ARS | Publication request: Mosquitocidal and water purification properties of Cynodon dactylon, Aloe vera, Hemidesmus indicus and Coleus amboinicus leaf extracts.

Submitted to: Parasitology Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 7, 2011
Publication Date: N/A

Interpretive Summary: According to the WHO more than a billion people worldwide lack access to safe drinking water. Nearly 2 million of these people die each year from water-borne diarrheal-related disease pathologies. Conventional water treatment methods use aluminum sulfate to enhance sedimentation and chlorine to kill bacteria. These chemicals are seldom available for water purification purposes in developing countries. As an alternative, natural plant materials have been used to decrease turbidity and to improve water purity characteristics. In this study Indian and ARS scientists found that leaf extracts from plants such as lemon grass, Aloe, and Coleus when tested for sedimentation and/or purification effects in stored water also killed the mosquito larvae in the water. These larvae emerge later as adult mosquitoes and can transmit malaria, filariasis, and dengue pathogens to humans.

Technical Abstract: Ethanolic extracts of Cynodon dactylon, Aloe vera, Hemidesmus indicus and Coleus amboinicus were tested for toxicity to 3rd instar Anopheles stephensi, Culex quinquefasciatus, and Aedes aegypti. Median lethal concentrations (LC50) were, respectively, 0.44%, 0.51%, 0.59% and 0.68%. Cynodon dactylon extract induced the highest overall mortality against all three mosquito species in both laboratory and field tests. Extracts from each plant species were shown to exhibit water sedimentation and purification properties. Water color, turbidity, and pH were changed significantly following treatment with C. dactylon (to: 13 HU, 31.5 mg/l and 6.9, respectively), H. indicus (to: 13.8 HU, 33 mg/l and 7.1, respectively), A. vera (to: 16 HU, 33.8 mg/l and 7.4, respectively) and C. amboinicus (to: 21 HU, 35 mg/l and 7.5, respectively) extracts. Leaf extract phytochemicals from C. dactylon, A. vera, H. indicus and C. amboinicus have potent mosquitocidal properties and may be useful for inducing sedimentation in water sources and increasing water purity.