Evaluation of naturally occurring curcuminoids and related compounds against mosquito larvae

The three curcuminoid components commonly isolated from Curcuma longa, curcumin (1), demethoxycurcumin (2), and bis-demethoxycurcumin (3) were separated and isolated from a commercially available turmeric extract product in high purity and sufficient amounts. Three more derivatives of curcumin, the di-O-demethylcurcumin (4), di-O-methylcurcumin (5) and the di-O-acetylcurcumin (6) were also synthesized and characterized. All six compounds were evaluated for their larvicidal effect against the mosquito Culex pipiens. Curcumin (1) exhibited highly potent larvicidal activity with LC50 value of 19.07 mg L−1. Moreover, di-O-demethylcurcumin (4), was found to be equally active with LC50 value of 12.42 mg L−1. Based on the LC90 values of the two compounds, di-O-demethylcurcumin (4) was the most active of all, resulting in an LC90 value of 29.40 mg L−1, almost half of the LC90 value 61.63 mg L−1 found for compound 1. The rest of the compounds were inactive at concentrations even as high as 150 mg L−1 indicating a dependence of the larvicidal activity upon the substitution patent and the presence of aromatic hydroxyl and methoxy moieties. These results show for the first time the potential of this valuable natural product regarding its use as vector control agent.