Inc.