Toxicity of aristolochic acids isolated from Aristolochia indica Linn (Aristolochiaceae) against the malarial vector Anopheles stephensi Liston (Diptera: Culicidae)

- Aristolochia indica leaves fractions were identified and estimated for their larvicidal properties against the A. stephensi.
- Effective phytocomponents were purified, and functional groups were identified through HPLC and FTIR.
- Bioactive compounds were further confirmed through 1H and 13C NMR.
- Aristolochic acid I and II were proved as a larvicidal agent against the malarial vector A. stephensi.
- The greater damage to the gut epithelial cells was observed through histology.

With the growth of resistance to overused insecticides, vector management has become highly problematic. Hence more concentration has been focused on botanicals. Therefore our present study was aimed to evaluate the toxicity of compounds, aristolochic acid I and aristolochic acid II from the methanol extract of Aristolochia indica L. (Aristolochiaceae) leaves on larvae of Anopheles stephensi L. (Diptera: Culicidae) employing World Health Organization standard larvicide testing procedures. The soxhlet extraction was carried out using polar solvent, methanol. The isolated toxic compounds were purified through RP-HPLC. The FTIR spectroscopic studies revealed different peak values with functional groups in the mixed compounds (AA-I and AA- II). These two aristolochic acids were further studied through 13C and 1HNMR analysis with confirmed by structures. Bioassay-guided fractionation through flash chromatography lead to the isolation of two larvicidal compounds namely aristolochic acid I and II. In these bioassays, the larvae were exposed to concentrations of 100, 250, 500,750 and 1000 ppm for each compound. Between the two, AA-I exerted no significant toxicity difference (P < 0.05) on mosquito larvae with LC50- 171.3, 209.8, 269.1, 502.3 ppm and LC90-751.6, 963.8, 972.7, 990.8 ppm compared to AA-II with LC50-134.8, 166.7, 240.4,543.2 ppm and LC90- 636.7, 792.5, 990.8, 986.2 ppm against first, second, third and fourth instars, respectively. Further, the isolated compounds were severely affecting the mosquito gut. From the results, A. indica toxic compounds could be considered as one of the influential applicant to bring about useful botanicals so as to prevent the resurrection of mosquito vectors.

Graphical Abstract